Relation between solution properties and degree of acetylation of chitosan: role of aging.

Aging of solutions of chitosan varying in degree of acetylation (DA) and degree of dissociation (alpha) was studied using two techniques. The first concerned potentiometric experiments performed during 3 days on solutions having the same concentration of amino groups (5.2% < DA < 70.6% and 0 < alpha < 1.1). The presence of aggregates at low alpha certainly depends on electrostatic interactions for low DA values and on hydrophobic interactions and H-bondings for high values. When alpha increases, the role of the cationicity of the amine groups, which depends on DA, seems to play a more important role on the behavior of the polymer chains. The second regarded capillary viscometric experiments performed during 5 days on solutions of the same polymer concentration (5.2% < DA < 70.6% and 0 < alpha < 0.30). The observations mentioned above and the results obtained in a previous paper (Biomacromolecules 2001, 2 (3), 765) are confirmed, and the influence of the electroviscous effects is discussed.