(115a) Dependence of the Hydrolytic Degradation of Poly(ester-anhydride) Copolymers on pH, Temperature, and Time

Renewable resource copolymers were developed containing both ester and anhydride linkages to allow for hydrolytic degradation with the objective of being able to control degradation time under variable temperature and pH conditions. It was expected that the anhydride bonds would hydrolyze initially, thereby reducing the molecular weight significantly, and a slower hydrolysis of the ester bonds would follow until complete degradation was achieved. Copolymers derived from 1,3-propanediol and malonic acid (PDO-MA) and 1,3-propanediol and itaconic acid (PDO-IA) were synthesized in a previous study at 155 °C using aluminum chloride. Water absorption and changes in dry weight of samples are monitored as a function of pH, time, and temperature. Changes in copolymer chemical structure as a function of pH, time, and temperature were analyzed with Fourier transform infrared (FTIR) spectroscopy by monitoring the absorbance changes corresponding to the anhydride and ester groups. The changes in molecular weight and polydispersity index are monitored by gel-permeation chromatography (GPC). The hydrolytic degradation of renewable poly(ester-anhydride) copolymers was studied as a function of pH, time, and temperature.