Polymer Electrolyte Membranes Derived from New Sulfone Monomers with Pendent Sulfonic Acid Groups

New monomers containing two or four pendent phenyl groups were synthesized by bromination of bis(4-fluorophenyl) sulfone, followed by Suzuki coupling with benzeneboronic acid. The resulting monomers were converted to the corresponding sulfonated monomers having two or four pendent sulfonic acid groups, predominately at the p-phenyl position. Aromatic nucleophilic substitution (SNAr) polycondensation using the di- and tetrasulfonated monomers provided sulfonated poly(arylene ether sulfone) copolymers S2-PAES-xx and S4-PAES-xx, respectively, where xx refers to the molar ratio of the sulfonated to non-sulfonated pendent phenyl monomer. Copoly(arylene ether sulfone)s based on the corresponding nonsulfonated monomers were also synthesized for a parallel study on postpolymerization sulfonation of these copolymers. Postsulfonation occurred predominately at the para-pendent phenyl site, and the reactions were complete within a short time (about 30 min), without evidence of chain degradation. Flexible and tough membranes having high mechanical strength were obtained by solution casting of all four series of copolymers. The copolymers with two or four pendent sulfonic acid groups had high proton conductivities in the range of 44-142 mS/cm for S2-PAES-xx and 51-158 mS/cm for S4-PAES-xx at room temperature, respectively. The methanol permeabilities of these copolymers were in the range of 0.8 x 10-8-15.0 x 10-7 cm2/s, which is lower than Nafion (16.7 x 10-7 cm2/s). The S4-PAES-xx membranes displayed better properties (lower water uptake and higher proton conductivities) than the S2-PAES-xx membranes, which can be attributed to the more blocky architecture of the sulfonic acid groups in the S4 membranes. A combination of high proton conductivities, low water uptake, and low methanol permeabilities for some of the obtained copolymers indicated that they are good candidate materials for proton exchange membrane in fuel cell applications.De nouveaux monom\ue8res comportant deux ou quatre groupes ph\ue9nyliques lat\ue9raux ont \ue9t\ue9 synth\ue9tis\ue9s par bromuration du bis(4-fluoroph\ue9nyl) sulfone, suivie du couplage de Suzuki par l\u2019acide benz\ue8ne-boronique. Les monom\ue8res ainsi obtenus ont \ue9t\ue9 transform\ue9s en leurs monom\ue8res sulfon\ue9s correspondants, ces derniers pr\ue9sentant deux ou quatre groupes d\u2019acide sulfonique lat\ue9raux, principalement en position para-ph\ue9nyle. La polycondensation par substitution nucl\ue9ophile aromatique (SNAr) au moyen de monom\ue8res disulfon\ue9s et t\ue9trasulfon\ue9s a permis la synth\ue8se des copolym\ue8res poly(aryl\ue8ne \ue9ther sulfone) S2-PAES-xx et S4-PAES-xx respectivement, o\uf9 xx correspond au rapport molaire du monom\ue8re de ph\ue9nyle lat\ue9ral sulfon\ue9 sur celui non sulfon\ue9. On a \ue9galement synth\ue9tis\ue9 des copolym\ue8res poly(aryl\ue8ne \ue9ther sulfone) \ue0 partir des monom\ue8res non sulfon\ue9s correspondants pour effectuer une \ue9tude comparative de la sulfonation apr\ue8s la polym\ue9risation de ces copolym\ue8res. La postsulfonation a eu lieu essentiellement aux groupements ph\ue9nyles lat\ue9raux en position para et les r\ue9actions ont pris peu de temps (environ 30 minutes) \ue0 s\u2019effectuer, sans qu\u2019il y ait d\ue9gradation des cha\ueenes. On a obtenu, par fusion, des membranes flexibles et solides pr\ue9sentant une force m\ue9canique \ue9lev\ue9e pour les quatre s\ue9ries de copolym\ue8res. Les copolym\ue8res ayant deux ou quatre groupes d\u2019acide sulfonique lat\ue9raux pr\ue9sentent des conductivit\ue9s protoniques \ue9lev\ue9es allant de 44 \ue0 142 mS/cm dans le cas des S2-PAES-xx et de 51 \ue0158 mS/cm dans le cas des S4 PAES xx, \ue0 temp\ue9rature ambiante. La perm\ue9abilit\ue9 au m\ue9thanol de ces copolym\ue8res varie de 0,8 x 10-8 \ue0 15,0 x 10-7 cm2/s, ce qui est plus faible que dans le cas du NafionMD (16,7 x 10-7 cm2/s). Les membranes de S4-PAES-xx montrent de meilleures propri\ue9t\ue9s (absorption d\u2019eau faible et conductivit\ue9s protoniques \ue9lev\ue9es) que celles des membranes S2 PAES-xx, ce qui peut \ueatre attribuable \ue0 l\u2019architecture poly\ue9drique plus importante des groupes d\u2019acide sulfonique dans le cas des membranes S4. La combinaison d\u2019une conductivit\ue9 protonique \ue9lev\ue9e, d\u2019une absorption d\u2019eau faible et d\u2019une perm\ue9abilit\ue9 faible au m\ue9thanol, dans le cas de certains des copolym\ue8res obtenus, montre qu\u2019ils feraient de bons mat\ue9riaux pour la production des membranes \ue9changeuses de protons utilis\ue9es dans les piles \ue0 combustible.Peer reviewed: YesNRC publication: Ye