Random copolymerization of epsilon-caprolactone with lactide using a homosalen-Al complex.

The bulky substituents of homosalen complexes decelerate the ring-opening polymerization of racemic lactide (LA). The substituent effects provide the first catalysis for the random copolymerization of epsilon-caprolactone (CL) with LA (CL/LA = 1:1). The copolymerization of CL with LA (CL/LA = 1:1) by the iPr(3)Si-substituted homosalen-Al complex 2 affords the practically random copolymer in a controlled manner. The reactivity ratios, average sequence lengths of CL and LA during the copolymerization, abundance ratios of the triad caproyl sequences, and T(g) value of the obtained copolymer indicate that the copolymer was random with a somewhat alternative tendency (r(CL)r(LA) = 0.80).