Coordination polymerization of lactides, 1. Structure determination of obtained polymers

Racemic lactide was polymerized with various initiators containing Zn and Al, and the structures of the obtained polymers were determined by means of ¹³C NMR spectroscopy. The extent of transesterification reactions was calculated on the basis of the analysis of the methine carbon signal in the polymer ¹³C NMR spectra. Three groups of initiators can be distinguished in view of their influence on transesterification: ZnCl₂ exhibits the strongest transesterification activity, ZnEt₂ and ZnEt₂/Al(OiPr)₃ are among those of medium activity, and Al(acac)₃ does not show transesterification activity at all.