Topological defects in liquid crystals as templates for molecular self-assembly

Abstract

Topological defects in liquid crystals (LCs) have been widely used to organize colloidal dispersions and template polymerization, leading to a range of assemblies, elastomers and gels. However, little is understood about molecular-level assembly processes within defects. Here, we report that nanoscopic environments defined by LC topological defects can selectively trigger processes of molecular self-assembly. By using fluorescence microscopy, cryogenic transmission electron microscopy and super-resolution optical microscopy, we observed signatures of molecular self-assembly of amphiphilic molecules in topological defects, including cooperativity, reversibility and controlled growth. We also show that nanoscopic o-rings synthesized from Saturn-ring disclinations and other molecular assemblies templated by defects can be preserved by using photocrosslinkable amphiphiles. Our results reveal that, in analogy to other classes of macromolecular templates such as polymer-surfactant complexes, topological defects in LCs are a versatile class of three-dimensional, dynamic and reconfigurable templates that can direct processes of molecular self-assembly.

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

“…When an additive is attracted to the disclination core, two possible morphologies are expected: (i) continuous thread-like assembly, or (ii) a linear array of discrete beads. The disclination-templated assemblies reported so far had a threadlike shape, as observed for polymers in the so-called blue phases (15) and for molecular amphiphiles at the cores of nematic disclinations (9,10).…”

“…The accumulation of inclusions at the cores of disclinations is a general phenomenon reported for thermotropic liquid crystals (3,4,(8)(9)(10)(11)(12)15). Inclusions replace the strongly distorted director field and thus reduce the associated elastic energy of the system (4).…”

“…As one approaches the "core" of the defect, director deformation becomes so strong that the degree of orientational order varies in space. Disclinations can attract additives, e.g., colloidal particles (3)(4)(5)(6)(7)(8) and even small molecules (9,10). Such an attraction is energetically favored, as the strongly distorted disclination core region is replaced with the additive (4).…”

Monodisperse Cylindrical Micelles of Controlled Length with a Liquid‐Crystalline Perfluorinated Core by 1D “Self‐Seeding”

“…Similar to all symmetry-breaking materials, liquid crystals permit the existence of topological defects, which are regions of the order forced to be discontinuous. [22] The defects in LC structures have been used to direct molecular assembly, [22] organize nanoparticles, [23] gelate colloidal dispersions, [24] and template polymerization. [25] We therefore attempted to load solvophobic molecules inside the P2VP68-b-PFMA41 micelles.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…For further functionalization of the LC polymer materials, molecular orientation, defect control and domain formation should be more precisely controlled. 269 For example, new techniques 44,[270][271][272][273] are proposed to control alignment using LC polymers. New materials will be used for the preparation of liquid crystals.…”