Lipase-catalyzed ring-opening polymerization and copolymerization of 15-pentadecanolide

Enzymatic ring-opening polymerization of a 16-membered lactone, 15-pentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization with Pseudomonas fluorescens lipase (lipase PF) catalyst afforded the corresponding polyester in high yields. The rate of the polymerization catalyzed by lipase PF at a temperature lower than 45°C was very small, whereas the polymerization at higher polymerization temperature (≥60°C) proceeded much faster. Lipase derived from Pseudomonas cepacia was also active for the polymerization of PDL. The polymerization catalyzed by Candida cylindracea lipase at high temperature (75°C) afforded the polymer with molecular weight up to 2.0 × 104. The polymerization behavior of PDL through lipase catalysis has been compared with that of Ε-caprolactone (Ε-CL). PDL showed an enzymatically higher polymerizability than Ε-CL, despite the smaller ring-strain of PDL, which is due to the stronger recognition of PDL by lipase. Enzymatic copolymerization of PDL with other lactones using lipase PF catalyst produced copolymers with molecular weight of several thousands. From 13C NMR analysis, the diad sequence distributions were determined.