Abstract
Monte Carlo simulations of chiral liquid-crystals, represented by a simple coarse-grained chiral Gay–Berne model, were performed to investigate the effect of central longitudinal dipole interactions on phase behavior. A systematic analysis of the structural properties and phase behavior of both achiral and chiral systems, with dipole interactions, reveals differing effects; strong dipole interactions enhance the formation of layered structures; however, chiral interactions may prevent the formation of such phases under certain conditions. We also observed a short-ranged smectic structure within the cholesteric phases with strong dipole interactions. This constitutes possible evidence of presmectic ordering and/or the existence of chiral line liquid phases, which have previously been observed in X-ray experiments to occur between the smectic twisted grain boundary and cholesteric phases. These results provide a systematic understanding of how the phase behavior of chiral liquid-crystals changes when alterations are made to the strength of dipole interactions.
Highlights
The different types of thermotropic liquid-crystals can be characterized by varying degrees of molecular orientational and positional order
The results clearly indicate that the smectic-nematic and nematic-isotropic phase transition points are shifted to higher temperatures with increased dipole strength
Molecular simulations for model liquid-crystals were performed to investigate the effect of chirality and dipole strength upon the phase behavior
Summary
The different types of thermotropic liquid-crystals can be characterized by varying degrees of molecular orientational and positional order. Analogous to the relationship between nematic and cholesteric phases, the smectic twisted grain boundary (TGB) phase retains strong smectic ordering on a local scale, while exhibiting a larger-scale chiral rotation of the ordering director. In this case, the rotation occurs between adjacent slabs of smectic ordering, which are separated by grain boundaries. Examples include optically-tunable helical twisting power [12,13] and reflections [14], and light-driven handedness of helical superstructures inversion [15,16] as well as other-types of structural changes [13,17,18] These developments will serve to promote the design and application of intelligent advanced functional materials [19]
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