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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Focus: Amphiphilic Systems I

CPP 1.2: Vortrag

Montag, 23. März 2009, 11:15–11:30, ZEU 222

Interfaces in bicontinuous surfactant phases — •Maxim Belushkin and Gerhard Gompper — Theoretical Soft-Matter and Biophysics, IFF, Forschungszentrum Juelich, Juelich, Germany

Surfactant molecules added to an oil-water system self-assemble into a large variety of structures on the mesoscopic scale. In particular, bicontinuous and lamellar structures are observed. In bicontinuous phases, the surfactant monolayer separates continuous channels of oil and water. In regions of the phase diagram close to the lamellar phase, bicontinuous phases with long-range order emerge. In these cubic phases the surfactant monolayer forms triply periodic minimal surfaces. In amphiphilic systems many kinds of interfaces occur: between two ordered phases, between ordered and disordered phases, and between two grains of the same ordered phase.

Using a Ginzburg-Landau theory of ternary amphiphilic systems we study two classes of interfaces in bicontinuous surfactant phases - twist grain boundaries in cubic phases and microemulsions in contact with hydrophilic/hydrophobic surfaces. Twist grain boundaries are found to be minimal surfaces. The interfacial tension is very small and exhibits a non-monotonous dependence on the twist angle. For microemulsions near a hydrophilic wall, the nucleation of a lamellar phase at the surface is observed for regions in the phase diagram close to the microemulsion-lamellar phase transition.