Cyclopolymerization. III. Kinetics of polymerization and copolymerization of vinyl‐<i>trans</i>‐cinnamate

Abstract

Abstract The kinetics of cyclopolymerization and cyclo‐copolymerization of vinyl cinnamate were studied. The mechanism of chain propagation during the cyclopolymerization of vinyl cinnamate was considered. By determination of the residual unsaturation of the polymer (I.R. and U.V. spectrometry and bromometry) at different monomer concentrations, it was possible to evaluate the ratio of the cyclization rate constant to the vinyl propagation rate constant; it is equal to 13. In the range of low monomer concentrations the polymerization of vinyl cinnamate is of first order with respect to monomer concentration, and of one half order with respect to initiator concentration. At monomer concentration higher than three mole·1. minus;1 the reaction becomes independent of monomer concentration, and first order with respect to the initiator. Modified copolymer composition equations were derived taking due account of the different reactivity of the monomer radical before and after cyclization; consequently three reactivity ratios r 1 , r 2 , and r 3 have been defined, and the experimental methods for their evaluation determined. On the basis of these equations the following reactivity ratios have been evaluated: vinyl cinnamate(M 1 )‐vinyl acetate r 3 = 1.2 ± 0.1 and r 2 = 0.04; M 1 ‐vinyl pyrrolidone r 3 = 1.15–1.30 and r 1 = 0.01; M 1 ‐methacrylonitrile r 3 = 0.15 and r 2 = 4; M 1 ‐styrene r 1 = 0.25 ± 0.1 and r 2 = 1.25 ± 0.1. The interpretation of these data suggests formation of a pseudo‐cyclic benzyl radical stabilized by resonance before addition of the second vinyl monomer.