Synthesis And Characterization Of Sulfonated Arylene Polyimides: Candidates For Proton Exchange Membrane

A series of novel polymers, polyimide (PI), poly(arylene ether ketone) (PEK), poly (arylene ether sulfone) (PES) and poly(arylene ether nitrile) (PEN), hold excellent thermo stability and mechanical performance. Various approaches improve proton transport and proton conductivity of the polymers by modification (sulfonation in general). These modified polymers have properties desirable for proton exchange membranes (PEM) in fuel cells.A novel diamine, disodium 4, 4'-di(4-aminophenoxy)-3, 3'-disulfonate-l, 1'- diphenyl ketone, was prepared from the nucleopluTic substitution of disodium 4, 4'- difluoro-3, 3'-disulfonate-1,1'-diphenylketone and p-aminophenol. Polymerization of this diamine and 4, 4'-diamino-1, 1'-diphenyl ether with 3, 3', 4, 4'-tetracarboxyl dianhydride-1,1'-diphenyl ketone gave proton exchange copolyimide. The new diamine and its polyimide were charac terized with 1H-NMR, FT-IR and mass spectrum. Intrinsic viscosities, the thermostability were measured.A new bisphenol with imide ring can be synthesized by p-aminophenol and 3, 3', 4, 4'-tetracarboxyl dianhydride-1, 1'-diphenyl ketone (DTDA). Sulfonated poly (arylene ether ketone)s, poly (arylene ether sulfone)s containing pendant sodium sulfonated groups and imide rings were prepared by direct copolymerization. Fourier transform infrared,1H NMR, 13C NMR, 1H-1H COSY spectrum, HMBC spectrum were used to characterize the structures of the monomer and polymers. Membranes of SPEK-PI with DFK/Na-SDFK molar feed ratios of up to 40/60 and SPE S-PI with DFS/Na-SDFS molar feed ratios of up to 50/50 were cast from dimethyl sulfoxide polymer solutions. Membranes in acid form were then obtained by the treatment of the sodium-form membranes in 2N sulfuric acid at room temperature. Intrinsic viscosities, the thermostability, the mechanical properties, the conductivity, water uptake content and swelling ratio were measured. The sodium-form copolymers were thermally more stable than their acid forms. The proton conductivities of the copolymers were higher than 10-2 S/cm.Poly (arylene ether nitrile) were prepared by the similar method with 2, 6-difluro benzo-nitrile (DFBN), disodium 4, 4'-di(4-aminophenoxy)-3, 3'-disulfonate-l, l'-diphenylketone (Na-SDFK), the new bisphenol with imide ring or 2, 7-dihydroxy naphthalene. The polymers were characterized with FT-IR spectrum. Intrinsic viscosities, the thermostability, the mechanical properties, water uptake content and swelling ratio were measured.