Chitosan is only soluble in acidic solutions, so how can we dissolve it in a basic solution?
Volume 131, Issue 3 February 5, 2014
J of Applied Polymer Science
Dissolution and stability of chitosan in a sodium hydroxide/urea aqueous solution
Maybe you can find some information for chitosan be dissolved in NaOH in this paper.
The deacetylation of chitin was studied as a function of NaOH concentration, re-action time and temperature as determined by acid-base titration. Deacetylationwas performed by classical heating or under microwave irradiation. Microwaveexperiments were carried out to compare the results with selected examples fromthe Chinese literature. The maximum degree of deacetylation (88 %) was ob-tained after 30 min of classical heating (135 °C) in 50 wt % NaOH solution.
Chitin and chitosan are copolymers of N-acetylglucosamine(2-acetamido-2-deoxy-b-D-glucopyranose) and D-glucos-amine (2-amino-2-deoxy-b-D-glucopyranose). The differenceis due to the different degree of deacetylation (DD). In general,chitin with a DD of > 75 % is called chitosan (see [13]). Thepreparation of chitosan is, in principle, not difficult but verytime-consuming, which is typical of natural products. Deace-tylation was frequently carried out in concentrated NaOH so-lution under classical conditions [14–18], Chinese researchersin particular performed deacetylation under microwave irra-diation [19–22]. The conditions differ in temperature, reactiontime, ratio of chitin to NaOHaq, and concentration of causticsoda solution.The solubility of the biopolymer is determined by theamount of free NH2groups, hence chitosan can be removedfrom chitin by extraction with diluted acids (acetic acid, HCl).Except for the OH groups, these NH2functions are the func-tionalities where most chemical modifications take place. TheDD determines the amount of potential functionalities, wheremodifications may take place. This in turn will affect the stabil-ity, solubility and catalytic activity of the catalyst system. Toprepare chitosan with a particular DD, it is important to knowthe influence of the different parameters on the deacetylationreaction
You can actually dissolve it in ionic liquids as well, such as EMIM OAc or BMIM Cl for example.
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