Well defined block copolymers of ε‐caprolactone and <scp>L</scp>‐lactide using Y₅(μ‐O)(OⁱPr)₁₃ as an initiator

Abstract

Abstract Diblock copolymers composed of poly(ε‐caprolactone) and poly(L‐lactide) were synthesized via sequential living ring‐opening polymerization of ε‐caprolactone and L‐lactide in dichloromethane initiated by Y 5 (μ‐O)(O i Pr) 13 (yttrium isopropoxide). A series of diblock copolymers was synthesized with ε‐caprolactone blocks of constant length (DP = 70) and lactide blocks of varying length (DP = 5–80), with polydispersities of 1,18–1,27. Molecular weights were close to theoretical values. 13 C NMR spectroscopy shows the absence of transesterification reactions and racemization. The thermal properties of the block copolymers were studied using differential scanning calorimetry. The block copolymers show a certain degree of phase mixing depending on the length of the poly(L‐lactide) blocks. Crystallization of L‐lactide sequences did not occur when the block length consisted of less than 40 L‐lactic acid residues.