New multiblock copolymers of sulfonated poly(4′-phenyl-2,5-benzophenone) and poly(arylene ether sulfone) for proton exchange membranes. II

Rigid-rod poly(4′-phenyl-2,5-benzophenone) telechelics were synthesized by Ni(0) catalytic coupling of 2,5-dichloro-4′-phenylbenzophenone and the end-capping agent 4-chloro-4′-fluorobenzophenone. The degree of polymerization was determined by 13C NMR. The telechelics produced were selectively sulfonated by concentrated sulfuric acid at 50 °C. The degree of sulfonation was controlled by varying the reaction time and was determined by titration. The nucleophilic step copolymerization of the fluoroketone activated sulfonated poly(4′-phenyl-2,5-benzophenone) oligomer (Mn=3.05×103 g/mol) with hydroxyl terminated biphenol based polyarylethersulfone (Mn=4.98×103 g/mol) afforded an alternating multiblock sulfonated copolymer that formed flexible transparent films, in contrast to the high molecular weight rigid rod homopolymers. They were tested for water absorption and proton conductivity by specific impedance. The synthesis and characterization of these multiblock copolymers are reported.