Surface Induced Ordering on Model Liquid Crystalline Dendrimers

We present results from Monte Carlo simulations of liquid crystalline dendrimers (LCDrs) adsorbed on flat, impenetrable substrates. A tractable coarse grained force field for the inter-dendritic and the dendrimer-substrate interactions is introduced. We investigate the conformational and ordering properties of single, end-functionalized LCDrs under homeotropic, random (or degenerate) planar and unidirectional planar aligning substrates. Depending on the anchoring conditions of the mesogenic units of the LCDr and on temperature a variety of stable LCDr states, differing in their topology, are observed and analysed. The influence of the denritic generation and core functionality on the surface-induced ordering of the LCDrs are examined.Comment: 23 pages, 11 figure

Polar Molecular Organisation in Liquid Crystals

Various possibilities of polar self-organisation in low molar mass nematic, smectic and columnar liquid crystals are discussed with particular focus on the underlying molecular symmetries and interactions. Distinction is made between vector and pseudovector polarities, their quantification in terms of molecular order parameters and their relation to spontaneous electric polarisation and to molecular chirality. The understanding of the molecular mechanisms that give rise to polar ordering in existing lamellar and columnar phases may be useful for the design of new polar variants of common a-polar liquid crystals. Keywords:Polar Nematics; Ferroelectric Liquid Crystals; Polar Ordering.Comment: RevTex4, 10 pages, 8 figures, to be published in Mol. Cryst. Liq. Crys

On the structure of the Nx phase of symmetric dimers: inferences from NMR

NMR measurements on a selectively deuterated liquid crystal dimer CB-C9-CB, exhibiting two nematic phases, show that the molecules in the lower temperature nematic phase, NX, experience a chiral environment and are ordered about a uniformly oriented director throughout the macroscopic sample. The results are contrasted with previous interpretations that suggested a twist-bend spatial variation of the director. A structural picture is proposed wherein the molecules are packed into highly correlated chiral assemblies