Effect of Low-Temperature Solution Polymerization Conditions of Acrylonitrile on the Molecular Characteristics of Polyacrylonitrile

Abstract

Acrylonitrile (AN) was solution-polymerized in dimethyl sulfoxide (DMSO) and tertiary butyl alcohol (TBA) at 30,40 and 50°C using a low temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN), and effects of polymerization conditions were investigated in terms of molecular structures of polyacrylonitrile (PAN). Low polymerization temperature by adopting ADMVN proved to be successful in obtaining PAN of high molecular weight with smaller temperature rise during polymerization. Through a polymerization of AN in DMSO at 30°C, PAN having weight-average molecular weight (M w ) of 931,000 was obtained, whose polydispersity index of 1.89. For the same polymerization conditions, DMSO was slightly superior to TBA in increasing molecular weight of PAN. In addition, DMSO was superior to TBA in diminishing molecular structural defects such as enaminonitrile structure in PAN polymerized, indicating that differences in polymerization and termination rates due to a different polymerization mechanisms using two polymerization solvents. The M w , linearity, molecular structural regularity, and whiteness were higher with PAN polymerized at lower temperatures.