Rheology of sphingans in EPS-surfactant systems.

A model-based rheological characterization of four sphingans in combination with four prominent surfactants of cosmetic formulations of cationic, anionic, zwitterionic and neutral headgroup characteristics was performed. The impact of the surfactants on the rheological properties, based on changes in the mechanical models was evaluated in respect to the closely related structural differences of the polysaccharides, to give an insight on the structure-function relationship of these interactions. The side chains of the sphingans Welan, Diutan and S-88 seem to be involved in the masking of the anionic charge of the polysaccharide backbone, making them highly compatible even with cationic surfactants. The effect of a disaccharide side chain of Diutan also impacts its intermolecular interactions opposed to Welan and S-88, resulting in different surfactant interactions as well as temperature stability. The lack of a side chain in Gellan leads to large incompatibilities with zwitterionic and cationic surfactants due to high polysaccharide-surfactant interactions.