Surfactant-polysaccharide complexes based on quaternized chitosan. Characterization and application to emulsion stability
Résumé
The interactions between a polyelectrolyte and an oppositely charged surfactant allows obtaining complexes with specific properties. Such complexes between a quaternized chitosan, obtained from the reaction between chitosan and quaternary ammonium epoxides, and sodium 1-decanesulfonate were studied. Physico-chemical characteristics were obtained from conductimetric experiments as well as surface tension studies. A strong associative electrostatic interaction between the polysaccharide and the surfactant was shown from conductimetric experiments and a degree of association equal to 0.74 was determined. The complex presents better interfacial properties than surfactant and polysaccharide alone. The critical aggregation concentration is much smaller than the critical micellar concentration of the surfactant alone in solution. Moreover the viscoelastic moduli of the interfacial layer was increased in presence of the complex by comparing with surfactant alone. All these considerations allow using the surfactant-polysaccharide complex as a better emulsion stabilizer than either surfactant or polysaccharide alone.