Chitosan is
a copolymer of N-acetyl-glucosamine and glucosamine. This polymer
is a weak base with a pKa value of the glucosamine residue of
w6.2e7.0. Therefore, it is insoluble at neutral and alkaline pH
values. In acidic media, the amino groups will be positively charged,
conferring to the polysaccharide a high charge density