Polylactones, 2 Copolymerization of glycolide with β‐propiolactone, γ‐butyrolactone or δ‐valerolactone

Abstract

Abstract Numerous copolymerizations of glycolide with β‐propiolactone, γ‐butyrolactone or δ‐valerolactone were conducted either in bulk or in nitrobenzene solution at temperatures in the range of 20 to 150°C. Three classes of catalysts were used, namely acidic catalysts initiating cationic polymerizations, complexing catalysts initiating insertion mechanisms, and anionic catalysts. The molar composition of the copolyesters was determined from 1 H NMR spectra and the sequence distribution of the comonomers from 13 C NMR spectra. No reasonable copolymerization of glycolide and βhyphen;propiolactone was obtained at 20°C in nitrobenzene, whereas all catalysts yielded copolyesters at 100°C. In the case of glycolide/γ‐butyrolactone only bulk copolymerizations at 60°C with acidic initiators were successful. Under other conditions only homopolymerization of glycolide was observed. Copolymerizations of glycolide and γ‐valerolactone were performed in bulk and in nitrobenzene with both acidic and complexing initiators, whereas anionic initiators only caused homopolymerization of glycolide. Acidic initiators favored the incorporation of δ‐valerolactone, whereas the complexing initiators favored the incorporation of glycolide. The crystallinity of the glycolide/δ‐valerolactone copolymers was characterized by means of differential scanning calorimetry, and a good agreement with the expectations from both molar composition and sequence distribution was found.