Tailor-made polyesters based on pentadecalactone via enzymatic catalysis

Copolyesters of pentadecalactone (PDL) with gamma-methacryloyl-epsilon-caprolactone (McrCL) and gamma-benzoyl-epsilon-caprolactone (BenzCL) were successfully prepared by means of enzymatic copolymerization using Novozyme 435 as catalyst and were characterized by means of NMR, SEC and DSC analyses. With gamma-acetyl-epsilon-caprolactone (AcetCL) and gamma-acryloyl-epsilon-caprolactone (AcrCL) as comonomers for PDL enzymatic copolymerization failed. Under polymerization conditions AcetCL and AcrCL rearrange into the thermodynamically more stable butyrolactones. An enantiomeric excess of BenzCL, not of McrCL, was found in the corresponding copolymer (poly(PDL-co-BenzCL)). DSC results prove clearly that by introducing functional caprolactone units along the PPDL backbone, the crystallinity of PPDL decreases. PDL based copolymers with double bonds, epoxide and amide groups in the main chain were obtained via enzymatic copolymerization of PDL with Ambrettolide (Am), the corresponding epoxide (AmE) and 1-oxa-8-aza-cyclotetradecan-9,14-dione a 14-membered cyclic ester amide (cEA). The presence of these functional groups in the PPDL backbone allows tuning of the composition and consequently the properties of PPDL by lowering its crystallinity.