Effects de la substitution du cycle pyrrolidone‐2 par un groupement méthyle sur le processus de polymérisation

Abstract

AbstractWe tried to evaluate the reason for the very low polymerizability of methyl derivatives of 2‐pyrrolidone in the presence of anionic polymerization catalysts. The polymerizability estimated from the influence of the methylated group on the reactivity of the lactam ring (steric, inductive, and thermodynamic factors) does not agree with the experimental results of homopolymerization and copolymerization of 2‐pyrrolidone. The substitutional effects on the propagation process were analyzed and an explanation which is based on the slow‐down of the molecular growth and the crystallization of the reaction mixture is proposed. Thus, in copolymerizations with a small percentage of substituted lactams, the propagation is very slow with regard to the crystallization, which would allow a quick encagement of the active site by hydrogen bonds, and lead to the spontaneous blocking of polymerization. If this percentage increases, the crystallization cannot take place, and this would, as a consequence. favor all the secondary reactions leading to the formation of bicyclic dimer and oligomers.A “chain multiplication” reaction was found in some cases.