Comparative in vitro degradation of surface-eroding poly(alkylene carbonate)s

Abstract

The current study probed and compared the susceptibility of five poly(alkylene carbonate)s, namely poly(ethylene carbonate), poly(trimethylene carbonate), poly(propylene carbonate) and two end-group modified poly(ethylene carbonate)s, to hydrolytic, enzymatic and oxidative degradation in vitro.None of the utilized polymers showed relevant signs of degradation in the pH range of 2–12. However, in the presence of cholesterol esterase and superoxide radical anions, all polymers underwent a significant mass loss without a change of the molecular weight, a clear sign for a surface erosion process. Poly(ethylene carbonate) was the most susceptible polymer to cholesterol esterase and superoxide radical anions and complete degradation occurred within only 4 and 2 weeks, respectively. By contrast, poly(trimethylene carbonate) and poly(propylene carbonate) only lost ~10–25 % of their initial mass under the same experimental conditions. An acetylation and lauroylation of the terminal hydroxyl groups of poly(ethylene carbonate) attenuated the enzyme- and oxidation-triggered surface erosion profile. For cholesterol esterase, >20 % of modified polymer was left after 4 weeks of incubation, while in the presence of superoxide radical anions >20 % remained after 3 weeks.Among the tested poly(alkylene carbonate)s, poly(trimethylene carbonate) and poly (propylene carbonate) revealed higher “stability” towards enzymatic and oxidative surface erosion compared to poly(ethylene carbonate). An end-capping of poly(ethylene carbonate) represents a promising strategy to modify (decelerate) the rate of polymer degradation.