Concentrated sulfonated poly (ether sulfone)s as proton exchange membranes

A novel bisphenol monomer containing concentrated electron rich phenyls is synthesized, which provides a locally and densely postsulfonation sites. Based on this monomer, a series of new sulfonated poly (ether sulfone)s (SPESs) are successfully obtained by nucleophilic substitution reaction, followed by postsulfonation using concentrated sulfuric acid. All the polymer membranes are readily prepared by solvent casting and exhibit excellent thermal stability and mechanical properties. As ion exchange capacity (IEC) ranging from 0.98 to 1.66 mequiv g(-1), the polymers afford considerable proton conductivity and water absorption. SPES-3 with IEC = 1.66 mequiv g(-1) shows equal proton conductivity (0.131 S cm(-1)) to Nafion 117 at 100 degrees C under fully hydrated state. At low IEC level (IEC = 0.92 mequiv g(-1)) SPES-1 also exhibits higher conductivity (>10(-2) S cm(-1)) than some earlier reported sulfonated random polymers. Their excellent performance is attributed to the internal structure of the polymers, which formed distinct phase separation between hydrophilic and hydrophobic moiety observed by SAXS. A combination of high proton conductivities, moderate water uptake, suitable mechanical properties and low swelling ratios for some of the obtained SPES indicates that they are good candidate materials for proton exchange membranes (PEMs). (C) 2012 Elsevier B.V. All rights reserved.