Imprinting substrate structures onto a nematic liquid crystal

Abstract

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.

Nanoconfinement-Induced Structures in Chiral Liquid Crystals

“…The model has been demonstrated subsequently [19,32–38] to be capable of reproducing properties of liquid crystals in a variety of contexts, ranging from the formation of nematic phases [32–35] to the development of defect topologies arising near the surface of spherical colloidal particles immersed in a nematic liquid-crystal host phase [19]. The introduction of chirality through the pseudoscalar on the far right side of Equation (4) follows in spirit a suggestion by Memmer et al [27] for the classical Gay-Berne model [39].…”

Keith E. Gubbins: A retrospective

“…With colleague Marco Nardelli in physics at NCSU (now at North Texas University), Keith's group used quantum‐mechanical methods to understand the influence of confinement on reaction pathways 49‐51 . He also collaborated with Martin Schoen and the late Gerhard Findenegg of the Technical University of Berlin to study self‐assembly processes on surfaces 52,53 . These collaborations eventually led to a larger program, the International Graduate Research Training Group 1524 sponsored by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG), involving two dozen faculty members in Berlin and the US and an international exchange program for doctoral students.…”

“…[49][50][51] He also collaborated with Martin Schoen and the late Gerhard Findenegg of the Technical University of Berlin to study self-assembly processes on surfaces. 52,53 These collaborations eventually led to a larger program, the International Graduate Research Training Group 1524 sponsored by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG), involving two dozen faculty members in Berlin and the US and an international exchange program for doctoral students. Among many other applications, Keith's group at NCSU has also used theoretical and computational approaches to investigate the phase behavior of complex mixtures, 54,55 surfactant self-assembly in various solvents, [56][57][58][59] adsorption and transport phenomena in carbon nanotubes, [60][61][62] and reactive adsorption in metal-organic frameworks and nanocomposites.…”

Cationic Copper(II)-containing Surfactants: Molecular Structures, Film Morphology, and Influence on the Alignment of Nematic Mesogens

“…We examine their interfacial behavior, domain evolution and patterning at the air–water interface, and morphology of the resulting LB films. Finally, considering the increasing experimental − and theoretical , interest in the influence of modified surfaces as orientation directors for liquid crystals, we demonstrate that interfacial contact between the LB film of a select metallosurfactant and N -(4-methoxybenzylidene)-4-butylaniline (MBBA) leads to alterations of alignment, as monitored by optical microscopy.…”