Solubility of amylose/ionic surfactant complexes in dilute aqueous solutions: Dependence on surfactant concentration

The solubility in dilute aqueous solutions of amylose complexed with ionic surfactants has been investigated by turbidity measurements. The turbidity depended on both the amylose and the surfactant concentrations. Low and high surfactant concentrations resulted in macroscopic phase separation, while mixtures at intermediate surfactant concentrations remained monophasic for at least one month. The solubility of the complexes was sensitive to the addition of salt as well as to the surfactant charge and hydrophobic chain length. These results are interpreted in terms of an electrostatic stabilisation of soluble complexes. Complexes with a non-ionic surfactant were not soluble at any mixing ratio.