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

Christina Krause,Andreas Schönhals,Reiner Zorn,Bernhard Frick,B Frick,M M Koza,M Boehm,H Mutka

doi:10.1051/epjconf/20158302017

Abstract

In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate. For both compounds characteristic low frequency excess contributions to the vibrational density of states are found. Therefore it is concluded that these liquid crystals show a glass-like behaviour. Elastic scans further show that in these materials a rich molecular dynamics takes place.

Highlights

Discotic Liquid Crystals (DLCs) are self-assembled materials
In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate
At low temperatures DLCs exhibit a plastic crystalline phase. This phase can be followed by a hexagonal columnar liquid crystalline phase where the disc-shaped molecules organize into columns that further assemble into two-dimensional hexagonal arrays

Summary

Introduction

Discotic Liquid Crystals (DLCs) are self-assembled materials. The molecules consist of a flat and rigid aromatic core substituted by aliphatic side chains [1,2,3]. Self-assembly is driven by noncovalent intermolecular interactions of the cores and the nonfavoral interactions of the cores and the side chains. At low temperatures DLCs exhibit a plastic crystalline phase. This phase can be followed by a hexagonal columnar liquid crystalline phase where the disc-shaped molecules organize into columns that further assemble into two-dimensional hexagonal arrays. The alkyl chains fill the intercolumnar space giving so rise to a nanophase separation. Besides hexagonal nematic structures can appear [3]

Materials

Methods

Results

Vibrational density of states

Mean squared displacement