One‐Pot Random Copolymerization of Lactide and ε‐Caprolactone Mediated by a Tri‐Coordinated Zinc Catalyst

ABSTRACT

A zinc complex bearing imino‐phosphanamidinate chalcogenide ligands efficiently promotes the ring‐opening polymerization (ROP) of rac ‐lactide ( rac ‐LA) and ε‐caprolactone (ε‐CL), as well as their copolymerization. The complex demonstrated good control over the ROP of rac ‐LA, affording isotactic poly (lactic acid) (PLA) with high stereoselectivity ( P _m  = 0.82) and narrow dispersity (Ð < 1.3). One‐pot ring‐opening copolymerization (ROCOP) of rac ‐LA and ε‐CL in the presence of the zinc complex has been shown to produce random copolymers with predictable molecular weights. The fact that the randomization of the copolymers is driven concurrently by the formation of a gradient/partially random copolymer species and slow transesterification was established via in situ NMR spectroscopy. PLA‐ co ‐CL copolymers with varying CL/LA ratios were synthesized, displaying a single glass transition temperature ( T _g ) within the range between the T _g values of the corresponding homopolymers.