Directing the Handedness of Helical Nanofilaments Confined in Nanochannels Using Axially Chiral Binaphthyl Dopants.

Abstract

In this work, we demonstrate control of the handedness of semicrystalline modulated helical nanofilaments (HNFmods) formed by achiral bent-core liquid crystal molecules by axially chiral binaphthyl-based additives as guest molecules solely under spatial nanoconfinement in anodic aluminum oxide nanochannels. The molecules of the same chiral additives are expelled from the HNFmods in the bulk, and as a result thereof do not affect the handedness or helical pitch of bulk HNFmods, resulting in an HNFmod conglomerate with chirality-preserving growth within each domain. However, under confinement these axially chiral guest molecules, likely embedded in the HNFmod host, do affect the helicity of the HNFmods. The configuration of the axially chiral molecules decides the HNFmod helix handedness and their concentration, and the helix angle is related to the helical pitch of the HNFmods. In addition to local imaging data obtained by scanning electron microscopy, global studies by thin-film circular dichroism spectropolarimetry support the imaging results.