Proton exchange membrane for fuel cell application was synthesized from a hydrophobic polystyrene-butadiene rubber (PSBR) via sulphonation at different temperatures (22, 35, 55, 65, and 75 degrees C) and varying time with chlorosulphonic acid. Infra-red spectroscopy (IR) and proton nuclear magnetic resonance (H-1-NMR) were used to confirm the occurrence of sulphonation. Sulphonation occurred only on the phenyl ring with a maximum degree of sulphonation of 70.96 mole percent. Consequently, 10(-3)-10(-2) S/cm proton conductivity was achieved. Two models for the reaction kinetics were investigated: first-order reversible and first-order irreversible, respectively. However, the reaction kinetic was found to obey the first-order reversible model. The activation energy (E-a) of the reaction was calculated to be 41.56 kJ/mol of PSBR repeat unit, which is an indication that the reaction is nonspontaneous. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3473-3479, 2010