Block Copolymerization of ϵ‐Caprolactone andL‐Lactide by Lanthanumtris(2,6‐Dimethylphenolate)s

Block copolymers of ϵ‐caprolactone (CL) and L‐lactide (LLA) can be prepared by ring‐opening polymerization in toluene using a single component lanthanum tris(2,6‐dimethylphenolate)s [La(ODMP)3] as a catalyst. The mutual reactivity of these two comonomers indicates the order of their addition is critical, that is CL must be first polymerized followed by the LLA polymerization. 1H and 13C NMR spectra of the polymer prepared clearly show the diblock copolymer structure without random placement. Analysis of the thermal property by differential scanning calorimetry (DSC) indicates that block copolymer has two melting endothermic peaks at 56.5°C and 155.6°C, corresponding to the poly(ϵ‐caprolactone) (PCL) block and poly(L‐lactide) (PLLA) block, respectively.