Surface phenomena for lamellar phases in microemulsions
Institute of Physical Chemistry, Polish Academy of Sciences - 01-224 Warszawa,
Accepted: 10 December 1998
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.
PACS: 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems / 68.55.Jk – Structure and morphology; thickness
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