Pattern-induced anchoring transitions in nematic liquid crystals. (21st December 2016)

• Record Type: Journal Article
• Authors: Rojas-Gómez, Óscar A; Romero-Enrique, José M; Silvestre, Nuno M; Telo da Gama, Margarida M
• Is Part Of: Journal of physics. Volume 29:Number 6(2017)
• Publication Date: 2016-12-21
• Subjects: nematic liquid crystals -- patterned substrates -- anchoring transition -- elastic model; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/1361-648X/29/6/064002
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: In this paper we revisit the problem of a nematic liquid crystal in contact with patterned substrates. The substrate is modelled as a periodic array of parallel infinite grooves of well-defined cross-section sculpted on a chemically homogeneous substrate which favours local homeotropic anchoring of the nematic. We consider three cases: a sawtooth, a crenellated and a sinusoidal substrate. We analyse this problem within the modified Frank–Oseen formalism. We argue that, for substrate periodicities much larger than the extrapolation length, the existence of different nematic textures with distinct far-field orientations, as well as the anchoring transitions between them, are associated with the presence of topological defects either on or close to the substrate. For the sawtooth and sinusoidal cases, we observe a homeotropic to planar anchoring transition as the substrate roughness increases. On the other hand, a homeotropic to oblique anchoring transition is observed for crenellated substrates. In this case, the anchoring phase diagram shows a complex dependence on the substrate roughness and substrate anchoring strength.