13C NMR study of the influence of the Aerosil surface charge on the short-chain surfactant adsorption

C-13 NMR chemical shift measurements have been used to study the adsorption of short-chain ionic surfactants on the Aerosil surface from aqueous solutions. The investigations were carried out in a wide concentration range above and below the critical micelle concentration value. The values and the character of the chemical shift changes of Delta delta are mainly determined by the surface charge, which is generally assumed to change with the initial pH value of the silica aqueous dispersion. Most sensitive to changes of the surface charge are the C-13 NMR parameters of the first and second carbon atoms in the hydrophobic chain of the surfactant molecules. This allows investigating the influence of the Aerosil surface charge on the structure of the adsorbed aggregates.