Block and random copolymers of ε-caprolactone

Conditions of the living homopolymerization of epsilon-caprolactone (CL), lactides (LA), and of the homo-oligomerization of gamma-butyrolactone (BL) are briefly described. Then block and random copolymerizations of CL with LA are shortly reviewed. The microstructure of the resulting copolyesters in relation to some peculiarities of these processes is discussed in more detail. It is also shown that the otherwise 'non-polymerizable' BL does form high molecular weight copolymers with CL, containing up to 50 mol% repeating units derived from BL. Their molecular weight is controlled by the concentrations of the consumed comonomers and the starting concentration of the initiator. NMR and DSC data indicate the random structure of copolymers. TGA traces of the BL/CL copolymers show that the presence of the gamma-oxybutyryl repeating units randomly distributed within the poly(CL) chains improves the thermal stability of the latter. (C) 1998 Elsevier Science Limited. All rights reserved.