OPTIMIZATION TECHNIQUES FOR CARBODIIMIDE ACTIVATED SYNTHESIS OF POLY((RS)-3,3,3-TRIFLUOROLACTIC ACID) - STATISTICALLY DESIGNED EXPERIMENTS TO OPTIMIZE POLYMERIZATION CONDITIONS

Poly(( RS)-3,3,3-trifluorolactic acid) was synthesized from the alphah ydroxy acid, ( RS)-3,3,3-trifluorolactic acid, by esterification with 1,3-diisopropylcarbodiimide condensing agent and catalytic salts of 4- (dimethylamino)pyridine and protic acids. Literature data of related e sterification chemistry indicated that temperature, solvent, and catal yst can affect the polymerization chemistry. Optimization of polymer p roduct yield was desirable to understand better how to control the rea ction as well as producing high molecular weight polymer in sufficient quantity for subsequent characterization. The goals of this study wer e to maximize the polymer yield and molecular weight through the use o f statistically designed polymerization experiments. A D-optimal desig n was developed for the completion of this study. Two different solven ts and catalysts were investigated. Also, the level of catalyst was va ried. As a result of this experimental design study, optimum condition s for highest product yield and molecular weight (indicated by solutio n viscosity) were identified. Response surface plots show that polymer ization in methylene chloride at 5-7 degrees C with the catalytic salt 4-(dimethylamino)pyridinium 4-toluenesulfonate (DPTS) at fractional m olar equivalent (with respect to monomer) quantities provided polymer consistent with the study objectives. (C) 1998 Elsevier Science B.V. A ll rights reserved.