Water droplets in a spherically confined nematic solvent: A numerical investigation |
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Authors: | H. Stark J. Stelzer R. Bernhard |
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Affiliation: | Institut für Theoretische und Angewandte Physik, Universit?t Stuttgart, Pfaffenwaldring 57, 70550, Stuttgart, Germany IMPACT Me?technik GmbH, Maybachstr. 25, 71332, Waiblingen, Germany
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Abstract: | Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets, but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a defect between them. Received 11 December 1998 |
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Keywords: | PACS. 77.84.Nh Liquids, emulsions, and suspensions liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals |
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