Anionic polymerization of lactones initiated by alkali graphitides. I. Polymerization of ϵ-caprolactone initiated by KC24

The influence of the reaction conditions (time, temperature, concentrations of the monomer, and the initiator) on the amount and composition of the oligomers and high molecular products formed during the heterogeneous anionic polymerization of ?-caprolactone was investigated. The polymerization was initiated by KC₂₄ in xylene or tetrahydrofuran. Conditions were found under which intra- and intermolecular transesterification was strongly suppressed, thus providing the opportunity for the formation of polyesters with viscometric molecular masses of more than 300,000 and good yields (80% and higher). The total quantity of products with a viscometric molecular mass below 2500 did not exceed 15%; that of the cyclic dimer was not in excess of 5%. Peculiar features of the KC₂₄ initiated polymerization are the insignificant rise in the number of oligomers and the formation of high polymers even in strongly diluted solutions of ?-caprolactone (0.2 mol/L and lower). The quantity and molecular mass of the polymers obtained decreased as the temperature increased. It was also established that the polymerization of the cyclic dimer of ?-caprolactone is not initiated by KC₂₄.