title: Directed self-assembly of nematic liquid crystals on chemically patterned surfaces: morphological states and transitions.
abstract: The morphology and through-film optical properties of nematic liquid crystals (LCs) confined between two surfaces may be engineered to create switches that respond to external electric fields, thereby enabling applications in optoelectronics that require fast responses and low power. Interfacial properties between the confining surfaces and the LC play a central role in device design and performance. Here we investigate the morphology of LCs confined in hybrid cells with a top surface that exhibits uniform homeotropic anchoring and a bottom surface that is chemically patterned with sub-micron and micron- wide planar anchoring stripes in a background of homeotropic anchoring. In a departure from past work, we first investigate isolated stripes, as opposed to dense periodic arrays of stripes, thereby allowing for an in-depth interpretation of the effects of patterning on LC morphology. We observe three LC morphologies and sharp transitions between them as a function of stripe width in the submicron and micron regimes. Numerical simulations and theory help explain the roles of anchoring energy, elastic deformation, entropy, pattern geometry, and coherence length of the LC in the experimentally observed behavior. The knowledge and models developed from an analysis of results generated on isolated features are then used to design dense patterned substrates for high-contrast and efficient orientational switching of LCs in response to applied fields.
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu and Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Li
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu and División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, León (Gto.) 37150, Mexico, USA.
authors.forename: Julio C
authors.identifier: http://orcid.org/0000-0002-4118-1202
authors.initials: JC
authors.lastname: Armas-Perez
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Jose A
authors.identifier: http://orcid.org/0000-0001-7257-8889
authors.initials: JA
authors.lastname: Martinez-Gonzalez
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Liu
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Helou
authors.initials: H
authors.lastname: Xie
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Camille
authors.initials: C
authors.lastname: Bishop
authors.affiliation: Departamento Materiales y Minerales, Universidad Nacional de Colombia - Medellin, Calle 75 # 79A-51, Bloque M17, Medellin, Colombia and Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Juan P
authors.identifier: http://orcid.org/0000-0003-0404-9947
authors.initials: JP
authors.lastname: Hernandez-Ortiz
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu and Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: de Pablo
authors.affiliation: Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA. depablo@uchicago.edu nealey@uchicago.edu and Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.
authors.forename: Paul F
authors.initials: PF
authors.lastname: Nealey