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

A random terpolymer Of L-lactide (LL), epsilon -caprolactone (CL) and glycolide (G) has been synthesized in bulk at 130 degreesC 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, (HNMR)-H-1, (CNMR)-C-13, DSC and TG. Molecular weight characterization by GPC shows a unimodal molecular weight distribution with values of (M) over bar (n)=1.01 x 10(5) g mol(-1) and (M) over bar (w)/(M) over bar (n)=2.17. Compositional and microstructural analysis by (HNMR)-H-1 and (CNMR)-C-13, 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. (C) 2001 Society of Chemical Industry.