Functional and degradable copolyesters by ring-opening copolymerization of epoxides and anhydrides

Abstract

The ring-opening copolymerization (ROcoP) of epoxides and anhydrides is exploited to afford 4 structurally diverse and functional copolyesters. Mixtures of 2 epoxides (allyl glycidyl ether and butylene oxide) with 1 anhydride (succinic, glutaric, phthalic and homo phthalic anhydride) are copolymerized in the presence of bis(triphenylphosphine)iminium chloride (PPNCl) as organocatalyst. All monomer combinations yield vinyl-functionalized materials with alternating epoxide-anhydride units, statistical incorporation of both epoxides along the polymer chain and molar masses up to 28.3 kg/mol. The copolyesters are amorphous with a Tg between –39 °C and 38 °C. Together with the molar mass, the anhydride dictates the thermal stability of the copolyesters with glutaric anhydride resulting in a remarkably high thermal stability up to 310 °C. In a post-polymerization step, the pendant double bonds are radically crosslinked to gels with swelling ratios above 1500 % and comparable to enhanced thermal stability with respect to the non-crosslinked, parent copolyesters. The degradation of the 4 copolyesters (before and after crosslinking) is tested in abiotic and enzymatic conditions: The highest degradation rates are observed for the non-crosslinked materials in enzymatic conditions with a mass loss of up to 60 % after 27d. After crosslinking, the gels are more stable against degradation under both conditions, although a decrease in the gel content and a decrease in mass indicates that degradation still takes place.