Nematic ordering of hard rods under strong confinement in a dense array of nanoposts

Kye Hyoung Kil, Arun Yethiraj, Jun Soo Kim

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Abstract

The effect of confinement on the behavior of liquid crystals is interesting from a fundamental and practical standpoint. In this work, we report Monte Carlo simulations of hard rods in an array of hard nanoposts, where the surface-to-surface separations between nanoposts are comparable to or less than the length of hard rods. This particular system shows promise as a means of generating large-scale organization of the nematic liquid by introducing an entropic external field set by the alignment of nanoposts. The simulations show that nematic ordering of hard rods is enhanced in the nanopost arrays compared with that in bulk, in the sense that the nematic order is significant even at low concentrations at which hard rods remain isotropic in bulk, and the enhancement becomes more significant as the passage width between two nearest nanoposts decreases. An analysis of local distribution of hard-rod orientations at low concentrations with weak nematic ordering reveals that hard rods are preferentially aligned along nanoposts in the narrowing regions between two curved surfaces of nearest nanoposts; hard rods are less ordered in the passages and in the centers of interpost spaces. It is concluded that at low concentrations the confinement in a dense array of nanoposts induces the localized nematic order first in the narrowing regions and, as the concentration further increases, the nematic order spreads over the whole region. The formation of a well-ordered phase at low concentrations of hard rods in a dense array of nanoposts can provide a new route to the low-concentration preparation of nematic liquid crystals that can be used as anisotropic dispersion media.

Original languageEnglish
Article number032705
JournalPhysical Review E - Statistical, Nonlinear, and Soft Matter Physics
Volume101
Issue number3
DOIs
StatePublished - Mar 2020

Bibliographical note

Funding Information:
J.S.K. acknowledges the financial support from the National Research Foundation of Korea (NRF) under Grants No. NRF-2018R1D1A1B07043246 and No. NRF-2019R1A2C1084414. A.Y. acknowledges the financial support from US Department of Energy, Basic Energy Sciences through Grant No. DE-SC0017877.

Publisher Copyright:
© 2020 American Physical Society.

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