Synthesis of poly(ester-anhydride)s based on poly(ε-caprolactone) prepolymer

The objective of this study was to prepare high molecular weight poly(ester-anhydride)s by melt pol condensation. The polymerization procedure consisted of the preparation of carboxylic acid terminated poly( epsilon -caprolactone) prepolymers that were melt polymerized to poly (epsilon -caprolactone)s containing anhydride functions along the polymer backbone. Poly( epsilon -caprolactone) prepolymers were prepared using either 1,4-butanediol or 4-(hydroxymethyl)benzoic acid as initiators, yielding hydroxyl-terminated intermediates that were then converted to carboxylic acid-terminated prepolymers by reaction with succinic anhydride. Prepolymers were then allowed to react with an excess of acetic anhydride, followed by subsequent polycondensation to resulting high molecular weight poly(ester-anhydride)s. Upon coupling of prepolymers, size exclusion chromatography analyses showed an increase from 3600 to 70,000 g/mol in number-average molecular weight (M-n) for the 1,4-butanediol initiated polymer, and an increase from 7200 to 68,000 g/mol for the 4-(hydroxmethyl)benzoic acid-initiated polymer. 4-Hydroxybenzoic acid and adipic acid were also used as initiators in the preparation of poly(epsilon -caprolactone) prepolymers. However, with these- initiators, the results were not satisfactory. (C) 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 176-185, 2001.