Figure 1.

Carboxymethylation and cross-linking methods of chitosan. Carboxymethylation of chitosan is a chemical modification process that produces different derivatives of chitosan. The reaction with ClCH₂COOH and NaOH leads to two products, i.e., O-carboxymethyl chitosan and N,O-carboxymethyl chitosan. There are also different types of cross-linking that carboxymethyl chitosan can undergo including physical, chemical, enzymatic, and radiation cross-linking. Each cross-linking method forms connections among the polymer chains, chemical bonds, or interactions based on affinity.