Abstract
Ring-opening polymerization of ε-caprolactone has been successfully conducted using an immobilized form of Candida antarctica lipase B as catalyst. The effects of enzyme concentration, reaction medium, reaction temperature and time on monomer conversion and product molecular weight were investigated. Through optimization of reaction conditions, poly(ε-caprolactone) (PCL) was obtained with 99% monomer conversion and a number-average molecular weight (Mn) of 18870 g/mol. The reaction system was then scaled up, and PCL was synthesized in 78% isolated yield, with Mn and polydispersity index of 41540 g/mol and 1.69, respectively. The solid-state properties of this sample were systematically evaluated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The product PCL showed excellent thermal stability, with degradation of the main chain in the temperature range of 280–450°C. Remarkably, this high molecular weight PCL was a typical crystalline polymer with a high degree of crystallinity observed by DSC, WAXD and POM.
Acknowledgements
The research was supported by Natural Science Foundation of China (21074042). Helpful discussions and corrections from Prof. Xuexun Fang are gratefully acknowledged.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.