Preparation of Alkali Swelling Chitosan and its Freezing-Swelling Behaviour

Abstract

Chitosans with different structure were prepared by deacetylation of chitin by means of orthogonal design experiment and research on the swelling behaviours of the chitosan after LiOH-freezing treatment was conducted. It was found that low temperature and the presence of LiOH played a significant role in promoting the swelling of chitosan. The degree of swelling first increased and then decreased with the increase of LiOH concentration and reached the maximum swelling ratio when the concentration of LiOH was 2.5 mol L^-1. According to the experimental results, alkali concentration, reaction temperature and time in deacetylation reaction had a more obvious impact on alkali swelling degree of chitosan. FT-IR spectra and X-ray diffraction showed that deacetylation made the structure of chitosan looser, which facilitated the diffusion and penetration of little molecules. By changing the alkali concentration and regulating the temperature and deacetylation time, chitosan with higher molecular weight and capable of swelling in alkali solution can be produced.