Eco-design and tunable structure-properties of chitosan-epoxy-glycerol-silicate biohybrids using integrated crosslinking.

Tunable structure-properties were achieved for chitosan-epoxy-glycerol-silicate (CHTGP) biohybrids, eco-designed via integrated amine-epoxy and waterborne sol-gel crosslinking reactions. Medium molecular weight chitosan (CHT), with 83 % degree of deacetylation was prepared by microwave-assisted alkaline deacetylation of chitin. The amine group of chitosan was covalently bonded to the epoxide of 3-glycidoxypropyltrimethoxysilane (G) for further crosslinking with a sol-gel derived glycerol-silicate precursor (P) from 0.5 % to 5 %. The impact of crosslinking density on the structural morphology, thermal, mechanical, moisture-retention and antimicrobial properties of the biohybrids were characterized by FTIR, NMR, SEM, swelling and bacterial inhibition studies and contrasted with a corresponding series (CHTP) without epoxy silane. Water uptake was significantly reduced in all biohybrids with a 12 % window of variation between the two series. Properties observed in biohybrids with only epoxy-amine (CHTG) or sol-gel crosslinking reactions (CHTP), were reversed in the integrated biohybrids (CHTGP) to impart improved thermal and mechanical stability and antibacterial activity.