Proton conducting polymers derived from polybenzoyl-1,4-phenylene (PBP) and poly-p-phenoxybenzoyl-1,4-phenylene (PPBP) were synthesized by the 'Colon synthesis technique'. The sulfonation of these proton conducting polymers was carried out using either sulphuric acid or tetramethylsiliylchlorosulfonate (TMSCl) as sulfonating agent, and their thermal properties were evaluated. Both sulfonated PBP and PPBP are thermally stable up to at least 215°C. The sulfonated sPPBP exhibited good conductivity as proton conducting membranes at room temperature and were tested as electrolyte membranes for a single direct methanol fuel cell (DMFC) in terms of water absorption, methanol permeability and electrical performance. The water uptake of the sPPBP was found to be larger than that of the sPBP, i.e., 65 and 43 mol%, respectively. The permeability to methanol was found to be 10 times lower than sPPBP and sPBP compared to a Nafion Ò membrane. In spite of this, performance in a single DMFC was found to be twice inferior to that with Nafion Ò 117. Optimisation of the sulfonation level and of the electrode-membrane interfaces was lead to better results.

Poly(para-phenylene)s (PPPs) are an interesting class of rigid-rod polymers that have excellent thermal and mechanical properties. Because of their high degree of crystallinity and lower permeability to methanol, PPPs are insoluble and infusible. A number of methods have been developed to synthesize substituted sulfonated PPPs bearing lateral chains to improve their solubility. In this work, a comparison of the physicochemical properties of three PPPbased polymers is made with respect to Nafion membranes. One of these polymers was prepared with the postsulfonation method, and the other two were made with a new method of grafting developed in the Commissariat à l'Energie Atomique laboratory (a grafted sulfonated PPP polymer and a grafted perfluorinated sulfonated polymer). The sulfonated PPP polymers were examined for their mechanical properties, small-angle X-ray scattering, water absorption, proton conductivity, and methanol permeability. Relations between structures and properties were also investigated. Performances in fuel-cell tests were also investigated.

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