STUDIES ON ALKALINE DISCOLORATION OF ACRYLONITRILE POLYMER IN DIMETHYLFORMAMIDE

Abstract

Alkaline discolorations of poylacrylonitrile, acrylonitrile-methyl acrylate copolymer and polyacrylonitrile-polymethyl acrylate blend in dimethylformamide were investigated in terms of conjugated double bonds formation. Viscosity and infrared spectrum of recovered polymer were also measured.The experimental results are summarized in the followings:1) Discoloration is time dependent, but the change of viscosity occurs instantaneously. Therefore, discoloration reaction and chain degradation may be considered to be two independent processes. Residual discoloration after acidification of discolored solution is also time dependent so that at least two types of mechanisms may be presumed for the discoloration.2) Alkaline discoloration of polyacylonitrile decreases remarkably with introduction of comonomer and the behavior of discoloration is reasonably explained in terms of the sequence length of acrylonitrile which relates to the conjugated double bonds formation. The large difference in discoloration behavior between copolymeric system and polymer blend provides an useful method to investigate the microstructure of acrylonitrile polymer.3) By the application of the method, it was confirmed that the fractionation of acrylonitrilemethyl acrylate copolymer had been carried out in accordance to molecular weight, but not polymer composition.4) Viscosity of alkaline degradated polymer seems to be independent of the original molecular weight and increases with increased of comonomer content. This phenomenon is discussed from the view point of abnormal linkage between acrylonitrile units in the polymer.5) Infrared spectrum of alkaline treated polymer is compared with that of heat treated polymer.6) The effects of polymerization conversion on polymer composition was investigated in terms of alkaline discoloration for different copolymeric system. The experimental result satisfies qualitatively the calculated relationship expected from monomer reactivity ratios.