Effect of reaction medium on radical copolymerization of acrylonitrile with vinyl acids

Radical polymerization of acrylonitrile (AN) with methacrylic acid (MAA) an d itaconic acid (IA) was carried out in a mixture of dimethylformamide (DMF ) and water at 70 degreesC using alpha, alpha'-azobisisobutyronitrile (AIBN ) as an initiator. Monomer feed in the polymerization vessel was 98:2 (AN:M AA/IA) in the molar ratio, and the DMF: H2O ratio was varied between 20:80 and 80:20 (w/w). Copolymers were characterized by FTIR, carbon, hydrogen, n itrogen elemental CHN analysis, H-1- and C-13-NMR, and viscometry. The rate of polymerization (R-p) was found to decrease with an increase in DMF conc entration in the reaction medium, that is, in 20% DMF for AN-MAA system, th e R-p is 1.23% min(-1) in 1 h of polymerization, while in 80% DMF, R-p is r educed to 0.37% min(-1). The nature of the vinyl acid also affects the R-p. It has been shown that the rate of polymerization is higher for an AN-MAA system as compared to an AN-IA system (R-p = 1.0% min(-1)) and the methacry lic or itaconic acid content in the copolymer increases with an increase in the DMF concentration. The MAA content in the poly(AN-MAA) polymer produce d in 20% DMF is 3.2 mol %, which increases to 6.1 mol % (calculated through FTIR spectra) when DMF is increased to 80% in the reaction medium. The int rinsic viscosity [eta] of the poly(AN-IA) and poly(AN-MAA) copolymers in DM F was found to be in the range of 0.67-2.90 dLg(-1) depending on the reacti on medium. In determining the intrinsic viscosity, a definite deviation fro m rectilinearity of the concentration dependence in the high-dilution regio n is observed, thereby demonstrating the polyelectrolyte behavior of these polymers. Through FTIR and NMR spectral studies, PAN homopolymer and other copolymers have shown the formation of a small quantity of acrylamide units . In addition copolymer P-10, which contains 10.1 mol % IA, has shown anhyd ride formation. (C) 2000 John Wiley & Sons, Inc.