Microstructure and mixing behavior of benzalkonium chloride with triblock polymers in aqueous medium

Interaction of cationic surfactant (benzalkonium chloride) with nonionic polymeric surfactants, triblock polymers (F127, P105, L64, P123) has been investigated using surface tension, dynamic light scattering (DLS), small angle neutron scattering (SANS) and viscosity measurements. Addition of triblock polymers to the micellar solution of benzalkonium chloride decreases the critical micellar concentration (cmc) and enhances the surface properties. This decrease in cmc values and negative values of interaction parameter show synergism in the binary mixtures of benzalkonium chloride and triblock polymer. Average dimensions of the mixed micelles like diffusion coefficient and hydrodynamic diameter measured from DLS indicate micellar growth in these binary mixtures. SANS data analysis reveal the prolate ellipsoidal shape and micellar growth for the mixed micelles of these binary mixtures. Resultant micellar growth for the proposed binary mixtures is attributable to reduced head group repulsions and hydrophobicity effect. Results from the present study can be helpful in the selection of surfactant mixtures for surfactant-based applications.