Surface phenomena for lamellar phases in microemulsions

Institute of Physical Chemistry, Polish Academy of Sciences - 01-224 Warszawa, Poland

Received: 3 July 1998
Accepted: 10 December 1998

Abstract

Surface phenomena in fluids exhibiting structure on the nanoscale (microemulsions, copolymers etc.) are studied. We argue that for such systems the Landau-Ginzburg functional of suitably chosen order parameter should on the nanoscale have the same form, as the Landau-Ginzburg density-functional for simple fluids on the microscale. We define such order parameter for lamellar ordering by averaging the lamellar structure given by density profiles over a period of the density oscillations. The resulting Landau-Ginzburg functional leads to surface-induced order or disorder and to the associated wetting phenomena. We verify our hypothesis by explicit mean-field calculations in a lattice model of microemulsions in the presence of a surface. Perfect agreement is found. Our results also agree with recent experiments.