A series of novel copoly(p-phenylene)s (PPs) containing an alkyl pendant were successfully synthesized via Ni(O)-catalyzed coupling polymerization. Sulfonated copolymers (SPPs) were achieved by postsulfonation from concentrated H2SO4. SPPS showed good solubility in polar aprotic solvents and gave flexible, tough, and transparent free-standing films by solvent casting. The ion exchange capacities (IECs) of the membranes ranged from 2.50 to 2.65 meq/g. All SPP membranes displayed proton conductivity similar to or higher than that of Nafion, especially at high relative humidity (>70% RH) (SPP-1: 0.271 Scm(-1), SPP-2: 0.284 Scm(-1), SPP-3: 0.212 S cm(-1), Nafion: 0.127 Scm(-1); at 80 degrees C and 95% RH). They also exhibited acceptable water uptake in the range of 52-56 vol% at 80 degrees C with little dimensional change. The gas permeability of the SPP membranes was much lower than that of Nafion 112. Therefore, these materials are promising for fuel cell application. (C) 2010 Elsevier Ltd. All rights reserved.