Lipase-Catalyzed Copolymerization of ω-Pentadecalactone (PDL) and Alkyl Glycolate: Synthesis of Poly(PDL-co-GA)

Candida antarctica lipase B (CALB) was found to be an efficient catalyst for copolymerization of ω-pentadecalactone (PDL) and ethyl glycolate (EGA) to form poly(PDL-co-glycolate) [poly(PDL-co-GA)] copolymers. The copolymerization reactions took place at 50-100 °C and were promoted by vacuum. The formed copolyesters contained up to 30 mol% glycolate (GA) units and had typical molecular weight (M w ) ranging from 18000 to 21000 and polydispersity values between 1.6 and 1.9. Compared to EGA content in the monomer feeds, the GA unit content in the corresponding copolymer products was found to be significantly lower primarily attributed to partial EGA elimination during the polycondensation under vacuum. NMR analyses, including statistical analysis on repeat unit sequence distribution, indicate that the PDL and GA unit arrangements in the copolymer chains are not completely random, but with a significant tendency toward an alternating structure. The synthesized poly(PDL-co-GA) copolyesters with various GA content were successfully transformed to nanoparticles with an average size between 170 and 190 nm.

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