Relation between Solution Properties and Degree of Acetylation of Chitosan:  Role of Aging

Abstract

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.

The Molecular Structure and Conformational Dynamics of Chitosan Polymers: An Integrated Perspective from Experiments and Computational Simulations

“…The transition between these distinct conformational states is modulated by the percentage and distribution of acetyl groups. The level of chitosan acetylation and the distribution of N-acetyl groups along the chain have been shown to influence properties such as solubility [142,143], biodegradability [144] and apparent pKa values [145,146]. Therefore, the percentage and distribution of acetyl groups are key parameters for determining if chitosan can effectively interact with biological systems [147].…”

“…Moreover, its apparent pKa is directly related to the level of acetylation, varying from 6.1 to 7.32 units accordingly to proton concentration in the milieu [145,[155][156][157][158]. Based on these observations, it was proposed that aggregation occurs upon high levels of acetylation due to reduction of the biopolymer net charge [145], implying in a predictable behavior of chitosan chains depending on its electric charge distribution in aqueous solution [145,146,159]. It was also proposed that the low tendency of fully deacetylated chitosan to form aggregates is due to electrostatic repulsion among protonated amino groups.…”

Influence of the Chemical Structure and Physicochemical Properties of Chitin- and Chitosan-Based Materials on Their Biomedical Activity

“…The solubility, conformation and dimensions of chitosan chains in aqueous media have been extensively studied as a function of the degree of acetylation (DA) (Berth et al, 1998;Berth & Dautzenberg, 2002;Schatz et al, 2003). Schatz et al have proposed general laws of chitosan behaviour in aqueous solutions (Schatz et al, 2003;Sorlier et al, 2001;Sorlier et al, 2002):…”

Viscous Degradation of Acidic Chitosan Solutions and its Ionic Probe Study

“…[3]. Впоследствии его объясняли либо кислотным гидролизом гликозидных связей (деструкцией) [2,[4][5][6][7][8], либо другими причинами: медленным образовани-ем внутримолекулярных водородных связей с уплотнением клубков [9,10], компактизацией макромолекул хитозана [11], снижением степе-ни структурированности растворов [12], пере-стройкой надмолекулярной структуры раствора [13], процессами структурной перестройки [14,15], агрегации [16], биодеградации [17]. Одна-ко авторы работы [2] замечают, что изменение конформаций макромолекул и степени структу-рирования не может приводить к практически полному разжижению концентрированных рас-творов полимера при длительном хранении.…”