Kinetics, absorption and diffusion mechanism of crosslinked Chitosan Hydrogels

Abstract

Green polymers are extremely useful for various environmental applications. One such biopolymer is Chitosan. In this study, crosslinked and physical Chitosan hydrogels were synthesized. The swelling of disc-shaped hydrogels crosslinked using different concentrations of Glutaraldehyde were compared with physical film and bead shaped hydrogels. Best swelling of around 3000% was observed in case of square film shaped hydrogels but they lacked rigidity and dissolved in mild acids. In case of crosslinked hydrogels, as the crosslinker concentration increased, the hydrogels entrapped less water but gained better mechanical strength. Characterization of synthesized crosslinked hydrogels was carried out using FTIR, TGA and DSC. Equilibrium swelling results indicated more water absorption at acidic pH (2.5). Simultaneously, increase in temperature led to enhancement of swelling degree. The hydrogels trapped more water leading to increased swelling, in case of lower molar salt concentrations. Second order kinetics was followed due to stress relaxation of polymeric chain. Diffusion was found to be anomalous since exponent values lied between 0.5 and 1. Peleg‟s and Exponential association model were used to carry out absorption modeling. The data was found to fit the Peleg‟s absorption model. Degree of swelling is a major factor for deciding a hydrogels utility. Swelling ability, biocompatibility and availability of lone pairs of oxygen and nitrogen on the surface of CS makes it ideal for applications in drug delivery, controlled release of fertilizers and adsorption of environmental contaminants.