Interfacial properties of dynamic association between chitin derivatives and surfactants

Carboxymethylchitin was modified by introducing a hydrophobic character by two methods: either by addition of a cationic surfactant which plays the role of counterion by electrostatic interaction (forming a surfactant-polyelectrolyte complex, SPEC) or by N-alkylation. The roles of the dynamic association leading to the formation of SPEC and that of the covalent alkylation on the interfacial properties are compared. The role of the degree of alkylation and of the length of the alkyl chains is examined. The experimental data concern the tensioactive properties of the alkylated chitosans and carboxylated chitin. The surface activity of alkylcarboxymethylchitin is demonstrated and the different mechanisms involved are discussed. The improved surface activity of the dynamic association between a polysoap (covalently alkylated carboxymethylated chitin) and a cationic surfactant compared to the activity of the surfactant alone is shown to depend on the length of alkyl side chains. (C) 1999 Elsevier Science B.V. All rights reserved.