Critical thickness of foam films stabilized by nonionic, ionic surfactants and their mixtures

Abstract

The critical thickness (hcr) for foam films of n-dodecyl β-D maltoside (C12G2) and of its mixed solutions with dodecanol (C12Е0), hexaethyleneglycol dodecyl ether (C12E6) and dodecyl trimethylammonium bromide (C12TAB) of different molar ratio (50:1; 1:1;1:50) at low and high ionic strength was measured interferometrically. It was found that the hcr increases with the increase of the film radius independently of solutions composition. At low ionic strength the type of surfactant affects the critical thickness and the equilibrium state of the film. hcr for the films of mixture with C12E0 increases with the increase of the total surfactant concentration, while hcr for the films of mixture with C12TAB decreases. For the values of the critical thicknesses for films from individual surfactant solutions the following sequence hcr (C12TAB) > hcr (C12E6) > hcr (C12G2) is found. At high ionic strength the quantity of nonionic additive does not substantially affect the value of hcr, while the quantity of ionic additive influences it by two different ways (i) in 50:1 mixture C12TAB supports C12G2 in the reducing of negative charge; (ii) in 1:1 mixture C12TAB recharges the film surfaces.

Hierarchical Au/CeO2systems – influence of Ln3+dopants on the catalytic activity in the propane oxidation process

“…78 The presence of the H3 hysteresis loop suggests the presence of slit-like pores between the oxide nanocrystallites that build the tube-like macroparticles. 82–84 The course of the isotherm for all 5 samples has the same character, but the value of the specific surface area ( S BET ) of the tested materials changes strongly (see Table 2). The size of the specific surface area increases with the addition of a dopant ion to the oxide structure, which was previously described in ref.…”