Colloidal Structures from Bulk Demixing in Liquid Crystals

Abstract

This experimental paper deals with phase separations of binary mixtures composed of a continuous liquid crystal phase and an isotropic dispersed phase. In contrast to isotropic binary mixtures, the investigated mixtures do not lead to a full phase separation but to a self-ordering of colloidal particles, as reported earlier (Loudet, J. C. et al. Nature 2000, 407, 611). We present here further aspects of such phase separations which include the kinetics of the phase separation, the origin of the formation of dislocation-like patterns, the influence of surfactants, chiral additives, and temperature on the formed colloidal structures. The present results show that (i) the dislocations in chain arrays can be seen as kinetically frozen defects, (ii) temperature can be used to control the size of the domains formed upon demixing, (iii) a slight change in surface chemistry, via the addition of surfactants, profoundly alters the formed colloidal structures, and (iv) chiral additives allow the formation of unique helical pearl chains which reflect the symmetry of the liquid crystal phase they are embedded in.

Tunable colloids: control of colloidal phase transitions with tunable interactions

“…Introducing a second particle induces a similar director field around the second particle, and thus the two particles interact via liquid-crystal anisotropy. The interaction of colloidal particles in the presence of such an anisotropic medium has indeed been studied experimentally and theoretically [167][168][169][170][171][172][173][174][175] (see ref. 170 for a review). A colloidliquid-crystal mixture phase separates into colloid-rich and colloid-poor regions, with the phase separation depending sensitively on the liquid crystal anchoring conditions at the colloid surface.…”

Around the corner: Colloidal assembly and wiring in groovy nematic cells

“…1(c)), while quadrupoles, aligning perpendicular to the field, generate either a zig-zag string ( Fig. 1(d)) or a straight line at an oblique angle with respect to the director field [7][8][9]. At the same time, colloids can act as impurities and be attracted to defect lines (disclinations) in the bulk, an effect that has been used to create wires of colloids spanning a cell from top to bottom [10][11][12].…”

Does transparent nematic phase exist in 5CB/DDAB/water microemulsions? From the viewpoint of temperature dependent dielectric spectroscopy

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] What make them highly intriguing are the novel properties arising from the elastic distortion of LCs induced by the dispersed particles or droplets and fascinating colloidal structures attributed to the interparticle interaction mediated by the elastic distortions of the LC host. These new properties and structures are generally absent in conventional LCs and colloidal systems but important in technological application and fundamental science.…”