Chemical modification of starch poly(vinyl acetate) materials

Starch-poly (vinyl acetate) materials were prepared through polymerization of vinyl acetate with starch using a ferrous ammonium sulphate-hydrogen peroxide redox system. Carboxymethylation through reaction with monochloroacetic acid in presence of alkali and graft polymerization with acrylamide and acrylonitrile of a material having 23% graft and 43% homopolymer were studied. Carboxymethylation occurs during the saponification process of starch-poly (vinyl acetate) in the alkaline medium of sodium monochloroacetate through reaction of the latter with the hydroxyl groups of starch and PVA. On the other hand, grafting seems to proceed via starch macroradicals which are created through the attack of the decomposition products of the redox system on the starch hydroxyl. Carboxymethylation of starch-poly (vinyl acetate) gives polyblended materials which exhibit 100% solubility at 100 degrees C. The same holds true with starch-poly (vinyl acetate) grafted with acrylamide after saponification. Replacement of acrylamide with acrylonitrile results in polyblended material, the solubility of which never exceeds 20% after saponification.