Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.1: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Phase-behavior of bidisperse ferrocolloids — •Gabriel M. Range and Sabine H.L. Klapp — Stranski-Laboratorium für Physikalische und Theoretische Chemie, Sekr. TC7, Fakultät II, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany

Using density functional theory in the modified mean-field (MMF) approximation we study the phase behavior of bidisperse ferrocolloids, consisting of a binary mixture of dipolar hard spheres (DHS). We focus on the fluid phase regime, where we consider both isotropic and anisotropic phases.

In a recent MMF study of binary mixtures of equisized DHS, differing only in their dipole moments, we found a rich phase behavior resulting from the interplay of isotropic-to-ferroelectric and demixing transitions. In systems with strongly asymmetric dipole moments the isotropic-to-ferroelectric transition is shifted towards significantly lower temperatures compared to the one-component case, while the demixing transition becomes more and more dominating. We also found, that demixing is always accompanied by spontaneous ferroelectricity in the MMF approach. Based on these findings we analyze the relative importance of differing sizes versus differing dipole moments on the phase-behavior of ferrocolloids. We also investigate the influence of external fields, particularly on demixing and size separation.