“One-pot” synthesis and characterisation of novel P(3HB)–ethyl cellulose based graft composites through lipase catalysed esterification

Abstract

In the present study a series of graft composites with poly(3-hydroxybutyrate) (P(3HB) as side chains and ethyl cellulose (EC) as a backbone polymer was successfully synthesised through enzymatic esterification. A range of composites between P(3HB) and EC with different P(3HB) : EC ratios were prepared using lipase as a model catalyst. Subsequently, the resulting composites were then removed from the casting surface under ambient conditions. Finally the target composites were characterised in detail by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the thermo-mechanical behaviours of the grafted composites were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analyser (DMA) measurements. Whereas, hydrophobic and hydrophilic characteristics were studied through drop contour analysis using water contact angle (WCA) measurements. SEM analyses revealed that the uniform P(3HB) dispersion in the backbone polymer increased the area of P(3HB)–EC contact which further contributed to the efficient functionality of the resulting composites as evidenced by XRD, thermo-mechanical and WCA characterisation profiles of the tested composites. In comparison to the untreated P(3HB) a clear shift in the XRD peaks was observed which clearly indicated the breakdown of some crystalline domains and the regeneration of the amorphous material at a specific region of 2θ values in the case of the grafted composites. Interestingly, untreated P(3HB) was hydrophobic in nature and after lipase treatment P(3HB) and P(3HB)–EC based graft composites attained higher levels of hydrophilicity which is a desired characteristic to enhance the biocompatibility of the materials for proper cell adhesion and proliferation therefore, suggesting P(3HB)–EC as a potential candidate for tissue engineering/bio-medical type applications.