Polymerization of lactides and lactones. II. Ring-opening polymerization of ε-caprolactone and DL-lactide by organoacid rare earth compounds

摘要

Ring-opening polymerization of lactone and lactide have been initiated with rare earth organoacid compounds, such as lanthanum acetate in bulk. The polymerization mechanism is in agreement with the `nonionic-coordination-insertion' mechanism, which involves the selective cleavage of the acyl-oxygen bond of the monomer. These organoacid rare earth initiators can give high yield of medium to high molecular weight products. An interesting aspect of this investigation is the good agreement between the performance of the initiator and the solubility of the initiator in the monomer. However, the relatively slow initiation step makes it difficult to control the molecular weight and results in a broad molecular weight distributions.