title: Homeotropic alignment of lyotropic chromonic liquid crystals using noncovalent interactions.
abstract: We report on the homeotropic alignment of lyotropic chromonic liquid crystals (LCLCs). Homeotropic anchoring of LCLCs is difficult to achieve, and this challenge has limited development of applications for LCLCs. In this work, homeotropic alignment is achieved using noncovalent interactions between the LCLC molecules and various alignment layers including graphene, parylene films, poly(methyl methacrylate) films, and fluoropolymer films. The LCLC molecules are unique in that they self-assemble via noncovalent interactions in water into elongated aggregates which, in turn, form nematic and columnar liquid crystal (LC) phases. Here we exploit these same noncovalent interactions to induce homeotropic anchoring of the nematic LCLC. Homeotropic alignment is confirmed by polarized optical microscopy and conoscopy. We also report on novel transient stripe textures that occur when an initial flow-induced planar alignment transforms into the equilibrium homeotropic alignment required by boundary conditions. An understanding of this behavior could be important for switching applications.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Joonwoo
authors.initials: J
authors.lastname: Jeong
authors.forename: Ganghee
authors.initials: G
authors.lastname: Han
authors.forename: A T Charlie
authors.initials: AT
authors.lastname: Johnson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Collings
authors.forename: Tom C
authors.initials: TC
authors.lastname: Lubensky
authors.forename: Arjun G
authors.initials: AG
authors.lastname: Yodh