title: Direct mapping of local director field of nematic liquid crystals at the nanoscale.
abstract: Liquid crystals (LCs), owing to their anisotropy in molecular ordering, are of wide interest in both the display industry and soft matter as a route to more sophisticated optical objects, to direct phase separation, and to facilitate colloidal assemblies. However, it remains challenging to directly probe the molecular-scale organization of nonglassy nematic LC molecules without altering the LC directors. We design and synthesize a new type of nematic liquid crystal monomer (LCM) system with strong dipole-dipole interactions, resulting in a stable nematic phase and strong homeotropic anchoring on silica surfaces. Upon photopolymerization, the director field can be faithfully "locked," allowing for direct visualization of the LC director field and defect structures by scanning electron microscopy (SEM) in real space with 100-nm resolution. Using this technique, we study the nematic textures in more complex LC/colloidal systems and calculate the extrapolation length of the LCM.
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104;
authors.forename: Yu
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104; Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104; Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Francesca
authors.initials: F
authors.lastname: Serra
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104;
authors.forename: Randall D
authors.initials: RD
authors.lastname: Kamien
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Kathleen J
authors.initials: KJ
authors.lastname: Stebe
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104; shuyang@seas.upenn.edu.
authors.forename: Shu
authors.initials: S
authors.lastname: Yang
keywords: dipole–dipole interactions; nanoscale imaging; nematic liquid crystal polymers; photo-cross-linking; topological defects