Electrolytic conductivity behaviors and solution conformations of chitosan in different acid solutions

Electrolytic conductivity behavior of chitosan in strong acid solution (0. 1 M hydrochloric acid) and in weak acid solution (0. 1 M propionic acid, 0.1 M acetic acid and 0.1 M formic acid) and its effective factors such as temperature, salt, degree of deacetylation and molecule weight of chitosan were investigated. The inner structure of chitosan films formed from their above different acid solutions were observed with a scanning electron microscope (SEM). It was found that the electrolytic conductivity behaviors of chitosan in the above two-type acid solutions were absolutely different and were all concentration-dependent from which we can deduce that chitosan chains interact with carboxylic acid molecules strongly in weak acid solutions and entangle strongly with each other while chitosan chains have weak impact on counterions chlorions in hydrochloric acid solution and they become extended coils because of electrostatic repulsion. The structure of chitosan films observed from their SEM photos supports this conclusion firmly. Unchanging activation energy for conduction of chitosan in carboxylic acid solution after a certain concentration also demonstrates that there is order structure formed by chitosan and carboxylic acid molecules. This is the first paper supplying detailed electrolytic data about chitosan solution; therefore, it will stimulate further theoretical studies and promote the application of chitosan. (c) 2005 Elsevier Ltd. All rights reserved.