Dynamic Surface Potential and Adsorption Kinetics of Nonionic Surfactants at the Air−Water Interface

Abstract

The surface potential kinetics of the nonionic surfactants tridecyldimethylphosphine oxide and dodecanoic acid at the air/water interface have been investigated by the vibrating plate method. An influence of the thickness of the solution layer on the surface potential and adsorption kinetics was observed. A mathematical solution for the case of diffusion controlled adsorption kinetics is presented. The experimental data were fitted for different models. As a result, the depth of the solution layer has to be taken into account in dynamic processes for small concentrations of these amphiphiles. This is important for strong surfactants. The fit parameters have reasonable values for the whole set of data by use of the derived equations. In the case of very low concentrations, a peculiar behavior in the surface potential kinetics during the initial adsorption time (t < 1 min) was found. We suppose this to be due to reorientation of the adsorbed surfactant molecules when the number of the molecules at the interface increases. This was previously observed by one of us on the basis of equilibrium surfactant adsorption isotherm analysis.

A disjoining pressure study of foam films stabilized by mixtures of a nonionic (C12DMPO) and an ionic surfactant (C12TAB)

“…There is considerable knowledge regarding the surface and bulk properties of C 12 DMPO with extensive surface tension [14][15][16][17][18][19][20][21] and surface rheology [22][23][24][25][26][27][28][29] studies in the past. Moreover, studies of adsorption layers and foam films of C 12 DMPO/protein mixtures were performed [30,31].…”

Purification, Surface Tensions, and Miscibility Gaps of Alkyldimethyl and Alkyldiethylphosphine Oxides

“…For example, extensive surface tension [7][8][9][10][11][12][13] and surface rheology [14][15][16][17][18][19][20] studies have been carried out with a focus on the properties of C 12 DMPO. In addition, the binary water-surfactant phase diagrams of C 8 DMPO [21], C 10 DMPO [21], C 12 DMPO [2,3,21], and C 14 DMPO [2,3] were studied, and the formation of microemulsions with C 10 , C 12 , and C 14 DMPO was investigated [3].…”

Film formation and surface gelation of gelatin molecules at the water/air interface

“…The measured contact potential difference is made up of the potential of the protein solution V P and the surface potential of the pure solvent V S . 19 The surface potential, thus measured, describes a relative potential difference between the filmcovered and the pure water surface. Spreading surface-active substances at the interface effects a change of the electrical properties and consequently a change of the contact potential difference.…”