Poly(L-lactide) microspheres with controlled crystallinity

Biodegradable polyester microspheres were synthesized directly from L-lacti de by ring-opening dispersion polymerization. Diameter distributions of the se particles were narrow (D-w/D-n < 1.27), molecular weight of polymer cons tituting microspheres ranged from 7 to 270 kDa, and its molecular weight po lydispersity was low (M-w/M-n < 1.2). Degree of crystallinity of poly(L-lac tide) in microspheres was controlled in the range from 0 to 60%, by the app ropriate thermal treatment of suspensions of microspheres. This procedure d id not affect diameters of microspheres, their colloidal stability, and mol ecular weight of poly(L-lactide) in polymer particles. It has been establis hed that the determination of the degree of crystallinity of poly(L-lactide ) in microspheres by C-13 CP-MAS NMR yielded results more reproducible than determined by DSC. (C) 2000 Elsevier Science Ltd. All rights reserved.