Assembly of sodium dodecyl sulfate at the wool/water interface

The adsorption isotherms for sodium dodecyl sulfate (SDS) adsorption from aqueous solutions (pH 4.69) onto wool/water interfaces at 15, 25 and 35 °C, respectively, are satisfactorily expressed in linear plots based on a stoichiometric displacement model of adsorption (SDM-A). The studies on adsorption parameters of SDM-A suggest that assembly of SDS molecules on the wool/solution interface follows the partition regularity and stoichiometric displacement relation between the two phases based on the SDM-A. The fact that the general displacement adsorption heats obtained in the calorimetric measurement and the enthalpies calculated by the thermodynamics of SDM-A in the presentation are well in accordance with each other shows that thermodynamic function fraction study of SDM-A is reliable. The studies on thermodynamic parameters and function fractions suggest that at the start of adsorption, the SO4− groups occupy the sites from which the water molecules are released and simultaneously driven to the edges of alkyl chains closed to polar heads. The surface hydrophobic interactions increase in the way that the adsorbed SDS molecules on the surface favor to form bilayer micelles while every individual SDS molecule in the surface micelles may attach to surface first. The investigation of fluorescence probe of pyrene indicates that surface micelle formation begins in lower surface coverage while the aggregation numbers of micelles grow at high surface coverage.