Synthesis of novel proton‐conducting highly sulfonated polybenzimidazoles for PEMFC and the effect of the type of bisphenyl bridge on polymer and membrane properties |
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Authors: | Feifei Ng Jennifer Péron Deborah J. Jones Jacques Rozière |
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Affiliation: | Institut Charles Gerhardt, UMR CNRS 5253, Laboratoire Agrégats, Interfaces et Matériaux pour l'Energie, Université Montpellier II, 34095 Montpellier Cedex 5, France |
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Abstract: | Six series of novel highly sulfonated polybenzimidazoles (sPBIs) with high molecular weight were prepared by direct polycondensation between 3,3′‐diaminobenzidine and original multisulfonated dinuclear dicarboxylic acids containing bridging ether, sulfone, and hexafluoroisopropylidene moieties. All reactions were carried out in polyphosphoric acid, which acts as both solvent and catalyst. The degree of sulfonation was modulated in the final products by varying the proportion of sulfonated to nonsulfonated dicarboxylic acids used in the synthesis. The high purity of the disulfonated and tetrasulfonated monomers allows wholly sulfonated homopolymers to be obtained. Confirmation of the chemical structure and the degree of sulfonation were derived from 1H nuclear magnetic resonance spectroscopy. Inherent viscosity was estimated as between 0.70 and 5.33 dL g?1 for sPBIs with ion exchange capacity in the range 0.87–4.68 mequiv g?1. Dynamic thermogravimetric analysis in air showed no weight loss below 350 °C (heating rate 5 °C min?1). The nature of the bisphenyl bridge has clear influence on the water uptake and proton conduction properties of the resulting sPBI membranes, with hexafluoroisopropylidene links providing materials of highest conductivity as well as favoring film‐forming characteristics. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 |
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Keywords: | characterization copolymerization electrolyte membrane films fuel cell highly sulfonated monomers ionomers polybenzimidazole polycondensation proton conductivity proton electrolyte |
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