Styrene-butadiene rubber membranes with methylene bridges, stemming from the concomitant in situ Friedel-Crafts alkylation during a chloromethylation reaction, were prepared and used in the pervaporative separation of benzene/cyclohexane mixtures. A set of four membranes with different crosslinking extents was achieved by the variation of the [Trimethylchlorosilane (TMCS)]/[Paraformaldehyde (PF)] molar ratios with respect to the styrene (St) unit. Study of the swelling of membranes by the mixture components individually and by their feed mixture compositions, 1 : 1 and 1 : 9, was conducted. The total flux (J) and the separation factor (alpha) were assessed as a function of the feed composition, temperature, and [St unit]/[TMCS]/[PF] molar ratios. The highest J and alpha measured in this study were 1401 g m(-2) h (1) and 28.50, respectively. The diffusion selectivity was found to depend on the crosslinking extent of the membrane. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1455-1467, 2012