Viscosity study of interactions between sodium alginate and CTAB in dilute solutions at different pH values

Interactions between anionic polyelectrolyte sodium alginate and the cationic surfactant cetytrimethylammonium bromide (CTAB) have been investigated by viscosity measurement techniques. The polymer–surfactant interactions are observed between alginate and CTAB at different pH in dilute solution. The results show that the rheological response of alginate dilute solutions is sensitive to a change of pH in the low pH range. The steady shear and intrinsic viscosity measurements reveal that the strong association between alginate and CTAB by electrostatic attraction above pH 5.0. However, as the pH value of solution decrease from 5.0 to 3.0, the strong association between alginate and CTAB is affected by not only electrostatic attraction but also hydrophobic interaction.