Micellization and adsorption thermodynamics of novel ionic surfactants at fluid interfaces

We report the synthesis of three novel anionic surfactants: sodium 12-N,N-diethylamino-9-octadecenoate (AR1S), sodium 12-N,N-diethylamino-octadecanoate (AE1S) and sodium 12-N,N-diethylamino-9,10-dihydroxy-octadecanoate (AE2S). Surface tension measurements were carried out at 27 degreesC. As a way of improving the understanding of the surface and adsorption behavior of ionic surfactants, equilibrium surface tension and adsorption models were investigated and Frumkin adsorption equilibrium isotherm was employed to model the results. Thermodynamic parameters were determined from surface tension experimental data. The presence of functional groups (N(C2H5)(2), -C=C- and OH) in the hydrophobic part of the compounds favor the effect of lateral adsorption of hydrocarbon chains, thus avoiding formation of monolayers normally oriented towards the surface, as indicated from analysis of the values of the lateral interaction parameters determined by the Frumkin model. (C) 2002 Elsevier Science B.V. All rights reserved.