1. Tolman’s length and near critical asymmetric interfacial profiles
Mikhail A. Anisimov, Dept. of Chemical and Biomolecular Engineering,. University of Maryland
The nature of the asymmetric interfacial profile and the curvature dependence of the interfacial tension are fundamental issues in the mesoscopic thermodynamics of asymmetric fluid interfaces. In some fundamentally and practically important fluid systems exhibiting smooth interfaces, such as near-critical fluids and polymer solutions, the amplitude of the first curvature correction to the interfacial tension, known as Tolman’s length d , may become as large as the thickness of the interface itself, and may therefore significantly affect the interfacial tension.
Tolman’s length depends crucially on the degree of asymmetry in the fluid phase coexistence and on the mesoscopic fluctuations of density or concentration. We have adopted a semi-phenomenological approach, based on “gradient theory” and scaling ideas in mesoscopic thermodynamics in order to calculate the asymmetric corrections to the interfacial profile (lower left). We have used these corrections to verify and extend a previously proposed thermodynamic relationship for Tolman’s length (left).
This research potentially impacts filtration through micro porous media in oil recovery, microfluidics, nanoscale liquid bridges, nucleation phenomena, and all instances where science and technology deal with fluid droplets at submicron and nano scales. In particular our investigations focus on the interfacial properties of highly asymmetric polymer solutions and polymer blends, ionic fluids near the critical points of phase separation, and two-dimensional phase separation on the surface of vesicles and lamellae.