Discotic liquid crystals: From dynamics to conductivity

Discotic liquid crystals: From dynamics to conductivity

Kruglova, O.V.

Kearley, G.J. (promotor)
Mulder, F.M. (promotor)

Applied Sciences

2007-04-23

The dynamics and conductivity of the discotic liquid-crystal, hexakis(n-hexylox) triphenylene (HAT6), and charge-transfer complex that it forms with 2,4,7trinitro-9-fluorenone (TNF) are studied using quasielastic neutron-scattering (QENS) and Pulse-Radiolysis Time resolved Conductivity. These two techniques measure the molecular dynamics and conductivity decay, respectively, are interpreted in terms of a single model for the relaxation kinetics for a correlating environment. Use of a single model supposes that the molecular and charge dynamics are described by the same kinetic equation, which allows description of the system behaviour in space and time when combined with fractional diffusion equation. This supposition is substantiated by relating the two systems through the dispersion parameter, I2. This enables the range of the charge mobility to be linked to the length-scale of the molecular motion from which a coupling parameter is derived. The conductivity and molecular dynamics of HAT6 and HAT6-TNF are analysed in terms of the dynamical and coupling parameters. The thermal motion of a short column of HAT6 is simulated by a molecular dynamics simulation in order to provide the correct distribution of distorted molecular units, including the effects of the alkoxy tails. Ab-initio calculations are then used to determine the electronic structure of the distorted triphenylene cores and the time dependence of the interaction between these. A compact model for the vibrational dynamics of HAT6 is derived from the combined use of inelastic neutron scattering spectroscopy and first-principles calculations. It reproduces the essential features of the vibrational dynamics and electronic structure on the aromatic core of HAT6.

liquid crystals
neutron scattering
dynamics
conductivity

http://resolver.tudelft.nl/uuid:cf3d25a8-0dd0-41a5-b51e-7fc02ed3aaa3

IOS Press

978-1-58603-745-1

Institutional Repository

doctoral thesis

(c) 2007 O.V. Kruglova