Effect of preparative variables on the properties of poly(dl-lactide-co-glycolide)- methoxypoly(ethyleneglycol) copolymers related to their application in controlled drug delivery

The effect of certain preparative variables, such as the composition of the feed, the reaction time and the reaction temperature, on the properties of prepared poly(dl-lactide-co-glycolide)-methoxypoly(ethyleneglycol) (PLGA-m PEG) copolymers and on the yield of the reaction was investigated. The resu lts with regard the molecular weight and yield were discussed in relation t o a polymerization mechanism proposed recently (Du et al., 1995. Macromolec ules 28, 2124-2132). The higher the PEG content of the feed the lower the m olecular weight of the copolymer and the yield of the reaction. The breadth of the molecular weight distribution decreased initially with time, but ap peared to stabilize later at low values. Both the ethylene oxide content an d the lactide to glycolide molar ratio in the copolymer depended on the rea ction temperature and varied with the reaction time. PLGA and mPEG appeared to be partially miscible, and copolymers containing approximately 40% mol or higher ethylene oxide exhibited crystallinity. (C) 1999 Elsevier Science B.V. All rights reserved.