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.nematic liquid crystal polymers | dipole-dipole interactions | topological defects | photo-cross-linking | nanoscale imaging

Around the corner: Colloidal assembly and wiring in groovy nematic cells

“…2(d). This configuration was observed in other LC/colloidal systems with similar geometries [15,22,23].…”

Structural Transition in Liquid Crystal Bubbles Generated from Fluidic Nanocellulose Colloids

“…Figure 4d,e shows the magnified view of the disclination ring at the bubble boundary.Itwas apparent that the line defect formed ad omain wall between the two adjacent regions,w ith the structure considerably isotropic, that was,within the topological defect the orientational order was substantially lower than in the bulk of liquid crystal phase. [16] This showed that there existed ap hase transition during the evaporation process,f rom an ematic bubble surface to an isotropic state of the bubble boundary.O nt he other hand, in the bubble-free region, al arge area of longrange helical structure with rod-like textures was observed, along with ad irector that anticlockwise twisted (see Figure 4f;S upporting Information, Figure S10, S11). [8a] This suggested astructure transition between the bubble boundary and bubble-free region, with the CNC ordering changing from an isotropic to ac hiral nematic arrangement.…”

Chiral Phases of a Confined Cholesteric Liquid Crystal: Anchoring-Dependent Helical and Smectic Self-Assembly in Nanochannels

“…This sparse knowledge of the phase behavior and dynamics of ChLCs in confinement contrasts the one of achiral mesogens. The miniaturization trends in electronics and optoelectronics, but also the general goal to manipulate and understand matter at the nanoscale has motivated detailed studies of the structural, dynamical and thermodynamical properties of confined and semiconfined achiral mesogens. , Despite recent experimental advancements to directly probe orientational order parameter profiles in the proximity of planar, solid walls, − achieving the spatial (and temporal) resolution necessary to rigorously explore these phenomenologies at the nanoscale remains experimentally extremely demanding. Still, it could be revealed that both the collective orientational (I–N) and the translational (Sm–I or Sm–N) transitions are significantly affected by finite size and interfacial (solid–liquid or liquid–liquid) interactions introduced by confining walls − or the geometrical constraints in nanoporous media. ,− …”