Correlation Between Bulk Orderings and Anchoring Structures of Liquid Crystals Studied by Scanning Tunneling Microscopy

Abstract

The anchoring structures of a homologous series of liquid crystals, n -alkylcyanobiphenyls ( m CBs: m =7-12), on molybdenum disulfide (MoS 2 ) are directly observed by scanning tunneling microscopy (STM) in order to analyze the alignment mechanism of liquid crystals. Based on highly reproducible STM images, the anchoring structures of m CBs are clearly divided into two categories, a monolayer (single-row) type (7CB, 8CB, 9CB and 11CB) and a bilayer (double-row) type (10CB and 12CB). Here we propose the monolayer is the anchoring structure of a nematic phase, while the bilayer is the anchoring structure of a smectic phase. The correlation between bulk phase orderings and anchoring structures of liquid crystals is discussed from the viewpoint of surface-phase formation for the m CBs and different solid substrates.