Ring‐opening polymerization of 1‐methyltrimethylene carbonate by rare earth initiators

Abstract

Abstract Ring‐opening polymerization of 1‐methyltrimethylene carbonate (MTMC) initiated by highly active single‐component rare earth tris(2,6‐di‐ tert ‐butyl‐4‐methylphenolate)s [Ln(OAr) 3 , Ln = La, Dy, Y] or yttrium isopropoxide [Y(O i Pr) 3 ] is reported for the first time. PolyMTMC ( M w = 8.4 × 10 4 , molecular weight distributions = 1.5) initiated by La(OAr) 3 at [MTMC]/[initiator] = 1000 was obtained with the yield over 99% in toluene within 1 h at 30 °C. Random and block copolymers of MTMC with ε‐caprolactone (CL), 2,2‐dimethyltrimethylene carbonate (DTC) or polyethylene glycol (PEG) including poly(MTMC‐ r ‐CL), poly(MTMC‐ b ‐CL), poly(MTMC‐ r ‐DTC), poly(MTMC‐ b ‐DTC), and poly(MTMC‐ b ‐PEG‐ b ‐MTMC) were synthesized. The differential scanning calorimetry results show that thermal behaviors of the polymers sensitively depend on their compositions and chain structures. Furthermore, the measurements of 1 H‐ 1 H COSY and density functional theory calculation are applied to investigate the mechanism. The polymerization of MTMC takes place according to a coordination‐insertion mechanism, and the ring is opened via acyl‐oxygen bond cleavage resulting in a LnO active center. There exist two ring‐opening modes of MTMC in which mode b , breaking the CH 2 OCO bond, is the major pathway. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3807–3815, 2010