Enzymatic ring-opening polymerization of ε-caprolactone by Yarrowia lipolytica lipase in ionic liquids

Abstract

Yarrowia lipolytica (YLL), Candida rugosa (CRL), and porcine pancreatic lipase (PPL) were employed successfully as catalysts in the enzymatic ring-opening polymerization (ROP) of ε-caprolactone in the presence of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-butylpyridinium tetrafluoroborate ([BuPy][BF4]), 1-butylpyridinium trifluoroacetate ([BuPy][CF3COO]), 1-ethyl-3-methylimidazolium nitrate ([EMIM][NO3]) ionic liquids. Poly(ε-caprolactone)s (PCLs) with molecular weights (Mn) in the range of 300–9000 Da were obtained. 1H- and 13C-NMR analyses on PCLs formed by YLL, CRL, and PPL showed asymmetric telechelic -hydroxy-ω-carboxylic acid end groups. Differences between CP-MAS and MAS spectra are observed and discussed in terms of morphology. MALDI-TOF spectra show the formation of at least seven species. Differential scanning calorimetry (DSC) and Wide Angle X-Ray Scattering (WAXS) results demonstrate the high degree of crystallinity present in all the polyesters.