Chitin was derivatized to extend its applications in the field of water soluble systems. It was first carboxymethylated and then alkylated. Two technics were used for that purpose : ionic surfactants playing the role of counterions form an electrostatic complex, and covalent derivatization. The difference between covalent alkylation and dynamic association (SPEC) is discussed in relation with the length of the alkyl chain and the density of alkylation.