Chlorine atoms of polyvinylchloride were replaced by sulfo and benzimidazolyl groups by nucleophilic substitution. It was shown that the reaction of the polymer with 2-mercaptobenzimidazole sodium salt and sulfuric or chlorosulfonic acid proceeds via dehydrochlorination. The synthesized materials were used for preparing proton-conducting membranes with a proton conductivity of 5.6 x 10(-4) to 5.9 x 10(-3) S/cm.