title: Surface Dipole Control of Liquid Crystal Alignment.
abstract: Detailed understanding and control of the intermolecular forces that govern molecular assembly are necessary to engineer structure and function at the nanoscale. Liquid crystal (LC) assembly is exceptionally sensitive to surface properties, capable of transducing nanoscale intermolecular interactions into a macroscopic optical readout. Self-assembled monolayers (SAMs) modify surface interactions and are known to influence LC alignment. Here, we exploit the different dipole magnitudes and orientations of carboranethiol and -dithiol positional isomers to deconvolve the influence of SAM-LC dipolar coupling from variations in molecular geometry, tilt, and order. Director orientations and anchoring energies are measured for LC cells employing various carboranethiol and -dithiol isomer alignment layers. The normal component of the molecular dipole in the SAM, toward or away from the underlying substrate, was found to determine the in-plane LC director orientation relative to the anisotropy axis of the surface. By using LC alignment as a probe of interaction strength, we elucidate the role of dipolar coupling of molecular monolayers to their environment in determining molecular orientations. We apply this understanding to advance the engineering of molecular interactions at the nanoscale.
authors.affiliation: California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Physics & Astronomy, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Schwartz
authors.affiliation: California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Mendoza
authors.affiliation: California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Natcha
authors.initials: N
authors.lastname: Wattanatorn
authors.affiliation: California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Vinh T
authors.initials: VT
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Chemistry and the International Institute for Nanotechnology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Spokoyny
authors.affiliation: Department of Chemistry and the International Institute for Nanotechnology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Chad A
authors.initials: CA
authors.lastname: Mirkin
authors.affiliation: Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, v.v.i. , č.p. 1001, 250 68 Husinec-Řež, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Baše
authors.affiliation: California NanoSystems Institute, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Chemistry & Biochemistry, University of California, Los Angeles , Los Angeles, California 90095, United States.|Department of Materials Science & Engineering, University of California, Los Angeles , Los Angeles, California 90095, United States.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Weiss