Synthesis of graft copolymers of chitosan-poly(caprolactone) by lipase catalysed reactive extrusion

Publication date: Available online 15 April 2019Source: Carbohydrate PolymersAuthor(s): Alankar A. Vaidya, Ibrar Hussain, Marc Gaugler, Dawn A. SmithAbstractChitin is an abundant natural polymer and its deacetylated derivative chitosan has been a focus for the development of biobased, biocompatible and antimicrobial materials. In this work, a green and scalable route to grafting polycaprolactone (PCL) to chitosan using an enzyme catalysed reactive extrusion process is described. FTIR, 1H and 13C NMR spectroscopy and HSQC analysis confirm grafting of PCL to chitosan and show differences in the grafting pattern obtained using two commercially produced lipase enzymes from Candida antarctica (CALB® and NovoCor®). The thermostable NovoCor enzyme gave a much higher grafting yield (96.3%) than the less thermostable CALB enzyme (5.90%). In the esterification reaction, CALB preferentially catalyses reaction on primary –OH groups at the C-6 position of chitosan, whereas NovoCor catalyses on the secondary –OH groups of chitosan at the C-3 position. This is related to the differences in the selectivity of the two lipase enzymes. The control copolymer synthesized without enzyme did not show any grafting reaction. The degree of crystallinity and thermal stability of the lipase catalysed copolymer was reduced compared to unmodified chitosan. Moreover, the PCL grafted chitosan produced by a solvent free reactive extrusion route retained antimicrobial property against E.coli. Such graft...
Source: Carbohydrate Polymers - Category: Biomedical Science Source Type: research