Synthesis of Novel Biodegradable Poly(Ester-Anhydride)s

Abstract

Poly(ϵ-caprolactone)s containing one and variable numbers of anhydride functions along the polymer backbone were synthesized and characterized. The inclusion of a single anhydride unit involved the coupling of monofunctional carboxylic acid-terminated prepolymers using diphenyl chlorophosphate. The prepolymers were produced using stannous octoate as catalyst and ethanol as the initiator, yielding mono-functional hydroxyl-terminated intermediates which were reacted with succinic anhydride in the presence of 1-methylimidazole. Diphenyl chlorophosphate was then added to a solution of the carboxylic acid-terminated prepolymer and triethylamine in 1,2-dichloroethane, and the reaction was carried out for 5 hours at room temperature to yield a polyester containing a single anhydride unit. The synthesis of polymers containing a variable number of anhydride linkages per chain was carried out in a similar manner using difunctional carboxylic acid-terminated prepolymers as chain-extending segments, and monofunctional carboxylic acid-terminated prepolymers as end-capping units. The difunctional hydroxyl-terminated poly(ϵ-caprolactone) prepolymers were produced using diethylene glycol as the initiator, and then reacted with succinic anhydride to form difunctional carboxylic acid-terminated prepolymers.