Cation-exchange composite materials were prepared by the sulfonation of the copolymer of styrene (St) and divinylbenzene (DVB) coated on glass fibers previously surface-treated by a silane coupling agent. The results show that the surface treatment of the glass fibers by the coupling agent gamma-(methacryloyloxyethyl) trimethoxysilane led to a vinyl functionalized fiberglass surface, which served to covalently bond the copolymer to the fiberglass. Increasing the amount of the coupling agent increased the degree of coating of the copolymer on the fiberglass. A cation-exchange composite with an exchange capacity of 4.08 mmol/g of resin was prepared by the copolymerization of St and DVB at a weight ratio of 95 : 5 for 30 min; this was followed by sulfonation of the copolymer at 100 degrees C for 12 h. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 944-949, 2011