Solution polymerization behavior of acrylonitrile by moderate temperature azoinitiator

Acrylonitrile (AN) was solution-polymerized in dimethyl sulfoxide (DMSO) and tertiary butyl alcohol (TBA) at 30, 40 and 50 degrees C using a moderate temperature initiator, 2.2'-azobis(2.4-dimethylvaleronitrile) (ADMVN); the effects of type and amount of solvent, polymerization temperature, and initiator concentration were investigated. On the whole, the experimental results corresponded to predictions. Moderate: polymerization temperature using ADMVN proved to be successful in obtaining polyacrylonitrile (PAN) of high molecular weight and high conversion with smaller temperature rise during polymerization. The polymerization rates of AN in DMSO and in TEA were proportional to the 0.61 and 0.94 powers of ADMVN concentration, respectively. For the same polymerization conditions, DMSO was slightly superior to TEA in increasing molecular weight of PAN. On the other hand, DMSO was inferior to TEA in causing conversion to polymer, indicating that the initiation rate of AN in DMSO was less than that in TEA. These effects could be explained by an activation energy difference. For PAN produced in DMSO at 30 degrees C, weight-average molecular weight of 865,000 was obtained, with a polydispersity index of 1.89. (C) 1999 Elsevier Science Ltd. All rights reserved.