Glycerol-modified poly(ε-caprolactone): an biocatalytic approach to improve the hydrophilicity of poly(ε-caprolactone)

Novel poly(ε-caprolactone) (PCL)–glycerol polyester was synthesized in one step in the presence of Novozym 435 under mild reaction conditions. The objective of the study was to investigate the feasibility of enhancing the hydrophilicity of PCL by condensing it with glycerol through biocatalytic approach. Effect of reaction time, glycerol-to-CL ratio and CL-to-toluene ratio was studied. The 1H NMR and GPC results established that self-condensation of CL units and condensation of CL with glycerol units take place simultaneously. When the glycerol content was 10 and 20 mol% with regard to CL, condensation continued for 6 h; further extension of reaction time resulted in the cleavage of ester linkages. When the glycerol content was increased to 40 mol%, the condensation of CL–glycerol units was accomplished in 4 h; however, the reaction had to get extended beyond 6 h for complete condensation of CL–CL units. The study revealed that the crystallinity and the melting temperature (Tm) of the products altered with an increase in the glycerol content. Furthermore, TGA and contact angle values of water on PCL and its glycerol derivative films revealed that the water uptake capacity of PCL too increased significantly with the increase in glycerol content, rendering PCL more hydrophilic