Poly(vinyl chloride) (PVC) pipes were chemically modified to produce a sulfonated polymer with dehydrochlorinated PVC samples as intermediates. Two intermediates were formed: (1) partially dehydrochlorinated PVC with long sequences of conjugated double bonds and (2) the product of the partial dehydrochlorination of PVC and the nucleophilic substitution of chlorine by hydroxyl groups. The IR spectra showed that the dehydrochlorinated samples were heterogeneous materials, showing different proportions of elimination products, hydroxyl substitution, and partial oxidation. Samples dehydrochlorinated with poly(ethylene glycol) with a molecular weight of 400 g/mol for 24 h and 15 min showed the highest sulfonation yield, which was related to the sulfonation mechanism occurring predominantly because of the presence of hydroxyl groups in a mixture of vinyl alcohol and vinyl chloride units. The sulfonation was confirmed by the presence of a medium-intensity band at 1180 cm(-1) assigned to sulfonic groups. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1474-1479, 2010