The interaction between polymer and surfactant as revealed by interfacial tension
The aging of aqeusous ethyl(hydroxyethyl)cellulose (EHEC) solution and mixed solutions of polymer and sodium dodecyl sufate (SDS) in contact with cyclohexane was studied by measurement of interfacial tension, using the pendant drop method. Studies were performed over the concentration ranges 0–18 mM SDS with fixed concentration 0.2% w/w EHEC, and 0–16 mM SDS with no polymer added. EHEC was found t be very surface active, and the kinetics of polymer adsorption to the water/cyclohexane interface is extremely slow. The mixed solutions of polymer and surfactant showed a more typical timescale for adsorption. The variation in the equilibrium interfacial tension of the mixed polymer-surfactant solutions was assumed to reflect the variation of the activity of polymer, and the interactions between the polymer and other particles in the system. The observed effects were explained as due to the changes in polymer-solvent and polymer-surfactant interactions, resulting in a changed conformation of the polymer, as well as the formation of micelle-like clusters and free micelles.
Key wordsInterfacial tension cellulose derivative surfactant micelle polymer-surfactant interaction pendant drop method
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