Excited-state resonance Raman spectroscopy as a probe of alumina-sodium dodecyl sulfate hemimicelles

Abstract

consolute phase boundary.11 However, the values increase slightly for C12AC but scarcely for C16DAC, CUDAC, and C14DAB, as the temperature approaches the consolute boundary of the liquid-liquid phase separation. Therefore, the rigidity or expansion of rodlike micelles is not necessarily related to the liquid-liquid phase separation.The difference in the rigidity or expansion of rodlike micelles seems to manifest itself in the shear rate dependence of the viscosity. The shear thickening phenomenon was observed for almost all of aqueous sodium halide solutions of C16DAC, C14DAC, C14DAB, and C12AC, rodlike micelles of which may have more expanded character: the relative viscosity shows the shear thickening at low shear rates, before the shear thinning occurs. The expanded long rodlike micelles entangle further at low shear rates, and then entangled micelles are aligned or destructed at high shear rates. On the other hand, shear-induced association may occur for shorter rodlike micelles of C12AC.The strong shear thinning or pseudoplastic behavior happened for solutions of more flexible rodlike micelles of C16TAC, C16TAB, and C14TAB.9 The entanglement of such flexible micelles can be aligned or destructed easily, if the shear stress is applied. The same discussion can be applicable to the shear rate dependence on the viscosity of aqueous NaCl solutions of C"E7. As the rigidity or expansion of rodlike micelles increased with a rise in temperature, the relative viscosity changed from shear thinning to shear thickening.11The shear rate dependence on the viscosity was reported for aqueous NaBr solutions of alkylpyridinium salicylate, aqueous solutions of tetradecyltrimethylammonium salicylate, and their mixture.25,26 The possibility of the shear-induced phase transition was suggested for these solutions.

Adsorption of organic molecules on silica surface

“…Hemimicellar micropolarity is found to be comparable to that of a micellar system, but the hemimicellar microviscosity shows marked difference (about ten times more) from the bulk micellar viscosity. Somasundaran et al [322] studied the orientation of the sodium dodecyl sulphate molecules on alumina surface by excited state Resonance Raman Spectra of Ru (bpy) 3 2+ in the adsorbed layer of surfactant. The study clearly shows several transitions sensitive to the evolution and structure of hemimicelles.…”

Interactions between Surfactants and Particles: Dispersion, Surface Modification, and Adsolubilization

“…Surfactant adsorbed layers formed on particles exhibit hydrophobic properties which have been characterized by many techniques including ESR and fluorescence spectroscopy (23)(24)(25)(26)(27). Accordingly, water-insoluble compounds can be incorporated into the surfactant adsorbed layers, which is called adsolubilization.…”

A comparison study of the flotation and adsorption behaviors of diaspore and kaolinite with quaternary ammonium collectors

“…Several experimental techniques such as electron spin resonance (Chandar et al, 1987b;Waterman et al, 1986), UV spectroscopy and fluorescence probe studies (Chandar et al, 1987a;Somasundaran et al, 1986), and Raman spectroscopy (Somasundaran et al, 1989) have been employed to study the adsorption mechanisms as well as the structure of adsorbed collectors. The adsorption of cationic collectors on dioxide minerals is governed mainly by the electrostatic interaction and hydrophobic interaction (Cases and Villieras, 1992) which includes interaction between the collector and the surface as well as the interaction between collector molecules.…”