An Evaluation of the Effect of Reaction Conditions in the Enzymatically Catalyzed Synthesis of Poly(ϵ‐Caprolactone)

Abstract

AbstractPolycaprolactone (PCL) is a biocompatible polymer that degrades slowly in physiological environments. Properties, including flexibility and easy processability, endow PCL with a high potential for being used in biomedical and pharmaceutical applications. Typically, PCL is synthesized by high energy‐consuming ring‐opening polymerization processes catalyzed by metallic compounds. In addition, obtaining safe PCL requires tedious purification procedures that, in turn, reduce yield and generate large amounts of toxic emissions. As an alternative, PCL can be synthesized by employing lipases as enzymatic catalysts. However, the properties of the resulting polymer are highly dependent on the experimental conditions. In this paper, we studied the effect of synthesis variables, such as solvent, temperature, the concentration of monomer and catalyst, and lipase source, on the molecular weight of PCL and the reaction yield. According to the results, the highest molecular weight and monomer conversion were obtained when ϵ‐caprolactone was polymerized by 10 % of heterogeneous catalyst that contains Candida Antarctica lipase B in toluene at 70 °C. Under these conditions, polymerization exhibited controlled characteristics and allowed obtaining a polymer with a molecular weight of 14.12 kDa while the dispersion index was 1.34. The enzymatic catalyst was stable and allowed PCL formation over five usage cycles with minor activity loss. The reported findings suggest that immobilized Candida Antarctica lipase B is a suitable catalyst for the synthesis of PCL and could be employed at a large scale with minor energy consumption and shorter reaction times compared with the conventional processes.