Organization of amphiphiles VI. A comparative study of the orientation of polyoxyethylated alkyl phenols at the air‐water and the silica‐water interface

Abstract

The adsorption behavior on silica of a series of polyoxyethylated alkyl phenols of varying hydrophobicities and hydrophilicities was studied by determining the adsorption isotherm along with the zeta potential of silica. An increase in the concentration of each of the surfactants caused the zeta potential to become less negative and ultimately to reach a plateau; similarly, the adsorption isotherm also plateaued. These results were attributed to the flat orientation of the surfactants caused by hydrogen bonding of the oxygen atom of the oxyethylene group with the silanol group of the silica, which led to the formation of a thin oxyethylene layer at the silica-water interface. This layer masked a constant fraction of the silica surface. A model for the orientation of the surfactants at the silica-water interface was proposed, based on a "molecular parking area" (i.e., space occupied by the molecule during adsorption at the silica-water interface) of the surfactants on the silica surface.

Organization of amphiphiles, Part VIII: Role of polyoxyethylated alkylphenols in optimizing the beneficiation of hydrophilic mineral

“…From adsorption and fluorescence studies we have seen that NP-10, NP-15, NP-20 and OP-10 form hemimicelles at silica-water interface (Somasundaran, 1975;Misra et al, 2003), whereas OP-30 and NP-40 adsorb as surfactant monomers throughout the adsorption isotherm (Figs. 3 and 4).…”

“…At low concentration, the surfactant molecules adsorb due to the possibility of hydrogen bonding between ethoxyl oxygen atoms with silanol group with the polyoxyethylene group lying flat on the silica surface and the alkyl chain pointing towards the bulk solution ( Fig. 13: Misra and Somasundaran, 2004). With the same alkyl chain length of the surfactant, with greater number of oxyethylene groups the more will be the coverage of the surface and the greater will be the reduction of surface charge and the surface hydrophilicity.…”

Investigation of bovine serum albumin-surfactant aggregation and its physicochemical characteristics

“…The excitation and emission slits were set at 5 nm. A required amount of the stock solution of pyrene (10 −3 M in pure methanol (Anal R grade, Sisco-chem, India) was added to a vial to maintain a low concentration of pyrene (1 × 10 −6 M) in the solution to exclude excimer formation or any type of perturbation to the organization [20,28] in situ. To the residue of pyrene after evaporation, different concentrations of surfactant solutions were added.…”

Organization of amphiphiles. Part XI: Physico-chemical aspects of mixed micellization involving normal conventional surfactant and a non-ionic gemini surfactant

“…6) in case of all surfactants. The decrease in zeta potential may be attributed to the mechanical displacement of the shear plane being projected some distance beyond the original shear plane or coverage of a fraction of coal surface due to the adsorption of bulky surfactant molecules at the micelle-water similar to that of particle-water interface [29,65,67]. The trend of zeta potential values of the conventional surfactants however, does not change in presence of BAM possibly due to the formation of loosely packed mixed micelles of conventional-gemini surfactants in the mixed state.…”