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Title: Structural Transitions in Cholesteric Liquid Crystal Droplets

Abstract

Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potentialmore » use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1351117
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Nano; Journal Volume: 10; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; ChLC; Landau−de Gennes model; chirality; liquid crystal

Citation Formats

Zhou, Ye, Bukusoglu, Emre, Martínez-González, José A., Rahimi, Mohammad, Roberts, Tyler F., Zhang, Rui, Wang, Xiaoguang, Abbott, Nicholas L., and de Pablo, Juan J. Structural Transitions in Cholesteric Liquid Crystal Droplets. United States: N. p., 2016. Web. doi:10.1021/acsnano.6b01088.
Zhou, Ye, Bukusoglu, Emre, Martínez-González, José A., Rahimi, Mohammad, Roberts, Tyler F., Zhang, Rui, Wang, Xiaoguang, Abbott, Nicholas L., & de Pablo, Juan J. Structural Transitions in Cholesteric Liquid Crystal Droplets. United States. doi:10.1021/acsnano.6b01088.
Zhou, Ye, Bukusoglu, Emre, Martínez-González, José A., Rahimi, Mohammad, Roberts, Tyler F., Zhang, Rui, Wang, Xiaoguang, Abbott, Nicholas L., and de Pablo, Juan J. 2016. "Structural Transitions in Cholesteric Liquid Crystal Droplets". United States. doi:10.1021/acsnano.6b01088.
@article{osti_1351117,
title = {Structural Transitions in Cholesteric Liquid Crystal Droplets},
author = {Zhou, Ye and Bukusoglu, Emre and Martínez-González, José A. and Rahimi, Mohammad and Roberts, Tyler F. and Zhang, Rui and Wang, Xiaoguang and Abbott, Nicholas L. and de Pablo, Juan J.},
abstractNote = {Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.},
doi = {10.1021/acsnano.6b01088},
journal = {ACS Nano},
number = 7,
volume = 10,
place = {United States},
year = 2016,
month = 7
}
  • We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis.more » Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.« less
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  • No abstract prepared.