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Title: Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals

Abstract

Liquid crystals are known to be particularly sensitive to orientational cues provided at surfaces or interfaces. In this work, we explore theoretically, computationally, and experimentally the behavior of liquid crystals on isolated nanoscale patterns with controlled anchoring characteristics at small length scales. The orientation of the liquid crystal is controlled through the use of chemically patterned polymer brushes that are tethered to a surface. This system can be engineered with remarkable precision, and the central question addressed here is whether a characteristic length scale exists at which information encoded on a surface is no longer registered by a liquid crystal. To do so, we adopt a tensorial description of the free energy of the hybrid liquidcrystal surface system, and we investigate its morphology in a systematic manner. For long and narrow surface stripes, it is found that the liquid crystal follows the instructions provided by the pattern down to 100 nm widths. This is accomplished through the creation of line defects that travel along the sides of the stripes. We show that a "sharp" morphological transition occurs from a uniform undistorted alignment to a dual uniform/splay-bend morphology. The theoretical and numerical predictions advanced here are confirmed by experimental observations. Ourmore » combined analysis suggests that nanoscale patterns can be used to manipulate the orientation of liquid crystals at a fraction of the energetic cost that is involved in traditional liquid crystal-based devices. The insights presented in this work have the potential to provide a new fabrication platform to assemble low power bistable devices, which could be reconfigured upon application of small external fields.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2];  [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [4]
  1. Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States; División de Ciencias e Ingenierı́as, Campus León, Universidad de Guanajuato, Loma del Bosque 103, León, Guanajuato 37150, México
  2. Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
  3. Departamento de Materiales, Universidad Nacional de Colombia, Sede Medellín, Medellín, Colombia
  4. Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States; Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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:
1417669
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Langmuir; Journal Volume: 33; Journal Issue: 43
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Armas-Pérez, Julio C., Li, Xiao, Martínez-González, José A., Smith, Coleman, Hernández-Ortiz, J. P., Nealey, Paul F., and de Pablo, Juan J. Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals. United States: N. p., 2017. Web. doi:10.1021/acs.langmuir.7b02522.
Armas-Pérez, Julio C., Li, Xiao, Martínez-González, José A., Smith, Coleman, Hernández-Ortiz, J. P., Nealey, Paul F., & de Pablo, Juan J. Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals. United States. doi:10.1021/acs.langmuir.7b02522.
Armas-Pérez, Julio C., Li, Xiao, Martínez-González, José A., Smith, Coleman, Hernández-Ortiz, J. P., Nealey, Paul F., and de Pablo, Juan J. 2017. "Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals". United States. doi:10.1021/acs.langmuir.7b02522.
@article{osti_1417669,
title = {Sharp Morphological Transitions from Nanoscale Mixed-Anchoring Patterns in Confined Nematic Liquid Crystals},
author = {Armas-Pérez, Julio C. and Li, Xiao and Martínez-González, José A. and Smith, Coleman and Hernández-Ortiz, J. P. and Nealey, Paul F. and de Pablo, Juan J.},
abstractNote = {Liquid crystals are known to be particularly sensitive to orientational cues provided at surfaces or interfaces. In this work, we explore theoretically, computationally, and experimentally the behavior of liquid crystals on isolated nanoscale patterns with controlled anchoring characteristics at small length scales. The orientation of the liquid crystal is controlled through the use of chemically patterned polymer brushes that are tethered to a surface. This system can be engineered with remarkable precision, and the central question addressed here is whether a characteristic length scale exists at which information encoded on a surface is no longer registered by a liquid crystal. To do so, we adopt a tensorial description of the free energy of the hybrid liquidcrystal surface system, and we investigate its morphology in a systematic manner. For long and narrow surface stripes, it is found that the liquid crystal follows the instructions provided by the pattern down to 100 nm widths. This is accomplished through the creation of line defects that travel along the sides of the stripes. We show that a "sharp" morphological transition occurs from a uniform undistorted alignment to a dual uniform/splay-bend morphology. The theoretical and numerical predictions advanced here are confirmed by experimental observations. Our combined analysis suggests that nanoscale patterns can be used to manipulate the orientation of liquid crystals at a fraction of the energetic cost that is involved in traditional liquid crystal-based devices. The insights presented in this work have the potential to provide a new fabrication platform to assemble low power bistable devices, which could be reconfigured upon application of small external fields.},
doi = {10.1021/acs.langmuir.7b02522},
journal = {Langmuir},
number = 43,
volume = 33,
place = {United States},
year = 2017,
month = 8
}
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