A conductometric study of interactions between gelatin and sodium dodecyl sulfate (SDS) in aqueous-rich mixtures of dimethylsulfoxide

In this work we have traced micellization behavior of SDS in aqueous gelatin solutions to protein–surfactant interactions. The findings are particularly informative with respect to the head group contribution. CMC dependence on gelatin concentration correlates well with the interdependence between charge neutralization of SDS due to electrostatic interaction and hydrophobic interaction that lead to unfavorable exposure of hydrocarbon chains to water. A consistent increase in CMC with added DMSO is suggested as being due to structural consequences of intermolecular interaction. Supporting evidence is reported from thermodynamic data (ΔHmo, ΔSmo and ΔGmo). Both, ΔHmo and ΔSmo correlate well with the testimony that bears the head group contribution of SDS. A compensation observed between ΔHmo and ΔSmo values is supported further by a weak gelatin concentration dependence of ΔGmo<0.