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Volume 59, Issue 8
Displaying 1-5 of 5 articles from this issue
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Yasumasa TOBA2002 Volume 59 Issue 8 Pages 449-459
Published: August 25, 2002
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSBased on our recent studies on photoinitiator systems, two onium borates, onium butyltriphenylborates for radical photopolymerization and onium tetrakis (pentafluorophenyl) borates for cationic photopolymerization, are discuss. The onium butyltriphenylborates were photodecomposed by various sensitizers and generated free radicals to initiate radical polymerization of acrylates. The rate of photoporimerization (Rp) by the onium borates was a few hundred folds higher than that for the corresponding onium salt or borate initiators. The high Rp value for the onium borates is due to the fact that two free radical species are generated from both the onium cation and the borate anion of the onium borates. The onium tetrakis (pentafluorophenyl) borates initiated the photopolymerization of epoxides and vinyl ethers by both the direct photolysis and the sensitized photolysis using anthacene sensitizers. An acid generated by photodecomposition of the onium borates was thermally decomposed and formed neutral compounds. The photoinitiation process between onium borates and sensitizers is based on the photoinduced electron transfer reaction. It was proved that the more negative the free energy change of the photoinduced electron transfer reaction, the higher the Rp value of cationic polymerization.View full abstractDownload PDF (2784K) -
Kenji MIYATAKE2002 Volume 59 Issue 8 Pages 460-473
Published: August 25, 2002
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSOur synthetic approaches toward the development of high temperature proton-conducting polymer electrolyte membranes for the application in fuel cells are reviewed. Aromatic polyethers and polysulfides with acidic function are targeted. Oxidative polymerization or polycondensation of thioanisole derivatives gave sulfonium-containing precursor polymers, which were sulfonated to afford poly (phenylene sulfide) bearing up to two sulfonic acid groups per repeating unit. Poly (phenylene sulfide sulfonic acid) shows good thermal stability and high proton conductivity (>10-2 Scm-1) at 180°C and 100% RH. Composite materials of poly (phenylene sulfide sulfonic acid) with poly (ethylene oxide) have been prepared for non-aqueous proton conduction. Unlike the conventional proton migration as hydronium ions, bare protons could move through the composite membranes along with the segmental motion of poly (ethylene oxide). Novel aromatic polyether copolymers composed of sulfonated tetraphenylphenylene (or hexaphenylbiphenylene), perfluorobiphenylene and hexafluoropentylene moieties have been synthesized. These polyether electrolytes are stable to hydrolysis and oxidation and show high proton conductivity. Analogs containing phosphonic acid and phosphinic acid have also been synthesized, of which electrolyte properties are investigated.View full abstractDownload PDF (3150K) -
Mitsutoshi JIKEI2002 Volume 59 Issue 8 Pages 474-483
Published: August 25, 2002
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSHyperbranched aromatic polyamides were prepared by one-step polycondensation of AEx type monomers. Despite the rigid aromatic structure, the hyperbranched polyamides showed good solubility and low viscosity in solution, which is typical for dendritic macromolecules. Direct polycondensation of AB4 and AB8 monomers gave polymers with a high degree of branching. Copolymerization of AB2 and AB monomers resulted in the formation of copolymers with low branching density. The influence of the branching density on the properties of resulting polymers is discussed. It is interesting to note that the small amount of AB2 branching point affected the properties of resulting copolymers dramatically. A novel successful thermal polycondensation of AB2 type monomers to form hyperbranched polyamides is also described.View full abstractDownload PDF (2283K) -
Yuichi OHYA2002 Volume 59 Issue 8 Pages 484-498
Published: August 25, 2002
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSPoly (lactic acid) s (PLAs) have a great potential for biodegradable biomedical materials. However limitation of their use still exists because of their crystallinity, lack of functionality, and so on. For further improvement of their properties and functionalities, the author synthesized various lactic acid copolymers having reactivity and amphiphilicity and/or branched structures such as poly (LA-random-depsipeptide), polydepsipeptide-block-PLA, comb-type PLA, branched PLA, PLA with terminal saccharide residues, and PLA-grafted polysaccharides. Microsphere (MS) s having reactive surfaces could be prepared using poly (LA-random-depsipeptide). Polydepsipeptide-block-PLA was convenient for preparation of MSs and polymeric micelles having highly reactive surfaces. It was found that the degradability and mechanical property of PLA could be controlled by introduction of branch points into PLA using comb-type PLA or branched PLA. PLA with terminal saccharide residues could provide PLA materials covered with saccharide residues. PLA-grafted polysaccharides showed phase-separated microstructure and controllable degradability. These lactic acid copolymers obtained are expected to be applied as novel biodegradable biomedical materials.View full abstractDownload PDF (4245K) -
Keiko TAWA2002 Volume 59 Issue 8 Pages 499-509
Published: August 25, 2002
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSImportant factors controlling a polarized-light induced orientation of azo-dyes in a polymer matrix were studied by polarized spectroscopies, i. e., polarized FT-IR, polarized UV-vis, and surface plasmon spectroscopy. In polymer matrices dispersing azo-dyes, polar groups or free volume in polymers were found to contribute to the isomerization process of azo-molecules and the photoinduced anisotropy ratio by the evaluation of orientation factors. In the polymer linked with an azo-dye, higher orientation was observed. This is due to the suppression of the rotational diffusion by linkage with a polymer chain, which causes gradual reorientation during frequent trans-cis-trans isomerization cycles. In thin polymer films, the reorientation was observed in the direction normal to the film plane.View full abstractDownload PDF (2534K)
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