FREE-RADICAL AQUEOUS SLURRY POLYMERIZATIONS OF ACRYLONITRILE .1. END-GROUPS AND OTHER MINOR STRUCTURES IN POLYACRYLONITRILES INITIATED BY AMMONIUM PERSULFATE SODIUM METABISULFITE

Polyacrylonitriles prepared by aqueous free-radical slurry polymerizat ion at 40 degrees C using ammonium persulfate and sodium metabisulfite as redox initiator have been examined by FTi.r. and by high-field C-1 3 and H-1 n.m.r. They have been shown to contain small quantities of a crylamide and acrylic acid units and to possess predominantly sulfonat e and non-sulfur containing end-groups derived principally from transf er to bisulfite ion during the polymerization. Other end-groups presen t in low concentration are sulfate and hydroxyl; the former probably a rises from initiation by sulfate radical anions and the latter either from transfer to water or by adventitious hydrolysis of some of the su lfate end-groups. Because they contain few groups capable of initiatin g intramolecular cyclization, the polyacrylonitriles are white with no sign of discoloration.