Influence of hydroxypropylmethyl cellulose–sodium dodecylsulfate interaction on the solution conductivity and viscosity and emulsion stability

The conductivity, viscosity and rheological measurements were used to study the interaction of HPMC with an anionic surfactant-sodium dodecylsulfate (SDS) in aqueous solutions of different concentrations. The properties of HPMC solutions (0.1–1.0%) with increasing SDS concentrations (0–2.0%) were investigated. On the basis of following the changes of the system during the HPMC–SDS interaction, the characteristic concentrations of SDS at which interaction starts (the critical aggregation concentration (CAC)) and at which it ends (polymer saturation point (PSP)), were determined, and an interaction mechanism was proposed. The linear relationship between the PSP and HPMC concentrations was found, while CAC remained constant. To show that the interaction of the components in the continuous phase of dispersed systems can change their properties, the changes of stability of HPMC-stabilized oil-in-water emulsions with SDS addition were also examined. It was found that stability of the emulsions was influenced by the HPMC–SDS interaction. After the preparation, stability of emulsions increased with increase in continuous phase viscosity and stability changed with time according to the mechanism of HPMC–SDS interaction in the continuous phase.