Nonlinear macroscopic description of liquid crystalline elastomers in external fields
type: CreativeWork
description: We concentrate on a continuum characterization of the macroscopic behavior of side-chain liquid single crystal elastomers (SCLSCEs). These materials consist of chemically crosslinked polymer backbones, to which mesogenic units are attached as side-groups. Due to specific routes of synthesis SCLSCEs feature a monodomain of the liquid crystalline order in the ground state. Their macroscopic coupling of liquid crystalline order and elastic mechanical deformations makes them unique. In particular, we investigate the macroscopic behavior of cholesteric and nematic SCLSCEs in external electric and mechanical fields. We characterize the respective liquid crystalline state using the director field and describe the current state of mechanical distortion by a displacement field. The specific coupling between these two components is taken into account explicitly by additional macroscopic variables. These are the relative rotations between the director orientation and the polymer network. Using this kind of description, we first study the influence of an external electric field on the state of a cholesteric SCLSCE. For this purpose, the field direction is chosen to be parallel to the helical axis of the cholesteric mesogen alignment. Director reorientation and mechanical distortions are analyzed to linear order. In the case of low electric field amplitudes, we find an effect that has been termed rotatoelectric. Here, with increasing electric field amplitude, the director arrangement rotates around the helical axis, relative to the polymer network. This effect is specific for cholesteric SCLSCEs. We discuss several aspects important for an experimental observation of this effect. Next, we investigate the dielectric instabilities of a cholesteric SCLSCE in a Frederiks splay geometry at higher electric field amplitudes. On the one hand, we find a scenario that corresponds to the Frederiks transition in conventional low molecular weight liquid crystals. Here, the director reorienta…
abstract: We concentrate on a continuum characterization of the macroscopic behavior of side-chain liquid single crystal elastomers (SCLSCEs). These materials consist of chemically crosslinked polymer backbones, to which mesogenic units are attached as side-groups. Due to specific routes of synthesis SCLSCEs feature a monodomain of the liquid crystalline order in the ground state. Their macroscopic coupling of liquid crystalline order and elastic mechanical deformations makes them unique. In particular, we investigate the macroscopic behavior of cholesteric and nematic SCLSCEs in external electric and mechanical fields. We characterize the respective liquid crystalline state using the director field and describe the current state of mechanical distortion by a displacement field. The specific coupling between these two components is taken into account explicitly by additional macroscopic variables. These are the relative rotations between the director orientation and the polymer network. Using this kind of description, we first study the influence of an external electric field on the state of a cholesteric SCLSCE. For this purpose, the field direction is chosen to be parallel to the helical axis of the cholesteric mesogen alignment. Director reorientation and mechanical distortions are analyzed to linear order. In the case of low electric field amplitudes, we find an effect that has been termed rotatoelectric. Here, with increasing electric field amplitude, the director arrangement rotates around the helical axis, relative to the polymer network. This effect is specific for cholesteric SCLSCEs. We discuss several aspects important for an experimental observation of this effect. Next, we investigate the dielectric instabilities of a cholesteric SCLSCE in a Frederiks splay geometry at higher electric field amplitudes. On the one hand, we find a scenario that corresponds to the Frederiks transition in conventional low molecular weight liquid crystals. Here, the director reorienta…
author: Menzel, Andreas
date published: 2009-02-04
date modified: 2026-07-27T18:49:19Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth