A THEORETICAL INTERPRETATION OF CATIONIC SURFACTANT ADSORPTION ON MICA, MONITORED BY ELECTRON-SPECTROSCOPY FOR CHEMICAL-ANALYSIS - EFFECTS OF THE SURFACE ENERGETIC HETEROGENEITY OF MICA

The works published by Cases and co-workers have shown that the energetic heterogeneity of the actual (really existing) solids influences strongly the mechanism of the ionic surfactant adsorption onto polar solid surfaces. However, in spite of the progress which has been made in understanding that adsorption mechanism, one important problem deserves further extensive study. This is the combined effect of the surface energetic heterogeneity and the multisite occupancy adsorption at lower surface coverages. There, the surfactant molecules are attached to the surface not only by their polar head but also by a certain number of their hydrophobic segments. A theoretical approach is proposed to describe that combined effect and then is used successfully to describe the experimental isotherms of cationic surfactant adsorption on mica reported by Herder et al. Because of its well-defined structure and molecularly smooth surface, mica seemed to be a convenient model adsorbent to investigate that combined effect of surface heterogeneity and multisite occupancy adsorption.