The mechanism of cationic polymerization of β-propiolactone

Abstract

The mechanism of cationic polymerization of β-propiolactone (PL) in methylene chloride under action of has been studied by the kinetic method. In the absence of additives, the process proceeds steadily via the active centers–acyl ions–and it involves the following reactions: 1. chain propagation, and 2. reversible combination of the active centers and carbonyl groups of monomer and polymer. The dielectric constant of the medium affects the reaction in the range of low monomer concentrations. In the presence of ether and ester additives another combination reaction between the active centers and additives is observed. Kinetical treatment of the results was performed, and the ratios were determined for the respective equilibrium constants and the rate constant of chain propagation which are a measure of relative basicity of ethers and esters. Ketones were shown to be inhibitors of the process. The rate constants of chain termination were estimated for different ketones on the basis of kinetic data.