SURFACTANT AND COSURFACTANT PACKING IN THE LYOTROPIC LIQUID-CRYSTALLINE PHASE-D AND ADSORBED ON A SOLID-SURFACE

Competitive adsorption of sodium dodecyl sulfate (SDS) and 1-butanol (C4OH) onto solid Al2O3 from aqueous solution of 0.3 M NaCl has been studied. Itis found that the affinity of C4OH toward the solid surfaceis significantly lower than that of SDS. A bulk concentration of 1 10 renders a surface concentration of 1 1. A method of separating the area requirements for the components is proposed in analogy to the geometries in the lamellar lyotropic liquid crystalline phase D. Calculation gives 0.39 nm2 for SDS and 0.30 nm2 for C4OH on alumina. The last value is higher than the comparable value from D phases, which may indicate a more horizontal orientation of the adsorbed molecule at the solid surface. These conclusions are, however, based on a complete coverage of the solid surface by the adsorbed species. © 1990.