Thin liquid films

On Hamaker constants: A comparison between Hamaker constants and Lifshitz-van der Waals constants

The force as a function of separation has been measured between two molecularly smooth surfaces immersed in the liquid octamethylcyclotetrasiloxane (OMCTS) whose molecules are quasispherical of diameter ∼1.0 nm. The force is an oscillatory function of distance, varying between attraction and repulsion, with a periodicity equal to the size of the liquid molecules to within the experimental resolution of ∼0.1 nm. The oscillations decay rapidly with distance: their measurable range is 6–10 molecular diameters and their magnitude exceeds that of conventional van der Waals forces at small distances. The magnitude of the oscillations is insensitive to changes in temperature, but sensitive to the chemical nature of the surfaces, and very sensitive to the presence of water. The results are considered, qualitatively, within the context of current theories of the liquid state near solid interfaces, and some implications for surface chemistry and colloid science are discussed.

Direct measurement of structural forces between two surfaces in a nonpolar liquid

Adsorption dynamics of surfactants at the air/water interface: a critical review of mathematical models, data, and mechanisms

Temperature‐dependence measurements have been made on the chemical shift of the proton of a water molecule in the liquid state and in the gas state at varying pressure. The problem of relating these experimental data to the intermolecular forces leading to cohesion and to hydrogen‐bond formation between water molecules is considered in detail. It is shown that a consistent treatment of the chemical shift, thermal, and dielectric data for water can be given based on a two‐state model involving an equilibrium between a hydrogen‐bonded ``icelike'' fraction and a ``monomer'' fraction whose interaction with the lattice arises entirely from London dispersion forces.Using semiempirically derived values of the chemical shift and energy associated with the condensation of water vapor to ``monomer,'' the magnitude of the shift associated with the transformation to ice is calculated. It is then shown that, on the assumption that the hydrogen bond is electrostatic in character, the ``polar'' contribution to this shif...

Proton Resonance Shift of Water in the Gas and Liquid States

The conditions under which the two black films—the first of greater and variable thickness and the second of about 44 A—are formed by solutions of sodium dodecyl sulphate in the presence of NaCl are established and the effect of several additives upon the relative stability of these two films is investigated. Specific effects of counterions upon this behaviour are marked and are interpreted in terms of an ionic size effect upon the structure of the second black film and of preferential surface adsorption. Some conclusions about the composition and heat of formation of the second black film are drawn using Le Chatelier's principle. At higher ionic strengths counterions have also specific effects upon the thickness of the first black film in line with their hydrated size and adsorption.

Stability and some properties of the second black film

A Study of Double Layer Repulsion and van der Waals Attraction in Soap Films

: An improved experimental method for studying vertical soap films slowly pulled out of a solution is described and the interpretation of the optical thickness measurements is discussed. The behavior of mobile films presents complications which are described. Rigid films on the other hand give results for films thicker than 800 1100 Angstroms, which agree very closely with Frankel's law relating film thickness to the velocity of pull-out. Since Frankel's law is derived on the assumption that the viscosity is constant up to the monolayer, this agreement proves the absence of any thick rigidified water layers (or of slip) in the neighborhood of the surface. (Author)

Karol J. Mysels

Papers

Stability and some properties of the second black film

A Study of Double Layer Repulsion and van der Waals Attraction in Soap Films

Flow in Thin Liquid Films

Diffusion-controlled adsorption kinetics. General solution and some applications

Flow of Gasoline Thickened by Napalm