Chitosan is a weak base and is insoluble in water, but
soluble in dilute aqueous acidic solutions below its pKa
(~6.3), in which it can convert glucosamine units (-NH2
into the soluble protonated form (-NH+3). The solubility of chitosan depends on its biological origin, molecular weight
and degree of acetylation[3]. Since chitosan is soluble
in diluted acid solutions, films can be readily prepared
by casting or dipping, resulting in dense and porous
structure[4,5].