Dissolution behavior and conformation change of chitosan in concentrated chitosan hydrochloric acid solution and comparison with dilute and semidilute solutions

Abstract

Viscosity, pH and electrolytic conductivity of dilute, semidilute and concentrated chitosan solution with hydrochloric acid adding were compared and the change in conformation of chitosan in concentrated solution was discussed. The dissolution behavior of chitosan in concentrated chitosan hydrochloric acid solution was investigated through determination of solution turbidity, microstate and size of chitosan particle. It was found that the concentration, degree of deacetylation (DD) of chitosan and content of hydrochloric acid in solution showed significant effects on the changes in viscosity, pH, and electrolytic conductivity of chitosan solution as hydrochloric acid added. And the transforms of above properties of chitosan solution during dissolution were corresponding to the proportion of hydrochloric acid to chitosan from which we could deduced that the confirmation of chitosan changed from entangling with each other to becoming compact coils due to electrostatic screen of Cl− and hydrophobic aggregation of chitosan with high concentration. In concentrated suspension solution, chitosan particles agglomerated first and then expended before disintegrating and dissolving with hydrochloric acid adding, resulting in solution turbidity, size and microstate of chitosan particle changed obviously during dissolution.