Surface activities and aggregation behaviors of cationic - anionic fluorocarbon - hydrocarbon surfactants in dilute solutions

Abstract

In mixtures of sodium perfluoropolyether carboxylate (PFPE-Na) and cetyltrimethylammonium bromide (CTAB) in dilute solutions, the surface activities and aggregation behaviors have been investigated by the surface tension, dynamic surface tension, contact angle methodologies, dynamic light scattering (DLS), transmission electron microscopy (TEM) and dye encapsulation experiments. The surface tension measurements provided the critical micelle concentration (CMC) and the surface tension at the CMC (γCMC) at different molar ratios. In addition, surface activity parameters of the maximum surface excess concentration (Γmax) and the minimum surface area/molecule (Amin) at the air/water interface were evaluated. The adsorption and wetting abilities of FC-poor mixed systems were studied. Mixed systems of fluorocarbon - hydrocarbon surfactants show better ability to reduce the surface tension and more efficiency to reduce the surface tension. Adding tiny amount of PFPE-Na to CTAB solution (1:20–1:50) has little effect to adsorption, but it enhances the surface activity and wetting ability of mixed system distinctly. Meanwhile, the mixed system can form stable vesicle spontaneously near the PFPE-Na/CTAB ratio of 2:1 in aqueous solution, it may be used as drug delivery vehicles and cold be used as micro/nanotemplates for material synthesis [1–4].