Oligomerization and copolymerization of gamma-butyrolactone - A monomer known as unable to homopolymerize .1. Copolymerization with epsilon-caprolactone

Copolymerization of gamma-butyrolactone (gamma BL) with epsilon-caprolactone (epsilon CL) initiated with aluminium isopropoxide trimer ([Al((OPr)-Pr-i)(3)](3), (A(3))) is described. Copolymers with molecular weights (<(M)over bar (n)>) up to 3 . 10(4) and containing up to 43 mol-% repeating units derived from gamma BL are prepared. Their molecular weight is controlled by the concentrations of the consumed comonomers and the starting concentration of initiator (<(M)over bar (n)> = (86.09 . [gamma BL](c) + 114.14 . [epsilon CL](c))/3 [Al((OPr)-Pr-i)(3)] + 60.10). C-13 NMR and DSC data are indicative of a pseudoperiodic or random copolymer structure.