The concept of negative hamaker coefficients, II. Thermodynamics, experimental evidence and applications

Abstract

Via a surface-thermodynamic approach the experimental conditions can be predicted under which the effective Hamaker coefficient A132 (of a system comprising two different materials 1 and 2, immersed in a liquid medium 3) acquires a negative value. These predictions could be confirmed by a number of different experimental approaches. The realization that experimental conditions leading to a negative value for A132 can be readily achieved, has opened the way to a number of novel separation methods, and also furnishes a clearer explanation for the mechanism of a few older separation processes. With the surface-thermodynamic approach it becomes a simple matter to determine the A132 value of a system. The precise point at which the A132 value of a system changes signs is usually accompanied by an easily observable physical phenomenon, e.g., a minimum of interaction, a maximum stability, a phase change, or a sudden detachment or elution of particles, cells or macromolecules.