Phase behavior of a nematic liquid crystal in contact with a chemically and geometrically structured substrate

Harnau, Ludger; Kondrat, Svyatoslav; Poniewierski, A.

doi:10.1103/physreve.72.011701

Cited by 18 publications

(17 citation statements)

References 36 publications

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“…It is well known that the nematic director field, in the presence of a structured substrate, may be distorted, leading to an elastic contribution to the free energy. Since the seminal work by Berreman [12,13], this problem has been extensively studied and generalized in the literature [4,[14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Wetting and filling transitions by nematic on these grooved surfaces [28][29][30][31] have also been studied.…”

Section: Introductionmentioning

confidence: 99%

Generalized Berreman's model of the elastic surface free energy of a nematic liquid crystal on a sawtoothed substrate

Rojas-Gómez

Romero-Enrique

2012

Phys. Rev. E

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In this paper we present a generalization of Berreman's model for the elastic contribution to the surface free-energy density of a nematic liquid crystal in presence of a sawtooth substrate which favors homeotropic anchoring as a function of the wave number of the surface structure q, the tilt angle α, and the surface anchoring strength w. In addition to the previously reported nonanalytic contribution proportional to −q ln q, due to the nucleation of disclination lines at the wedge bottoms and apexes of the substrate, the next-to-leading contribution is proportional to q for a given substrate roughness, in agreement with Berreman's predictions. We characterize this term, finding that it has two contributions: the deviations of the nematic director field with respect to a reference field corresponding to the isolated disclination lines and their associated core free energies. Comparison with the results obtained from the Landau-de Gennes model shows that our model is quite accurate in the limit wL > 1, when strong anchoring conditions are effectively achieved.

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Section: Introductionmentioning

confidence: 99%

Generalized Berreman's model of the elastic surface free energy of a nematic liquid crystal on a sawtoothed substrate

Rojas-Gómez

Romero-Enrique

2012

Phys. Rev. E

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“…Nematic configurations induced by a single substrate patterned with stripes of mixed perpendicular and parallel anchoring properties have been studied theoretically in refs. [22][23][24][25] and experimentally in refs. [26][27][28].…”

Section: Introductionmentioning

confidence: 79%

Nematic films at chemically structured surfaces

Silvestre

Gama

Tasinkevych

2016

J. Phys.: Condens. Matter

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We investigate theoretically the morphology of a thin nematic film adsorbed at flat substrate patterned by stripes with alternating aligning properties, normal and tangential respectively. We construct a simple "exactly-solvable" effective interfacial model where the liquid crystal distortions are accounted for via an effective interface potential. We find that chemically patterned substrates can strongly deform the nematic-air interface. The amplitude of this substrate-induced undulations increases with decreasing average film thickness and with increasing surface pattern pitch. We find a regime where the interfacial deformation may be described in terms of a material-independent universal scaling function. Surprisingly, the predictions of the effective interfacial model agree semiquantitatively with the results of the numerical solution of a full model based on the Landau-de Gennes theory coupled to a square-gradient phase field free energy functional for a two phase system.

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“…13 However, in this work the stripes on the two opposite substrates are shifted with respect to one another and the distortion free energy of the liquid-crystalline phase is investigated as a function of substrate separation. The combined impact of substrate topology and chemical decoration has been studied by Harnau et al 14 Within the framework of Frank-Oseen theory Kondrat et al computed the solvation force for a liquid crystal interacting with a patterned substrate. 15 Haddadan and Dietrich studied lateral and normal forces in a liquid crystal confined between plane parallel substrates decorated with periodically varying regions of different anchoring conditions.…”

Section: Introductionmentioning

confidence: 99%

Imprinting substrate structures onto a nematic liquid crystal

Greschek

Gubbins

Schoen

2012

The Journal of Chemical Physics

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By means of Monte Carlo simulations in the grand canonical ensemble we study the morphology of the nematic phase of a simple model liquid crystal interacting with an alternating sequence of chemically different stripes. The stripes anchor molecules such that their orientation is either parallel or perpendicular with the substrate plane. The different molecular orientations are realized through anchoring functions that cause an energetic penalty for molecules oriented in an undesired fashion. We consider combinations of monostable and degenerate anchoring fields. The nature of the nematic phase is characterized through both the local nematic order parameter and the associated local director field. We observe states of uniaxial or biaxial symmetry depending on the ratio of stripe widths and the range of fluid-substrate attraction. In some cases the specific substrate pattern causes regions of biaxial symmetry to coexist with a bulk-like regime sufficiently far away from the substrates in which the local director field indicates a (homogeneous) bent state of the nematic liquid crystal.

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Phase behavior of a nematic liquid crystal in contact with a chemically and geometrically structured substrate

Cited by 18 publications

References 36 publications

Generalized Berreman's model of the elastic surface free energy of a nematic liquid crystal on a sawtoothed substrate

Generalized Berreman's model of the elastic surface free energy of a nematic liquid crystal on a sawtoothed substrate

Nematic films at chemically structured surfaces

Imprinting substrate structures onto a nematic liquid crystal

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