Synthesis and characterization of sulfonated-fluorinated, hydrophilic-hydrophobic multiblock copolymers for proton exchange membranes

Nanophase separated ionic-hydrophobic block copolymers may be more suitable as proton exchange membranes than random copolymers. A series of multiblock copolymers, composed of alternating segments of fully disulfonated poly(arylene ether sulfone) and highly fluorinated poly(arylene ether sulfone), were synthesized from hydrophilic and hydrophobic telechelic oligomers having a variation of molecular weights. The high reactivity of the fluorinated oligomers made unnecessary the use of high reaction temperatures, and thus the coupling reactions may be free of ether-ether interchange side reactions. The copolymers were characterized with regard to proton conductivity, water uptake and self-diffusion coefficient of water, and the results were compared to those of Nafion and a partially disulfonated BPSH-35 random copolymer.