Homeotropic Alignment and Director Structures in Thin Films of Triphenylamine-Based Discotic Liquid Crystals Controlled by Supporting Nanostructured Substrates and Surface Confinement

Abstract

We explore the effects of nanoscale morphology of supporting solid substrates on alignment, defects, and director structures exhibited by thin films of triphenylamine-based discotic liquid crystals. Fluorescence confocal polarizing microscopy and intrinsic polarized fluorescence properties of studied molecules are used to visualize three-dimensional director fields in the liquid crystal films. We demonstrate that, by controlling surface anchoring on supporting or confining solid substrates such as those of carbon nanotube electrodes on glass plates, both uniform homeotropic and in-plane (edge-on) alignment and nonuniform structures with developable domains can be achieved for the same discotic liquid crystal material.

Pillar‐Assisted Epitaxial Assembly of Toric Focal Conic Domains of Smectic‐A Liquid Crystals

“…The TFCDs form spontaneously when the decrease in surface energy obtained by planar anchoring on the substrate outweighs the elastic energy cost of bending the layers and the increase in surface energy due to the dimple-like deformation of the LC/air interface. Regular hexagonal lattices of TFCDs have been used to create microlens arrays, [ 11 ] matrices for the self-assembly of soft microsystems, [12][13][14] lithographic templates, [ 15 ] 2D charge transport models, [ 16 ] and patterned functional surfaces. The ability to control the size and arrangement of TFCDs is currently under investigation; for instance, studies have employed substrates presenting different surface chemistries, [16][17][18][19] confi nement within 1D microchannels, [ 16 , 20-23 ] and randomly patterned planar and depressed substrates.…”

Self-assembled 1D Semiconductors: Liquid Crystalline Columnar Phase

“…Planar alignment of triphenylene and phthalocyanine columnar DLCs with control of the azimuthal angle was achieved by isotropic phase dewetting on chemically patterned surfaces [119]. Spin-coating of triphenylamine-based DLCs on the SWNT-coated substrate is reported to exhibit homeotropic alignment in thin films in its hexagonal columnar phase [120].…”

Generation of liquid crystallinity from a Td-symmetry central unit

“…1 Owing to the long-range self-assembling, ease of processing, solubility in a variety of organic solvents, and high charge-carrier mobilities along the stacking axis has made DLCs ideal candidates for organic semiconductor device applications. [2][3][4][5][6][7][8][9][10][11] The ability of a molecule to exhibit a particular mesophase is closely related to its shape, dipolar property, aspect ratio, conformational dynamics, and specific intermolecular associations. 12 Disc-shaped molecules generally self-assemble into columnar phases, while rod like molecules often display nematic or smectic phases.…”