The Impact of Colloidal Surface-Anchoring on the Smectic A Phase

Abstract

Liquid-crystalline phases are known for their unique properties, i.e., the combination of fluidity and long-range orientational and/or positional order. The presence of a colloidal particle gives rise to perturbations of this order locally. These perturbations are the origin of intercolloidal forces driving the colloidal self-assembly in a directed manner. Hence, the understanding of these perturbations is the first step in understanding and controlling the self-assembly process. Here, we perform Monte Carlo simulations to investigate the perturbations of orientational and positional order in a smectic A phase caused by a spherical colloid. We model the host phase via an interaction potential that reproduces characteristic features of phase behavior, structure, dynamics, and elasticity [S. Püschel-Schlotthauer et al. J. Chem. Phys. 2016, 145, 164903]. For strong homeotropic anchoring conditions, we find a Saturn ring defect and an onion structure in the smectic A phase; the latter has never been reported for colloids so far. For strong planar anchoring conditions, we find Boojum defects that become elongated at low temperature, similar to what is observed in experiments. However, for weak planar anchoring conditions, a double surface ring defect is exhibited in the smectic A phase.

Emergent biaxiality in nematic microflows illuminated by a laser beam

“…These structures were observed experimentally [60,61] but remained unexplained for nearly twenty years. Another example concerns the development of defect topologies that form when a colloidal particle is immersed into a nematic or smectic A carrier fluid [62]. Our theoretical results [63] are in good qualitative agreement with experimental findings [64,65].…”

“…Another example concerns the development of defect topologies that form when a colloidal particle is immersed into a nematic or smectic A carrier fluid [62]. Our theoretical results [63] are in good qualitative agreement with experimental findings [64,65]. Our last example concerns biaxial binary mixtures of two uniaxially symmetric compounds that pertain also to the present class of model systems [25].…”

Particle-resolved topological defects of smectic colloidal liquid crystals in extreme confinement

“…Due to their simultaneous orientational and positional ordering, defects in the smectic phase naturally exhibit an even higher degree of complexity. The main emphasis has been put hitherto on the positional layering [23][24][25][26][27] or orientational textures 19,28,29 alone, as well as, on coarse-grained calculations 1,19,25,[29][30][31][32] and computer simulation of particle models [33][34][35][36] .…”

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

“…The most prominent type of ordering, which is typically found in liquid crystals, is orientational (nematic) ordering, where the characteristically shaped subunits, i.e, molecules or colloidal particles in close proximity, show a tendency to align. If this preferred order gets frustrated, e.g., by confinement to a finite container [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], constraining on a surface [50][51][52][53][54][55][56][57] or insertion of obstacles [58][59][60][61][62][63][64][65][66][67], topological defects emerge, which are discontinuities in the ordered structures that can display particlelike properties themselves [6,16,[68][69][70]. * Rene.Wittmann@hhu.de FIG.…”