Multiblock sulfonated–fluorinated poly(arylene ether)s for a proton exchange membrane fuel cell

• Published in: Polymer (Guilford) 2006-05, Vol.47 (11), p.4132-4139
• Main Authors: Ghassemi, Hossein, McGrath, James E., Zawodzinski, Thomas A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Morphology; Multiblock copolymers; Organic polymers; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Proton exchange membrane
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2006.02.038

New proton exchange membranes were prepared and evaluated as polymer electrolytes for a proton exchange membrane fuel cell (PEMFC). Sulfonated–fluorinated poly(arylene ether) multiblocks (MBs) were synthesized by nucleophilic aromatic substitution of highly activated fluorine terminated telechelics made from decafluorobiphenyl with 4,4′-(hexafluoroisopropylidene)diphenol and hydroxyl-terminated telechelics made from 4,4′-biphenol and 3,3′-disulfonated-4,4′-dichlorodiphenylsulfone. Membranes with various sulfonation levels were successfully cast from N-methyl-2-pyrrolidinone. An increase sulfonated block size in the copolymer resulted in enhanced membrane ion exchange capacity and proton conductivity. The morphological structure of MB copolymers was investigated by tapping mode atomic force microscopy (TM-AFM) and compared with those of Nafion ® and sulfonated poly(arylene ether) random copolymers. AFM images of MBs revealed a very well defined phase separation, which may explain their higher proton conductivities compared to the random copolymers. The results are of particular interest for hydrogen/air fuel cells where conductivity at high temperature and low relative humidity is a critical issue.