Nematic liquid crystals in planar and cylindrical hybrid cells: Role of elastic anisotropy on the director deformations.
Nematic samples filling a flat cell or the annular region between two concentric cylinders with hybrid anchoring conditions at the boundaries are investigated by setting up and minimizing their Frank elastic free energy. The coupling with the surfaces is taken to be strong on one side and weak on the other. The equations are numerically solved and the conditions for which the molecular organization inside the cell becomes uniform are analyzed. The classical calculation performed by G. Barbero and R. Barberi [J. Phys. 44, 609 (1983)] is reproduced and investigated from a different point of view, in order to compare the results of planar and cylindrical geometries. The results suggest that the cylindrical cell presents some unusual features deserving a more complete investigation. Although most part of the transitional phenomena are found for K(11)>K(33), a case not common for ordinary (lyotropic and thermotropic) liquid crystals, it is possible to find a completely uniform cell even for K(11)<K(33) in both the geometries considered here.
Universidade Tecnológica Federal do Paraná, Campus Apucarana, Rua Marcílio Dias 635, 86812-460 Apucarana, Paraná, Brazil.
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Teixeira-Souza
Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Via Irnerio 46, 40126 Bologna, Italy.
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Chiccoli
Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Via Irnerio 46, 40126 Bologna, Italy.
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Pasini
Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo, 5790-87020-900 Maringá, Paraná, Brazil.
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Evangelista
Dipartimento di Chimica Industriale "Toso Montanari" and INSTM, Università, Viale Risorgimento 4, 40136 Bologna, Italy.
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Zannoni