Copolymerization of 2-carboxyphenyl acrylate with styrene and N-vinyl-2-pyrrolidone: Reactivity ratios, molecular weights and 13C n.m.r. spectra

Abstract

The free radical polymerization of 2-carboxyphenyl acrylate ( 1), styrene ( 2a) and N-vinyl-2-pyrrolidone ( 2b), was carried out in the presence of 2,2′-azobisisobutyronitrile, (AIBN), in N, N-dimethylformamide solutions at 50°C. Five copolymer samples of 1 and 2a and seven of 1 and 2b were prepared under similar conditions and the copolymer compositions were determined by elemental microanalysis. The results were used to calculate the corresponding copolymerization reactivity ratios by both the Fineman-Ross(FR) and Kelen-Tüdos (KT) methods. The reactivity ratios were r 1 = 0.61 ± 0.06 , r 2 a = 0.49±0.04 ; r 1 = 0.62±0.07 , r 2 b = 0.00±0.03 as determined by the KT method. These values are in good agreement with those determined by the FR method. The molecular weights of the homopolymers were determined by g.p.c. Molecular weights of copolymer samples were also measured by g.p.c. but no simple relationship between copolymer molecular weights and compositions was observed, probably due to the widely differing chemical structures of the samples in each series, and also due to the possibility of chemical transformations in the 1–2b series. 13C n.m.r. spectra of 2-carboxyphenyl acrylate, its homopolymer and its equimolar copolymer with N-vinyl-2-pyrrolidone were recorded in CDCl 3, and some assignments made from the off-resonance spectra. There was evidence of intra- and intermolecular hydrogen bonding in poly( 1) and in copoly( 1–2a).