Polymerization of coordinated monomers. I. Stereoregulation in the free‐radical polymerization of methyl methacrylate‐zinc chloride or methyl methacrylate–stannic chloride complexes

Abstract

Abstract Stereoregulation in free‐radical polymerization was studied for the polymerization of the 2:1 or 1:1 complex of methyl methacrylate with ZnCl 2 or SnCl 4 . The complexes were polymerized with the use of a free‐radical initiator or γ‐ray irradiation either in the liquid or solid state at various temperatures ranging from −196 to 110°C, and the tacticities of the resulting polymers were determined by NMR spectroscopy. The polymers had different and characteristic values of tacticities depending upon the complex species, i.e., the kind of metal chloride and the stoichiometry. The tacticities were found to be independent of the polymerization temperature in both the liquid and solid states, in contrast with the fact that tacticities of the polymer from pure monomer changed markedly with the temperature. A temperature dependence appeared in the polymerization system, which contained more monomer than that corresponding to the 2:1 complex. The effect of the viscosity or the solid phase on the stereoregulation was examined in comparison with the polymerization of a mixture of methyl methacrylate and liquid paraffin. Two possible explanations regarding the stereoregulation mechanism are offered in relation to the structures of the complexes.