A detailed characterization of hydroxylated poly(vinyl chloride) (PVC), obtained by modification of PVC with p-mercaptobenzyl alcohol and its crosslinked homologues, is described. The selective character of the modification with respect to the thiol group and the presence of free hydroxyl groups in the polymer is shown using H-1-NMR. The stereoselectivity of the reaction is provided from C-13-NMR. The presence of physical interactions in the system by hydrogen bonding is deduced from light scattering measurements and analysis of the thermal and mechanical properties. The critical concentration of hydroxyl groups required in the chains in order to form an efficient physical network is determined to be about 4%. Chemical networks are obtained by reaction of hexamethylene diisocyanate with the hydroxyl groups present in the polymer, and the process is followed by IR spectroscopy.