Abstract

Redox targeting reaction is an emerging idea for boosting the energy density of redox-flow batteries: mobile redox mediators transport electrical charges in the cells, whereas large-density electrode-active materials are fixed in tanks. This study reports 4 V-class organic polymer mediators using thianthrene derivatives as redox units. The higher potentials than conventional organic mediators (up to 3.8 V) enable charging LiMn₂O₄ as an inorganic cathode offering a large theoretical volumetric capacity of 500 Ah/L. Soluble or nanoparticle polymer design is beneficial for suppressing crossover reactions (ca. 3% after 300 h), simultaneously contributing to mediation reactions. The successful mediation cycles observed by repeated charging/discharging steps indicate the future capability of designing particle-based redox targeting systems with porous separators, benefiting from higher energy density and lower cost.

This paper reports a facile synthesis of telechelic poly(phenylene sulfide)s through the Friedel–Crafts type electrophilic substitution of the poly(phenylene sulfide) precursors and the halogenated electron-deficient aromatic sulfonium cation.

Materials informatics and cheminformatics struggle with data scarcity, hindering the extraction of significant relationships between structures and properties. The "Ugly Duckling" theorem, suggesting the difficulty of data processing without assumptions...

A quantum-inspired annealing system with a hybrid algorithm accelerates functional material discovery, shown by high-conductivity polymer electrolytes.

A novel quaternized polymer was synthesized by introducing butanediol into poly(allylamine) and converting the remaining amino groups into quaternary ammonium cations. The polymer accelerated the dehydrogenation of butanediol due to...

Electrochemical kinetics of dissolved redox-active polymers are formulated. The model can be used for the rational design of redox-flow cells.

Abstract

Data-driven material exploration is a ground-breaking research style; however, daily experimental results are difficult to record, analyze, and share. We report a data platform that losslessly describes the relationships of structures, properties, and processes as graphs in electronic laboratory notebooks. As a model project, organic superionic glassy conductors were explored by recording over 500 different experiments. Automated data analysis revealed the essential factors for a remarkable room temperature ionic conductivity of 10⁻⁴–10⁻³ S cm⁻¹ and a Li⁺ transference number of around 0.8. In contrast to previous materials research, everyone can access all the experimental results, including graphs, raw measurement data, and data processing systems, at a public repository. Direct data sharing will improve scientific communication and accelerate integration of material knowledge.

Automated molecule design by computers has been an essential topic in materials informatics. Still, generating practical structures is not easy because of the difficulty in treating material stability, synthetic difficulty, mechanical properties, and other miscellaneous parameters, often leading to the generation of junk molecules. We tackle the problem by introducing supervised/unsupervised machine learning and quantum-inspired annealing. Our autonomous molecular design system can help experimental researchers discover practical materials more efficiently. Like the human design process, new molecules are explored based on knowledge of existing compounds. A new solid-state polymer electrolyte for lithium-ion batteries is designed and synthesized, giving a promising room temperature conductivity of 10^-5 S/cm with reasonable thermal, chemical, and mechanical properties.

We introduce quantum circuit learning (QCL) as an emerging regression algorithm for chemo- and materials-informatics. The supervised model, functioning on the rule of quantum mechanics, can process linear and smooth...

A series of poly(phenylene sulfide) (PPS) derivatives can be bleached while maintaining high refractive indices, by partially incorporating sulfoxide bonds through their mCPBA oxidation, owing to the loss of lone pairs around the sulfide atoms.

Polymers bearing hydrogen storage units store hydrogen gas via chemical bond formation, and have inherent advantages as quasi-solid polymeric hydrogen carriers, such as handling easiness and high safety. A recent study demonstrated that a poly(6-vinyl-1,2,3,4-tetrahydroquinoxaline) gel-like solid was dehydrogenated over 5 h under 120°C and air, and then the material was reversibly hydrogenated under 60°C and ambient hydrogen pressure in the presence of an iridium complex catalyst. The present work aimed to improve the dehydrogenation rate via the substitution of methyl groups for hydrogen atoms on carbon atoms adjacent to the nitrogen atoms in the quinoxaline unit. The dramatic improvement was attributed to the electron donating property of methyl group, and stabilization of the dehydrogenated state. The poly(6-vinyl-2,3-dimethyl-1,2,3,4-tetrahydroquinoxaline) gel-like solid was rapidly dehydrogenated within 2 h under the same mild conditions. This article provides a guideline for the molecular design of nitrogen heterocyclic compounds for rapid dehydrogenation.

<p>Electron transfer and mass transport kinetics between two redox couples in nitroxide radical polymers was investigated. Such impact on two-electron storage in radical polymer batteries was exemplified by two macromolecular structures.</p>

<p>In this study we tailor the reversibility of the reduction process of three TEMPO derivatives – TEMPOL, 4-cyano-TEMPO, and 4-oxo-TEMPO – using ionic liquids.</p>

<p>We review the electrochemical theory, material design, and device fabrication for nitroxide radical polymers in emerging plastic energy storage and organic electronics.</p>

1,4-Naphthoquinone (NQ) undergoes a two electron and two proton redox process in one step at a potential of -0.05 V (vs Ag/AgCl) in 0.05 M H2SO4 aqueous solution. Its heterogeneous electron transfer rate constant is comparable to those of electrochemically reversible redox-active molecules. Therefore, NQ is a potential electrode-active material candidate in acidic aqueous electrolyte. Simple nucleophilic substitution of 2-bromo-1,4-naphthoquinone and poly(allylamine) yields NQ-substituted poly(allylamine) (PNQ), enabling us to adjust the hydrophilicity of the redox polymer according to the NQ introduction rate. A polymer-air secondary battery composed of the PNQ anode, the Pt/C cathode, and 0.05 M H2SO4 aqueous electrolyte displayed high cyclability (>100 cycles) and C-rate capability (∼15 C) with a moderate voltage of 0.8 V during discharging.

A rechargeable acidic polymer-air battery was firstly fabricated with poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM) as the anode, the conventional Pt/C cathode catalyst, and acidic aqueous electrolyte (pH 1). This battery yielded a high discharging capacity of 349 mA h g with a long-lifetime of >500 cycles and high rate capabilities (up to 10C). polymer -1

Organic materials receive increasing attention as environmentally benign and sustainable electrode-active materials. We present a conducting redox polymer (CRP) based on poly(3,4-ethylenedioxythiophene) with naphthoquinone pendant group, which is formed from a stable suspension of a trimeric precursor and an oxoammonium cation as oxidant. This suspension allows us to easily coat the polymer onto a current collector, opening up use of roll-to-roll processing or ink-jet printing for electrode preparation. The CRP showed a full capacity of 76 mAh g even at a high C rate of 100 C in acidic aqueous electrolyte. These properties make the CRP a promising candidate as anode-active material; a polymer–air secondary battery was fabricated with the CRP as anode, a conventional Pt/C catalyst as cathode, and sulfuric acid aqueous solution as electrolyte. This battery yielded a discharge voltage of 0.50 V and showed good cycling stability with 97 % capacity retention after 100 cycles and high rate capabilities up to 20 C. −1

Copyright © Materials Research Society 2020. The incorporation of small amounts of phenolic antioxidants, such as 2,6-di-tert-butyl-4-cresol and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], into photovoltaic organo-lead halide perovskite layers significantly suppressed the degradation of the perovskite compounds via light irradiation in the presence of ambient oxygen. While the facile incorporation of the antioxidants did not decrease both the quality of the formed perovskite crystal grains and the photovoltaic conversion performance of the cells, it enhanced the antioxidizing property and water repellency of the perovskite layer owing to the elimination of superoxide anion radical and hydrophobic molecular structure and improved the durability of the cells.

Manganese-based aqueous batteries have attracted significant attention due to their earth-abundant components and low environmental burden. However, state-of-the-art manganese-zinc batteries are poorly rechargeable, owing to dendrite formation on the zinc anode. Organic materials could provide a safe and sustainable replacement. In the present work, a conducting redox polymer (CRP) based on a trimer of EPE (E=3,4-ethylenedioxythiophene; P=3,4-propylenedioxythiophene) and a naphthoquinone (NQ) pendant group is used as anode in polymer-manganese secondary batteries. The polymer shows stable redox conversion around+0.05 V vs. Ag/AgCl, and fast kinetics that involves proton cycling during pendant group redox conversion. For the first time, a CRP-manganese secondary battery was fabricated with pEP(NQ)E as the anode, manganese oxide as the cathode, and manganese-containing acidic aqueous solution as the electrolyte. This battery yielded a discharge voltage of 1.0 V and a discharging capacity of 76 mAh/g over >50 cycles and high rate capabilities (up to 10 C). anode

Hydrogen is an attractive future energy source. Developing a hydrogen carrier, without any safety risk, i.e., high pressure and toxicity, is an urgent issue. Herein we present a fluorenone/fluorenol polymer sheet as a hydrogen carrier featuring high safety, moldability, and ease of handling. An iridium catalyst allows the polymer sheet to fix and release hydrogen gas under milder conditions (< 100 degrees C and ambient pressure), compared to those required by other hydrogen carriers. The polymer sheet, swollen with a small amount of water including the iridium complex catalyst, was hydrogenated at 25 degrees C and ambient hydrogen pressure, stored hydrogen via chemical bond formation, and then released it within 5 h when simply being warmed to 95 degrees C.

Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential, transportation, and portable applications. Currently, a high-pressure tank is the state-of-the-art mode of hydrogen storage; however, the energy cost, safety, and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP), which is a solid-state organic hydride, as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylene-based PEM) enhances the operable time, reaching up to ca. 10.2 s mg , which is more than a factor of two longer than that (3.90 s mg ) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable, at least up to 50 cycles. The features of this RCFC system, including safety, ease of handling, and light weight, suggest applications in mobile, light-weight hydrogen-based energy devices. HSP HSP −1 −1

Isotactic polyacrylonitrile (iso-PAN) is synthesized via template polymerization using the two-dimensional layered space of a CoCl2 crystal as a template. Isotacticity of polyacrylonitrile reaches a meso/meso triad = 93% (mm = 0.93), which indicates a superior packing of polymer chains, leading to a high breakdown strength. Tacticity enhancement is correlated with the interatomic (metal-metal) distance of template -layered crystals. Due to a large dipole moment (4.3 D) of nitrile group and a high stereoregularity, iso-PAN demonstrates a high discharge energy density of 6.7 J/cm(3) at 660 MV/m, nearly six times that of atactic polyacrylonitrile (ata-PAN) and biaxially oriented polypropylene (BOPP), a commercially available dielectric polymer film. Moreover, it exhibits a charge-discharge efficiency of ca. 90% in a wide applied electric field range, which is higher than the efficiencies of ata-PAN and BOPP. These results suggest that iso-PAN, exhibiting a large dipole moment and high stereoregularity, is a promising candidate for high energy density and low loss capacitor dielectrics.

© 2019 American Chemical Society. Poly(vinylcarbazole) (PVCz) dispersed the typical fullerene derivative, PCBM, well in its solution, which was then coated onto a mesoporous titanium oxide (TiO2) layer. PVCz served as a scaffold to fix PCBM homogeneously and to prevent its elution out upon the following perovskite layer formation. A series of perovskite cells were fabricated upon the PVCz/PCBM-modified TiO2 layer. Many of the cells were characterized by a photovoltaic conversion efficiency of >20%, and the top cells had an efficiency of 21.1% (with an average of 21.0%). Fluorescence decay from the perovskite layer of the cell was unchanged with the PVCz/PCBM modification, suggesting an efficient charge transport to the electron-transporting layers. On the other hand, the PVCz/PCBM modification or passivation significantly reduced electroluminescence intensity under an inverse bias application, supporting an efficient suppression of carrier recombination at the TiO2 and perovskite interface.

The radical polymerization of 2-vinylfluorenol, an alcohol derivative of vinylfluorene, gives poly(vinylfluorenol), which quantitatively releases hydrogen gas (≈110 mL per gram polymer at standard temperature and pressure) by simply warming at 100 °C with an iridium catalyst. A high population of fluorenol units in the polymer accomplishes a large formula-weight-based theoretical hydrogen density (1.0 wt%). The dehydrogenated ketone derivative, poly(vinylfluorenone), exhibits reversible negative-charge storage with a high density of 260 mAh g . The electrolytically reduced poly(vinylfluorenone) is momentarily hydrogenated in the presence of an electrolyte with water as the hydrogen source to be converted to the original poly(vinylfluorenol). The formed poly(vinylfluorenol) almost quantitatively evolves hydrogen gas similar to the starting poly(vinylfluorenol). Both hydrogen and charge storage with the organic fluorenol/fluorenone polymer suggest a new type of energy-storage configuration. −1

Li-ion batteries (LIBs) raise safety and environmental concerns, which mostly arise from their toxic and flammable electrolytes and the extraction of limited material resources by mining. Recently, water-in-salt electrolytes (WiSEs), in which a large amount of lithium salt is dissolved in water, have been proposed to allow for assembling safe and high-voltage (>3.0 V) aqueous LIBs. In addition, organic materials derived from abundant building blocks and their tunable properties could provide safe and sustainable replacements for inorganic cathode materials. In the current work, the electrochemical properties of a conducting redox polymer based on poly(3,4-ethylenedioxythiophene) (PEDOT) with hydroquinone (HQ) pendant groups have been characterized in WiSEs. The quinone redox reaction occurs within the potential region where the polymer is conducting, and fast redox conversion that involves lithium cycling during pendant group redox conversion was observed. These properties make conducting redox polymers promising candidates as cathode-active materials for safe and high-energy aqueous LIBs. An organic-based aqueous LIB, with a HQ-PEDOT as a cathode, Li Ti O (LTO) as an anode, and ca. 15 m lithium bis(trifluoromethanesulfonyl)imide water/dimethyl carbonate (DMC) as electrolyte, yielded an output voltage of 1.35 V and high rate capabilities up to 500C. 4 5 12

Facile charge transport by a hydrophilic organic radical-substituted polymer and the 3D current collection by a self-assembled mesh of single-walled carbon nanotube bundles lead to the operation of an ultrahigh-output rechargeable electrode. Exceptionally large current density beyond 1 A cm−2 and high areal capacity around 3 mAh cm−2 are achieved, which are 101−2 times larger than those of the previously reported so-called “ultrafast electrodes.” A sub-millimeter-thick, flexible, highly safe organic redox polymer-based rechargeable device with an aqueous sodium chloride electrolyte is fabricated to demonstrate the superior performance.

Arylamine polymers were prepared via the facile one-step addition condensation of N,N′-diphenyl-N,N′-bis(4-methylphenyl)-1,4-phenylenediamine and 4-methoxytriphenylamine with paraldehyde. The polymers were highly soluble in common organic solvents. The non-conjugated arylamine polymer structure was characterized and found to form tough, homogeneous, amorphous layers with a glass transition temperature above 200 °C on a substrate by a simple spin-coating process. The polymer layers exhibited a hole mobility of the order of 10−5 cm2 V−1 s−1, which was comparable with those of previously reported arylamine polymers, and a highest occupied molecular orbital level of −5.38 eV appropriate for the hole-transporting layer of perovskite solar cells. The perovskite cells fabricated with the polymers gave a photovoltaic conversion efficiency of 16.0%. © 2018 Society of Chemical Industry.

Application of the concept of three-color (red (R), green (G), and blue (B)) light-mixing to obtain white light is the most suitable way to realize white-light-emitting devices with very high color-rendering indices (CRI). White-light-emitting devices based on the three-color-mixing method could be used to create lighting and display technologies. Here, white-light-emitting electrochemical cells (LECs) with very high CRIs are reported, which were fabricated by using blend films composed of a fluorescent π-conjugated polymer (FCP), poly(9,9-dioctylfluorene-co-benzothiadiazole) (PFBT), and a phosphorescent iridium complex, [Ir(ppy)2(biq)]+(PF6)− (where (ppy)−=2-phenylpyridinate and biq=2,2′-biquinoline). The LECs fabricated with PFBT, the benzothiadiazole content of which is 0.01 mol %, showed blue electroluminescence (EL) emission originating from the fluorene segments and green EL emission from the benzothiadiazole units simultaneously. White LECs were then realized by adding red-emitting Ir complexes as guest molecules to the blue-green-emitting PFBT. By optimizing the proportions of the PFBT and Ir complexes in the active layers (PFBT/[Ir(ppy)2(biq)]+(PF6)−=1:0.2 (mass ratio)), white-light emission with Commission Internationale de l′Eclairage (CIE) coordinates of (0.29, 0.34) and a very high CRI value of 91.5 was achieved through RGB color-mixing. It was noted that the emission mechanism was based on Förster resonance energy transfer and Dexter energy transfer from excited PFBT to [Ir(ppy)2(biq)]+(PF6)−. The utilization of LECs based on blue-green FCPs and red Ir complexes looks very promising for the prospect of realizing white-light-emitting devices with very high CRIs.

Oxoammonium cation of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) was used as an oxidizing dopant of triaryl amines to efficiently and almost quantitatively generate radical cations of the amines or a hole carrier. The doped-triaryl amines yielded an amorphous and homogeneous layer without any residual oxidant or neutral TEMPO molecule through its sublimination or warming the layer. The TEMPO cation-doped spiro-OMeTAD [tetrakis(dimethoxyphenylamine)spirobifluorene] produced a high hole mobility of 2 × 10-4 cm2/Vs. The perovskite solar cell fabricated with the TEMPO cation-doped or residual dopant-free spiro-OMeTAD as the hole-transporting layer displayed a photo-conversion efficiency of 20.1% with durability.

Charge transport processes in nonconjugated redox-active polymers with electrolytes were studied using a diffusion-cooperative model. For the first time, we quantitatively rationalized that the limited Brownian motion of the redox centers bound to the polymers resulted in the 103-4-fold decline of the bimolecular and heterogeneous charge transfer rate constants, which had been unexplained for half a century. As a next-generation design, a redox-active supramolecular system with high physical mobility was proposed to achieve the rate constant as high as in free solution system (&gt
107 M-1 s-1) and populated site density (&gt
1 mol/L).

Poly(diphenanthrenequinone-substituted norbornene) (PQN) as a novel class of organic electrode-active material was reported. A Li coin cell composed of the PQN/carbon composite electrode as the cathode exhibited 2.8V and great cycle performance maintaining a capacity higher than 100mAh/g for more than 100 cycles at 60C. Among many types of o-quinonecontaining polymers for Li-ion batteries reported so far, the present research provides the first example of introducing phenanthrenequinone as the pendant group per repeating unit of polymers, which proved to be especially advantageous in terms of robustness and cyclability by virtue of the fused-ring structure to protect the reactive positions of the o-benzoquinone. The functional group tolerance against many types of redox-active groups, which we have established for the initiator and the propagating end of norbornene derivatives, apply for the phenanthrenequinone-substituted monomer, giving rise to a reversible redox activity.

Dibenzothiophenesulfone undergoes a two-electron reduction in a single step at a very negative potential of -1.8 V (versus Ag/AgCl) in organic electrolytes, due to the electron-withdrawing sulfone group and the stability of the resulting dianion. The heterogeneous electron-transfer rate constant for the reduction is approximately 10 cm s , which is significantly faster than most redox-active species. The results presented herein suggest that dibenzothiophenesulfone is a potential candidate for use as an anode-active material with high-energy density. In addition, radical polymerization of vinyldibenzothiophenesulfone yielded poly(vinyldibenzothiophenesulfone) with a high molecular weight. A rechargeable device is fabricated with only organic compounds; poly(vinyldibenzothiophenesulfone) as the anode, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-substituted poly(methacrylate) as the cathode, and tetraethylammonium salt and organic solvent as the electrolyte. This device yields a maximum output voltage of 2.6 V in these organic devices, and the active component of the anode displays a very high-energy density of >500 mWh g . -1 -1 -1

The authors present high-color-rendering-index (CRI) white polymer light-emitting electrochemical cells (PLECs) based on ionic host-guest systems. PLECs were fabricated with blend films composed of a blue fluorescent cationic pi-conjugated polymer, poly(9,9-bis[60-(N, N, N,-trimethylammonium) hexyl] fluorineco- alt-1,4-phenylene) bromide (PFN+Br-), used as a host, and a red phosphorescent cationic iridium complex, [ Ir(ppy)(2)(biq)](+)(PF6)(-) (where (ppy)(-) = 2-phenylpyridinate and biq = 2,2'-biquinoline), used as a guest. By optimizing the composition of PFN+Br- and [Ir(ppy)(2)(biq)](+)(PF6)(-) in the active layers, white light emission with Commission Internationale de l'Eclairage (CIE) coordinates of (x = 0.28, y = 0.31) and a very high CRI of 95.8 was achieved through mixing of blue and red light at an applied voltage of 4.0 V. The white light emissions were obtained at a low [Ir(ppy)(2)(biq)](+)(PF6)(-) concentration (PFN+Br- :[Ir(ppy)(2)(biq)](+)(PF6)(-) = 1: 0.01 (mass ratio)), showing that [Ir(ppy)(2)(biq)](+)(PF6)(-) acts as a suitable energy acceptor. The emission mechanism of the ionic host-guest PLECs can be explained by Forster resonance energy transfer (FRET) and Dexter energy transfer (DET) from the excited PFN+Br- to [Ir(ppy)(2)(biq)](+)(PF6)(-). Utilization of ionic host-guest PLECs is a very promising method for realizing white light-emitting devices with very high CRI. (C) 2017 Elsevier B.V. All rights reserved.

The authors present Ag nanocluster-based color converters (Ag NC color converters), which convert part of the blue light from a light source to yellow light so as to create white organic light-emitting devices that could be suitable for lighting systems. Ag NCs synthesized by poly(methacrylic acid) template methods have a statistical size distribution with a mean diameter of around 4.5 nm, which is larger than the Fermi wavelength of around 2 nm. Hence, like free electrons in metals, the Ag NC electrons are thought to form a continuous energy band, leading to the formation of surface plasmons by photoexcitation. As for the fluorescence emission mechanism, the fact that the photoluminescence is excitation wavelength dependent suggests that the fluorescence originates from surface plasmons in Ag NCs of different sizes. By using Ag NC color converters and suitable blue light sources, white organic light-emitting devices can be fabricated based on the concept of light-mixing. For our blue light sources, we used polymer light-emitting electrochemical cells (PLECs), which, like organic light-emitting diodes, are area light sources. The PLECs were fabricated with a blue fluorescent p-conjugated polymer, poly[(9,9-dihexylfluoren-2,7-diyl)-co-(anthracen- 9,10-diyl)] (PDHFA), and a polymeric solid electrolyte composed of poly(ethylene oxide) and KCF3SO3. In this device structure, the Ag NC color converter absorbs blue light from the PDHFA-based PLEC (PDHFA-PLEC) and then emits yellow light. When the PDHFA-PLEC is turned on by applying an external voltage, pure white light emission can be produced with Commission Internationale de l'Eclairage coordinates of (x = 0.32, y = 0.33) and a color rendering index of 93.6. This study shows that utilization of Ag NC color converters and blue PLECs is a very promising and highly effective method for realizing white organic light-emitting devices. Published by AIP Publishing.

Robust radical-substituted polymers with ideal redox capability were used as "command surfaces" for liquid crystal orientation. The alignment of the smectic liquid crystal electrolytes with low-dimensional ion conduction pathways was reversible and readily switched hi response to the redox states of the polymers. In one example, a charge storage device with a cooperative redox effect was fabricated. The bulk ionic conductivity of the cell was significantly decreased only after the electrode was fully charged, due to the anisotropic ionic conductivity of the electrolytes (ratio &gt;10(3)). The switching enabled both a rapid cell response and long charge retention. Such a cooperative Command surface of-self-assembled structures Will give rise to new highly energy efficient supramolecular-based devices including batteries, charge carriers, and actuators.

In the presence of diphenyl sulfide, oxygen-oxidative polymerization of diphenyl disulfide gave highly crystalized poly( 1,4-phenylene sulfide) (PPS) using a vanadyl-strong acid catalytic system. Effect of the sulfide, which was inactive to the vanadyl catalyst, was ascribed to the enhancement of the electrophilic substitution with a sulfonium cation onto a thiophenyl end. The finally purified PPS showed high crystallinity (X-c = 44%), which was even higher than that of the reagent grade PPS produced by the conventional polycondensation process.

A supramolecular gelator, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-substituted cyclohexanediamine derivative, was synthesized, and its excellent charge-transporting capability was explored. The gels with organic solvents and electrolytes, or with ionic liquids, were formed via reversible sol-gel phase transition at ca. 50 degrees C. The organogels displayed electrochemical redox responses at E-1/2 = 0.72 V (vs Ag/AgCl) ascribed to the TEMPO moiety. Charge diffusion coefficient of the gel reached 3.3 x 10(-7) cm(2)/s even in the quasi-solid state, which was comparable to those of the homogeneous solution (ca. 10(-6)). The high charge-transporting capability led to the tremendously large current density (a diffusion limited one) of ca. 1.0 mA/cm(2) on a current collector and long distance for the charge-transporting beyond the organogel thickness of 50 mu m. A half-cell of the organogel performed a plateau output voltage at the E-1/2, very high rate, and almost quantitative charging-discharging, and it had cydability without any additives such as conductive carbons and binder polymers.

A thin layer of a polymer containing densely populated redox-active nitroxide radicals, photocrosslinked poly[2,3-bis(2',2',6',6'-tetramethylpiperidin-1'-oxyl-4'-oxycarbonyl)-5-norbornene] (PTNB), was employed to demonstrate an electrochemical transistor-like behavior in the form of a polymer-sandwiched nanogap device. A significant and sensitive change in the current in response to the applied electrode potential was produced, owing to the fast formation of the steep redox gradient of the electroactive species through the polymer layer. A current response to an alternating voltage obtained from the polymer-sandwiched nanogap device exhibited the electrochemical amplification effect based on the facile redox conduction.

Totally organic polymer-based, submillimeter-thick, bendable rechargeable devices were fabricated using hydrophilic polymers as electrode-active materials and brine as the electrolyte. The rapid and reversible electrochemical reactions of the polymers enabled quick charging within minutes, long life, and a moderate operation voltage of more than 1V. Quantitative discharge was achieved even when the devices were in a bent state with a radius of curvature of 1 mm.

Next-generation, power-efficient organic lighting systems, which ideally would be low-cost and mass-producible, are urgently needed because more than 20% of total electricity use goes to lighting. This study presents polymer light-emitting electrochemical cells (PLECs) made using mass-producible nanoimprinted corrugated substrates, which effectively improve light extraction efficiency. The corrugated substrates are fabricated using roll-to-roll methods, using self-assembled block copolymers on glass and film substrates (glass: 0.45 m x 0.55 m, film: 0.6 m wide). Using the glass-type corrugated substrates, two PLECs based on (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene]) and (super-yellow poly(p-phenylene vinylene)) (SY-PPV) are fabricated by solution-based spin-coating methods, which can in practice be replaced by roll-to-roll methods. The corrugated PLECs with SY-PPV show high brightness of 1740 cd cm(-2) and 2.1 times greater efficiency without changing the original spectrum or angular dependence. This successful combination of corrugated substrates and PLECs is one of the best examples of a promising cost-effective, high-performance lighting technology.

Quinaldine-substituted poly(acrylic acid) (PQD) and its hydrogenated 1,2,3,4-tetrahydroquinaldine derivative (PHQD) were prepared, and a cycle of hydrogen fixing and hydrogen evolution in and from the polymer, respectively, is described. A PQD layer coated on a carbon substrate was electrochemically reduced or hydrogenated using water as a hydrogen source, accompanied by the electrodeposition of nickel microparticles in the polymer layer, to convert PQD to PHQD. The conversion efficiency was enhanced by coating PQD on the substrate as a scaffold of nickel electrodeposition, in comparison with that of quinaldine and PQD dissolved in the electrolyte. The formed PHQD evolved hydrogen by simply warming it in water containing an iridium complex catalyst. Hydrogen fixing and evolution under mild conditions could suggest a new system of hydrogen carriers. (c) 2017 Society of Chemical Industry

Redox-active copolymer containing organic robust radical, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), and charge neutralizing anion, trifluoromethanesulfonylimide (TFSI-) was synthesized as a cathode material of a Li-ion battery. The copolymer, poly(2,2,6,6-tetramethylpiperidin-1-oxy-4-yl methacrylate-co-styrenesulfonyl(trifluoromethanesulfonyl)imide) (1)(TMA-co-TFSI)), was designed to give rise to the Li+ migration during its charge-discharge process, based on the self charge compensation of TEMPO with TFSI- bound to the polymer chain in a widely used electrolyte system for Li-ion battery, organic carbonate mixtures. Copolymerization was performed to achieve efficient self-charge compensation with uniformly distributed TFSI- units. The P(TMA-co-TFSI) layer electrode exhibited reversible redox reaction at 0.73 V vs Ag/AgCl. Electrochemical measurements combined with quartz crystal microbalance analysis evidenced that the redox reaction involved the Li+ migration in binary system of ethylene carbonate and diethyl carbonate. A test cell fabricated with the P(TMA-co-TFSI) cathode exhibited high discharging voltage of 3.7 V and high -rate charge -discharge capability at 30 C (i.e., full charging in 2 min).

Electrochromic (EC) polymers such as polyviologens have been attracting considerable attention as wet-processable electrodes for EC displays, thanks to their brilliant color change accompanied with reversible redox reactions. To establish wider usage, achieving multicolor and high-resolution characteristics is indispensable. In this paper, we demonstrated that the introduction of substituents such as methyl groups into bipyridine units changed the stereostructure of the cation radicals, and thus shifted the color (e.g., ordinary purple to blue). Also, by relaxing excessive pi-stacking between the viologen moieties, the response rate was improved by a factor of more than 10. The controlled charge transport throughout the polyviologen layer gave rise to the fabrication of EC displays which are potentially suitable for the thin film transistor (TFT) substrate as the counter electrodes with submillimeter pixels. The findings can be versatilely used for the new design of polyviologens with enhanced electrochemical properties and high-resolution, multicolor EC displays.

Finding a safe and efficient carrier of hydrogen is a major challenge. Recently, hydrogenated organic compounds have been studied as hydrogen storage materials because of their ability to stably and reversibly store hydrogen by forming chemical bonds; however, these compounds often suffer from safety issues and are usually hydrogenated with hydrogen at high pressure and/or temperature. Here we present a ketone (fluorenone) polymer that can be moulded as a plastic sheet and fixes hydrogen via a simple electrolytic hydrogenation at -1.5V (versus Ag/AgCl) in water at room temperature. The hydrogenated alcohol derivative (the fluorenol polymer) reversibly releases hydrogen by heating (80 degrees C) in the presence of an aqueous iridium catalyst. Both the use of a ketone polymer and the efficient hydrogen fixing with water as a proton source are completely different from other (de) hydrogenated compounds and hydrogenation processes. The easy handling and mouldable polymers could suggest a pocketable hydrogen carrier.

Two bis(acetylide)-functionalized platinum(II) polymers containing ferrocenyl pendant ligands, trans[(-Pt(PBu3n)(2)-C CRC C-)(n) P1 (R = 9-ferrocenylmethylene-2,7-diethynylfluorene) and P2 (R = ferrocenylmethylene-2,5-diethynylbenzene), were prepared in good yields and were characterized by NMR spectroscopy and GPC. Electrochemical characteristics with copolymers P1 and P2 as the cathode active materials for rechargeable lithium batteries showed chemical and electrochemical reversibility. The thin layer polymer electrodes of P1 and P2 exhibited reversible redox peaks at the potentials of 0.54 and 0.64 V (vs. Ag/AgCl), respectively. The P1 or P2/carbon composites are also used as cathode-active materials to enhance the conductivity and durability. The electrodes exhibited good cycle life of over 50 charging/discharging cycles and no reversible n-type redox abilities seemed to be available. (C) 2015 Elsevier B.V. All rights reserved.

Organic-based solar cells potentially offer a photovoltaic module with low production costs and low hazard risk of the components. We report organic dye-sensitized solar cells, fabricated with molecular designed indoline dyes in conjunction with highly reactive but robust nitroxide radical molecules as redox mediator in a quasi-solid gel form of the electrolyte. The cells achieve conversion efficiencies of 10.1% at 1 sun, and maintain the output performance even under interior lighting. The indoline dyes, customized by introducing long alkyl chains, specifically interact with the radical mediator to suppress a charge-recombination process at the dye interface. The radical mediator also facilitates the charge-transport with remarkably high electron self-exchange rate even in the quasi-solid state electrolyte to lead to a high fill factor.

Two new organometallic copolymers (PVFVM1 and PVFVM1-1) bearing different molar ratios of ferrocene and triphenylamine pendants were successfully designed and synthesized as cathode active materials for organic-battery applications. Their structural and thermal characteristics were determined by H-1 NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). Cyclic voltammograms of the as-prepared polymers show that the electrochemical reactions of the ferrocene and triphenylamine moieties are reversible after the first cycle. A composite electrode based on copolymer PVFVM1 exhibits an initial specific discharge capacity of 102 mAhg(-1), which corresponds to 98% of its theoretical capacity (104 mAhg(-1)). The cycle endurances for both polymers have been evaluated for over 50 cycles. Our results show that both copolymers are good candidates as a new class of cathode active materials and charge-storage materials for rechargeable batteries.

Carbon-sulfur (C-S) bond formation is one of the important synthetic routes in organic chemistry. Among sulfur sources for C-S bond formation, organosulfur cations (RS+) and their synthetic equivalents are unique reagents. These cationic sulfur species are easily prepared as compared with the oxonium analogues, because of their low ionization potentials. This review describes various synthetic methods for C-S bond formation, mainly focusing on electrophilic reactions, addition to olefins, and substitution to aromatic rings. A breakthrough has been anticipated for RS+ electrophiles, based on their versatile utility in aromatic polymer synthesis.

The ionic conductivity of a liquid crystal electrolyte was switched along with redox reactions of polyviologen. The surface charge of the polymer determined the alignment and the bulk conductivity of the electrolyte. The cooperative switching firstly enabled the suppression of self-discharging and quick-response, giving rise to facile and persistent charge storage.

Oxygen-oxidative polymerization of diphenyl disulfide gives poly(1,4-phenylene sulfide) (PPS), catalyzed by a vanadyl complex and a protic acid. N,N'-Ethylenebis(salicylideneaminato)oxovanadium(IV) (VO(salen)) which has been reported to be catalytically inactive at ambient temperature because of the insufficient reactivity of its oxidized state, an oxovanadium(V) complex, for the oxidation of the monomer turned out to exhibit an excellent catalytic activity on raising the reaction temperature above 100 degrees C. The enhanced reactivity of VO(salen)-acid or bis(2,4-pentanedionato)oxovanadium(IV) (VO(acac)(2))-acid catalytic systems at elevated temperatures gave insight into the catalytic mechanism where oxidation of the monomer with the oxovanadium(V) complex dominated the reactivity, which was also accelerated by a second redox shuttle molecule, such as quinones with a potential near that of the [VO(salen)](0/+) couple.

Two pendant-type naphthalene diimide (NDI) polymers bearing a polynorbornene backbone were prepared and their electrochemical properties explored. The NDI-based polymers displayed reversible redox responses in 1 M LiClO4 gamma-butyrolactone electrolyte. Polymer 1, bearing a N-methyl group, exhibited remarkable charge-storage capabilities which demonstrated its potential usefulness as an organic cathode-active material in rechargeable devices with excellent performances such as large charge capacity, high rate capability, and charge-discharge cyclability.

Totally reversible redox-active polymers, 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl functionalized polyacrylic acid (PTAm-A) and poly(tripyridiniomesitylene) (PTPM), both of which possessed rapid charge transport properties in an aqueous electrolyte, were applied to a polymer-sandwiched device to offer an electrochemical current rectification functionality. Single-layer and bilayer devices were fabricated employing the PTAm-A and/or PTPM thin layer(s) as charge transport media. Single-layer devices with a 1 cm(2) electrode area demonstrated large currents in the order of several milliamperes, which were established by redox mediation based on a fast electron self-exchange reaction between adjacent redox sites in the polymer layers. A current-voltage response obtained from the bilayer device exhibited a rectification effect due to thermodynamically favoured cross reaction at the polymer/polymer interface, retaining the large current densities. The observed currents were comparable to those predicted from the diffusion-controlled charge transport kinetics. Potentiostatic measurements revealed that the rectified current readily achieved a steady state in response to the applied voltage. These results demonstrate that the PTAm-A/PTPM thin-layer heterojunction enabled a large current rectification based on the redox mediation process, providing insight into ideal charge flow systems in various electrochemical devices.

A newly established catalyst system for oxygen-oxidative polymerization of diphenyl disulfide is reported. Combination of vanadyl compounds (e.g., VO(acac)(2)) and triphenylmethylium tetrakis(pentafluorophenyl) borate (TrB(C6F5)(4)) proceeds the polymerization to give poly(1,4-phenylene sulfide) (PPS) at 100 degrees C. When triphenylmethylium tetrafluoroborate (TrBF4) is applied with vanadyl tetraphenylporphyrin (VO(TPP)) or N,N'-(ethylenebis(salicylideneaminato)) oxovanadium (VO(salen)), PPS is also given via polymerization under conditions near 160 degrees C. Combination of the vanadyl complex and the borate affords the first protic-acid-free catalytic system for the polymerization of the disulfide, suggesting the overall reaction to produce PPS and H2O from O-2 and protons that are eliminated from the monomer.

Oxidative polymerization of diphenyl disulfide under molten conditions at moderately elevated temperatures gave poly(1,4-phenylene sulfide) (PPS), using a vanadyl complex strong acid catalyst with oxygen as the ultimate oxidant. Origin of the selectivity of the sulfonium electrophile for the formation of the 1,4-thiophenylene chain, characterized by the presence of a disulfide bond at the chain end, was determined by the behavior of polymerization and structural analysis of the product together with a computational calculation, which revealed a unique chain growth-type polycondensation process.

Block copolymers of 2,2,6,6-tetramethyl-4-piperidyl methaaylate and glycidyl methactylate were prepared by atom transfer radical polymerization. The block copolymer was immobilized on an indium-doped tin oxide substrate by simply coating the copolymer solution and annealing. The copolymer layers were efficiently converted to those of the corresponding 2,2,6,6-tetramethylpiperidin-1-oxy (TEMPO) polymer. The TEMPO layers were swelled with but not eluted into common electrolyte solutions such as acetonitrile and ethylene carbonate, and showed excellent electrochemically reversible redox cycling at 0.81 V vs. Ag/AgCl. The layer with the thickness of micron meters exhibited both a sufficient charge diffusivity (10(-10) cm(2) s(-1)) and a very large storage capacity (beyond 120 mC cm(-2)), which was applicable to a cathode of organic-based rechargeable devices. (C) 2015 Elsevier Ltd. All rights reserved.

A dye-sensitized solar cell (DSSC) was fabricated with a viologen polymer as a charge-storable electrode and an aqueous electrolyte. The polyviologen was prepared via electrolytic polymerization of the 4-cyanopyridine moiety: It displayed reversible two-electron redox reactions at -0.48 and -0.86 V vs. Ag/AgCl in the aqueous electrolyte, which were appropriate for the acceptance of an electron from the photo-anode or TiO2 conduction band by the charge-storable electrode. The DSSC using the polyviologen electrode achieved both photo-current generation with a high open-circuit voltage of ca. 0.8 V upon light irradiation, and a charge-supply after irradiation at a constant voltage of ca. 0.4 V with a discharging capacity of ca. 75% of the polyviologen electrode. The potential tuning of the organic-based polyviologen electrode was described. (C) 2015 Elsevier Ltd. All rights reserved.

A nitroxide radical-substituted polyether, poly(TEMPO-substituted glycidyl ether) (PTGE), was synthesized using a potassium tert-butoxide/18-crown-6 initiator. The presence of 18-crown-6 effected significant improvement in the reactivity of the chain end, thus allowing the polymerization to proceed at moderate temperatures to suppress the deactivation of the pendant nitroxide group. A high molecular-weight polyether with a theoretical radical concentration was first obtained in high yield. Charging and discharging cyclability was much improved by cross-linking, which helped the electrode-active material stay on a current collector during the electrolysis. The polymer/vapor-grown carbon nanofiber composite electrode exhibited a redox capacity comparable to the formula weight-based theoretical density over 10(3) cycles and fast charging/discharging capability up to a rate of 60C which corresponded to full charging and discharging in 60s. The redox capacity was almost maintained for a composite layer with a remarkably high polymer ratio of 90%, which demonstrated the presence of effective percolation network of the carbon nanofiber due likely to the affinity of the polyether to the carbon material.

An excellent functional group tolerance of ruthenium complex catalysts for olefin metathesis gave rise to ring-opening polymerization of norbornene functionalized with redox-active anthraquinone (AQ) pendants, yielding a high-molecular-weight and processable polynorbornene with large redox capacity. A thin layer of the polymer cast on current collectors showed reversible redox reaction at -0.85 V vs Ag/AgCl when immersed in basic aqueous electrolyte solutions. Good cycle performance was observed with a capacity comparable to the formula weight-based theoretical density of 212 mAh/g, which was the largest among those for the previously reported redox-active polynorbornenes. This suggested that all of the AQ units in the layer were redox-active, that electroneutralization was accomplished by successive compensation of counterions throughout the layer, and that the mechanical strength of the polymer layer prevented dissolution or exfoliation from the current collector surface. A robust polymer-air secondary battery with the high capacity was fabricated by using the polymer layer as the anode-active material. The battery showed a discharge voltage of 0.68 V and long life of over 300 cycles of charging/discharging, maintaining the moderate energy density of 143 mWh/g.

Concurrent and cathodic electrolysis of tris(cyanopyridinio)mesitylene and zinc chloride gave redox-active polyviologen, densely formed around the zinc oxide nanorod, on a substrate, which displayed a large charging discharging capacity and an excellent rate performance based on a large diffusivity of charge, and was useful as an anode-active material.

A copolymer of TEMPO-and aniline-substituted norbornene was prepared by ring-opening metathesis polymerization of the corresponding monomers. Electropolymerization of the pendant aniline groups in the copolymer gave a layer of polynorbornene populated with the redox-active TEMPO pendants, in which polyaniline chain was incorporated. Electroactivity of the TEMPO pendants throughout the layer and its excellent charging/discharging cyclability, in addition to the amorphous nature of the layer, suggested that the polyaniline chain was homogeneously dispersed in the layer and that each chain served as crosslinking moiety. The effect of the polyaniline chains was further enhanced when they were formed by in-situ electropolymerization of the aniline group in the preformed layer of the copolymer/polyaniline composite. The polyaniline chain served as a conducting path to reduce the charge-transfer resistance for redox mediation, which gave rise to an excellent rate performance for the charging/discharging process of the layer, compared with those for the composite layers of TEMPO-substituted polymers with polyaniline and other conductive additives prepared by the conventional grinding methods.

Reactivity of redox-active molecules for heterogeneous electron-transfer processes at the surface of doped zinc oxide substrates depended on their energy levels. The redox-active molecules with negative redox potentials displayed a reversible electrochemical response but those with positive redox potentials were characterized by slow electrode kinetics, which was attributed to more than three times larger heterogeneous electron-transfer rate constant for the former redox-active molecules. A photovoltaic cell using methyl viologen as an acceptor molecule, TEMPOL as a donor molecule, and the doped ZnO as the transparent conducting substrate gave high photovoltage, which was ascribed to the reactivity of the redox-active molecules at the doped ZnO surface.

A crosslinked poly(4-glycidyloxy TEMPO) was synthesized via anionic ring-opening copolymerization of 4-glycidyloxy TEMPO and a diglycidyl ether using a pentaerythritol/phosphazene base initiator. A fast and reversible charge storage capability was established for the polyether/SWCNT composite layer with a large layer thickness of several tens of micrometres, despite the low SWCNT content of 10% which was much closer to the percolation limit than the amount required for the previously reported TEMPO-substituted polymethacrylate.

Electrolytes highly enriched with oxygen for lithium-oxygen (Li-O-2) batteries were prepared by combining perfluorohexyl bromide as an oxygen-uptake perfluorochemical (PFC) medium with lithium perfluorooctane sulfonate (LiPFOS) as a perfluoro-surfactant and a supporting electrolyte, which allowed an exceptionally high miscibility of PFCs with tetraethylene glycol dimethyl ether (TEGDME). The electrochemical reduction current of oxygen was enhanced three times in the LiPFOS-TEGDME electrolyte with ca. 60 wt% PFC content in comparison with that of a conventional Li-O-2 battery electrolyte, which was ascribed to the high oxygen solubility of the electrolyte. A Li-O-2 cell fabricated with the PFC-based electrolyte exhibited an excellent discharging capacity of 6500 mA h g(-1) which was approximately 1.5 times higher than that obtained with the conventional electrolyte.

Poly(norbornene)-g-poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl) (PNB-g-PTMA) was prepared by a grafting-through approach based on anionic polymerization of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl using a norbornene-substituted diphenylhexyllithium to yield a norbornene-functionalized macromonomer (NB-PTMA) and subsequent ring-opening metathesis polymerization of NB-PTMA using a Grubbs third-generation catalyst, which avoided critical side reactions involving the nitroxide radical of TEMPO moiety. The anionic polymerization resulted in high yields (&gt;94%), narrow polydispersity indices (&lt;1.20), and radical concentrations (0.95 radicals per monomer unit). The ROMP also resulted in high yields (&gt;98%) and high radical concentrations (0.95 radicals per monomer unit), by virtue of the functional group tolerance of these reactions. Single molecular dimension of PNB-g-PTMA was measured by dynamic light scattering and by atomic force microscopy (AFM), which precisely reflected the bottlebrush structure to reveal the presence of the TEMPO group crowded at the periphery of the molecule. The lengths of PNB-g-PTMA along the macromolecular side chains and the polynorbornene main chain were both approximately equal to the theoretical lengths estimated by the degree of polymerization for each chain. The number-average diameter of PNB-g-PTMA in THF increased with initial NB-PTMA ratio to the Grubbs catalyst. Photo-cross-linked thin layer electrodes of PNB-g-PTMA demonstrated the reversible redox reaction at 0.80 V vs Ag/AgCl corresponding to the TEMPO/TEMPO+ couple and quantitative charging/discharging processes even at 120 C rate (i.e., full charging in 30 s). As a novel application of redox-active polymers, PNB-g-PTMA exhibited 95% efficiency of the theoretical charge capacity in a flow cell system, based on the unique properties of bottlebrush polymers such as the defined molecular dimension and relatively low solution viscosity in comparison with corresponding linear polymers.

A ferrocenylimidazolium salt was found to be an efficient iodine/iodide-free redox mediator for a dye-sensitized solar cell (DSSC), giving rise to a photoconversion efficiency of 4% under optimized electrolyte conditions. The excellent redox mediation process was ascribed not only to the electrochemically reversible nature of the molecule with a large heterogeneous electron-transfer rate constant in the order of 10(-2) cm s(-1) at electrodes, but also to an exceptionally high solubility up to 2.7 M to produce a large redox gradient in the mediation layer, thus allowing the increase of diffusion-limited current. The high solubility originating from the imidazolium group in the mediator molecule was reminiscent of ionic liquids, which are typically characterized by small absorption coefficients in a visible region. These properties provided a mass-transfer-based concept of molecular design for organic redox mediators in DSSCs.

A hydrophilic nitroxide radical molecule, 4-hydroxy-2,2,6,6-tetramethylpiperidinoxyl (TEMPOL), was immobilized in a Nafion layer yielding a redox-active modified electrode which enhanced the reduction peak current: The modified electrode and the TEMPOL aqueous electrolyte were applied in a dye-sensitized solar cell to achieve a 2.1% conversion efficiency.

Anionic polymerization of 4-methacryloyloxy-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl) was successfully carried out using methyl methacrylate-capped 1,1-diphenylhexyllithium (DPHLi/MMA), of which nucleophilicity is moderate enough to suppress the side reaction between the nitroxide radical of TEMPO moiety and the carbanion of DPHLi, to yield the radical polymer with well-controlled molecular weight, narrow polydispersity index (PDI &lt; 1.10), high yield (&gt;95%), and almost 1.0 radicals per monomer unit.

A couple of totally reversible redox-active molecules, which are different in redox potentials, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and viologen (V2+), were employed to give rise to a rectified redox conduction effect. Single-layer and bilayer devices were fabricated using polymers containing these sites as pendant groups per repeating unit. The devices were obtained by sandwiching the redox polymer layer(s) with indium tin oxide (ITO)/glass and Pt foil electrodes. Electrochemical measurements of the single-layer device composed of poly-norbornene-bearing TEMPO (PTNB) exhibited a diffusion-limited current-voltage response based on the TEMPO+/TEMPO exchange reaction, which was almost equivalent to a redox gradient through the PTNB layer depending upon the thickness. The bilayer device gave rise to the current rectification because of the thermodynamically favored cross-reaction between TEMPO+ and V+ at the polymer/polymer interface. A current-voltage response obtained for the bilayer device demonstrated a two-step diffusion-limited current behavior as a result of the concurrent V2+/V+ and V+/V-0 exchange reactions according to the voltage and suggested that the charge transport process through the device was most likely to be rate-determined by a redox gradient in the polymer layer. Current collection experiments revealed a charge transport balance throughout the device, as a result of the electrochemical stability and robustness of the polymers in both redox states.

Poly(3,4-ethylenedioxythiophene) (PEDOT), for use as a hole-transporting layer in dye-sensitized solar cells (DSSCs), was synthesized via in-situ polymerization using a gas-phase oxidant. Highly volatile iodine was used as the gas-phase oxidant to fill up a porous TiO2 substrate. The conductivity of PEDOT increased to 0.9 S/cm upon the addition of a base, 4-tert-butylpyridine, to the monomer solution. A solid-state DSSC was fabricated using PEDOT as the hole-transporting layer, which displayed photo-electric conversion.

A highly cross-linked polyviologen hydrogel, poly(tripyridiniomesitylene) (PTPM), has been designed as an anode-active material. It displays a reversible two-electron redox capability at -0.4 and -0.8 V vs Ag/AgCl in an aqueous electrolyte. The PTPM layer coated on a current collector by electropolymerization via a 4-cyanopyridinium electro-coupling reaction demonstrates a rapid charging-discharging reaction with a redox capacity comparable to that obtainable using the formula weight-based theoretical density, because of the combination of the redox-active viologen moieties built into the hydrogel. A test cell that has been fabricated using the developed PTPM anode, a poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm)-based cathode, and an aqueous electrolyte exhibits a discharging voltage of 1.1 and 1.5 V, and has proven its ability to be recharged more than 2000 times.

Ambipolar redox-active polymers with a reversible charging and discharging capability were synthesized via ring-opening metathesis polymerization (ROMP) of nitronyl nitroxide radical (NN) mono- and disubstituted norbornenes which exhibited p- and n-type redox processes (i.e., one-electron oxidation and reduction per NN group, respectively), using Grubbs catalyst to N avoid side reactions of the radical moiety allowing over 95% of radicals to survive after ROMP. ROMP of the NN monomers was accomplished with well-controlled molecular weights of the resulting NN polymers which were coincident with theoretical values in the ratio of [monomer]/[catalyst] = 25-200, narrow polydispersity index (ca. 1.2), and high yields even with [monomer]/[catalyst] &gt; 600. The living character for the ROMP of the NN monomers also allowed block copolymerization. NN-containing block copolymers were synthesized through sequential ROMP with benzyl ether-containing norbornene in high yields. The NN polymer/carbon composite electrode exhibited both p- and n-type charging/discharging with plateau potentials near the redox potentials of the polymer at 0.78 and -0.80 V vs Ag/AgCl, respectively. The spin-coated layer electrode of the NN polymer immobilized on a current collector also demonstrated a fast charging/discharging performance in the range of 10-100 C rates and a cycle stability especially for the p-type reaction. These results made the NN polymer accessible as ambipolar electrode-active materials and also encouraged other organic radicals to be candidates for electroactive polymers.

'Self-doping' inspired high-density redox copolymers were designed and prepared via free radical copolymerization of 2,2,6,6-tetramethyl-4-piperidyl methacrylate and vinylsulfonic acid (VSA) with a view to preventing a change in salt concentration during the one-electron oxidation of the nitroxide radicals to N-oxoammonium cations in a polymer layer. A copolymer composition of TEMPO-sulfonate anionic group = 1/1 for density-maximized charge neutralization was achieved by controlling the feed ratio of the copolymerization. The formation of copolymers was evidenced by 2D nuclear Overhauser enhanced spectroscopy (NOESY) and diffusion ordered spectroscopy (DOSY) NMR. Poly(TEMPO methacrylate-stat-VSA) was considered to have the alternating tendency due to the acid-base interaction in the comonomers, which were supported not only by the single crystal structure of the 2,2,6,6-tetramethyl-4-piperidyl methacrylate and VSA complex, but also by the 1H-1H correlation in NOE signals. In an aqueous electrolyte with 0.5 M NaCl, the copolymer electrode showed a redox response near 0.66 V (vs. Ag/AgCl), and the excellent cycle performance during 1000 cycles. During the one-electron oxidation of the nitroxide radical, anionic sulfonate groups led to charge compensation of the N-oxoammonium cation. Consequently, the copolymer electrode exhibited the cation migration, which was evidenced by mass-transfer analysis using an electrochemical quartz crystal microbalance (EQCM) technique. The copolymer could be applied as an aqueous electrolyte-type organic rechargeable device. Moreover, this design proposes the ultimate principle toward the strategy of maximizing energy density in organic charge storage devices. © The Royal Society of Chemistry 2013.

Photocharging of anthraquinone (AQ)-populated polymers was accomplished by incorporating chromophores with redox potentials suitable for the 2e- reduction of the AQ pendants near -1 V versus Ag/AgCl in aqueous basic electrolytes. The photoactive polymers were designed to exhibit redox-isolated behaviors and reversible charge-discharge responses, either by employing a polyacetylene main chain with the π-π* absorption bands in a visible region, or with an aliphatic chain incorporating a BODIPY dye in the form of a multilayer. The charge storage density was maximized by minimizing the molecular weight of the compact repeating units, thus reducing the redox site-to-site distance to allow redox gradient-driven electron self-exchange reactions to proceed throughout the slab of the polymer layer. Homogeneous layers of poly(2-ethynylanthraquinone) and poly(2-vinylanthraquinone) were both sufficiently robust for charge storage application, swellable, and yet insoluble in aqueous basic electrolyte solutions. Such properties allowed the accommodation of external cations from the electrolyte to permeate through the layer for electroneutralization of the negative charge produced by the electroreduction, which led to the repeatable charging and discharging cycles of the photoanodes without degradation of the charge storage capabilities. By virtue of the swelling properties of the polymer layers in the basic aqueous electrolyte, exploration of the aqueous electrochemistry and photochemistry of AQ that had been inaccessible by the lack of the solubility in H2O became feasible. A striking feature of the photoanodes was the capability of employing a hydroxide ion (OH-) as the sacrificial reducing agent, which enabled the use of the O2/OH- redox couple for the cathode reaction during discharging. Combination of the photoanodes with the MnO2/carbon composite cathode, sandwiching the electrolyte layer of aqueous KOH, gave rise to photorechargeable battery effect under irradiation and repeatable discharging with the consumption of O2 at the cathode. © 2012 Springer Science+Business Media, LLC.

The radical polymer of redox-active nitroxide was first terminally modified and then grafted onto multi-walled carbon nanotubes (MWNTs) by a facile terminating reaction. The radical polymer-grafted MWNTs allowed a high dispersibility in organic solvents and fadeless redox ability of nitroxide. The TEM images revealed that the radical polymer was successfully wrapped around a MWNT with nanometre thickness showing a core-shell nanotube structure homogeneously over the whole MWNTs. The radical polymer wrapping around the MWNT exhibited quantitative and high-rate redox properties of nitroxide suitable for a cathode-active material, which was prominent when compared with a radical polymer-grafted MWNT via a "grafting from" method. These results demonstrate that nano-scale homogeneous wrapping prevented the aggregation of the radical polymer and allowed the rapid counterion accommodation leading to quantitative and rapid charge propagation.

Poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate-co-styrenesulfonate) was prepared and utilized as a Li+ host material for a cathode in a Li-ion battery. The polymer allowed high density incorporation of the Li+ ion per repeating unit at a positive redox potential near 0.6 V vs. Ag/AgCl. Redox equilibrium involving the Li+ migration was proved by the theoretical approach based on the Nernst equation as well as a microgravimetry analysis using an electrochemical quartz crystal microbalance technique. A cell fabricated with the polymer as the cathode-active material showed a high power rate capability with an average discharging potential near 3.9 V vs. the lithium metal anode.

Electrochemical reversibility and fast bimolecular exchange reaction found for VO(salen) gave rise to a highly efficient redox mediation to enhance the photocurrent of a dye-sensitized solar cell, leading to an excellent photovoltaic performance with a conversion efficiency of 5.4%. A heterogeneous electron-transfer rate constant at an electrode (k(0)) and a second-order rate constant for an electron self-exchange reaction (k(ex)) were proposed as key parameters that dominate the charge transport property, which afforded a novel design concept for the mediators based on their kinetic aspects.

An indoline dye-coupled polyviologen was designed as a possible photoanode material for organic photovoltaic cells. A new donor-acceptor (D- A) coupled molecule (CVD131) was immobilized on a current collector by the reductive electropolymerization of its two cyanopyridinium moieties. The formed polyviologen could efficiently accept an excited electron from the indoline dye moiety. © 2012 The Japan Society of Applied Physics.

An indoline dye-coupled polyviologen was designed as a possible photoanode material for organic photovoltaic cells. A new donor-acceptor (D-A) coupled molecule (CVD131) was immobilized on a current collector by the reductive electropolymerization of its two cyanopyridinium moieties. The formed polyviologen could efficiently accept an excited electron from the indoline dye moiety. (C) 2012 The Japan Society of Applied Physics

Dynamic interactions and electronic processes in macromolecule-metal complexes established in 1970s provided conceptual basis for the development of a new class of functional polymers. Principles of soft/multiple interaction and multielectron processes have been pursued by exploring the macromolecule-metal complexes and polyion complexes, which gave rise to more generalized concept of macromolecular complexes. As one of the multiple interaction, reversible binding of O-2 in aqueous media and facilitated transport of O-2 were first accomplished by macromolecular metal complexes. The related oxygen technologies have led to the development of unprecedented materials to allow oxygen enrichment in cathodes of fuel cells and air batteries. Properties of electric/ionic conduction and electron transfer mediation in macromolecular complexes suggested our avenue toward the "radical batteries'' as entirely organic, rare metal-free, and rechargeable burst power sources. Combination of the photoelectrochemistry of macromolecular complexes and the methods for the precision control of charge separation, transport, and storage in polymers derived from the battery research have inspired design principles of novel photovoltaic polymers useful for organic solar cells. In this paper, recent developments of energy-related materials originated from the idea of the macromolecular complexes are focused.

A hydrophilic radical polymer, poly(2,2,6,6-teteramethylpiperidinyloxyl-4-yl acrylamide) (PTAm), was synthesized via oxidation of the corresponding precursor polymer, poly(2,2,6,6-teteramethylpiperidine-4-yl acrylamide). Electrochemical properties of the PTAm layer were characterized in three aqueous electrolytes of sodium chloride (NaCl), sodium tetrafluoroborate (NaBF4), and sodium hexafluorophosphate (NaPF6) to optimize its activity as an organic cathode. The counter anion species significantly affected the capacity and the cycle performance of the PTAm layer. The PTAm layer in the presence of BF4 (-1) displayed quantitative redox capacity beyond 1 mu m layer thickness and maintained the discharging capacity of 110 mAh g(-1) (97% vs. the calculated capacity) even after 1000 cycle charging/discharging, which could be ascribed to its appropriate affinity to the aqueous electrolyte without any dissolution into the electrolyte. A totally organic-based rechargeable cell was fabricated using PTAm and poly(N-4,4'-bipyridinium-N-decamethylene dibromide) as the cathode and the anode, respectively, and the aqueous electrolyte of NaBF4. The cell gave a plateau voltage at 1.2 V both on charging and discharging and an excellent charging/discharging cyclability of &gt; 2000 with high coulombic efficiency of &gt; 95%.

Charge transport in poly(oxoammonium cation/nitroxyl radical) redox gels was investigated by chronoamperometry on the basis of an infinite-diffusion model without a volume change during the redox reaction and a limit of the diffusion distance by means of fabricating the bulk solid gels. Charge transportation in the redox gels was found to be dominated by the mobility of electrolyte anion rather than the concentration of redox centers. Furthermore, the ionic conductivity of the redox gel was estimated to be almost one third of that of the liquid electrolyte. The result indicates that larger ionic conductivity in the gel also brings faster charge transportation through the redox centers.

A layer of poly(2-vinylanthraquinone) on current collectors underwent reversible electrode reaction at 0.82 V vs Ag/AgCl in an aqueous electrolyte. A repeatable charging/discharging cycles with a redox capacity comparable to the formula weight-based theoretical density at the negative potential suggested that all of the anthraquinone pendants in the layer was redox-active, that electroneutralization by an electrolyte cation was accomplished throughout the polymer layer, and that the layer stayed on the current collector without exfoliation or dissolution into the electrolyte during the electrolysis. The charging/discharging behavior of the polymer layer in the aqueous electrolyte revealed the capability of undergoing electrochemistry even in the nonsolvent of the pendant group, which offered insight into the nature of the anthraquinone pendants populated on the aliphatic chain. Charging/discharging capability of air batteries was accomplished by using the polymer layer as an organic anode-active material. A test cell fabricated using the conventional MnO(2)/C cathode catalyst exhibited a discharging voltage at 0.63 V corresponding to their potential gap and a charging/discharging cycle of more than 500 cycles without loss of the capacity.

A transparent nanocomposite of a radical polymer, the poly(2,2,6,6-tetramethylpiperidine-1-oxy-4-yl methacrylate) (PTMA), and single-walled carbon nanotubes (SWNTs) display a reversible charging and discharging, allowing full discharge in seconds. This is ascribed to the reversible electrochemical reaction of the pendant radical group in PTMA aided by both PTMA wrapping at a molecular level and the SWNT network for electrical conduction.

Charge/discharge processes of organic radical batteries based on the radical polymer&apos;s redox reaction should be largely influenced by the structure and the composition of the composite electrodes. AC impedance measurement of the composite electrodes reveals a strong correlation between the overall electron transfer resistance of the composite electrode and the material of the current collector, and suggests that the electric conduction to the current collector through the contact resistance should be crucial. We also find that the adhesion and the contact area between the composite electrode and the current collector strongly influence the contact resistance rather than the work functions and the volume resistivities of the composite electrode and the current collector. It is also confirmed that the charge/discharge performance of the composite electrode is related to the overall electron transfer resistance of the composite electrode. These results indicate that the charge/discharge performance of the radical battery is dominated by the interfacial electron transfer processes at the current collector/carbon fiber interface. In fact, the composite electrode which has a high adhesion to the current collector shows a small overall electron transfer resistance and an excellent charge/discharge performance. The rate performance would be much improved by suitably designing the interfacial structure including adhesion and contact area. (C) 2010 Elsevier B.V. All rights reserved.

Condensation of anthraquinone-2-carboxylic acid with poly(4-chloromethylstyrene) afforded a high-density redox polymer containing the anthraquinone pendants with reversible charge storage capability at negative potentials near -1V versus Ag/AgCl. Electrochemically reversible redox response of the polymer, which was ascribed to the reduction of the pendant group to the anion radical and the dianion, suggested that the polymer was sufficiently robust in these redox states for charge storage application. Immobilizing the anthraquinone groups on current collectors was accomplished by the use of the polymer which was swellable and yet insoluble in both aqueous and nonaqueous electrolyte solutions. Such properties allowed the accommodation of external cations from the electrolyte solution to permeate through the polymer layer for electroneutralization of the negative charge produced at the reduced state, which led to the repeatable charging and discharging cycles without degradation of the charge storage capacity. Exploration of the aqueous electrochemistry of anthraquinone, which had been inaccessible by the lack of the solubility of the conjugated and fused-ring molecule in H2O, became feasible by virtue of the swelling property of the polymer layer in the aqueous electrolyte. While negative charge was relatively difficult to be stored with redox polymers compared to the positive charge due to the enhanced reactivity in their reduced states and small varieties of the appropriate redox sites, the present polymer was characterized as the excellent organic electrode-active materials that operated at sufficiently negative potentials which was essential for the fabrication of entirely organic batteries. Copyright (C) 2011 John Wiley & Sons, Ltd.

The electrochemical redox reactions of organic polymers bearing robust unpaired electrons were investigated to determine the applicability of these polymers to rechargeable batteries. Such an "organic radical battery" would be environmentally friendly and have high-power characteristics. This highlight review describes the performance of a battery using a nitroxyl radical polymer as the cathode active material. The electron-transfer mechanism and recent developments that should lead to the practical application of the organic radical battery are also described.

An electrode-attached layer of poly(phenylacetylene) bearing a pendant nitronyl nitroxide group per repeating unit, obtained by the Rh-catalyzed polymerization of 2-(4-ethynylphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, underwent oxidation and reduction at 0.80 and 0.84 V vs. Ag/AgCl, respectively. The magnetically determined unpaired electron density of 92% was coulometrically reproduced, which supported the presumption that the radical survived during the course of the polymerization to allow both positive and negative charging of the pristine neutral polymer substantially per repeating unit. Galvanostatic Coulomb titration revealed the charge storage capability of the polymer, which demonstrated usefulness as organic electrode-active material with unprecedented ambipolar chargeability.

The p- and n-type bipolar redox-active radical polymer with a nitronylnitroxyl group, poly(nitronylnitroxylstyrene), expands its utilization as a cathode-or anode-active material in organic polymer-based rechargeable devices with two unprecedented configurations: a poleless battery and a "rocking-chair type" battery. These batteries exhibit a remarkably high power rate capability (chargeable within 20 s) and high cycle performance.
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The ring-opening polymerization of 5-methyl-1,3-dioxolane-2,4-dione (lactic O-carboxylic anhydride, LacOCA) using organometallic complexes, including Co(III) complexes with Schiff base ligands, Tin(II) alphatates and Al(III) complexes with Schiff base ligands, was explored. The polymerization was carried out by treatment of the organometallic complexes with LacOCA in toluene under mild conditions. The corresponding poly(lactic acid) was characterized by spectroscopy and thermal analyses, which revealed insight into the structure of the effective catalyst for the polymerization of LacOCA.

We present here the synthesis of two kinds of amphiphilic block copolymers, a diblock copolymer MPEG-b-PTAm and a triblock copolymer MPEG-b-PLA-b-PTAm, which can self-assemble into micelles with nitroxyl radicals-containing PTAm segment in the core. The structure of the block copolymers was characterized by H-1 NMR and GPC. Dynamic laser light scattering and transmission electron microscopy were used to study the micellar behavior of the two block copolymers in aqueous solution. The micelles carrying nitroxyl radicals in the core can generate electron paramagnetic resonance, which is stable for a period of time up to 8 min even in the presence of reducing reagent such as ascorbic acid. The enhanced stability against the reducing agent was ascribed to the inaccessibility of the nitroxyl radical core placed in the interior of the micelles. Combined with the biocompatibility, these micelles were promising to be used as the EPR probes for bioimaging in vivo. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5404-5410, 2010

To maximize the theoretical redox capacity of polymers containing cyclic nitroxides as redox active pendant groups for high density charge storage application, a compact five membered ring with the smallest equivalent weight among the robust cyclic nitroxides was directly bound to a poly(ethylene oxide) chain 2,2,5,5 Tetramethyl 3 oxiranyl-3-pyrrolin 1 oxyl was synthesized and polymerized via anionic coordinated ring-opening polymerization utilizing diethyl zinc/H2O as an initiator The unpaired electron in the monomer survived during the polymerization giving rise to a high density redox polymer with a weight-specific theoretical capacity of 147 mA h/g Cyclic voltammetry of the polymer layer confined at the surface of an electrode revealed a large redox capacity comparable to the theoretical capacity which was ascribed to the efficient swelling and yet insoluble properties of the polyether in electrolyte solutions by virtue of the high molecular weight of &gt;10(5) and adhesive properties allowing immobilization of the layer on the electrode surface The redox capacity also indicated that the ionophoric polyether matrix accommodated electrolyte anions through the polymer/electrolyte interface to neutralize positive charges produced by the oxidation of the neutral radicals at the polymer/electrode interface The diffusion coefficient for the redox gradient driven charge hopping process corresponded to a large second order rate constant in the order of 10(7) M-1 s(-1), which suggested an efficient electron self-exchange reaction throughout the polymer layer due to the large redox site population and hence to the small intersite distance Test cells fabricated with a polymer/carbon fiber composite layer on an aluminum current collector as the cathode and a Li anode sandwiching an electrolyte layer were capable of charging and discharging as a secondary battery with an output voltage near 3 7 V and were durable for more than 10(3) charging discharging cycles without substantial degradation

Copolymers composed of PLA and PTAm were prepared by a macromonomer approach. The PLA bearing vinyl group at chain end was copolymerized with 2,2,6,6-tetrametylpiperidine-4-ylacrylamide. The resulted copolymers were oxidized by a peroxide to give PTAm-g-PLA. The structures of the copolymers were confirmed by NMR and FTIR spectroscopy. The comparison of (1)H NMR results and SQUID measurements demonstrated that the oxidation of the PTAm fragment proceeded almost to completion. An MTT assay, cell adhesion and spreading evaluation showed that the copolymers exhibited improved cytocompatibility as compared to the PTAm homopolymer due to the introduction of the biocompatible PLA moiety.

Charge/discharge processes of organic radical batteries based on the radical polymer's redox reaction are largely influenced by carbon fibers consisting in the composite electrodes to help electron transfer. To find the optimal structure of the composite electrodes, the dominant electron transfer processes were determined by ac impedance measurement of the composite electrodes. A strong correlation between the overall electron transfer resistance of the composite electrodes and the materials of the current collector suggests that the electric conduction to the current collector through the contact resistance should be crucial. It was also confirmed that the charge/discharge performance of the composite electrode was related to the overall electron transfer resistance of the composite electrode. These results indicated that the charge/discharge performance of the radical battery was dominated by the interfacial electron transfer processes at the current collector/carbon fiber interface and that the rate performance would be much improved by suitably designing the interfacial structure.

A robust nitroxide radical, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its 4-subsituted derivatives (R-TEMPO) exhibit electrochemically reversible redox properties with tunable half-wave potentials (E-1/2) based on the substituent effect. Dye-sensitized solar cells using R-TEMPO as mediators with electron-withdrawing R groups showed significantly enhanced photovoltages compared with those obtained using iodides. The linearity between the open-circuit voltage (V-oc) and E-1/2 revealed that V-oc dominated by the energy gap between the Fermi level of TiO2 and the SOMO level of R-TEMPO.

A quartet triradical molecule, 2,6,10-tris[bis(p-methoxyphenyl)aminium]triphenylene, was characterized by the electronic interaction among the three aminium sites based on the fused-aromatic, triphenylene-linked, and non-Kekule connectivity, which lead to the stable high-spin triradical formation.

A series of cobalt complexes with N,N,O,O-tetradentate Schiff base ligands were prepared. All the complexes were characterized by spectroscopy and electrochemical methods. An X-ray crystal structure analysis revealed that L-1-Co-III-dnp was monomeric with a six-coordinated central cobalt(III) atom in the solid state. The complexes were employed as catalysts for the alternating copolymerization of CO2 and racemic propylene oxide. End group analysis of the resulting polymer provided strong evidence for a monomer insertion mechanism for the propagation step. The catalytic activity was interpreted using the redox potential of cobalt(II/III) for the L-Co-III-dnp complexes, which offered a measure of the bond strength, or the degree of inertness of the axial ligand, to promote or suppress the monomer insertion.

The reversible n-type charge-storage capability of polyimides was significantly enhanced in a polyimide/carbon nanocomposite prepared by cyclodehydration of the corresponding polyamic acid which was solution-processed into a composite layer on an electrode surface with a vapor-grown carbon nanofiber. The stepwise preparation process gave the first polyimide-based electrode-active material with a sufficient dispersion of the polyimide particles at the carbon nanofiber surface, while a simple grinding of the polyimide and the carbon nanofiber gave mixtures without charge retention capability due to gradual dissolution in the reduced state. The polyimide/carbon nanocomposites were characterized by negative redox potentials at -1.36 and -0.76 V vs. Ag/AgCl for poly(4,4'-oxydiphthalimido-1,4-phenylene) (1) and poly(pyromellitimido-1,4-phenylene) (2), respectively, which corresponded to a charging per repeating unit of the neutral polymers to radical polyanions. The 2/carbon nanocomposite underwent further reduction at -1.34 V to produce a dianion per repeating unit, giving rise to a high-density charging with a redox capacity of 185 mAh g(-1) based on the formula weight of 2. The typical redox capacity of the electrolyzed nanocomposites amounted to ca. 60% of the formula weight-based capacity, which was still larger than those of typical redox polymers with negative potentials, such as viologen-based polyelectrolytes. Additional advantages originated from the robustness of the polyimide framework, which allowed excellent charging/discharging cyclability. The polyimide/carbon nanocomposite electrodes would be highly promising as anode-active materials in organic rechargeable devices, owing to these excellent redox properties.

Poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) was designed and synthesized as an electrode-active polymer for an organic rechargeable device containing an aqueous electrolyte. The device demonstrated a 1.2 V output voltage, exceeded 2000 charging-discharging cycles, and had a high charging rate performance within 1 min.

Electrochemically oxidized patterns of stable poly(nitroxide radical)s at the nano-scale were demonstrated by controlling lithographic parameters, such as voltage, scan speed, and sweep duration.

Two redox-active poly(oxoammonium salt)s were synthesized via chemical oxidation of a TEMPO-substituted polymer, or conventional radical polymerization of the oxoammonium monomer, respectively. The diode-structured thin film device composed of poly(oxoammonium salt) with radical conc. of 6-43% exhibited a resistive switching behavior (ON-OFF ratio &gt; 10(3)), in contrast to the radical-free poly(oxoammonium salt), which revealed that the coexistence of radical/oxoammonium salts contributed to a significant change in I-V characteristics.

A radical polymer is an aliphatic organic polymer bearing densely populated unpaired electrons in the pendant robust radical groups per repeating unit. These radicals&apos; unpaired electrons are characterized by very fast electron-transfer reactivity, allowing reversible charging as the electrode-active materials for secondary batteries. Organic-based radical batteries have several advantages over conventional batteries, such as increased safety, adaptability to wet fabrication processes, easy disposability, and capability of fabrication from less-limited resources, which are described along the fashion of green chemistry.

A hydrophilic poly(vinyl ether)-backbone polymer bearing a pendant TEMPO radical, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl vinyl ether) (PTVE), was designed as a cathode-active material, which displays a reversible one-electron redox capability, even in an aqueous electrolyte. The PTVE layer coated on a current collector demonstrated a rapid charging-discharging rate based on the combination of the redox-active nitroxide radicals built into the hydrophilic polymer and the aqueous electrolyte that possessed a high electrical conductivity. A test cell fabricated with a PTVE cathode, a zinc anode, and an aqueous electrolyte gave an output voltage of 1.7 V and showed the ability to be recharged more than 500 times rechargeability.

Radical polymers are aliphatic or nonconjugated polymers bearing organic robust radicals as pendant groups per repeating unit. A large population of the radical redox sites allows the efficient redox gradient-driven electron transport through the polymer layer by outer-sphere self-exchange reactions in electrolyte solutions. The radical polymers are emerging as a new class of electroactive materials useful for various kinds of wet-type energy storage, transport, and conversion devices. Electric-field-driven charge transport by hopping between the densely populated radical sites is also a remarkable aspect of the radical polymers in the solid state, which leads to many dry-type devices such as organic memories, diodes, and switches.

Chiral poly[4,6-bis(alkylthio)-1,3-phenylene-alt-2-methyl-1,3-phenylene] was synthesized from 1,3-dibromo-2,6-bis(3-dodecyl-2-methylthio)benzene and 2-methyl-1,3-phenylenebis(pinacol borate) as a precursor of chiral poly(thiaheterohelicene). Circular dichroism (CD) spectra that arise from the poly(1,3-phenylene) backbone inverted according to the chirality of the side chains, which indicated that a helical conformation of the polymer was induced by the interaction between the side chains. The CD intensity of the polymer increased in non-polar solvents such as hexane. The decrease in the molar CD intensity and the broadening of a fluorescence band at higher concentrations Suggested that the aggregation of the polymer Suppressed the formation of the helical structure. The conformational changes were monitored by the CD and the (1)H NMR spectra at different temperatures. In a good solvent Such as dichloromethane, the CD intensity increased, and the (1)H NMR signal of benzene protons shifted to lower fields at low temperatures. In hexane. the CD spectra and the I H NMR signals were less dependent on temperatures, as a result of the strong interaction between the chiral alkyl chains in the polymer to freeze the helical conformation. (C) 2009 Elsevier B.V. All rights reserved.

A n-type and redox-active radical polymer bearing galvinoxyl radicals, poly (galvinoxylstyrene), is utilized as an anode-active material, which enabled, for the first time, the fabrication of a totally organic polymer-based rechargeable battery in conjunction with p-type redox-active radical polymer. This battery was characterized by its remarkably high power rate capability.

A film of poly( 2,2,6,6-tetramethylpiperidinyloxy-4-yl vinylether) coated on a current collector displayed a rapid and reversible electrochemical response in aqueous electrolytes, and allowed an ultrafast full charging of 3 mC cm(-2) in as short as 3 seconds by virtue of the combination of the hydrophilic radical polymer and the aqueous electrolyte possessing a high electrical conductivity.

A hydrophilic radical polymer electrode-based rechargeable battery was designed along the concept of green chemistry. A hydrophilic radical polymer, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl vinylether), was synthesized as an electrode-active material; its battery demonstrated a high charging-discharging rate and long cycle life. The combination of the hydrophilic polymer electrode and an aqueous electrolyte for the battery fabrication was expected to provide safety improvements such as a low ignition risk besides the high battery performance. The green characteristics were studied using the "i-Messe," an evaluation method proposed by the committee of the Green Sustainable Chemistry Network, Japan. The electrode-active polymer was evaluated for substantial improvements in disaster safety and health safety.

A Nafion membrane containing a cobaltporphyrin (CoP) complex as a fixed oxygen carrier was prepared with a view to facilitate oxygen transport through the membrane. The design concept of the CoP-loaded Nafion membrane was based on the CoP&apos;s modification to place the CoP complex in a hydrophobic domain of the microphase-separated structure, in order to facilitate the oxygen transport and to maintain proton conductivity. The oxygen permeability through the CoP-loaded Nafion membrane was higher than the nitrogen permeability, and significantly enhanced at relatively-low oxygen pressures of the upstream, indicating that the fixed Col? complex acted as an oxygen hopping site to facilitate the oxygen transport. The oxygen/nitrogen permselectivity increased with the content of CoP in the Nafion membrane. Electrochemical reduction of oxygen at a glassy carbon electrode, modified with a Pt/C catalyst and the CoP-loaded Nafion membrane, provided additional support for the facilitated oxygen transport by the membrane. Increased current for the reduction of oxygen on the modified electrode by loading CoP indicated that the CoP offered the oxygen hopping site in the Nafion membrane. (c) 2008 Elsevier Ltd. All rights reserved.

We prepared an anticancer drug based on a pH-sensitive liposome retaining Fe-porphyrin as an SOD mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Feporphyrin, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine, dimethylditetradecylammonium bromide, sodium oleate, and Tween-80. The Fe-porphyrin was released from the liposome at low pH, and the cytotoxicity for cancer cells by the liposome depended on the acidic environments of the endosomes in the cells. Furthermore, although the liposome exhibited an excellent anticancer effect on a gastric cancer cell line, the SOD activity of Fe-porphyrin was shown to have a significant influence on the cytotoxicity toward cancer cells. These findings suggest that the pH-sensitive liposome retaining the Fe-porphyrin as an SOD mimic promises to be a novel anticancer drug for endosomal escape. (C) 2008 Elsevier B.V. All rights reserved

Redox polymer layers with 2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl(TEMPO) groups showed nernstian adsorbate-like electrochemical behaviors up to submicrometer thicknesses, based on a fast charge propagation within the bulk layer and persistency in electrolyte solutions.

In search of polymer backbones to bind organic radical pendant groups as redox centers for high-density charge storage application, polyether was employed as a flexible chain with a low glass transition temperature and affinity to electrolyte solutions. Cyclic ethers bearing nitroxide radicals were synthesized and polymerized via ring-opening polymerization utilizing various initiators. Polyethers bearing robust radical substituents such as 2,2,6,6-tetramethylpiperidin-l-oxyl-4-yl and 2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-l-oxyl-3-yl groups with high density, i.e., per repeating unit with small equivalent weights, were prepared by the anionic polymerization of the corresponding epoxides. Cyclic voltammetry of the radical polyethers, obtained for polymer/carbon composites confined at an aluminum current collector, revealed large redox capacities comparable to the formula weight-based theoretical values, which was ascribed to the efficient swelling and yet insoluble properties of the polyethers in electrolyte solutions by virtue of their high molecular weights and adhesive properties to be held on electrode surfaces. The redox capacity also indicated that the ionophoric polyether matrix accommodated electrolyte anions to compensate positive charges produced by the oxidation of the neutral radicals at the polymer/electrode interface, allowing charge propagation deep into the polymer layer by a site-hopping mechanism. Test cells fabricated with the polymer/carbon composite as the cathode and a Li anode, sandwiching an electrolyte layer, performed as a secondary battery at output voltages near 3.6 V without substantial degradation even after 100 charging-discharging cycles.

The redox behavior of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) in the presence of different polyelectrolytes such as poly(sodium 4-styrenesulfonate) (PSS), poly(sodium 4-styrenesulfonate-co-sodium maleate) at two different comonomer compositions (P(SS1-co-MA(1)) and P(SS3-co-MA(1))), poly(sodium acrylate-co-sodium maleate) (P(AA(1)-co-MA(1))), and poly(sodium acrylate) (PAA) is studied. Due to aromatic-aromatic interactions, the polyelectrolytes containing benzene sulfonate groups produce a decrease on the reduction rate of TTC in the presence of ascorbic acid (ASC) and a shift of the anodic and cathodic peaks to higher negative potentials for the electrochemical reaction of TTC. As an important conclusion, these effects are a function of the linear aromatic density of the polyelectrolytes.

The oxidative polymerization of 2,6-dimethylphenol is a convenient engineering method to synthesize poly (2,6-dimethyl-1,4-phenylene ether) (PPE) as a high-performance engineering plastic in industrial fields. Recently, we reported the novel synthesis of PPE diblock copolymers based on the analysis of the polymerization mechanism. We report the preparation of PPE diblock copolymers bearing carboxylic or sulfonic acid as acid substituents. The resulting acid substituented PPE block copolymers, poly (2,6-dimethyl-1,4-phenylene etherblock-2-carboxy-6-methyl-1,4-phenylene ether) 3 and poly [2,6-dimethyl-1,4-phenylene ether-block-2-phenyl-6-(4-sulfophenyl)-1,4-phenylene ether] 5, were applied as polymer electrolyte membranes for fuel cells. 3 and 5 were soluble in polar organic solvents such as N,N-dimethylformamide, dimethylsulfoxide, and THF and gave tough membranes by casting. Sulfonated polymer 5 membrane showed high ion exchange capacity and high oxidative stability. The results suggested that the acid substituents attached onto the pendant phenyl groups were more stable than those on main chains.

Recently, there has been an increasing number of reports on cancer therapies such as photodynamic therapy and hyperthermia. However, there is a problem that the therapies can only be used for superficial thin tumor cells. In this study, we synthesized novel porphyrin having thiol group which can be adsorbed onto gold surface in order to obtain porphyrin-modified gold nanoparticles. We think that heat is generated around tumor cells in a deep part of a human body by the irradiation of electromagnetic wave to the gold nanoparticles. Gold nanoparticles are more stable than other nanoparticles, because of superior stability against oxidation and less toxicity. Porphyrin takes a role as a protective agent of gold nanoparticles, and is expected to promote the selective attachment of gold nanoparticles to tumor cells. The nanosize of the gold nanoparticles was accomplished by the sodium borohydride reduction method and citrate reduction method. The combination of thiol and gold nanoparticles was confirmed by the quenching of porphyrin in the fluorescence spectrum and shift of the Soret peak in the UV-vis spectrum. We evaluated the characteristics of porphyrin-modified gold nanoparticles by the measurement of the residence time in blood, permittivity, and cytotoxicity test.

An electrochromic (EC) cell using a viologen-based polymer as an EC material and a radical polymer bearing a redox-active 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) group per repeating unit as a counter electroactive material was fabricated. The radical polymer was spin-coated on an ITO/glass electrode as the counter electrode of the EC cell. The electrochromic material of the cell was a polyion complex consisted of poly(decyl viologen) and poly(styrene sulfonate) (PV 10-PSS), which was also spin-coated on the ITO/glass. An ion-conducting polymer gel Solution was sandwiched between the two electrodes. Electrochemical switching of the cell was monitored using the visible absorption of the PV 10-PSS complex (lambda(max) = 550 nm) that appeared in the reduced state, while the radical polymer was transparent in the visible region in both redox states. PV 10-PSS and the radical polymer were Concurrently reduced and oxidized, respectively, on each electrode during the charging process, which corresponded to the coloration of the cell. The decoloration of the polyion complex was effected by a discharging process under short circuit conditions. The electrochromic behavior of the cell was characterized by a remarkably low driving voltage, as a result of a small potential gap between PV 10-PSS and the radical polymer. The use of the organic redox polymers, not only for the low energy-driven electrochromic switching but also for the charge-storage purposes, allowed a universal design of a battery-like display device, with possible application to a flexible and totally organic electrochromic cell.

Manganese 5,10,15,20-tetrakis(N-methyl-2-yl) porphyrin (MnT2MePyP) was introduced to hemoglobin to use it as a drug carrier. Reconstituted hemoglobin was reacted with pyridoxal-5-phosphate and borohydride to yield pyridoxalated reconstituted hemoglobin (PLPrHb). The reaction of PLPrHb with activated polyethyleneglycol gave pegylated reconstituted hemoglobin (PEGrHb). PEGrHb was polymerized using glutaraldehyde to yield cross-linked pegylated reconstituted hemoglobin (Cross-link PEGrHb). The number average moleculer weight of Cross-link PEGrHb was estimated to be 1.0 x 10(5) by GPC. The modification of hemoglobin was checked by using SDS-PAGE. Stopped flow analysis showed a high SOD activity of Cross-link PEGrHb. A pharmacokinetic study of I'll-labelled Cross-link PEGrHb that was infused into mice revealed a long-term blood circulation. The novel Manganese porphyrin modified hemoglobin complex was found to remain long-term in the blood circulation without being removed by excretion. These results showed that this complex can be used as a high performance antioxidant.

Reactive oxygen species (ROS) such as the superoxide anion radical (O-2(-)center dot) play an essential role on normal cellular growth and homeostasis. However, excess ROS generated by perturbing O-2(-)center dot homeostasis under various conditions of oxidative stress induce high radical toxicity, resulting in many diseases such as a cancer, brain and mitocondrial infarction, and inflammation. Therefore, quantitative measurement of O-2(-)center dot in vivo is important for clarifying their relationship under various conditions. However, in most cases, the biological significance and mechanism of the O-2(-)center dot generation are not well understood yet. We have developed a O-2(-)center dot sensor composed of a thin film of N-methylimidazole-coordinated iron meso-tetra(3-thienyl)porphyrin ((Im)(2)FeT3ThP) for the electrochemical detection of O-2(-)center dot. The microsensor displayed high selectivity and activity for the oxidation of O-2(-)center dot and showed a linear relationship between electric current and O-2(-)center dot concentration. In this study, we have designed and synthesized a novel hexa-coordinated iron (111) porphyrin compound, which is more stable than the meso-tetra(3-thienyl)porphyrin coordinating imidazoles. This compound was electropolymerized onto the electrode and used as a O-2(-)center dot sensor. The redox potential of the electrode suggests that the molecular structure in the electropolymerized film is maintained. This novel modified electrode displayed a high activity for the oxidation of O-2(-)center dot even in the presence of H2O2 and showed a linear relationship between the electric current and O-2(-)center dot concentration.

Oxidative polymerization of 2,6-dimethylphenol (2,6-DMP) is a convenient method to prepare poly (2,6-dimethyl-1,4-phenyleneoxide) (PPO), an important plastic in engineering. The polymerization of 2,6-DMP is carried out in organic solvents under oxygen; thus, a solvent-recovery system and an anti-explosive reactor are required for the industrial application. The use Of scCO(2) instead of organic solvents is expected to make the polymerization of 2,6-DMP safer and environmentally more benign. We have studied the oxidative polymerization of 2,6-DMP in scCO(2). In this report, we have applied the &apos;double-step polymerization&apos; method in scCO(2) to synthesize PPO with better polymer properties, i.e., higher average molecular weight (M(w)) and narrower molecular weight distribution (M(w)/M(n)). In the first step, a prepolymer with a narrow molecular weight distribution (M(w)/M(n) = 1.4) was synthesized under a homogeneous-phase condition. The prepolymer was purified and dried to remove water. In the second step, the prepolymer was further polymerized to increase the molecular weight. The second-step polymerization was performed at 40 degrees C and 20 MPa. The M(w) was increased from 4.9 x 10(3) to 9.0 x 10(3), keeping the narrow molecular weight distribution (M(w)/M(n) = 1.4). We further optimized the polymerization condition in the second step to obtain higher molecular weight. The M(w) was increased to 3.4 x 10(4) (M(w)/M(n) = 2.3) at 80 degrees C and 15 MPa in the presence of CuBr (0.0004 mol) and pyridine (0.019 mol).

A ligand compound with strong coordinating property, 2-(1H-pyrrole-3-yl) pyrazine (pz-Py), was synthesized to increase the density of active sites for oxygen reduction. The obtained compound was coordinated with cobalt (11) ions strongly. It was revealed that the metal complex could be used as a cathode catalyst in fuel cells. The potential for oxygen reduction was positive (E-p = 0.27 V vs SCE) for the catalyst prepared by refluxing the corresponding compound, cobalt acetate tetrahydrate, and the carbon particles. This activity was superior to CoPy/C which was synthesized by refluxing pyrrole, cobalt acetate tetrahydrate, and the carbon particles, and it was shown that nitrogen atoms of pyrazine type contribute accumulation of cobalt ions. The activity of the catalyst was improved after heat treatment under Ar gas. These results show the potential use of the present catalyst as a novel cathode catalyst in fuel cells.

A nonvolatile, bistable, and rewritable organic memory device based on radical polymers was prepared and tested. The excellent performance of a battery-inspired memory architecture with a configuration of p- and n-type charge-transporting radical polymers sandwiching a dielectric layer was characterized. The ON-OFF ratio was more than 4 orders of magnitude, and retention and endurance cycles of more than 10(4) and 10(3), respectively, were accomplished.

We reported that carbon black modified with cobalt and various transition metal ions (M) incorporated in a polypyrrole film (Co+MPPy/C) were good electrocatalysts for the reduction of oxygen (O-2). After heat treatment of the catalysts at 600 to 650 degrees C under argon atmosphere, which were prepared using with iron and iridium ions as M. the resulted catalysts gave rise to the reduction of O-2 at a remarkably positive potential (E-p &gt; 0.40 V vs SCE). Rotating ring disk voltammetry (RRDV) revealed that Co+IrPPy/C reduced O-2 completely with four electrons (n(av) = 4.0). X-ray photoelectron spectroscopy and X-ray diffraction indicated that the cobalt and M ions were coordinated with nitrogen as the donor atoms and the active sites were maintained even after the heat treatment under argon atmosphere without aggregation of metals and formation of alloys.

Structures and electrochemical behaviors of nitroxide radicals reveal that their rapid and reversible redox reactions are based not only on their chemical stability but also on the increased sp(2) character of nitrogens which is intermediate between the purely sp(2) and sp(3) nitrogens in oxoammonium cations and amines, respectively.

Reactive Oxygen Spiecies (ROS) such as superoxide anion radical (·O₂^-) act as signals for the activation of stress-response and defense pathways. However, excess ROS generated by perturbing ·O₂^- homeostasis stimulated many environmental stress, including intense light, drought, temperature stress, herbicides, induce high radical toxicity. Consequently, quantitative analysis of ·O₂^- is a subject of intense research, since most of ROS are derived from ·O₂^-. Iron meso-tetrakis(3-thienyl)porphyrin complexes were electropolymerized onto a Au wire electrode. The modified Au electrode were applied to ·O₂^- sensor to detect catalytic oxidation current of ·O₂^- which was generated as an intermediate during the oxidation of xanthine by catalystic XOD. It was revealed that the sensor was quantitative to measure ·O₂^-. The modified Au electrode were applied to measure oxidation current of ·O₂^- in mung beans under environmental stress condition. Plants were grown in atmosphere, 25°C and in black darkness. The other plants were exposed to oxygen excess. The oxidation current of ·O₂^- were increased plants were grown by high-oxygen environment compared to plants were grown at atmosphere. This experiment was indicated that environmental stress such as hyperoxia induced excess ·O₂^- and Au wire sensor using iron porphyrin complexes is capable of ·O₂^- detection in plants under environmental stresses.<br>

Reactive oxygen species (ROS) are implicated in many disease such as inflammation, arteriosclerosis, cancer. Therefore, a water-soluble cationic metalloporphyrins with SOD activity are studied widely as antioxidant drugs. Further, liposomes are applied to drug delivery system (DDS) as drug carriers and investigated for example disposition and stability. We designed PEG modified liposomes for avoiding reticuloendothelial system (RES) and embedded cationic metalloporphyrins for DDS, evaluated antioxidant and anticancer property.<br>    Preservation of these particle size measured DLS in an in vitro system, in order to simulate in vivo conditions of flow. Result of this measurement, we found Pluronic F-68/ liposomes have a long circulation property, and avoid fusion with plasma protein. SOD activity was determined by the stopped-flow analysis and cytochrome c assay, which allowed the evaluation of k_cat and IC₅₀ for the reaction with a superoxide anion radical (·O₂^-). Anti cancer property was measured by cell viability test. We found that F-68/ liposomes were the most effective catalyst as antioxidant and anticancer. These results revealed that porphyrin-embedded PEG-liposomes had the property of long circulation in blood and that this compound was effective as a SOD model compound with a drug carrier capacity.<br>

A water-soluble cationic 5, 10, 15, 20-tetrakis(2-dimethylsulfoniophenyl)-porphinatomanganese(III) ion (MnT2M₂SuP) and a 5, 10, 15, 20-tetrakis(4-dimethylsulfoniophenyl)porphinatomanganese(III) ion (MnT4M₂SuP) were synthesized as superoxide dismutase (SOD) mimics which were introduced into PEG-liposome composed of dimyristoylphosphatidylcholine (DMPC) and Pluronic F-68 to examine the effect of the liposome on the capacity for use as drug delivery system (DDS) to maintain and perpetuate blood circulation. Fluorescence spectra in pseudo blood circulation experiments indicated that MnT4M₂SuP continued to be bundled in PEG-liposome, while fluorescence from cross-section of cell observed by confocal laser scanning microscope indicated that PEG-liposome was ingested into a cell. SOD activity was determined by stopped-flow analysis, which allowed the determination of k_cat values for the reaction of the metalloporphyrins with superoxide anion radical (&middot;O₂^-). Solution of PEG-liposome loaded with MnT2M₂SuP or MnT4M₂SuP were the most effective catalyst as a SOD mimic to decompose &middot;O₂^- at second-order rate constants of 3.5-4.5&times;10⁷ M^-1s^-1.<br>

Reactive oxygen species (ROS) have many vital functions including sterilizing function of white blood cell, carcinostatic function, aging, cell death, inflammation, and DNA damage. Among various ROS, superoxide anion radical (O-2(-) center dot) has been attracting great attention as a cause of human disease. We have developed an O-2(-) center dot sensor composed of a thin film of 1-methylimidazole(1m) coordinatied Bromoiron(III) meso-tetrathienyleporphyrin ([FeBr(ttp)]) for the electro-chemical detection. In this study, highly sensitive measurements of O-2(-) center dot by potentiometry were conducted. The potentiometric response for O-2(-) center dot was monitored in 10 mM phosphate buffer. The O-2(-) center dot sensor displayed a high catalytic activity for oxidation of O-2(-) center dot and showed a linear relationship between the sensor response and the logarithm of O-2(-) center dot concentration. This O-2(-) center dot sensor showed low interferences due to the electrochemical interferents H2O2 and uric acid. Measurement of O-2(-) center dot by potentiometry was able to detect the low concentrations of O-2(-) center dot (7 x 10(-7) M) that measurements of O-2(-) center dot by amperometry could not easily detect.

In this article the novel design of an anticancer drug delivery system is reported based on a pH-sensitive liposome retaining the Fe-porphyrin as a superoxide dismutase(SOD) mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Fe-porphyrin, L-ei-phosphatidylcholine (DMPC), dimethylditetradecylammonium bromide (DTDAB), sodispdum oleate (OA(Na)), and Tween-80. The size of the liposome was approximately 30 nm. The EC50 value (the effective concentration of compound required to produce a 50% lethal dose against cells) of the liposome was found to be significantly smaller than that of cisplatin as the control drug, suggesting that the liposome showed a high cytotoxicity toward the cancer cells. This is due to the fact that the pH-sensitive liposome rapidly corresponds to the acidic environments of the endosomes and is unstable, and the Fe-porphyrin is delivered into the cytosol. This result suggests that O-2 may be useful as a target molecule to induce the selective death of cancer cells and that a pH-sensitive liposome retaining Fe-porphyrin as an SOD mimic is a new class of anticancer agent. Copyright (c) 2006 John Wiley & Sons, Ltd.

Electroactive and transparent organic radical polymers offered a novel design of materials for electrochromic (EC) devices. A radical polymer containing 2,2,6,6-tetramethylpiperidinoxyl (TEMPO) groups as redox active sites per repeating unit was spin-coated on a counter ITO/glass electrode of the EC device which was also comprised of Prussian blue (PB) as an electrochromic material on ITO and ion-conducting polymer gel between the two electrodes. Electrochemical switching of the cell was monitored using the visible absorption of PB (lambda(max) = 700 nm) that appeared in the oxidized (mixed-valence) state, while the radical polymer was transparent in the visible region in both redox states. PB and the radical polymer were concurrently reduced and oxidized, respectively, on each electrode during the charging process, which corresponded to the decoloration of the cell. The coloration was effected by a discharging process. The electrochromic switching and stability of the cell was characterized by a low driving voltage AV and, consequently, a small driving energy integral Delta Vi(t)dt, as a result of a small potential gap between PB and the radical polymer. The optical switch was fast and fully reversible by virtue of the large heterogeneous electron transfer rate constant of the TEMPO center (k(0) approximate to 10(-1) cm/s). The polymeric counter electrode material, without dissolution into the electrolyte layer, led to a good open circuit memory that did not require refreshing charges to maintain the redox states of PB.

A conductive polyaniline (PAN) film was successfully synthesized in a homogeneous supercritical carbon dioxide (scCO(2))/acetonitrile (AN) system. The homogeneous supercritical state was confirmed by observations of the phase behavior of the system through a high-pressure cell with a viewing window. The flatness of the film in that system decreased with the further addition of CO2. This result suggests that the low Viscosity of ScCO2 plays an important role in improving the transfer rate of solvent. The roughness of the film prepared in the homogeneous ScCO2/AN system was reduced compared with that of the film prepared in dichloromethane itself as a solvent. The slow growth of the film and the high diffusion rate of the monomer seemed to account for the smooth and flat film formation.

5-(3-Thienyl)-10,15,20-triethyl-21H,23H-porphine (H-2(ttep)) was synthesized and characterized. Oxidative polymerization of H-2(ttep) gave a novel oligomeric porphyrin linked at the 2,5-positions of the thienyl group. Electric conductivity of 4 x 10(-1) S/cm after I-2 doping indicated that the oligomer had a pi-conjugated. structure with a delocalization of pi electrons over the thienylene backbone. PM3 calculations revealed a low HOCO-LUCO gap, which was consistent with the relatively high electric conductivity. Regioregular (head-to-tail) structure was inferred from spectroscopic and calculational results. The pendant porphyrin groups formed a regular J-type array along the thienylene backbone, which was indicated by a significant red shift of the Soret, band maximum. (c) 2006 Wiley Periodicals, Inc.

Surface-modified mesoporous silicas (MSs) were investigated for recyclable adsorption of an endocrine disrupter, bisphenol A (BPA). Surface-modified MSs were prepared by (i) post-synthesis surface modification of MSs using surface hydroxyl groups and organosilanes (m-MS) and by (ii) co-condensation of tetraethoxysilane and the corresponding organosilanes (d-MS). Infrared measurements indicated that organic groups mainly existed on the surface of m-MS, which resulted in a surface characterized by high hydrophobicity. Both organic groups and isolated hydroxyl groups existed on the surface of d-MS, resulting in both hydrophobicity and hydrophilicity on the surface. The amount of BPA adsorbed on surface-modified MSs per organic group was similar for m-MS and d-MS, however, the d-MS established equilibrium for BPA adsorption faster than m-MS, as measured by UV-vis spectra. A larger amount of BPA per surface area could be adsorbed on carbon materials than on the surface-modified MSs, however, the regeneration of carbon materials by washing could not be done easily. The surface-modified MSs retain adsorption capacity for BPA after several regeneration cycles, demonstrating that the surface-modified MSs are effective recyclable adsorbents of the endocrine disrupter, bisphenol A. Copyright © 2006 American Scientific Publishers All rights reserved.

Surface-modified mesoporous silicas (MSs) were investigated for recyclable adsorption of an endocrine disrupter, bisphenol A (BPA). Surface-modified MSs were prepared by (i) post-synthesis surface modification of MSs using surface hydroxyl groups and organosilanes (m-MS) and by (ii) co-condensation of tetraethoxysilane and the corresponding organosilanes (d-MS). Infrared measurements indicated that organic groups mainly existed on the surface of m-MS, which resulted in a surface characterized by high hydrophobicity. Both organic groups and isolated hydroxyl groups existed on the surface of d-MS, resulting in both hydrophobicity and hydrophilicity on the surface. The amount of BPA adsorbed on surface-modified MSs per organic group was similar for m-MS and d-MS, however, the d-MS established equilibrium for BPA adsorption faster than m-MS, as measured by UV-vis spectra. A larger amount of BPA per surface area could be adsorbed on carbon materials than on the surface-modified MSs, however, the regeneration of carbon materials by washing could not be done easily. The surface-modified MSs retain adsorption capacity for BPA after several regeneration cycles, demonstrating that the surface-modified MSs are effective recyclable adsorbents of the endocrine disrupter, bisphenol A.

Spontaneous and stable vesicles are formed from vinylbenzyltrimethylammonium chloride (VBTAC) and sodium dodecyl sulfate (SDS) ranging in molar composition from 3: 7 to 7: 3 in the presence of 30 mol % divinylbenzene (DVB). Dynamic light scattering analysis and transmission electron microscope observations revealed that microparticles with diameters around 120 nm (30%) and 580 nm (70%) were formed. Trapping efficiency of the vesicles examined with D-(+)-glucose amounted to ca. 15%. These vesicles were capable of undergoing polymerization in the presence of water-soluble radical initiators such as 2,2'-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride to fix the vesicular structure. Retention of the vesicle size and bimodal size distribution characteristics during the polymerization indicated that intravesicular polymerization prevailed over the intervesicular process. SDS was stably retained in the cross-linked vesicle and was not removed from the vesicle by exhaustive dialysis or ultrafiltration, due to the electrostatic interaction within the cross-linked polymeric framework produced from VBTAC and DVB. The resulting hollow nanospheres are readily redispersed in water without the aid of additional surfactants.

Polyphenol compounds were investigated as reducing agents for non-cyanide electroless gold plating for electronics assembly applications. The pH value and temperature were optimized to determine the conditions that lead to a high deposition rate without precipitation. The surface morphology was evaluated by scanning electron microscopy. Catechol, pyrogallol, and gallic acid yielded deposited films with good appearance and solderability under the optimized conditions. Among the tested reducing agents, catechol is the most suitable for use as a stable plating bath with a long life. It has a moderate reducing ability to stabilize the bath and deposit the film. The calculated values of the heat of formation and the highest occupied molecular orbital levels of the reducing agents supported the experimental results. (c) 2005 The Electrochemical Society.

An electrochemical sensor for reactive oxygen species like the superoxide anion radical using polymeric iron porphyrin complexes was developed by Yuasa et al. of the Tokyo University of Science. The present experiment was designed to develop a method for rapid measurement of reactive oxygen species in calf blood by employing this technique. The needle-type sensor, including an integrated microelectrode, was dipped into calf blood in a test tube. After xanthine oxidase (O_2^- ・ -generating enzmyme), superoxide dismutase (O_2^- ・ -scavenging enzyme) and opsonized zymosan (phagocyte stimulant) were successively administered in the blood, the current value detected by the sensor in the blood was recorded. The current value increased, decreased and reincreased after the successive administrations of xanthine oxidase, superoxide dismutase and opsonized zymosan, respectively. The sensor was proven to detect the reactive oxygen species of blood. Change in the reactive oxygen species concentration of calf blood following castration was investigated, by dipping the needle-type sensor in the calf blood just after sampling. The reactive oxygen species concentration increased to a maximum at 3 hr, decreasing gradually thereafter following the castration. The fluctuation was almost linked to those of the blood chemiluminescence activity and leukocyte count. Thus, we succeeded in perfoming a rapid measurement of the reactive oxygen species concentration in the peripheral blood of calves.

Partially oxidized dextran containing carboxyl a ups was prepared as an environmentally benign organic corrosion inhibitor for mild steel. Introduction of carboxyl groups was accomplished by oxidation of dextran using sodium hypochlorite under basic conditions. The structure of the product was confirmed by spectroscopic measurements. GPC analysis revealed that oxidation of dextran proceeded without significant molecular-weight degradation. H-1 NMR spectra revealed that up to 1.3 carboxyl groups per repeating unit were introduced into the polymer. The product showed moderate corrosion inhibition activity for mild steel. and biodegradability under conditions for cooling water systems.

[Meso-tetra(thiophen-3-yl)porphinato]cobalt (II) (CoT3ThP) complex, which undergoes facile electropolymerization, was synthesized by the dehydro-condensation reaction of pyrrole and 3-thienylaldehyde. The electroconductive thin film of CoT3ThP interconnected by 2,5-thienylene chains, was produced at the glassy carbon electrode by electrolysis. The catalytic activity for oxygen reduction at the modified electrode was evaluated by cyclic voltammetry. The catalytic current for the O-2 reduction appeared near E-p=0.2 V vs. SCE. It was found that the electrode modified with CoT3ThP film has a higher stability than that modified with porphyrin by absorption. Next, we chose carbon black with a high surface-area as a catalyst support, and CoT3ThP was electropolymerized under the condition of suspension of carbon black in an electrolyte solution. We found that the polymerized CoT3ThP was produced on the surface of the carbon nanoparticle. The carbon nanoparticles modified with polymerized CoT3ThP (polyCoT3ThP/C) were suspended in a Nafion solution, and a pseudo MEA (Membrane Electrode Assembly) was made by casting polyCoT3ThP/C on an edge-plane pyrolytic graphite electrode. The polyCoT3ThP/C catalyst was found to reduce O-2 mainly with four electrons (the number of electrons transferred n=3.8) at a positive potential of E-p=0.44 V vs. SCE. The catalytic activity of polyCoT3ThP/C was improved by heat treatment under an inert gas atmosphere (E-p=0.47 V vs. SCE, n=3.8). The results show the possibility of a novel cathode catalyst for use in fuel cells.

Conductive polymer ligand-coated carbon particles were prepared by a fluid-bed electrolysis of 2-(3-pyridyl)thiophene using carbon particles as a working electrode. The resulting particles were suspeneded in a DMF solution of cobalt acetate. The surface of carbon particles was successfully modified with the highly dispersed cobalt complex. The modified carbon particles were suspended in an alcoholic solution of Nafion, and a pseudo-MEA was prepared on an electrode by casting the solution. The electrocatalytic reduction of dissolved 02 was examined using the modified electrode. When the catalyst was prepared using a carbon black with a large surface area and pyrrole was added as a complementary ligand, the catalytic potential for the reduction of 02 appeared at E-p=0.37 V vs. SCE. The catalyst was found to reduce 02 mainly with four electrons (n=3.1). This activity was superior to that of the previously reported carbon nanoparticles modified with a cobalt polypyrrole complex. It was clearly shown that nitrogen atoms of the pyridine-type ligand contribute to accumulate cobalt ions on the surface of the catalyst. It was also revealed that the catalytic activity improved remarkably after heat treatment of the catalyst under argon. The catalyst revealed the possibility of its use as a cathode catalyst for platinum-free fuel cells.

Carbon nanoparticles modified with a cobalt-adsorbed polypyrrole film (Co/PPy/C) were found to be a good electrocatalyst for O-2 reduction. The Co/PPy/C catalyst was synthesized by a multiple modification method for the purpose of obtaining Co-N-4 structure in high density. The conventional Co/PPy/C catalyst was prepared by electropolymerization of pyrrole onto the surface of carbon particles dispersed in the electrolyte solution containing pyrrole, followed by complexation using cobalt acetate. The new Co/PPy/C catalyst was prepared by repeating the above operation. Compared with those of the conventional catalyst, the cobalt ions and nitrogen atoms constituting active centers increased remarkably. The carbon nanoparticles prepared by the multiple modification method was suspended in a Nafion solution, and pseudo MEA (Membrane Electrode Assembly) was made by casting the solution onto an edge-plane pyrolytic graphite electrode. It was revealed that the new catalyst reduced 02 mainly with four electrons, the number of electrons transferred n being 3.3 at a positive potential (E-p = 0.31 V vs. SCE). In addition, the catalytic activity of the catalyst was improved by optimizing the heat-treatment conditions (n = 3.8 at E-p = 0.42 V vs. SCE). These results show the potential use of the present catalyst as a novel cathode catalyst in the fuel cell.

The superoxide anion radical (O-2(-) center dot) has attracted much attention in many fields of biology since it was realized that superoxide anions are produced in significant quantities in various parts of biological systems, from microorganisms to mammals. Therefore, quantitative measurements of O-2(-) center dot in vivo are important for clarifying such relationships under various conditions. However, in most cases, the biological significance and the mechanism of the generation O-2(- center dot) are not yet well understood. We have developed an O-2(- center dot) sensor composed of a thin film of 1-methylimidazole-coordinated iron meso-tetra (3-thienyl) porphyrin ([Fe(im)(2)(ttp)]Br) for the electrochemical detection of O-2(-) center dot. The microsensor displayed high selectivity and activity for the oxidation of O-2(-) center dot and showed a linear relationship between the current and the O-2(-) center dot concentration. In this research, the improvement of the sensor sensitivity was accomplished by mixing polythiophene as the electroconductive polymer on the electrode surface. The sensors were prepared using various compositions of [Fe(im)(2)(ttp)]Br and thiophene as the monomers. During in vitro tests, O-2(-) (center dot) was generated as an intermediate during the oxidation of xanthine by xanthine oxidase (XOD), for detection using this sensor. The electric conductivity of the polymer increased, accompanied by the increase in the amount of the thiophene unit. The highest sensitivity was obtained at a monomer composition of [Fe(im)(2)(ttp)]Br : thiophene = 1 : 8.

meso-Substituted cobalt porphyrins adsorbed on carbon materials were prepared by using a homogenizer in mixing cobalt tetraethylporphyrin and various carbon materials. these electrocatalysts gave rise to electroreduction of O-2 at a remarkably positive potential (E-p = 0.44 V versus saturated calomel electrode (SCE)) and showed a high selectivity for the four-electron reduction (n = 3.9). The catalyst heat-treated at 600 degrees C showed higher potential (E-p = 0.44 V vs. SCE). Electrochemical study and X-ray photo spectroscopy (XPS) analysis revealed that the adsorbed amount of cobalt-porphyrin molecules caused highly effective catalysts for electroreduction of O-2.

A conductive polypyrrole (PPy) film was successfully synthesized in a homogeneous supercritical carbon dioxide (scCO(2))/acetonitrile (AN) system. The occurrence of a homogeneous supercritical state was confirmed by observations of the phase behavior of the system through a high-pressure cell with a viewing window. The concentration of a supporting electrolyte, tetrabutylammonium hexafluorophosphate (TBAPF(6)), significantly changed the phase behavior of the scCO(2)/AN system. The polymerization rate of the film in that system decreased with further addition of CO2. This result suggested that the low Viscosity of scCO(2) did not play an important role in improving the growth rate of the PPy film. The low polymerization rate might have been due to the electron-transfer resistance arising from the low dielectric constant of scCO(2)/ AN mixture. The roughness of the film prepared in the homogeneous scCO(2)/AN system was 1/10 that synthesized in AN itself as a solvent. The slow growth of film and the high diffusion rate of the monomer seemed to account for the smooth flat film formation.

Reactive oxygen species (ROS) such as superoxide anion radical (O-2(-.)) play an essential role on normal cellular growth and homeostasis. However, excess ROS generated by perturbing O-2(-.). homeostasis under various conditions of oxidative stress induce high radical toxicity, resulting in many diseases such as cancer, brain and myocardial infarction, and inflammation. Quantitative analysis Of O-2(-.) by a convenient method is a subject of intense research, since most of ROS are derived from O-2(-.). In situ real-time measurement Of O-2(-.) is very important to understand the relevance of ROS to many diseases. Recent progress in electrochemical sensors for the facile detection Of O-2(-.), including biosensors utilizing a variety of metalloproteins as sensing elements for O-2(-.) and very recently developed all-synthetic sensors with a high selectivity for O-2(-.) detection, is reviewed. Emphasis is placed on the possibility of the all-synthetic sensor for convenient in vivo measurement of ROS.

A novel gold(III) complex with a monodentate 5,5-dimethylhydantoin ligand, [Au(dmh)(4)](-), is square planar in geometry, inert and highly stable in alkaline solutions because of soft acid-base interactions, and electrochemically reduced near -0.3 V vs Ag/AgCl to give a gold(0) film with a high current efficiency.

meso-Substituted cobalt porphyrins adsorbed on carbon black were prepared as catalysts for the electroreduction of O-2. The catalyst, which was prepared by using a homogenizer in mixing cobalt tetraethylporphyrin and carbon black, gave rise to electroreduction Of 02 at a remarkably positive potential (E-P = 0.45 V versus saturated calomel electrode (SCE)) and showed a high selectively for the four-electron reduction (n = 3.8). Electrochemical study and extended X-ray absorption fine structure (EXAFS) analysis revealed that the adsorbed face-to-face dimeric aggregates of cobalt porphyrin molecules were highly efficient catalysts for electroreduction of O-2. Copyright (c) 2005 John Wiley & Sons, Ltd.

Oxidative polymerization of bromoiron(III) meso-tetrakis(3-thienyl)porphyrin gave a novel polymeric porphyrin complex randomly crosslinked at the 2,5-positions of the peripheral thienyl groups. The electrical semiconductivity of ca. 10(-5) S/cm after 12 doping indicated that the polymer had a pi-conjugated structure with a moderate delocalization of pi electrons over the thienylporphyrin units. PM3 calculations for free-base models revealed that HOCO (the highest occupied crystal orbital) band width was reduced by introduction of the porphyrin moieties into the thienylene backbone and yet low HOCO-LUCO (the lowest unoccupied crystal orbital) gap was maintained, which accounted for the relatively low electrical conductivity of the porphyrin polymer. The modified electrode prepared by electropolymerization was redox-active due to the presence of iron(II/III) couple and the semiconductivity of the film, which served as a novel non-enzymatic electrochemical sensor for superoxide anion radical based on the facile electrocatalytic oxidation of the superoxide. Copyright (c) 2005 John Wiley & Sons, Ltd.

A needle-type electrochemical sensor for the facile detection of superoxide anion radical (O-2(-)) was devised using an electrodeposited film of a polymeric porphyrin complex attached to a carbon microelectrode which was placed in a stainless steel 18G needle tube as an auxiliary electrode. The sensing element was prepared by means of electropolymerization of bromoiron(III) mesotetra(3-thienyl)porphyrin in the presence of 1-methylimidazole in CH2Cl2 containing 100 mM tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte, which gave a smooth film of the corresponding polymer. The film was electrochemically active to give a redox response near -0.05 V versus Ag/AgCl due to the iron(II/III) couple. The microsensor was applied to detect O-2(-). produced by xanthine oxidation catalyzed by xanthine oxidase. The amperometric response for O-2(-) was monitored at an electrode potential of 0.5 V versus the auxiliary electrode in a 10 mM phosphate buffer. The microsensor displayed a high catalytic activity for the oxidation of O-2(-) and showed a linear relationship between the current and the O-2(-) concentration. Axial coordination of an imidazole ligand to the iron porphyrin center enhanced selectivity for O-2(-) by impeding the undesired coordination of H2O2 that resulted from the dismutation of O-2(-). Copyright (c) 2005 John Wiley A Sons, Ltd.

We have prepared copper-containing mesoporous silica (Cu/MS) using solubilization of copper oleate in nonionic surfactant aggregates. The amount of copper loading in calcined Cu/MS corresponded to the amount of copper oleate solubilized in surfactant aggregates of the mixed solution.

Superoxide dismutase (SOD), catalase and glutathione peroxidase catalize the elimination of reactive oxygen species (ROS) such as a superoxide anion radical (O2 -·). But enzyme activity decreases in diseases in which ROS attacks DNA, lipid and blood vessels. Recent studies on SOD mimics indicate that manganese porphyrin (MnT2MePyP) express high SOD activity. But the half-life of MnT2MePyP in the blood is usually very short. In the present study, a novel reconstituted polymerized hemoglobin containing manganese porphyrins (MnT2MePyP-PolyHb) was synthesized. SOD activity of MnT2MePyP-PolyHb (IC50 = 1.1 μM, kc at = 7.3 × 106 M-1s-1) was found to be somewhat less than that of MnT2MePyP (IC50 = 0.23 μM, kcat = 60 × 106 M-1s-1). MnT2MePyP-PolyHb half-life in H2O2 (t1/2 = 1070 s) was found to be as much as four times that of MnT2MePyP (t1/2 = 250 s). MnT2MePyP-PolyHb may thus be a valid SOD model for effectively maintaining and prolonging blood circulation. © 2005, Japan Oil Chemists' Society. All rights reserved.

The catalytic activities and structural changes of Pd containing mesoporous silica (Pd/MCM-41) catalysts for the NO + CO reaction were investigated. Pd/MCM-41 after calcination in air showed a very high catalytic activity for the NO + CO reaction because Pd metal particles with an appropriate size for the reaction were formed by the reaction gases.

A water-soluble cationic 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphinatomanganese(III) ion (MnT4MPyP) and water-insoluble 5,10,15,20-tetrakis(N-3-furyl)porphinatomanganese(III) ion (MnT3FuP) were prepared and ion-complexed with an anionic phospholipid membrane to enhance the circulation persistence of the porphyrin complexes in vivo. Fluorescence spectra and fluorescence depolarization experiments indicated MnT3FuP to be situated within the hydrophobic interior of the vesicle composed of the phospholipid membrane, while MnT4MPyP was anchored to the membrane by lipophilic tails with the metalloporphyrin head-group located on the interface between the membrance and aqueous solvent. SOD activity was determined by stopped-flow analysis and cytochrome c assay, which allowed the determination of IC50 and kcat values for the reaction of the metalloporphyrins with superoxide anion radical (O2 -·). Sodium stearate-linked MnT4MPyP was the most effective catalyst as an SOD mimic to decompose O2 -· at a second-order rate constant of 1.9 × 107 M-1s-1 in dimyristoylphosphatidylcholine (DMPC) liposomes. SOD activity of MnT3FuP was less than that of MnT4MPyP. © 2005, Japan Oil Chemists' Society. All rights reserved.

Superoxide dismutase (SOD), catalase and glutathione peroxidase catalize the elimination of reactive oxygen species (ROS) such as a superoxide anion radical (O2 -·). But enzyme activity decreases in diseases in which ROS attacks DNA, lipid and blood vessels. Recent studies on SOD mimics indicate that manganese porphyrin (MnT2MePyP) express high SOD activity. But the half-life of MnT2MePyP in the blood is usually very short. In the present study, a novel reconstituted polymerized hemoglobin containing manganese porphyrins (MnT2MePyP-PolyHb) was synthesized. SOD activity of MnT2MePyP-PolyHb (IC50 = 1.1 μM, kc at = 7.3 × 106 M-1s-1) was found to be somewhat less than that of MnT2MePyP (IC50 = 0.23 μM, kcat = 60 × 106 M-1s-1). MnT2MePyP-PolyHb half-life in H2O2 (t1/2 = 1070 s) was found to be as much as four times that of MnT2MePyP (t1/2 = 250 s). MnT2MePyP-PolyHb may thus be a valid SOD model for effectively maintaining and prolonging blood circulation. © 2005, Japan Oil Chemists' Society. All rights reserved.

Cationic manganese (III) 5,10,15,20-tetrakis(N-methylpyridinium-2-yl) porphyrin (MnT2MPyP) and manganese (III) 5,10,15,20-tetrakis(N-methylpyridinium-4-yl) porphyrin (MnT4MPyP) complexes were synthesized as superoxide dismutase (SOD) mimics which were introduced into niosomes so as to examine this effects on the capacity of drug delivery system (DDS) to maintain and perpetuate blood circulation. All the niosomes were prepared from polyoxyethylene solbitan monostearate (Tween 61) by the conventional sonication method. SOD activity was measured by the stopped-flow analysis and the cytochrome c method. Sodium stearate-linked MnT2MPyP was found to be the most effective catalyst along with SOD activity for decomposing O2 - • at a second-order rate constant of 2.0 × 107 M-1s-1 in Tween 61 niosomes. Rate constants of metalloporphyrin-embedded niosomes for reaction with hydrogen peroxide (H2O2) and half-life times in H2O2 were also determined. Metalloporphyrin-embedded niosomes were found to have greater half-life times compared to metalloporphyrin without niosomes. The present findings clearly indicate that metalloporphyrin-embedded niosomes are highly effective for bringing about O2 -• decomposition and should thus find application as DDS in antioxidant drugs. © 2005, Japan Oil Chemists' Society. All rights reserved.

Free radicals and related species derived from O2 such as superoxide anion radical (O2 -·), hydrogen peroxide (H2O2), hydroxyl radical (·OH) and peroxynitrite ion (ONOO-) are often generated in organisms with possibly consequent diseases. The enzyme, superoxide dismutase (SOD), catalyzes the reaction which eliminates O2 -· As models of SOD, manganese porphyrins such as [meso-tetrakis(N-methylpyridinium-4-yl)porphyrinato] manganese(III) (MnT4MPyP) have been investigated. However, the half-life of any one of these in the blood is usually quite short. We undertook the design of a novel hexameric manganese porphyrin (HexMnP) capable of remaining for a prolonged period in the blood. The SOD activity of HexMnP (IC50 = 2.1±0.7 μM) was found to be somewhat less than that of MnT4MPyP (IC50 = 0.71 μM), but to exceed that of reconstituted hemoglobin (MnT4MPyP-Hb) (IC50 = 2.0 μM) prepared in a previous study. HexMnP proved to be an effective SOD model in which HexMnP had the capacity to remain over a long period of time in the blood, owing to its molecular diameter of more than 80Å. © 2005, Japan Oil Chemists' Society. All rights reserved.

Functional and environmentally benign water-soluble polymers which have characteristic heat-resistant properties, mechanical strength values, and depolymerization capabilities were designed by introducing ionic groups as side chains to poly (phenylene ether) s (PPE). Two water-soluble PPE polymers were prepared by oxidation of 3-methylsalicylic acid and 5-methylsalicylic acid. They were evaluated as functional coating materials for paper production. The compounds showed important characteristics as paper coating materials: high solubility in alkaline water, low viscosity values of polymer solutions and mixtures with inorganic pigments at high shear rates, and adhesion to pulp fiber and inorganic pigments. High glass transition temperature values of the compound provided stiffness and strong resistance against heat blocking of sheet media when a thin layer of compound was applied to a surface of a paper sheet. Additionally, the compounds were found to depolymerize into oligomers by oxidation in the presence of methylsalicylic acid monomers. Such properties of the water-soluble PPE polymers allowed applications to advanced strong and recyclable coating materials.

The electron-transfer rate constants of nitroxide derivatives, 4-(N-t-butyl-N-oxylamino)-t-butylbenzene, 4-(N-t-butyl-N-oxylamino)methoxybenzene, and 2,2,6,6-tetramethylpiperidinyl-N-oxyl, were investigated by electrochemical methods, which demonstrated that these radicals can potentially be used as a high power-rate electrode-active material due to their fast electron-transfer process.

A novel design of anticancer drug delivery system, based on an electrostatic binding of negatively charged liposomes and cationic metalloporphyrins under physiological conditions, is reported. A lack of cytotoxicity of the iron(III) porphyrin-loaded liposomes and an efficient generation of a toxic hydroxyl radical (OH center dot) from a superoxide anion radical (O-2(-center dot)) through the iron(III)-catalyzed dismutation and the Fenton-like reaction allow for a targeted necrosis of tumor cells where the concentration of O-2(-center dot) is locally increased as a result of the reduced activity of superoxide dismutase and catalase in these cells.

The redox behavior of a decavanadium complex [(V=O)(10)(mu(2)-O)(9)(mu(3)-O)(3)(C5H7O2)(6)] (1) was studied using cyclic voltammetry under acidic and basic conditions. The reduction potential of V(V) was found at less positive potentials for higher pH electrolyte solutions. The oxygen reduction at complex I immobilized on a modified electrode was examined using cyclic voltammetry and rotating ring-disk electrode techniques in the I M KOH solutions. On the basis of measurements using a rotating disk electrode (RDE), the complex I was found to be highly active for the direct four-electron reduction of dioxygen at -0.2 V versus saturated calomel electrode (SCE). The complex I as a reduction catalyst of O-2 with a high selectivity was demonstrated using rotating ring-disk voltammograms in alkaline solutions. The application of complex I as an oxygen reduction catalyst at the cathode of zinc-air cell was also examined. The zinc-air cell with the modified electrode showed a stable discharge potential at approximately I V with discharge capacity of 80 mAh g(-1) which was about five times larger than that obtained with the commonly used manganese dioxide catalyst. (C) 2004 Published by Elsevier B.V.

Cobalt complexes that reversibly bind and release O-2 functioned as O-2 carriers, or O-2-enriching media, at the surface of a cathode to enhance the current for the reduction of O-2. The effect of the cobalt complex to accumulate O-2 was evidenced by the higher open-circuit potential, which reflected the equilibrated concentration of O-2 at the electrode surface. The combination of the cobalt complex and the conventional Pt/C catalyst resulted in a significant increase in the steady-state Current for the four-electron reduction of O-2, particularly at small overpotentials where typical fuel cells operate, based on the facilitated transport of O-2 from the atmosphere to the catalyst at the electrode Surface.

A novel carbon-sulfur (C2S) analogue of polyacene has been synthesized and characterized. The polymer is composed of a nondegenerate trans-cisoid polyacetylene backbone in which all hydrogen atoms are replaced with sulfur atoms to form thiophene rings that are fused into a linear cross-conjugated ladder-type structure. The newly developed synthetic route of the ladder-type polymer is based on an intramolecular condensation of a prepolymer consisting of 3-(alkane-1-sulfinyl)thiophen-2,5-diyl units in triflic acid. The geometric and band electronic structure of the ladder-type polymer were calculated and analyzed at the PM5 level of theory. The fused ring structure imposes strong quinonoid-type character to the originally benzenoid polyene backbone, which destabilizes the HOMO and stabilizes the LUMO and thus reduces the band gap. The shift of absorption and emission maxima to longer wavelengths responding to lower pi-pi* transition energies than those of polythiophene and the smaller gap between electrochemical p- and n-doping potentials are consistent with the reduction of the band gap. The microstructure of the isolated oligomers in their neutral, singly oixidzed, and doubly oxidized states were computed for short and intermediate chain length. Various energetic and structural aspects of the convergence behavior from the properties of small cations or dications to those of an isolated polaronic or bipolaronic defects on a sufficiently long chain were monitored and are discussed. The geometric structures of the p-doped ladder-type polymer in the form of either polaron or bipolaron were calculated by adopting suitable boundary conditions to represent charged unit cells. The geometry relaxation process for the charged ladder-type backbone induces the appearance of a stronger quinonoidic character than that in the case of polythiophene, which suggests that the fused rings more easily adopt quinonoid forms than thiophene rings. Calculated energetic aspects of the doping behavior and the paramagnetic resonance spectra of p-doped polymers revealed that the ladder-type polymer possesses polaron as the prevailing charged species, in contrast to many other pi-conjugated polymers where bipolaron is the lowest-energy charge storage configuration.

The reversible oxygen-binding properties of tetraphenylporphyrinatocobalt(II) (CoTPP) complexed with poly(3,4-azopyridylene) ( PAP) were established. The CoTPP complexes functioned as oxygen carriers at the surface of a cathode to enhance the current for the reduction of oxygen. PAP was synthesized by the oxidative polymerization of 3,4-diaminopyridine in a DMF solution at 25degreesC using a Cu/pyridine catalyst. The combination of the CoTPP complex and the conventional Pt/C catalyst resulted in a significant increase in the steady-state current for the four-electron reduction of O-2, particularly at small overpotentials where typical fuel cells operate, based on the facilitated transport of O-2 from the atmosphere to the catalyst at the electrode surface.

Crystal structure of [Fe(salphen)Cl] (H(2)salphen = N,N'-(1R,2R)-1,2-diphenylethylenebis(salicylideneimine)) reveals that a steric effect induced by the bulky substituent on the Schiff base ligand brings about drastic changes in the reactivity of the complex; the typical dimerization of the chloroiron(III) complex upon basification to yield mu-oxo complexes are suppressed, resulting in the high-yielding conversion to a hydroxide salt. (C) 2003 Published by Elsevier Science B.V.

Superacidification of aromatic sulfoxides effects the electrophilic substitution reaction of the resulting hydroxysulfonium ions onto aromatic rings with the elimination of H2O at room temperature. The product, the alkyldiarylsulfonium ion, allows the synthesis of alkylsulfonio-bridged (lambda(4)-alkylsulfanyliumdiyl) aromatic polymers. High molecular-weight poly(alkylsulfonioarylene) salts have been made accessible by the regioselective condensation of aryl sulfoxides. Polymers having a wide variety of structural dimensionalities such as linear, hyper-branched and ladder-type structures can be prepared by this method, which possess interesting properties such as good solubility in polar organic solvents and sometimes even in H2O, susceptibility to nucleophiles to provide thioarylene derivatives, photo-degradability, and electric semiconductivity based on a 3d-2p interaction in aryl sulfonium ion.

Depolymerization of an engineering plastic, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (M-n = 1.0 X 10(4), M-w/M-n = 1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to M-n = 4.9 X 10(2) (M-w/M-n = 1.5). By a pro-longed reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.

Unlike common oxovanadium(IV) complexes with tetradentate Schiff base ligands, [N,N'-(2,2-dimethyl-1,3-propylene)bis(salicylideneiminato)]oxovanadium(IV) ([VO(salptn)]) was easily oxidized by dioxygen in aqueous CH3CN. The [VO(salptn)]-O-2 stoichiometry was 4:1. This particular reactivity comes from the preference of [VO(salptn)] to be six-coordinate rather than five, that drives the formation of an O-2-complex. The structure of the oxidized product, [VO(salptn)]OH, was characterized by single-crystal X-ray diffraction. The results are consistent with a mechanism involving an attack of O-2 at the vanadium(IV) center, followed by the formation of the mu-dioxo dimmer as a transient species and the subsequent splitting of the O-O bond by hydrolysis to yield [VO(salptn)]OH. (C) 2003 Elsevier B.V. All rights reserved.

A polyelectrolyte containing a sulfonium cation, poly(methylsulfonio-1,4-phenylenethio-1,4-phenylene trifluoromethanesulfonate) (1) was tested as a separator in a zinc-air cell. In comparison with the commercially available separators such as polypropylene, polysulfonium 1 was highly effective to prevent cation permeation from the anode to cathode and effectively increased the capacity six-fold greater than that of polypropylene during discharge. This phenomenon was explained by the ion-exchange process of the membrane 1, which showed an anion-permselectivity toward OH- at low KOH aqueous solution concentrations (&lt;1 M). (C) 2003 Elsevier Science B.V. All rights reserved.

This review summarizes the recent advances in the chemistry of oxovanadium(III-V) mononuclear complexes and their linear assemblies bearing tetradentate Schiff base ligands. Structural parameters of the oxovanadium assemblies are compiled, which reveal the preference of specific coordination geometries around vanadium atoms according to the valence state. Emphasis is placed on the catalysis of multielectron redox reactions by oxovanadium(IV) complexes which disproportionate to vanadium(III) and oxovanadium(V) complexes under suitable conditions. Their biological implications and synthetic applications are described. (C) 2002 Elsevier Science B.V. All rights reserved.

The oxidation of oxovanadium(IV) complexes [(LVO)-O-IV] (L = tetradentate Schiff-base ligands such as N,N'-ethylenebis(salicylideneaminate)(2-) (salen) and N,N'-2,2-dimethylpropylenebis(salicylideneaminate)(2-) (salpn)) to [(LVO)-O-v](+), believed to be responsible for the voltammetric response near 0.6 V vs Ag/AgCl in CH2Cl2 in the presence of tetrabutylammonium tetrafluoroborate as a supporting electrolyte, is in fact coupled to a homogeneous process where [LVO](+) coordinates BF4- to form a neutral complex formulated as [LVOBF4]. The formation constants for [VO(salen)BF4] and [VO(salpn)BF4] are evaluated to be K-salen(-1) = 1.1 X 10(2) M-1 and K-saipn(-1) = 1.4 x 10 M-1, respectively. Crystal structure of [VO(salen)BF4] reveals that one of the fluorine atoms in BF4- is so close to the vanadium(V) atom as to be practically bound in the solid state.

Superacidification of sulfoxides and sulfinates effects the electrophilic substitution reaction of the resulting hydroxy-sulfonium ions onto aromatic rings with the elimination of H2O at room temperature. The present account emphasizes the utility of the reaction for use as an elementary step in organic synthesis. The product, the alkyldiarylsulfonium ion, often quantitatively obtained, allows the synthesis of alkylsulfonio-bridged (lambda(4)-alkylsulfanyliumdiyl) aromatic polymers. High molecular-weight poly(alkylsulfonioarylene) salts with a wide range of structural dimensionalities from linear to network architectures have been made accessible by the regioselective condensation of aryl sulfoxides. The polymers possess interesting properties such as good solubility in polar organic solvents and sometimes even in H2O, susceptibility to nucleophiles to provide thioarylene derivatives, photo-degradability, and electric semiconductivity, according to the dimensionality of the molecule. The synthetic chemistry of the alkylsulfonioarylene polymers as well as their possible applications in high molecular-weight poly(thioarylene) synthesis, photochemical recycling processes of an engineering plastic poly(thio-1,4-phenylene), and photo-resist technologies, are reviewed.

The electroreduction of O-2 in acidic aqueous solutions at an electrode modified with a decavanadium cluster [(V=O)(10)(mu(2)-O)(9)(mu(3)-O)(3)(C5H7O2)(6)] (1) revealed that it produces H2O with four electrons per O-2 molecule near 0.5 V versus SCE. The usefulness of the complex as a reduction catalyst of O-2 with a high selectivity was demonstrated. (C) 2002 Elsevier Science B.V. All rights reserved.

A cationic polyelectrolyte of various poly(arylenesulfonium salt)s were coated on the surface of glassy carbon electrodes with an incorporated ferricyanide anion from the electrolyte solutions. The apparent diffusion coefficients of Fe(CN)(6)(3-), that are electrostatically bound were determined by chronoamperometry, chronocoulometry and mediated electron transfer from the rotating disk voltammetry. The complex incorporated by the S-cationic polyelectrolyte shows a high diffusion coefficient for the polyelectrolyte of poly(methylsufonio-1,4-phenylenethio-1,4-phenylene trifluoromethanesulfonate). The diffusion of poly(arylenesulfonio triflate) depended on the ionic exchange of the S-cation which has an alkyl bond and the crystalline structure that influenced the electrostatic motion of the anion within the polyelectrolyte modified electrode.

The superacid-induced condensation of o-methylsulfinylated thiophenyl(ene) compounds under dilute conditions induces an intramolecular electrophilic ring-closing reaction of a hydroxysulfonium cation onto the adjacent benzene ring to yield the thianthrenium ring systems, which disclose pi electron delocalization over sulfonio linkages demonstrating the efficacy of planarization of the benzene rings for the p-pi/d-pi interaction in arylsulfonium moieties. Crystal structure of the thianthrenium salt reveals that the S+-C(phenyl) bond is significantly shortened upon the ring closing as a result of the increased bond order by the resonance effect.

The synthetic routes to ladder polymers which consist of benzenetetrayl subunits with imino and methylsulfonio linkages are described. As the key intermediate, oligo- and polyaniline derivatives having pendant methylthio groups are prepared by the Pd-catalyzed aryl amination from various monomers. The oxidation of the polymers with H2O2 the presence of CH3COOH effects the high yielding conversion of methylthio to methylsulfinyl groups without the formation of the undesired methylsulfonyl groups. The superacid-induced condensation of the resulting polymers under dilution conditions induced the polymer-analogous intramolecular electrophilic ring closure reaction of the hydroxy(methyl)(phenyl)sulfonium cation onto the adjacent benzene ring to yield the required ladder polymers which have proved to be semiconductors with intrinsic electric conductivides of ca. 10(-5) S (.) cm(-1).

The picket-fence cobaltporphyrin (Col?) having rapid and reversible oxygen-binding properties was employed to accumulate oxygen from a bulk solution to a diffusion layer at an electrode surface. Modification of a carbon electrode with a thin CoP liquid membrane resulted in a significant increase in the reduction current of oxygen, which proved to be a new type of modified electrode to reduce the diffusion resistance of oxygen from the bulk solution onto the electrode surface.

The synthetic routes to ladder polymers that consist of benzenetetrayl subunits with oxo and methylsulfonio linkages are described. As the key intermediate, poly(phenylene oxide)s having pendant methylsulfenyl groups are prepared by copper-catalyzed oxidative polymerization of the corresponding phenols with O-2. The oxidation of the polymer with an equimolar amount of H2O2 in the presence of acetic acid effects the high-yielding conversion of methylsulfenyl to methylsulfinyl groups without the formation of the undesired methylsulfonyl groups. The superacidified condensation of the resulting polymer (Swern reaction of aryl sulfoxides) under dilution conditions induces the polymer-analogous intramolecular electrophilic ring-closing reaction of the hydroxymethylphenylsulfonium cation onto the adjacent benzene ring to yield the required ladder polymer, which has proved to be a semiconductor with an intrinsic electric conductivity of 2 x 10(-5) S/cm. A comparison of the spectroscopic properties of the ladder polymer with those of the model compounds such as 5-methylphenoxathiinium triflate and phenoxathiin discloses pi -electron delocalization over the methylsulfonio linkages, demonstrating the efficacy of the ladderization for p-pi /d-pi interactions in arylsulfonium moieties. This synthetic approach permits the thio and alkylsulfonio ladder linkages for a variety of phenyl ethers to form in high yields.

An aqueous solution of a [poly(ethyleneiminato)]cobalt(II) complex that reversibly binds and releases O-2 functions as an O-2-enriching medium for an O-2 electrode to enhance the current for the uncatalyzed reduction of O-2. The effect of the electrochemically inactive cobalt complex is to supply reducible O-2 to the solution within the diffusion layer near the electrode by releasing the bound O-2 from the O-2 adduct, which contributes to a decrease in the diffusion layer thickness of O-2. Based on the rapid release of O-2 from the O-2 adduct, a diffusion-limited current is obtained for the reduction of O-2. The hypothetical concentration of the enriched O-2 supplied under pure diffusion control (i.e. unperturbed by the kinetics of the O-2 binding) is several times larger than that of the actual concentration of O-2 due to the higher solubility of the O-2 adduct than the physical solubility of O-2 in H2O at room temperature under an atmosphere of air. An insoluble membrane of a cobalt( II) complex with a cross-linked poly( ethyleneimine) ligand that has the ability to swell serves as an O-2-enriching material to concentrate O-2 from aqueous electrolyte solutions. A new type of O-2-diffusion electrodes for metal/air batteries and fuel cells is proposed using the O-2-enriching material immobilized at the electrode surface.

The crystal structure of (mu -oxo)bis[N,N'-o-phenylenebis(salicylideneiminato)iron(III)] ([{Fe(salpn)}(2)(mu -O)]) revealed the shortest intermetallic distance among the crystallo graphically characterized mu -oxo diiron(III) complexes bearing macrocyclic ligands. X-ray data indicate that the Fe-Fe distances are mainly controlled by the steric effect of the ligand. Arrangement of the two Fe(salpn) moieties in close proximity with a fairly bent Fe-O-Fe bond is allowed by the reduced steric crowding of the salpn ligand. (C) 2001 Elsevier Science BN. All rights reserved.

The oxygenation of (2,9-dimethyl-1,10-phenanthroline)copper(I) chloride in THF, followed by a treatment with DMF and acidification with HCl, afforded dichloro[2-(dimethylamino) (hydroxy)methyl-9-methyl-1,10-phenanthroline] copper(LI) and (aqua)dichloro(2,9-dimethyl-1,10-phenanroline)copper(II) quantitatively.

4,4',4"-(1,3,5-Benzenetriyl)tris(2,g-di-tert-butylphenol) was prepared by the cross-coupling of 1,3,5-tribromobenzene and [4-(trimethylsiloxy)phenyl]magnesium bromide. X-ray analysis of the single crystal showed a propeller-like structure with a mean dihedral angle of 39 degrees between the hydroxyphenyl and the core benzene. The phenoxyl mono-, di-, and triradicals were generated by the electrochemical oxidation of the trianion. A stepwise radical formation was revealed by a differential pulse voltammogram, electrolytic ESR spectroscopy, and a comproportionation reaction between the radicals, which was discussed as an effect of the pi -conjugated but non-Kekule-type coupler. The quartet and triplet ground state for the tri- and diradical, respectively, were confirmed by a SQUID measurement.

The polymerization of 2,3,5,6-tetraphenylhydroquinone (or 2,2 ' ,3,3 ' ,5,5 ' -hexaphenyl-4,4 ' -dihydroxybiphenyl) with alpha ,w-tetrahydroperfluoroalkanediol and decafluorobiphenyl was carried out to synthesize a series of copolymers III (M-w = 49 100-80 900). The copolymers III are composed of arylene ether (10-30 mol %) and fluorinated alkane (90-70 mol %) moieties. The reaction of III with chlorosulfonic acid gave sulfonated polymers IV, which are soluble in polar organic solvents and form flexible and transparent films by casting from solution. The polymers TV have glass transition temperatures of 109-155 degreesC and decomposition temperatures of ca. 300 degreesC. The hydrated polymers show protonic conductivity (3.4 x 10(-3) S cm(-1)), which does not decrease at temperatures up to 170 degreesC.

A novel decavanadium cluster [(V=O)(10)(mu (2)-O)(3)(C-5-O)(3)(C5H7O2)(6)] bearing ten oxovanadium(V) centers linked with bridging oxygen atoms was prepared. In contrast to the well known decavanadate ion V10O286-, the molecule was soluble in organic solvents such as dichloromethane and 1,1,2,2-tetrachloroethane due to the peripheral acetylacetone ligands. X-ray crystallographic analysis revealed a molecular Framework formed by nine square-pyramidal VO5 polyhedra surrounding one VO4 tetrahedron linked through the corners. The molecule consists of approximate three-fold rotational symmetry, allowing the classification of ten vanadium atoms into four chemically equivalent categories. The unique metal core geometry persists in solution, which was demonstrated by the four peaks in the V-51-NMR spectrum. However, the four types of vanadium atom could not be distinguished by electrochemical measurements; consequently, the molecule was a multielectron reservoir which showed a broad cathodic wave near 0.6 V vs. Ag / AgCl due to the reduction of the vanadium(V) centers to vanadium(IV). (C) 2001 Elsevier Science B.V. All rights reserved.

A new type of cationic polyelectrolyte, poly(methylsulfonio-1,4-phenylenethio-1,4-phenylene trifluoromethanesulfonate)? that adheres to a glassy carbon electrode surface has been employed to bind a ferricyanide anion to the electrode surface from electrolyte solutions. The complex incorporated by the polyelectrolyte shows significant shifts in formal potential to less positive values due to the stronger binding of ferricyanide by the polycation coating than that of ferrocyanide. The apparent formal potential for the incorporated ferricyanide/ferrocyanide redox couple changes as the concentration of supporting electrolyte is varied. The polycation coating is anion-permselective when a methanesulfonate is used as a supporting electrolyte. (C) 2001 Elsevier Science B.V. All rights reserved.

Methyl phenyl sulfoxide was found to undergo self-polycondensation in triflic acid in the presence of diphenylamine to produce poly(methylsulfonio-1,4-phenylene triflate). Diphenylamine formed a charge-transfer (CT) complex with the hydroxy methyl phenyl sulfonium cation produced by the protonation of the sulfoxide, facilitating the electrophilic substitution reaction of the sulfonium cation onto the carbon atom of the terminal phenyl ring. The obtained polymer is a highly crystalline material whose structure was determined by X-ray analysis using the typical geometric parameters of the sulfoniophenylene dimer and trimer model compounds. The orthorhombic unit cell of the polymer (a = 10.875 Angstrom, b = 10.449 Angstrom, and c = 18.629 Angstrom) contains eight monomeric units. The space group is Pbcn (#60). Two molecular chains along the c axis pass through the unit cell, one through the corner and the other through the center. The crystal structure of the polymer not only revealed a structural relevance to those of oxy- and thiophenylene polymers but also provided support for CT complex formation between the polymer and diphenylamine.

2,4,6-Trimethylphenol was oxidized with oxygen in the presence of (1,4,7-tribenzyl-1,4,7-triazacyclononane)copper(II) chloride as a catalyst to produce exclusively a coupled product stilbenequinone, without the formation of oxygenated products.

[N,N'-Ethylenebis(salicylideneaminato)]manganese(III) benzoate ([Mn(salen)(O2CC6H5)] crystallized to form a solid-state dimer in which the Mn(salen) moiety is linked to its neighbor by two shared phenolate oxygen atoms, in striking contrast to the linear polymeric structure formed with bridging acetate ligands. A substantial cavity between the two manganese atoms was then produced by the weak coordination of the phenolate oxygen to the neighboring manganese bearing benzoate in a monodentate mode. (C) 2000 Elsevier Science S.A. All rights reserved.

Acidification of a solution of (mu-oxo)bis[(5,10,15,20-tetraphenylporphyrinato)iron(III)] ([{Fe(tpp)}(2)O], II) in CH2Cl2 produced equimolar amounts of a hydroxoiron(III) complex [(tpp)Fe-III(OH)] (III) and an iron(III) complex [(tpp)Fe-III(ClO4)] (TV). The complex IV was isolated as a perchlorate salt, which crystallyzed in the triclinic space group P (1) over bar (#2); a = 11.909(3), b = 19.603(4), c = 10.494(3) Angstrom, alpha = 95.74(2)degrees, beta = 107.91(2)degrees, gamma = 89.14(2)degrees, V = 2319.1(9) Angstrom(3), Z = 2, D-calc = 1.328 g cm(-3), mu(Mo K alpha) = 4.35 cm(-1), final R = 0.055 and R-w = 0.050. The crystal structure of IV revealed that ClO4- is coordinated to the iron atom, which may be driven by the preference of iron(III) to be five coordinate rather than four coordinate. Reduction of the complex II in the presence of acid by electrolysis and/or by a reducing agent, such as sodium dithionite, under argon produced [Fe-II(tpp)]. The addition of O-2 to a solution of [Fe(tpp)] in acidic CH2Cl2 in the presence of an equimolar amount of the reducing agent produced the complex III. When the complex II was adsorbed on an electrode surface and placed in aqueous acidic electrolyte solutions, electroreduction of the adsorbate proceeded according to the half-reaction:
[{Fe(tpp)}(2)O] +2H(+) +2e(-) --&gt; 2[Fe(tpp)] + H2O, at 0.031-0.059 pH V (vs. SCE, pH &gt; 1.0). Based on these results, ore-bridged iron(III) porphyrin dimers were used as electrocatalysts for the reduction of O-2. The catalytic reduction of O-2 proceeded at potentials in the vicinity of those for II. As a whole, the proportion of H2O as the product increased from 50% for adsorbed [(tpp)(FeCl)-Cl-III] to &gt; 90% for the adsorbed dimer. Thus, electroreduction of the dimer adsorbed on a carbon electrode immersed in aqueous acid produced two solid state, cofacially fixed iron(II) porphyrin molecules:
[(PFeOFeP)-O-III-P-III](ad) + 2H(+) + 2e(-) --&gt; [pFe(II) Fe(II)p](ad) + H2O (P = porphyrin dianion). Coordination of molecular oxygen to the adjacent two iron(II) centers under acidic conditions allowed formation of O-2-bridged iron(III) porphyrin [PFeIII(O-2) (FeP)-P-III](ad) at the electrode surface. Electroreduction of the adsorbate under acidic conditions produced H2O and allowed the reformation of [PFeII (FeP)-P-II](ad). The implication is that the electroreduction of the adsorbed ore-bridged dimer gives a cofacial geometry for PFeII on the electrode, facilitating the coordination and subsequent splitting of O-2.

Syntheses of a unique molecule, nickel(II) dithiocarbamate bearing two ferrocenyl groups (3), and its oxidized product, nickel(IV) dithiocarbamate bearing three ferrocenyl groups (4(+)), are reported. Spectroelectrochemical investigations have shown that the complex 4(+) undergoes a three-electron oxidation process, according to two quasireversible steps ([Ni(IV)(Fe(II))(3)](+) reversible arrow [Ni(IV)(Fe(II))(2)Fe(III)](2+)+e(-), [Ni(IV)(Fe(II)),Fe(III)](2+) reversible arrow [Ni(IV)(Fe(III))(3)](4+)+2e(-)), whose redox potentials are separated by Delta E= 250 mV. The value Delta E is related to the comproportionation equilibrium ( [Ni(IV)(Fe(II))3](+)+[Ni(IV)(FeIII)(2)Fe(II)](3+) reversible arrow [Ni(IV)Fe(III)(Fe(II))(2)](2+)) and results fi-om the combination of a statistical contribution and a term which reflects the electrostatic repulsive interaction between the metal centers. In spite of the chemical equivalence of the three ferrocenyl groups, the mixed-valence state [Ni(IV) Fe(III)(Fe(II))(2)](2+) (4(2+)) substantially persists in solution. Model studies with ethylene-bridged bis(ferrocenylimine) (6) have revealed that the electrostatic term is much lower in the absence of the nickel(IV) center. Preliminary force-field simulations on 4(+) have shown that enhanced electrostatic repulsion caused by the oxidation of the ferrocenyl subunits affects the conformation of the molecule, which results in a significant dimensional increment. Stereochemical features of the molecules are related to the electrostatic interaction and Delta G(0) associated with the comproportionation process is affected by such strong deformation that a decrease in electrostatic repulsion results.

Rodlike poly(1,4-phenyleneethynylene) fl-substituted with multiple pendant phenoxyls 1 was synthesized by polymerizing 4-bromo-2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethynylbenzene 10a using the catalyst of a palladium-triphenylphosphine complex and cuprous iodide and subsequent heterogeneous oxidation. The corresponding dimer 2 was also synthesized; X-ray analysis of its precursor 4 indicated a linear phenyleneethynylene backbone and twisted dihedral angles of 50 and 77 degrees for the pendant phenol groups, ESR spectra suggested a delocalized spin distribution from the pendant phenoxyl to the backbone. The diphenoxyl 2 had a triplet (S = 2/2) ground state. The spin concentration of the polyphenoxyl 1 could not be increased beyond 0.7 spin/unit due to its low solvent solubility; 1 with a spin concentration of 0.62 had an average S of 3/2.

Addition of stoichiometric quantities of trifluoromethanesulfonic (triflic) acid to solutions of (VO)-O-IV(salen) (H-2-salen = N,N'-ethylenebis(salicylideneamine)) in dichloromethane produces the mu-oxo dinuclear vanadium(IV) complex [(salen)(VOVIV)-O-IV(salen)](2+) ([(VOVIV)-O-IV](2+)). Addition of significant excesses of triflic acid converts the dimer into [V-IV(salen)](2+). In dichloromethane solutions containing 0.1 M tetrabutylammonium tetrafluoroborate, the [(VOVIV)-O-IV]2+ complex undergoes disproportionation and dissociation reactions to produce a solution containing an equimolar mixture of (VO)-O-IV(salen), [V-III(salen)](+), and [(VOVV)-O-IV](3+). The oxophilic [V-III(salen)](+) complex reacts with O-2 to accomplish a four-electron reduction of O-2: 2[V-III(salen)](+) + O-2 --&gt; 2[(VO)-O-V(salen)](+). These reactions can be exploited to carry out catalytic electroreductions of O-2 to H2O in acidified dichloromethane solutions of (VO)-O-IV(salen) at unusually positive potentials.

The crystal structure of a mu-oxo heterometallic porphyrin [(pip)(tpp)(CrOFeIII)-O-III(tpp)] (pip = piperidine) not only confirmed the proposed oxidation state of chromium and iron atoms, but also revealed a unique coordination environment around chromium(III), which is substantially protruded from the porphyrin plane.

A remarkable increase in the selectivity of four-electron reduction of O-2 at an iron phthalocyanine complex adsorbed on a carbon electrode is accomplished by the use of a peroxo-bridged pyFe(III)Pc-O-2-PcFe(III)py (py = pyridine, Pc = phthalocyanine dianion). Electroreduction of the dimer adsorbed on an electrode produced two solid state, cofacially fixed iron(II) phthalocyanine molecules under acidic conditions. Raman studies on the adsorbate revealed the restricted dynamics of the phthalocyanine rings adsorbed on a solid support that was responsible for the facile accommodation of an O-2 molecule between the adjacent two iron(II) atoms. The contrast with the catalytic behavior of a mononuclear iron(II) stems from the formation of a mu-peroxo bond upon the reaction with O-2, which subsequently cleaves under acidic conditions to produce two molecules of H2O.

The electrochemistry of a mu-oxo dimanganese(III) octaethylporphyrin (II) and those of the corresponding mononuclear complexes Mn-III(OEP)Cl (I), Mn-III(OEP)ClO4 (III) and Mn-III(OEP)OH (IV) (where OEP represents octaethylporphyrin) were studied. When complex II was adsorbed on an electrode and placed in aqueous acidic electrolyte solutions, efficient catalysis of the four-electron reduction of O-2 to H2O was accomplished. A control experiment using an electrode modified with the mononuclear manganese(III) complex I resulted in a significant decrease in the selectivity for the four-electron reduction. The hydroxomanganese(III) complex IV was produced in the course of the oxidation of Mn-II(OEP) to Mn-III(OEP)(+) with O-2 under acidic conditions. Complex I was isolated as single crystals and characterized by X-ray crystallography. Although complex II was not isolated as single crystals, the long manganese-axial ligand distance (2.385 Angstrom) in I provided an estimate that a similar geometry would be true for a allowing accommodation of an O-2 molecule between the two manganese atoms in the adsorbed cofacial porphyrins.

Electroreduction of an ore-bridged iron(III) porphyrin dimer adsorbed on an electrode surface produced solid state, cofacially fixed two iron(II) porphyrin molecules when immersed in aqueous acid, allowing an efficient catalysis of the four-electron reduction of O-2 to H2O.

The catalytic oxidation of pyrrole by the [(salen)(VOVV)-O-IV(salen)](3+) cation, which is formed on an electrode surface by the oxidation of [(salen)(VOVIV)-O-IV(salen)](2+), was examined by hydrodynamic voltammetry at a rotating glassy carbon disk electrode. The electron transfer rate constant for the cross-reaction [(salen)VOV(salen)](3+)/pyrrole was estimated to be 4 x 10(4) mol(-1) cm(3) s(-1). O-2-oxidation of the [(salen)VOV(salen)](+) cation gives rise to the catalysis for the O-2-oxidative polymerization of pyrrole. The polymerization was rate-determined by the reoxidation step of the catalyst by O-2. (C) 1997 Elsevier Science S.A.

The facilitated transport of oxygen in a liquid membrane containing [meso-alpha,alpha,alpha,alpha-tetrakis(o-pivalamidophenyl)porphyrinatocobalt(II)]-laurylimidazole (CoP) as an oxygen carrier leads to high permeability and permselectivity of oxygen against nitrogen. The oxygen permeation was properly analyzed by a dual-mode model and using the oxygen-binding constants spectroscopically determined, to give permeation parameters of the membrane such as the diffusion coefficient (D-CoP) of the CoP mobile carrier and the physical diffusion coefficient of oxygen. D-CoP was in accordance with that electrochemically determined. The facilitated permeation was represented by the product of the Cop concentration and D-CoP in the membrane solution. D-CoP decreased with solution viscosity and increased with the measured temperature. High oxygen permeability (10(-7) cm(3)(STP) cm cm(-2) s(-1) cmHg(-1)) was observed, e.g. for the membrane of the 31 wt % CoP methylanisole solution at 10 degrees C, where the facilitation factor and the oxygen/nitrogen permselectivity were over 20 and 40, respectively.

Tris(2,2'-bipyridine)ruthenium(II) chloride catalyzed the photo oxidative polymerization of diaryl disulfides by O-2, by which poly(thioarylene)s were efficiently produced. The polymerization proceeded through the electrophilic reaction of the sulfonium cation which was produced selectively by the photo-redox system.

In an attempt to provide confirmation for the postulated mechanism of O-2 reduction in vanadium-mediated oxidative polymerization of diphenyl disulfide, a series of divanadium complexes containing salen ligand (salen = N,N'ethylenebis(salicylideneamine)) were prepared, characterized, and subjected to reactivity studies toward dioxygen. A divanadium(III, IV) complex, [(salen)VOV(salen)][I-3] (II), was yielded both by treatments of solutions of [(salen)-VOV(salen)][BF4](2) (I) in acetonitrile with excess tetrabutylammonium iodide and by electroreduction of I followed by anion exchange with tetrabutylammonium triiodide. The complex II was characterized by a near-infrared absorption at 7.2 x 10(3) cm(-1) (epsilon = 60.1 M(-1) cm(-1) in acetonitrile) assigned to an intervalence transfer band. A crystallographically determined V(III)-V(IV) distance of 3.569(4) Angstrom is consonant with the classification of II as a weakly coupled Type II mixed-valence vandium (alpha = 3.0 x 10(-2)). Oxidation of the cation [(salen)VOV(salen)](+) with O-2 in dichloromethane yielded spontaneously the deep blue, mixed valent, divanadium(IV, V) species [(salen)VOVO-(salen)](+) which was structurally characterized both as its triiodide (III) and perchlorate (IV) sales. Crystal data for III: triclinic space group P (1) over bar (no. 2), a = 14.973(2) Angstrom, b = 19.481(2) Angstrom, c 14.168(2) Angstrom, alpha = 107.00 (1)degrees, beta = 115.56(1)degrees, gamma = 80.35(1)degrees, V = 3561.3(9) Angstrom(3), Z = 4, D-calc = 1.953 g/cm(3), mu (MoK alpha) = 31.74 cm(-1), final R = 0.057 and R(w) = 0.065. Crystal data for IV: triclinic space group P (1) over bar (no. 2), a = 11.923(3) Angstrom, b = 14.25(1) Angstrom, c = 11.368(7) Angstrom, alpha = 112.92(5)degrees, beta = 92.76(4)degrees, gamma = 99.13(4)degrees, V = 1743(1) Angstrom(3), Z = 2, D-calc = 1.537 g/cm(3), mu (CuK alpha) = 57.69 cm(-1), final R = 0.042 and R(w) = 0.061. The complexes III and IV were deoxygenated in strongly acidic nonaqueous media to produce [(salen)VOV(salen)](3+) as a high-valent complex whose reversible two-electron redox couple (VOV3+/VOV+) at 0.44 V vs Ag/AgCl has been confirmed. Its ability to serve as a two-electron oxidant provided a unique model of a multielectron redox cycle in oxidative polymerization.

Electroreduction of a vanadium dinuclear complex [(salen)V-IV-O-V-IV(salen)](2+) in the presence of Or resulted in the stoichiometric formation of a [(salen)V-IV-O-V-V-(salen)=O](+) complex. The process provided not only evidence for the interconversion of vanadium(III)/oxovanadium(V) in the action of vanadium complexes operating as redox catalysts, but also possibilities for the use of the vanadium complex as electrocatalysts for the 4-electron reduction of O-2.

Modification of the oligo(phenylene sulfide) chain at the ends with reactive groups such as chloro, bromo, iodo, and carboxyl to enhance its reactivtiy was performed. alpha,omega-Dihalooligo(p-phenylene sulfide) was synthesized through the oxidative polymerization of diphenyl disulfide in the presence of bis(4-halophenyl)disulfide. Linear oligo(p-phenylene sulfide) (OPS) terminated by Cl or Br with a high degree of functionality was obtained by a one-pot process. alpha-Carboxy-OPS was synthesized by the thermolysis of the disulfide-bond of the OPS in the presence of an aromatic iodide having a carboxyl group. The carboxy-terminated OPS was used for the synthesis of polyamide-graft-OPS copolymers.

Oligo(p‐phenylene sulfide) is synthesized by oxidative polymerization of diphenyl disulfide with oxygen catalyzed by vanadyl acetylacetonate under strongly acidic conditions. The mechanistic studies reveal that the redox cycles of the vanadyl complexes give rise to catalysis through a two‐electron transfer between diphenyl disulfide and molecular oxygen. The VO catalysts act as an excellent electron mediator to bridge a 1.0 V potential gap between the oxidation potential of disulfides and the reduction potential of oxygen. The VO‐catalyzed oxygen‐oxidative polymerization provides pure oligo(pphenylene sulfide)s containing an S–S bond. The polymeric product is of low molecular weight due to the insolubility under these conditions. (N,N′‐ethylenebis(salicylideneaminato))oxovanadium‐(IV), VO(salen), was used as an inert model compound to elucidate the redox chemistry of the vanadium complex. VO(salen) reacts with trifluoromethanesulfonic acid (CF3SO3H) or triphenylmethyl tetrafluoroborate (ϕ3C(BF4)) to form a deoxygenated complex, VIV(salen)2+, and a μ‐oxodinuclear complex, [(salen)VOV(salen)]X2, (X = CF3SO3− or BF4−). The dimerization of VO(salen) is initiated by deoxygenation to produce V(salen)2+ which enters into an equilibrium with a second VO(salen) complex to produce the μ‐oxo dimer. The two‐electron transfer of the μ‐oxo dinuclear vanadium complex is elucidated. Copyright © 1995 John Wiley &amp
Sons, Ltd.

The effect of substituents on the electropolymerization of benzene derivatives and the redox properrties of the corresponding polymers were determined using Brown's substituent constants (σ+). Electron‐donating groups lower the oxidation potential by which increase in the current efficiency was observed. However, stabilization of the produced cation radicals by the electron‐donating groups resulted in a decrease in the polymerization efficiency. The appropriate values of σ+ for the efficient polymerization ranged near −1.5. Copyright © 1995 John Wiley &amp
Sons, Ltd.

Photo-oxidation of bis(3,5-dimethylphenyl) disulfide proceeds in the presence of aromatic nitriles as sensitizers. Catalytic amounts of 9,10-dicyanoanthracene act as an electron mediator of the transfer from the disulfide to oxygen in the presence of biphenyl as a co-sensitizer. The photo-redox system enabled an efficient formation of poly(thio-2,6-dimethyl-1,4-phenylene) through electrophilic reaction of the sulfonium cation produced in the photo-oxidation.

A catalytic amount of Lewis acids ([Lewis acid]/[Disulfide]=1/200) facilitated electron transfer from diaryl disulfides to a stoichiometric amount of another oxidizing agent by which linear poly[thio(1,4-arylene)] was produced. Such Lewis acids as SbCl5 and FeCl3 facilitated oxidation of diphenyl disulfide by quinones more efficiently than protic acids such as CF3COOH, where the Lewis acid showed more than 200-fold more activity than the protic acid. Oxovanadium complex-catalyzed oxygen-oxidation of disulfides was also facilitated by these Lewis acids. The catalysis of these Lewis acids includes not only the activation of quinones or the oxovanadium complex, but also the lowering of the oxidation potential of the monomers.

Electrochemical confirmation that (N,N'-ethylenebis(salicylidenoaminato))oxovanadium(IV), VO(salen), reacts with trifluoromethanesulfonic acid (CF3SO3H) or triphenylmethyl tetrafluoroborate (Ph3C(BF4)) to form a deoxygenated complex, V(IV)(salen)2+, and a mu-oxodinuclear complex, [(salen)VOV(salen)]X2, (X = CF3SO3- or BF4-) is presented. Cyclic voltammograms of VO(salen) in the presence of CF3SO3H or Ph3C(BF4) exhibit reversible waves with formal potentials near 0.5 and 0.8 V (vs Ag/AgCl). The cathodic wave at 0.5 V is argued to arise from the combined reduction of V(salen)2+ and the mu-oxo dimeric complex and the wave at 0.8 V from the oxidation of the V(salen)2+ complex. The diffusion coefficients of these three complexes in acetonitrile were determined. The dimerization of VO(salen) is initiated by deoxygenation of the V=O center by H+ or Ph3C+ to produce V(salen)2+ which enters into an equilibrium with a second VO(salen) complex to produce the mu-oxo dimer. The kinetics of the second order dimerization reaction were monitored, and the equilibrium contant for the formation of the mu-oxo dimer in acetonitrile was evaluated as 0.7 mM-1.

Oxidative polymerization of benzene with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) under strongly acidic conditions produced structure-defined poly(1,4-phenylene) (PP). Addition of CF3SO3H prior to the stoichiometric oxidation enabled the efficient formation of the protonated sigma-complex of benzene through which linear PP (degree of the polymerization was ca. 30) was produced by the subsequent addition of DDQ.

Oxygen-oxidative polymerization of diphenyl disulfides with vanadyl acetylacetonate (VO(acac)(2)) was studied by the kinetics based on oxygen uptake. Lineweaver-Burk plots reveal that the oxidation of diphenyl disulfide is a rate-determining step for the VO-catalyzed oxidative polymerization of diphenyl disulfide. K-m (Michaelis constant) and V-max were determined to be 1.6x10(-2) moldm(-3) and 1.5x10(-4) moldm(-3) min(-1), respectively. The polymerization rate is influenced by the oxidation potential of disulfides. The reoxidation step of the catalyst by oxygen is the rate determining step in case of the polymerization of alkyl-substituted disulfides such as bis(3-methylphenyl)disulfide, bis(2,5-dimethylphenyl) disulfide, and bis (3,5-dimethylphenyl) disulfide because the oxidation step of the disulfides is facilitated due to their lower oxidation potentials.

Bis(3,5-dimethylphenyl) disulfide was subject to photo-oxidation in the presence of 2,3-dicyanonaphthalene as a sensitizer. The photo-redox system enabled efficient formation of poly(thio-2,6-dimethyl-1,4-phenylene) non-contaminated with metal salt at room temperature through the electrophilic reaction of the sulfonium cation produced by the photo-oxidation.

Mu-Oxo-bis[(N,N'-ethylenebis(salicylideneaminato))vanadium(IV)] tetrafluoroborate is prepared from (N,N'-ethylenebis(salicylideneaminato)) oxovanadium(IV) (VO(salen)) through an electrophilic reaction by triphenylmethyl tetrafluoroborate (Ph3CBF4) in dichloromethane. The voltammetric analysis of the binuclear complex in dichloromethane revealed a one-step two-electron transfer at 0.58V (vs Ag/AgCl) based on the disproportionation (2V(IV)OV(IV) reversible V(III)OV(IV) + V(IV)OV(V)).

Oligo(p-phenylene sulfide) is synthesized through oxygen oxidative polymerization of diphenyl disulfide catalyzed by vanadyl acetylacetonate. The mechanistic studies reveal that two redox cycles [V(M)/V(IV) and V(IV)/V(V)] give rise to catalysis through a 2-electron transfer between diphenyl disulfide and molecular oxygen. The VO catalysts act as an excellent electron mediator to bridge a 1.0-V potential gap between the oxidation potential of disulfides and the reduction potential of oxygen. The VO-catalyzed oxygen oxidative polymerization provides pure oligo(p-phenylene sulfide)s containing an S-S bond. The polymeric product is of low molecular weight due to the insolubility of poly(p-phenylene sulfide) under these experimental conditions.

Oligo(phenylene sulfide) (OPS) containing one disulfide bond at the end of the chain, which was obtained by the oxidative polymerization of diphenyl disulfide, had a relatively low Td10%(temperature for 10% weight loss) of 412 °C because of degradation of the disulfide bond. But this thermal cleavage of the disulfide bond promoted the curing reaction through thiophenoxy radical formation. OPS was allowed to react with diiodobenzene at 220 °C. The thermal stability of OPS was improved through the consumption of the disulfide bond and the coupling of the chain. Copyright © 1991 John Wiley &amp
Sons, Ltd.