Kinetics on the copolymerization of acrylonitrile with itaconic acid or methyl acrylate in dimethylsulfoxide by NMR spectroscopy

Abstract

The free radical solution polymerization of acrylonitrile (AN) with itaconic acid (IA) or methyl acrylate (MA) was carried out in dimethylsulfoxide (DMSO) using 2 2'-azobisisobutyronitrile (AIBN) as the initiator. Based on the monomer conversion versus time data, the copolymerization rate was retarded by IA but promoted by MA. The monomer sequence distribution was characterized by 13C NMR to explain the significant difference in the copolymerization kinetics of the ANIA and AN-MA copolymers. The results of the copolymer composition curves and 13C NMR spectral analysis illustrated that the penultimate model was suitable for describing the copolymerization behavior of AN-IA, and the terminal and penultimate models were adequate for AN-MA. The penultimate reactivity ratios, rMA, were ~2 times higher than rIA, indicating that the reactivity of AN-terminated radical having MA as the preceding group was higher than that with IA. Then, the corresponding content of triads sequence AN-AN-AN (AAA) in the AN-MA copolymers was higher than those in the AN-IA copolymers. The appearance of new resonance signals of the quaternary and methyl carbon indicated a higher content of IA in copolymers. The higher IA concentrations the lower viscosity-average molecular weight of the polymers. The decrease in the molecular weight was correlated to the formation of the oligomers.