A series of aromatic sulfonated polyimides (SPIs) bearing sulfophenoxy side groups have been successfully synthesized and evaluated as polymer electrolyte membranes for fuel cell applications. The SPIs had high viscosity and gave tough and flexible membranes. The SPI membranes showed anisotropic membrane swelling in water with much larger dimensional change in thickness direction than in plane one. They showed the better proton-conducting performance even in the lower relative humidity (RH) range than the other SPI membranes, for example, a high proton conductivity of 0.05 S/cm at 50 % RH and 120 C. They maintained high mechanical strength and conductivity after aging in water at 130 C for 500 h, showing much better water stability compared with the main-chain-type SPI and side-chain-type SPI membranes reported so far. In polymer electrolyte fuel cells (PEFCs) operated at 90 C and 84-30%RH, they showed fairly high cell performances and have high potential for PEFC applications.
Electrophilic addition of 1 -[o- (phenylsulfanyl)phenyI] -2-(p-methoxypheny1)ethyne with electrophiles such as perchloric acid, tetrafluoroboric acid, bromine, and benzenesulfenyl chloride gave 1 -phenyl-I -benzothiophenium salts exclusively. The substituent effect on the intramolecular cyclization with electrophiles has been examined. The aryl-substituted alkynes afforded predominantly the cyclized 1 -phenyl-I -benzothiophenium salts but methyl-substituted alkynes yielded a mixture of the cyclized salt and the 1,2-addition product. In addition to the intramolecular cyclization at the intermediate vinyl cation or bridged ion, it is proposed, on the basis of the product from the reaction of methyl-substituted alkyne, that the 71 complex partly participates in the i n t ra m ol ec u I a r cyc I izat i o n .
Reaction of u-(aryloxy) phenylalkynes with electrophiles such as perchloric acid, tetrafluoroboric acid, benzenesulfenyl chloride, and iodine monochloride yielded dibenz [b,f] oxepine derivatives. Cyclization to the dibenz[b,f]oxepines competed with 1,2-addition of the electrophiles. The effect of substituents on the alkyne is also discussed.
Paper 2/01532C
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