Elasticity-dependent self-assembly of micro-templated chromonic liquid crystal films

Abstract

We explore micropatterned director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on squarelattice cylindrical-micropost substrates. The structures are manipulated by modulating the LCLC mesophases and their elastic properties via concentration through drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films, dried from nematics, form two distinct director and defect configurations: a diagonally aligned director pattern with local squares of defects, and an off-diagonal configuration with zig-zag defects. The formation of these states appears to be tied to the relative splay and bend free energy costs of the initial nematic films. The observed nematic and columnar configurations are understood numerically using a Landau-de Gennes free energy model. Among other attributes, the work provide first examples of quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC films in general, and it demonstrates alignment and configuration switching of typically difficult-to-align LCLC films via bulk elastic properties.

Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

“…Both the collective orientational (isotropic-to-nematic) and the translational (smectic-toliquid or smectic-to-nematic) transitions have turned out to be significantly affected by finite size and interfacial (solid-liquid or liquid-liquid) interactions introduced by confining walls [1][2][3][4][5][6] or the geometrical constraints in nanoporous media [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Competition of lattice and basis for alignment of nematic liquid crystals

“…While the present study has considered a flat surface, the results may also be important for experimentalists using arrays of posts to align liquid crystals as has been reported in [13,38,39]. It seems that only a very modest amount of anisotropy in the shape of the pillars, for example using posts of elliptical cross section, may break the square symmetry and lead to significantly better azimuthal alignment if desired.…”

Bistable director alignments of nematic liquid crystals confined in frustrated substrates

“…With them, many types of structured surfaces for the liquid crystals and the resulting director alignments have been reported in the past few decades [9,11,23,[28][29][30][31]. For example, a striped surface, in which the homeotropic and planar anchorings appear alternatively, was used to control the polar angle of the director field in the bulk [32][33][34].…”

“…To sustain the deformed state, the external field has to be constantly applied to the liquid crystal substance. In order to reduce power consumption, a variety of liquid crystal systems showing multistable director configurations or storage effects have been developed [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In such systems, a pulsed external field can induce permanent changes of the director configurations.…”

“…that sandwiched between two parallel plates with homeotropic anchoring, shows a unique stable director configuration if external fields are not imposed. By introducing elastic frustrations, the nematic liquid crystals can have different director configurations of equal or nearly equal elastic energy [8][9][10][11][21][22][23][24][25][26]. For instance, either of horizontal or vertical director orientation is possibly formed in nematic liquid crystals confined between two flat surfaces of uniformly tilted but oppositely directed anchoring alignments [8].…”