陸川 政弘

We synthesized water-soluble fullerene C60 polyanions and polycations with sulfonic acid or amine groups. The layer-by-layer films were fabricated with these fullerene polyions and ionic polymers such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). The alternate deposition of fullerene polyions and counter ionic polymers was explored by UV-Vis absorption measurements after each immersion of polyanions (or polycations) and PAH (or PAA) aqueous solutions. Morphology of the obtained layer-by-layer films was investigated by atomic force microscopy.

Operation of polymer electrolyte fuel cells at high temperatures (&gt 100 °C) under anhydrous condition can minimize CO poisoning of Pt catalysts, improve the energy efficiency, and reduce the size of the fuel cell systems. Anhydrous proton conducting polymer electrolytes are mainly classified into acid doped polymer electrolytes and solid acid electrolytes. In this study, amine functionalized polysulfone (AEPSF) as a basic polymer of acid doped polymer electrolyes and a fullerene derivative with acid groups (PHSF) as a solid acid electrolyte were synthesized. Their properties and fuel cell performances were also investigated. The conductivity of an APESF/H3PO4 (H3PO4: 116 wt. %) film showed 10-2 S/cm above 100 °C without humidification. The conductivity of PHSF increased with temperatures, and acheived 10-4 S/cm at 120 °C.

By incorporating metallic nanoparticles into conjugated polymers matrix, novel optical and electronic properties can be obtained in nano-structured multilayer thin films. In this study, we fabricated the gold nanoparticles within polyelectrolyte layer-by-layer films fabricated from poly(thiophene-3- acetic acid) (PTAA) and poly(allylamine hydrochloride) (PAH). Alternate deposition of these polymers was confirmed by UV-Vis absorption and QCM measurements. The PAH/PTAA multilayer films were immersed into an aqueous solution of sodium tetrachloroaurate(III) hydrate for 30 h, and then reduced in an aqueous solution of dimethylamine borane for 2 h to form Au nanoparticles. In UV-Vis absorption spectra of the films after reduction, the characteristic surface plasmon resonance of the Au nanoparticles dominated the visible wavelength with a maximum centered around 538 nm. The transmission electron microscopy images of the films showed that spherical Au nanoparticles with diameters of approximately 60 nm were formed in the films.

Alternating copolymer of chiral thiophene and non-substituted thiophene, poly(3-[2-((S)-(+)-1-methyloctyloxy)ethyl]-2,2'-bithiophene) (P(S)MOET-T), was synthesized by Rieke method. The Head-to-Tail ratio of P(S)MOET-T was estimated to be 95 % by 1H NMR spectroscopy. The molecular weights of P(S)MOET-T was Mn = 17,800, Mw = 28,500, and Mn/Mw = 1.6. The aggregation behavior of P(S)MOET-T in CHCl3-CH3OH mixed solutions was studied using UV-Vis and circular dichroism (CD) spectroscopy. The P(S)MOET-T exhibited clear solvatochromism by changing the ratio of CHCl 3-CH3OH. At high CHCl3 content, P(S)MOET-T showed π-π* transition peak at 470 nm. The absorption maximum was red-shifted as the contents of CH3OH increased. When the content of CH3OH was over 40 vol%, the absorption maximum was red-shifted up to 540 nm. In this region, circular dichroism has appeared in the π-π* transition region. These results suggest that the aggregation of polymer induced the formation of a helical structure due to the regio and conformation regularity.

Sequential layer-by-layer adsorption of polyanions and polycations on charged surfaces have attracted much attention as a versatile and facile technique for creation of functional polyelectrolyte multilayers. In this study, poly-3-(thienyl)ethoxybutanesulfonate (PTEBS), which has sulfonic acid groups at the 3-position of thiophene ring, was synthesized by chemical oxidation with FeCl3. PTEBS showed good solubility in water and shows "self-doping" nature at an acidic condition. To form all-thiophene multilayers, PTEBS and poly-2-(3- thienyloxy)propyltriethylammonium chloride (PTPA), which is a cationic polythiophene derivative, were selected as the ionic pair. Effect of the preparation conditions (pH or concentration) on the electrical and structural properties of obtained SA films were investigated.

Superhydrophobic surfaces with a water contact angle over 150 ° are expected to be applied on medical and environmental fields. In this study, we fabricated Superhydrophobic thin films using poly(tetrafluoroethylene) (PTFE) particles and a polyelectrolyte containing phosphoric acid group (PPHP) by a conventional self-assembly method. Contact angles of water on PTFE/PPHP self-assembled (SA) films increased relative to the number of bilayers. The SA film with 80 bilayers showed a contact angle over 150 °, and this superhydrophobicity was maintained up to 120 bilayers. The XPS spectrum of the SA film indicated that both PTFE and PPHP were adsorbed on substrates. The AFM observations of SA film showed that microscopic fractal structure was formed on the SA film.

Although hydroxyapatite (Ca10(PO4) 6(OH)2 HAp) has biocompatibility, its mechanical strength is not enough for application of organism tissue substitution materials. In this study, HAp was hybridized with PLLA in order to achieve biocompatible materials with high toughness, and their mechanical properties and biocompatibility were investigated. HAp/PLLA composites were fabricated by synthesizing PLLA under lipase CA catalyst at 130°C for 7 days in porous HAp ceramics. With increasing the concentration of lipase CA, the molecular weight of PLLA tended to decrease, while the conversion of PLLA increased. In addition, the composite with the porosity below 15 % showed excellent bending strength compared with porous HAp. Osteoblast-like MC3T3-E1 cells were cultured with PLLA, lipase CA, and L-lactide. Any change in the rate of multiplication of MC3T3-E1 cells was not observed. This result suggested that the introduction of PLLA into HAp seem to have a positive effect in cell affinity.

Organic ring molecules constructed from rigid molecules have attracted a great deal of interest due to their unique cavity shape and size. These organic ring molecules are attractive materials for separation of gases or liquid molecules utilizing their cavities. In this study, the ring oligomers containing imide frameworks (6FDA-DABE) were prepared by one-pot polycondensation of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and diaminobenzoic ester (DABE) in dilute solutions of DMAc. The MALDI-TOF mass and FAB mass spectra of 6FDA-DABE indicated that the reaction product contained cyclic dimers. The 6FDA-DABE/PMDA-ODA, 6FDA-ODA, and PES composite films were fabricated by blend method. Benzene permeability of 6FDA-DABE/PMDA-ODA and PES composite films increased with the 6FDA-DABE content while that of 6FDA-DABE/6FDA-ODA composite films was almost constant. In the case of 6FDA-DABE/ MDA-ODA composite films, the maximum benzene/m-xylene selectivity was observed at 5 wt% of 6FDA-DABE content.

We have reported that hydrocarbon polymer electrolytes based on poly(phenylene), sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (S-PPBP), showed high proton conductivities and excellent fuel cell performances. Their mechanical properties at high water uptakes and stability of dimensional changes, however, were insufficient for fuel cell applications. In this study, polycyclic aromatic moieties, anthraquinone, were copolymerized with PBP in order to improve the mechanical properties of S-PPBP. A novel copolymer, poly(4-phenoxybenzoyl-1,4-phenylene-co-1,5-anthraquinone) (P(PBP-co-ANQ)), was synthesized by Ni(0) catalyzed coupling reaction. The weight-average molecular weight of sulfonated P(PBP-co-ANQ) (S-P(PBP-co-ANQ) determined by GPC was 91,300. The ion exchange capacity of the S-P(PBP-co-ANQ) was 2.84 meq g -1, as determined by titration. The swelling in water at 70°C of S-P(PBP-co-ANQ) membrane was about 1.6 times lower than that of S-PPBP membrane. The thermal decomposition temperature of S-P(PBP-co-ANQ) was about 214°C, which was comparable to that of the S-PPBP. The decomposition is due to the elimination of the sulfonic acid groups, as determined by FT-IR measurements. The conductivity of the S-P(PBP-co-ANQ) membrane achieved 1.88 × 10 -1S cm-1at 80°C and 90% RH, which was comparable to that of Nafion® membrane.

An electron affinity of polymers is important factor for the actual application of the polymer as an active material in LEDs. In this research, a conjugated copolymer consisting 9,9-dihexylfluorene (HF) and 3 -(benzothiazole-2-yl)thiophene (BIT), poly [(3 -(benzothiazole-2-yl)thiophene- alt-(9,9-dihexylfluorene) (PBTT-alt-HF), was prepared by Suzuki coupling method to control the electron affinity and improve quantum efficiency. Their homopolymers, poly(9,9-dihexylfluorene) (PHF) and poly(3-(benzothiazole-2-yl) thiophene (PBTT), were synthesized for a comparison. Two absorption bands were observed in the UV-Vis spectra of the obtained copolymer. In fluorescence spectra of the copolymer, there is only one peak which might derive from fluorescence of PBTT. The electroluminescence spectrum of PBTT-alt-HF was red-shifted with higher applied voltage. This indicated that luminescence was derived from the fluorene part at lower applied voltage and from the thiophene part at higher one.

Poly(lactic acid) (PLLA) and poly(glycolic acid) (PGA) which are biodegradable polymers have been applied to medical application due to their biocompatibility. It is necessary to control the biodegradability for expanding their applications. In this study, copolymers composed of PLLA and PGA, poly(lactic-co-glycolic acid) (PLGA), were synthesized by enzymatic polymerization using lipase in order to control the biodegradable behavior. The conversion of monomers and molar fraction of L-lactide (FL) in PLGA were calculated from the 1H-NMR spectra. The conversion rate of polymerization reached nearly 100% after 9 days at 100°C, and the F L was equal to the feed ratio of L-lactide. The 1H-NMR indicated that the reactivity of glycolide was higher than that of L-lactide. The weight losses of PGA and PLGA after enzymatic degradation were measured to investigate their biodegradation rates. The weight of PLGA decreased more slowly than that of PGA.

Althogh hydrocarbon polymer electrolytes having phosphoric acid groups, polyphosphoxyetyl-methacrylate (PPHM), showed excellent radical stability and water adsorption properties, their mechanical properties were insufficient for fuel cell applications. It has been reported that the mechanical and thermal properties of polymer materials were improved by introducing polyhedral oligomeric silsesquioxane (POSS) containing an inorganic Si8O 12 core surrounded by organic substitutes. In this study, copolymers consisting of PHM and POSS (poly(PHM-co-POSS)) were synthesized in order to improve the mechanical properties and control the water adsorption of PPHM and their electrical properties. The X-ray diffraction profiles of poly(PHM-co-POSS) showed that the crystalline structures formed in the copolymers due to the aggregation of POSS. The conductivity of poly(PHM-co-POSS) under low relative humidity (40-70 %) at 80°C was higher than that of PPHM homopolymers. The high conductivities of poly(PHM-co-POSS) under low humidity were attributed to the formation of the efficient proton conducting pathway caused by the aggregation of POSS.

Lead halide-based layered perovskites, (H3N-CnH 2n-NH3)PbX4 (X:I, Br), have attracted much attention because of their exceptional properties and quantum well structure. In this study, oligomer derivatives, 4,4′-bis-[5-(2-aminoethyl)thienyl] biphenylene dihydroiodides (AETP·HX), were introduced into organic layers of the layered perovskites. The XRD profile of (AETP)PbX4 films indicated that the layered structures were formed. The UV-Vis absorption spectrum of the (AETP)PbI4 film showed a sharp and intense absorption at 516 nm, while the (AETP)PbBr4 film exhibited an absorption band at 400 nm. In the photoluminescence spectrum of (AETP)PbI4 film, an emission at 516 nm due to the binding excitons was observed. On the contrary, (AETP)PbBr4 film showed a broad peak and an intense peak at 450 nm and 530 nm, respectively.

Superhydrophobic surfaces with a water contact angle over 150°are expected to be applied on medical and environmental fields. In this study, we fabricated Superhydrophobic thin films using poly(tetrafluoroethylene) (PTFE) particles and various polyelectrolytes containing a phosphoric acid group by a conventional self-assembly method. Contact angles of water on the SA films increased relative to number of bilayers. Contact angles of water on a PTFE/PPHP self-assembled (SA) film was over 150°, while that of a PTFE/P(PHP-co-TFEA) SA film was only 130 ± 3°. The SEM observation of SA films with 100 bilayers showed that PTFE/PPHP SA films had bigger surface roughness than that of PTFE/P(PHP-co-TFEA) SA films.

Fullerene, C60, have attracted a great deal of interests because of their unique structure, electrical and optical properties, and biological availability. In the past decade, a few investigations on nano-hybrid materials containing C60 derivatives were reported, while there have been numerous reports on application of C60 derivatives to superconductive, optelectronics, optical-limiting, and anti-HIV materials. In this study, we propose two examinations for hybridization of C60 at the nano scale. First, a C60 ammonium derivative was intercalated to PbI2 based layered perovskites, which were regarded as self-assembled quantum well materials. Novel layered perovskites, which contained C 60 ammonium derivatives in their organic layers, were fabricated as thin solid films to examine the effects of incorporation of C60 frameworks to quantum confinement effect. Secondly, we synthesized various water-soluble C60 polyions with sulfonic acid, carboxylic acid, or amine groups, and the layer-by-layer films were fabricated with these C 60 polyions and ionic polymers. Morphology observations of the obtained layer-by-layer films indicated that the nanoparticles consisting of C60 polyions and ionic polymers were formed on the quartz substrates.

Hydroxyapatite (Ca 10(PO 4) 6(OH) 2 HAp) has been widely used in clinical applications due to its similarity in structure and composition to bone minerals, and good biocompatibility to human tissue. However, the pure HAp is only suitable to the repair of non-load-bearing bones because of their low bending strength, and high Young's modulus. Hence, composites of HAp and biodegrable polymers have attracted much attention for good osteoconductivity, biodegrablity, and high mechanical strength. In this study, HAp was hybridized with PLLA, and then its mechanical properties and biocompatibility were investigated. PLLA/HAp composites were fabricated by synthesizing PLLA with lipase CA catalyst at 130°C for 7 days in porous HAp ceramics. The result of scanning electron microscopy showed that the pores of HAp were filled with PLLA. The bending strengths of the composites were about two-three times stronger, and the Young's modulus were about half comparing with porous HAp,. The result of citotoxicity tests showed that PLLA, lipase CA, and L-lactide had low toxicity. In addition, osteoblast-like MC3T3-E1 cells were culutured on the composites.

Lead halide-based layered perovskites, (H3N-CnH 2n-NH3)PbX4 (X :I, Br), have attracted much attention because of their exceptional properties and quantum well structure. The tunable optical properties and high crystallinilty of π-conjugated oligomers make them promising candidates as advanced materials for the optelectronic applications. In this study, π-conjugated oligomer derivatives, AETP·HX and AETF·HI, were incorporated into the organic layer of the layered perovskites. The UV-Vis absorption spectra of the oligomers were not dependent on the halogen. The XRD profile of hybrid films indicated that the layered structures were formed. The UV-Vis absorption specta of the (AETP)PbI4 and (AETF)PbI4 films showed a sharp and intense absorption at 516 nm and 514 nm, respectively, while the (AETP)PbBr4 film exhibited an absorption peak at 400 nm. In the photoluminescence spectrum of (AETP)PbI4 film, an emission at 516 nm due to the excitons was observed. On the contrary, (AETP)PbBr4 and (AETF)PbI4 films showed characteristic peaks. These results suggest that a novel energey interaction between organic and inorganic layers was formed in the layered perovskite films.

Sequential layer-by-layer adsorption of polyanions and polycations on charged surfaces has attracted much attention as a versatile and facile technique for creation of functional polyelectrolyte multilayers. In this study, poly-3-(thienyl)ethoxybutanesulfonic acid (PTEBS), which has sulfonic acid groups at the 3-position of thiophene ring, was synthesized by chemical oxidation with FeCl3. PTEBS aqueous solution and a cast film showed "self-doping" nature at an acidic condition. PTEBS and polyhydroxy hydrogen sulfated fullerene (PHSF) were selected to prepare self-assembly (SA) multilayers with a cationic polythiophene derivative, poly-2-(3-thienyloxy) propyltriethylammonium chloride (PTPA). A linear relationship of the UV-vis adsorption spectra observed in the PTPA/PTEBS and PTPA/PHSF SA films suggested that the alternate deposition of the polyions successfully formed polyelectrolyte multilayers.

The cost of perfluorinated membranes such as Nafion® is the highest barrier for the commercialization of polymer electrolyte fuel cells (PEFCs) on a large scale. From this reason, sulfonated hydrocarbon polymers have been studied as inexpensive materials for polymer electrolyte membranes (PEMs) of PEFCs. The durability of hydricarbon polymer electrolytes, however, was insufficient for fuel cell applications compared with fluorocarbon polymer electrolytes. In this study, hydrocarbon polymer electrolytes based on polyphenylene (S-PPBP), polyketone (S-PEEK), polysulfone (S-PES), and polyimide (SPI) were synthesized, and their chemical stability, mechanical properties, and fuel cell performances were investigated in order to clarify the durability behaviors of hydrocarbon PEMs. As a result of Fenton's tests, the chemical stability of S-PPBP was supiror to those of other hydrocarbon polymer electrolytes. Dimensional changes of PEMs were investigated by immersing the sample films into water at 80°C. The S-PPBP film showed a clear anisotropy in the film swelling, which was different from other hydrocarbon PEMs. The SPI film showed the best mechanical stability among the hydrocarbon PEMs. The fuel cell performances of the S-PPBP film under low humidities (42 %R.H.) showed the limiting current density of about 2.1 A/cm2, which was higher than that of the Nafion®112 film.

Direct methanol fuel cells (DMFCs) are promising candidates for portable power sources and electric vehicle applications due to the advantage of simple system design. Perfluorosulfonic acid membranes (e. g., Nafion®) are commonly used as solid electrolytes in DMFCs owing to good chemical properties and ion conductivity. However, their methanol permeability is too high to use in practical DMFCs. In this study, the preparation of polymeric complexes of sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (S-PPBP) and polymer electrolytes with phosphoric acid groups (PPHP) were attemped in order to obtain polymer electrode membranes with low methanol permeability. The conductivity of S-PPBP/PPHP membranes achieved 10-2 S/cm in the temperature range of 30 - 80°C at 90 %R.H. The methanol permeability of S-PPBP/PPHP (1 : 1) membrane is 1.77 × 10-6 cm2/s, which is lower than that of Nafion® membrane. DMFC performance of S-PPBP/PPHP was measured at 60°C under ambient pressure by using 1 M methanol aq. and air. The membrane electrode assembly consisting of a S-PPBP/PPHP membrane and Nafion® binder showed a maximum power density of about 67 mW/cm2. The OCV of the S-PPBP/PPHP DMFC (0.825 V) was higher than that of Nafion® based DMFC (0.603 V) due to the low methanol permeability of S-PPBP/PPHP membranes.

Hydroxyapatite (Ca10(PO4)6(OH) 2 HAp) has been used as a biomaterial due to its similarity to bone mineral in structure and composition, and its good biocompatibility to human tissue. Recently, much attention has been focused on the combination of HAp composites with biodegradable polymers to overcome the problem of poor mechanical properties of HAp. In this study, poly(lactic-co-glycolic acid) (PLGA) were synthesized by enzymatic polymerization using lipase in order to control the crystallinity and biodegradability, and PLGA/HAp hybrid materials were fabricated to control their mechanical properties. The molar fraction of L-lactide (FL) in PLGA was calculated from the 1H NMR spectra. The 1H NMR results indicated that the reactivity of glycolide was higher than that of L-lactide. The FL of PLGA polymerized in and outside HAp for 9 days was equal to the feed ratio of L-lactide. The DSC results showed that the Tm of PLGA decreased with increasing FL, indicating that the degree of crystallinity of PLGA decreased upon copolymerization with PLLA. The X-ray diffraction peaks of PLGA (F L = 50 %) was consistent with that of PGA. The ATR spectra, 1H NMR spectra, and SEM images showed that the PLGA was introduced into the HAp pores by the in-situ method.

Two-dimensional and multi-layered perovskites, [NH3(CH2)(12)NH3] PbBr4 and [NH3(CH2)(12)NH3](CH3NH3)(n-1)PbnBr3n+1, with a quantum confinement effect have been naturally formed by intercalating lead bromide into organic alkyldiammonium bromide frameworks.

Phenethylammonium-based perovskites, which can be regarded as a semiconductor/insulator multiple quantum well consisting of lead halide semiconductor layers sandwiched between phenethylammonium insulator layers were prepared. To investigate the effects of the electronic state and the orientation of organic insulator layers on the optical properties of layered perovskites, fluorine substituted analogues were also prepared. The structure and optical properties were investigated by the XRD, UV-Vis absorption, and fluorescence measurements. The exciton absorption peak was shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms. (C) 2004 Elsevier B.V. All rights reserved.

The preparation process of porous tricalcium phosphate (TCP) ceramics from calcium phosphate fibers as a matrix of biodegradable ceramics/polymer hybrids was discussed. The TCP/PLLA hybridization via bulk-polymerization using lipase as an enzyme was carried out. It was found that calcium phosphate fibers synthesized from the starting solutions possessing the Ca/P ratios of 1.33, 1.50 and 1.67 consisted of octacalcium phosphate, hydroxyapatite and a trace of monetite. Results show that the relative densities increase with firing temperature, and β-TCP was transformed into α-TCP when the firing temperature exceeded 1100 °C.

Polylactide (PLLA)/hydroxyapatite (HAp) hybrids were fabricated through bulk-polymerization for the purpose of achieving biocompatible materials with high toughness. The relationship between amount of enzyme and molecular weight of PLLA polymerized using various lipases was shown. Lipase PS indicated high activity on ring-opening polymerization of L-lactide to obtain PLLA with Mw higher than 150,000. The porous HAp contained a great number of pores with sized of several micrometers. The results indicated that OH groups of the porous HAp promoted the polymerization of L-lactide.

High-performance composites of poly(4-vinylpyridine-co-styrene) copolymer (P4VPy-St) and polyamic acids (PAA) were prepared by in-situ polymerization. High-performance composites could be obtained from a polymer pair that has an attractive interaction such as a hydrogen bonding interaction. The aggregation of the resulting polyimide (PI) took place easily in the P4VPy-St/PI composite film during the stepwise heat-treatment of the P4VPy-St/PAA composite film to convert PAA to PI. This was because of the disappearance of the carboxyl group due to the imidization of PAA. In this study, free carboxylic acid groups were introduced into the side chains of PI in order to improve the mechanical properties of P4Py-St/PI composites, and the carboxyl group content dependence of the tensile strength of the resulting composite films was investigated. The tensile strength of the resulting composite films increased with increasing carboxyl group content in PI. The hydrogen bonding interaction between the pyridine moiety in the P4VPy-St copolymer and the carboxyl group introduced into PI greatly enhanced both the compatibility and the tensile strength of the composite films.

Preparation and characterization of two-dimensional zirconium phosphonate derivatives in either crystalline or amorphous forms have been investigated. Composite zirconium phosphonates in single crystal phase have also been investigated and characterized by XRD and P-31-MASNMR. These compounds are lamellar structures comprising zirconium phosphates or organophosphonates. The hydroxyl groups or sulfomethyl groups are bonded through the phosphorous atoms to an inorganic framework made of oxygen and zirconium atoms. Compounds were characterized for their proton-conductivity as a function of temperature and relative humidity.

The structure and optical properties of a lead halide organic-inorganic perovskite compound containing an (R)-2-octylammonium cation have been investigated in order to confirm the construction of an optically active quantum well. As in the case of the general alkylammonium systems, a spin-coated film of the compounds took the form of a two-dimensional quantum confinement structure, and had stable excitons at room temperature. The polycrystalline film exhibited a definitive Cotton effect in inorganic and exciton absorption regions. The introduction of (R)-2-octyl ammonium into the organic layer easily enabled us to render the organic-inorganic multiple quantum well optically active. [DOI: 10.1143/JJAP.42.L698].

Time-resolved photoluminescence (PL) measurements on highly ordered and disordered films of a polythiophene (PT) derivative were compared. Although delocalization lengths of π electrons and the strengths of interchain interaction are quite different between the two films, a biexponential decay and a change in spectral shape, from one with a large 0-0 transition to one with a large 0-1 transition, were commonly observed. Therefore, we conclude that PL spectra of PT consist of two components having different spectral shapes and different lifetimes, and that these components originate from intrachain odd- and even-parity states that are coupled by electron-phonon interaction. This model explains the greatly reduced fluorescence yield for the ordered film as well as the time-resolved PL measurements. © 2003 The American Physical Society.

Time-resolved photoluminescence (PL) measurements on highly ordered and disordered films of a polythiophene (PT) derivative were compared. Although delocalization lengths of pi electrons and the strengths of interchain interaction are quite different between the two films, a biexponential decay and a change in spectral shape, from one with a large 0-0 transition to one with a large 0-1 transition, were commonly observed. Therefore, we conclude that PL spectra of PT consist of two components having different spectral shapes and different lifetimes, and that these components originate from intrachain odd- and even-parity states that are coupled by electron-phonon interaction. This model explains the greatly reduced fluorescence yield for the ordered film as well as the time-resolved PL measurements.

Thin films of lead iodide based perovskites [p-F(C6H5)C2H4NH3](2)(CH3NH3)(m-1)PbmI3m+1 (m=1, 2) with different inorganic well thickness using p-fluorophenethylammonium as an organic cation were systematically prepared, and the structure and optical properties were investigated. X-ray diffraction patterns demonstrated that the spin-coated film was highly oriented with the c-axis perpendicular to the substrate surfaces and that the control of the inorganic layer thickness in layered perovskites can be achieved by changing the ratio of the two organic amines and lead iodide. When the feed ratio of p-fluorophenethylammonium salt, methylammonium salt, and lead iodide was 2:3.5:3, the bilayer structure was formed. Using p-fluorophenethylammonium instead of alkylammonium as an organic cation, the spin-coated film with high crystallinity was obtained.

Aromatic ammonium-based perovskites and fluorine substituted analogues were prepared. The effects of the electronic structures of aromatic ammonium containing fluorine on the optical properties of layered perovskites were investigated by the XRD, UV-Vis absorption, and fluorescence spectrum measurements. The absorption peaks were shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms.

Regioregular poly(thiophene) derivatives with liquid crystal moiety, poly(3-[2-(4-fluorobenzyloxyethyl)]thiophene) (HT-PFBET) and poly(3-[2-benzyloxyethyl]thiophene) (HT-PBET), were synthesized using cross-coupling reaction according to the Rieke method. Thermochromism of HT-PFBET and HT-PBET was studied by electronic absorption measurements. HT-PFBET gave rise to a clear isosbestic point, while HT-PBET exhibited no isosbestic point with increasing temperature. This is due to a morphological effect induced by fluorine atoms.

The template-guided enzymatic polymerization of conducting poly(aniline) particles was investigated. In order to clarify the role of templates in this polymerization, various template polymers such as poly(ethylene oxide) (PEO), polyvinyl alcohol) (PVA), polyvinyl pyrrolidone) (PVP), and poly(sodium 4-styrenesulfonate) (SPS) were used in this study. The enzymatic synthesis of poly(aniline) was successful with a stoichiometric amount of hydrogen peroxide and a catalytic amount of the enzyme (horseradish peroxidase). The chemical structures of template polymers provided difference in particle size of obtained poly(aniline).

Formation of metal complexes from fullerene derivative and phthalocyanine (Pc) derivative was investigated. UV-Vis spectra of C-60 substituted with cyano group (C60CN) and phthalocyaninato iron(II) substituted with tert-butyl groups (FePcTB) showed charge transfer interaction in 1-chloronaphhtalene. The metal complex was synthesized by refluxing o-dichlorobenzene (ODCB) solution of C60CN and FePcTB. TOF-MS spectra indicated that the complex was composed of C60CN and FePcTB with mole ratio of 2/1.

Copolymers of acid phosphoxyethyl methacrylate (PHM) and 2,2,2-trifluoroethylacrylate (TFEA) were synthesized in order to construct hydrophilic and hydrophobic domains as well as Nafion(R) membrane. Thermal decomposition temperatures of PHM-TFEA copolymers were about 250 degreesC, which showed sufficient thermal stability for polymer electrolyte fuel cells (PEFC). Water uptake of these copolymers was higher than that of Nafion 115 under low relative humidity, and proton conductivity of these polymers exhibited about 10(-3) S cm(-1) under 90% relative humidity at 80 degreesC.

Polymeric thin films which had a high-ordered structure were fabricated from adipic acid (ADA), 4,4'-diaminodiphenylmethane dihydrochloride (DAM), and N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as condensing agents by a self-assembly method. UV-Vis and quartz crystal microbalance (QCM) measurements were used to monitor the layer-by-layer deposition process. FTIR reflection absorption spectroscopy (FTIR-RAS) was also carried out in order to confirm the polymerization of monomers. The surface morphology of the films was investigated with an atomic force microscope (AFM). These results indicated that ADA and DAM were alternately deposited and polymerized with condensing agents on nanoscale.

Poly(4-phenoxybenzoyl-1,4-phenylene) (PPBP), which has high thermal stability and mechanical properties, was phosphonated by the three-step reaction. The phosphonated PPBP (P-PPBP) was characterized by FT-IR, H-1-NMR, elemental analysis, and ICP emission spectroscopy. The thermal and electrical properties of P-PPBP were also investigated. The P-PPBP film containing 40 mol % phosphonic acid groups showed a proton conductivity of about 10(-4) S cm(-1) at 90 %R.H.

Poly(3-(perfuorohexyl)thiophene) (PFHT) was synthesized from 2, 5-dibromo-3-(perfluorohexyl)thiophene via Grignard metathesis method. Obtained polymer was dissolved in a wide variety of organic solvents such as chloroform, tetrahydrofuran, and o-dichlorobenzene. Transition temperatures of PFHT were observed at 54 C due to melting of perfluorohexyl groups. Electron-withdrawing effect of C-F bonds and weak interaction among the side chains were observed as shorter maximum absorption wavelengths. Stable monolayers of PFHT were formed on a water subphase due to strong hydrophobicity and the weak interactions of the perfluorohexyl groups.

This paper presents an overview of the possibility and problems of new proton-conducting polymer electrolyte membranes based on hydrocarbon polymers. Due to their chemical stability, high degree of proton-conductivity, and remarkable mechanical properties, perfluorinated polymer electrolytes such as Nafion^®, Aciplex^®, Flemion^®, and Dow membranes are some of the most promising electrolyte membranes for polymer electrolyte fuel cells. A number of reviews on the synthesis, electrochemical properties, and fuel cell applications of perfluorinated polymer electrolytes have also appeared. While perfluorinated polymer electrolytes have satisfactory properties for a successful fuel cell electrolyte membrane, the major drawbacks to large-scale commercial use involve high cost and low proton-conductivities at high temperatures and low humidities. Presently, one of the most promising ways to obtain high-performance proton-conducting polymer electrolyte membranes is the use of hydrocarbon polymers for the polymer backbone. The present paper attempted to summarize the synthesis, chemical and electrochemical properties, and fuel cell application of new proton conducting polymer electrolytes based on hydrocarbon polymers that have been made during the past decade.

Two kinds of polymers were fabricated and tested as candidates of proton-conducting membranes for polymer electrolyte fuel cell (PEFC) applications. Poly benzimidazole (PBI) and poly(4-phenoxybenzoyl-1,4-phenylene, Poly-X 2000) (PPBP) were sulfonated and characterized as proton-conducting membranes. PBI was sulfonated as PBI-PS (propanesultone) and PBI-BS (butanesultone). PPBP was prepared at various sulfonation levels. Proton conductivities were measured at 60-160 degreesC. Power output characteristics of both polymers were measured by using commercial Pt/C electrodes. (C) 2002 Elsevier Science B.V. All rights reserved.

Organic-inorganic semiconductor heterostructures have been successfully fabricated by incorporating a polydiacetylene backbone into layered perovskite compounds by photopolymerization. The gamma-ray irradiation caused polymerization of aminodiacetylene cations, RNH3+, where R=CH3(CH2)(13)C=C-C=CCH2, in the solid salts of (RNH3)(2)PbBr4.

Novel organic-inorganic hybrid compounds, C10H10N2PbBr4 and C10H22N2PbBr4 were prepared and characterized by X-ray and optical measurements. The result of single crystal X-ray analysis showed that the inorganic region of C10H10N2PbBr4 consisted of one-dimensional chains of line-sharing PbBr6 octahedra, whereas that of C10H22N2PbBr4 consisted of two-dimensional sheets of corner-sharing PbBr6 octahedra. Each crystal exhibited an excitonic band at 307 nm for C10H10N2PbBr4 and 383 nm for C10H22N2PbBr4, which is attributed to the excitonic states of low-dimensional inorganic structures. These results indicate that the dimensional structure of these compounds can be systematically controlled by changing the chemical structure of organic ligands.

Organic-inorganic layered perovskite compounds described by (RNH3)(2)MX4 [R: alkyl group, M: divalent metals, X: halogen] were reported to form self-organized quantum-well structures. In this study, we aimed to synthesize novel organic-inorganic self-organized compounds with quaternary ammonium ions instead of primary alkylammonium ions. New compounds, [(C12H25)(2)(CH3)(2)N]PbBr2 (DLDMPbBr) and [(C12H25)(2)(CH3)(2)N]PbI2 (DLDMPbI) were synthesized, and the structural characterizations were performed on X-ray diffraction and optical measurements. The absorption peaks of these compounds showed higher photon energy than those of conventional layered perovskite compounds with primary alkylammonium ions. This result indicated that novel quantum confinement structures were constructed with the DLDMPbBr and DLDMPbI.