Conformation, Defects, and Dynamics of a Discotic Liquid Crystal and Their Influence on Charge Transport

Abstract

Future applications of discotic liquid crystals (DLCs) in electronic devices depend on a marked improvement of their conductivity properties. We present a study of 2,3,6,7,10,11-hexakishexyloxytriphenylene (HAT6) and show how local conformation, structural defects, and thermal motions on the picosecond time scale strongly affect the efficient charge transport in DLCs. A direct and successful comparison of classical molecular dynamics (MD) simulations with both neutron powder diffraction and quasielastic neutron scattering (QENS) give a full insight into the structural and dynamical properties of HAT6. The local conformation of HAT6 molecules is characterized by a mutual rotation (twist) angle of about 37° and typically a mutual aromatic-core distance of 3.4 Å instead of the average distance of 3.65 Å usually quoted. We show that a considerable number of structural traps is present in HAT6, which persist at the picosecond time scale. We find that the high disorder in the mutual positions of the aromatic cores is an important factor contributing to the limited conductivity of HAT6 compared to larger DLCs.

Molecular dynamics simulations of alkyl substituted nanographene crystals

“…Ziogos and D.N. Theodorou atomistic simulations coupled with quantum mechanical methods were used for the calculation of charge transport properties of discotics [20,21,22,23]. A recent DFT study examined the effect of hydrogenation and Ca intercalation on the transport properties and local structure of HBC derivatives [24].…”

Supramolecular Self‐Assembly of Ionic Discotic Liquid Crystalline Dimer with DNA at Interfaces

“…Ionic discotic liquid crystals (DLCs) are fundamentally important model systems for studying anisotropic ion‐conduction through intriguing supramolecular architectures ,. Their long alkyl chains act as an insulating sheet for the ion conduction through well‐organized structures such as 1D columnar, 2D smectic or 3D bicontinuous cubic . These properties make ionic DLCs suitable for applications in batteries, photovoltaics, electroluminescence and electrochemical devices .…”

“…The most distinctive feature of DLCs is the π‐π stacking interaction between the aromatic cores, leading to intriguing supramolecular architectures . The more the number of aromatic cores, the stronger will be the stacking interaction.…”

Quasi- and inelastic neutron scattering to investigate the molecular dynamics of discotic molecules in the bulk

“…Moreover, the experimental data are compared to molecular simulations. For details see references [4][5][6] and work cited there. Employing inelastic neutron scattering phonons, electrons and charge transport have been considered (see for instance [7] and references cited there).…”