Synthesis and Properties of Sulfonated Poly(arylene ether)s with Flexible Oligomeric Phenylene Ether Segments

Novel sulfonated poly(arylene ether)s derived from omega,omega'-dihydroxypoly(1,4-phenylene ether)s (DHPE) and mixed dihalide monomers of 3,3'-disulfo-4,4'-dichlorodiphenylsulfone disodium salt (S-DCDPS) and 2,6-dichlorobenzonitrile were synthesized. As DHPE has molecular weight distribution with phenylene rings lower than ca. 10 units, experimental determination of its average molecular weight made it possible to be used as a monomer to prepare sulfonated poly(arylene ether)s. Membranes derived from resultant polymers showed a similar level of proton conductivity to those of other common sulfonated poly(arylene ether)s; however, its softening temperature was much lower. Therefore, good MEA was able to be obtained by hot-pressing at relatively lower temperature without shrinking around electrode. The membrane with an ion exchange capacity of 0.9 showed lower methanol permeability and dimensional change in methanol solution assuming a condition of DMFC than standard perfluorosulfonic acid polymer membrane (PFSA).