Effect of anionic surfactant on alginate-chitosan polyelectrolyte multilayer thickness

Alginate and chitosan are among the most common biopolyelectrolytes. Surfactants can be included in alginate and chitosan formulations in order to improve their physical and functional properties. In the present study, the effect of the anionic surfactant sodium dodecyl sulfate (SDS) on alginate-chitosan polyelectrolyte multilayer (PEM) films is reported for the first time. Layer-by-layer deposition technique was employed to prepare the PEM samples and the samples were characterized by ellipsometry, X-ray reflectivity, atomic force microscopy, and quartz crystal microbalance with dissipation. Incorporation of SDS into PEM formulations increased the film thickness and an increased adsorption behavior between alginate and chitosan layers are observed. Since the concentration of SDS was below its critical micelle concentration, no micelle formation was expected and hydrophobic-hydrophobic interaction between alginate and SDS might be the main reason.