Synthesis and characterization of a random terpolymer of L‐lactide, ϵ‐caprolactone and glycolide

A random terpolymer of L ‐lactide (LL), ϵ‐caprolactone (CL) and glycolide (G) has been synthesized in bulk at 130 °C using stannous octoate as the coordination–insertion initiator. The terpolymer, poly(LL‐ ran ‐CL‐ ran ‐G), has been characterized by a combination of analytical techniques: GPC, 1 H NMR, 13 C NMR, DSC and TG. Molecular weight characterization by GPC shows a unimodal molecular weight distribution with values of M n = 1.01 × 10 5 g mol −1 and M w / M n = 2.17. Compositional and microstructural analysis by 1 H NMR and 13 C NMR, respectively, reveal a terpolymer composition of LL:CL:G = 74:15:11 (mol%) with a chain microstructure consistent with random monomer sequencing. This latter view is supported by the terpolymer temperature transitions ( T g and T m ) from DSC and the thermal decomposition profile from TG. The results and, in particular, the conclusion that it is a random rather than a statistical terpolymer are discussed in the light of current theories regarding the mechanism of this type of polymerization.