A. G. Nekrasov

Aggregative Optical Activity of Colloidal Surfactants

The discovery of the aggregative optical activity for solutions of different colloid surfactants (anionic sodium dodecyl sulfate, cationic hexadecyltrimethylammonium bromide, and nonionic Brij 30) is reported. The optical activity develops only above the Kraft point, and, in the concentration plot, it is characterized by a distinct maximum in the vicinity of critical micelle concentration. The concentration at which the optical activity disappears corresponds to the formation of spherical micelles and is a new important parameter in the colloid chemistry of surfactants.

On the Theory of Heat Conductivity, Electrical Conductivity, and Hydraulic Conductivity of Polydisperse Polyhedral Foams and Highly Concentrated Emulsions

Rigorous formulas for the heat conductivity, electrical conductivity, and hydraulic conductivity of polydisperse polyhedral foams and highly concentrated emulsions are derived on the basis of the ideas recently formulated by one of the authors, with the structure of Plateau borders and films represented in the form of hierarchic series.

Optical Method of Studying Foam Structural Stability

A new method of studying the foam stability based on the determination of the evolution time of foam cell at a given level of foam column is developed. The method is based on optical measurements that allow one to determine the main structural parameters of a foam. Experimental results are reported for sodium dodecyl sulfate solutions.

On the Modulus of Transverse Elasticity of Thin Foam Films

The theory of transverse elasticity of thin foam films is formulated under the conditions when the action of Gibbs elasticity is excluded. The theory predicts the presence of maxima of the modulus of transverse elasticity and film thickness near the critical micellization concentration as functions of the content of surfactant at a given disjoining pressure. Theoretical conclusions are confirmed experimentally by measuring film thickness at various heights of equilibrium foam column.