Anionic polymerization of D,L-lactide initiated by lithium diisopropylamide

The anionic polymerization of D,L-lactide initiated by lithium diisopropyla mide.monoTHF complex was performed in different solvents and at various tem peratures. No polymerization took place in THF solution. In dioxane at 25 d egreesC the polymerization is fast and goes up to completion in few minutes . In toluene, due to solubility requirements, polymerizations were run at 7 0 degreesC. At initial stage of polymerization M-w/M(n)s were quite narrow, but at higher conversion a significant broadening occurred due to transest erification reactions. The latter were identified by C-13 NMR analysis, whi le MALDI-TOF spectra revealed the simultaneous presence of cyclic and linea r oligomers substantiating the occurrence of both intra and inter ester exc hange processes. At low conversion, polymers exhibited a highly syndiotacti c microstructure. (C) 2001 Elsevier Science Ltd. All rights reserved.