Surfactant-polymer interaction: effect of hydroxypropylmethyl cellulose on the surface and solution properties of gemini surfactants

Interaction of a nonionic polymer hydroxypropylmethyl cellulose (HPMC) with the cationic gemini surfactants, ethane-1,2-diyl bis (N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16), pentanediyl-1,5-bis (dimethylcetylammonium bromide) (16-5-16), hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16), and the conventional surfactant (cetyltrimethylammonium bromide, CTAB) has been investigated by surface tension and rheology measurements. Stronger interaction of HPMC with the geminis as compared to the conventional surfactant is indicated by the values of physicochemical parameters which include the critical aggregation concentration (cac), critical micelle concentration (cmc), ΔG \( {}_m^o \) (standard Gibbs free energy of micellization), Γ_max (maximum surface excess concentration at the air/solution interface), A_min (minimum area per surfactant molecule), and η (viscosity). Interaction between the surfactant and polymer in the mixed systems results in the formation of polymer-surfactant micelles; strength of the interaction is found to be dependent upon the nature of surfactant. On increasing the polymer concentrations, cac as well as cmc of the surfactant increases.