Abstract
Two types of sulfonated polyimides (SPIs) (main-chain-type and side-chain-type) were prepared from 1,4,5,8-naphthalenetetracarboxiylic dianhydride, sulfonated diamines such as 4,4'-bis(4-aminophenoxy)biphenyl-3,3'-disulfonic acid, 2,2'-bis(3-sulfopropoxy)benzidine, 3,3'-bis(3-sulfopropoxy)benzidine and nonsulfonated diamines. Membrane morphology, water vapor sorption, water stability and dimensional change, proton conductivity and methanol permeability of these SPI membranes were investigated. The resulting SPI membranes displayed high proton conductivities comparable to those of Nafion 117 at high relative humidity above 80%. They displayed excellent water durability and different dimensional change based on the membrane morphology. Most of the SPIs showed much lower methanol permeabilities than Nafion membrane and are expected to have great potential for polymer electrolyte fuel cell or direct methanol fuel cell applications
