Preparation of high molecular weight polyvinylalcohol by low temperature azoinitiator

Abstract

Vinylacetate was bulk-polymerized at 30, 40, and 50 degrees C using a low temperature initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (ADMVN), and effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of polyvinylacetate (PVAc) and the corresponding polyvinylalcohol (PVA) obtained by saponifying with sodium hydroxide. Low polymerization temperature and low conversion by adopting ADMVN proved to be successful in obtaining PVA of high molecular weight. At conversion of below 20%, PVAc having a number-average degree of polymerization (P-n) of 6800-10,100 was obtained, whose degree of branching for acetyl group was calculated to be 0.60-0.70, 0.75-0.90, and 1.05-1.45 at 30, 40, and 50 degrees C, respectively. Saponifying this PVAc yielded PVA having a P-n of 3100-6100. (C) 1997 Elsevier Science Ltd. All rights reserved.