Fast and Slow Dynamics in a Discotic Liquid Crystal with Regions of Columnar Order and Disorder

Feng, Xinliang; Macho, V.; Müllen, Kläus; Spiess, Hans Wolfgang; Floudas, George

doi:10.1103/physrevlett.107.257801

Cited by 39 publications

(56 citation statements)

References 27 publications

(36 reference statements)

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“…In our studies, we have focused primarily on the effect of the nature of the peripheral substitution. Further analyses with variable core sizes [3,46,47,48] and side chains with more complex chemical composition [3,49,50,51] would enlighten the overall understanding of the properties of soluble nanographene molecular crystals.…”

Section: Downloaded By [Selcuk Universitesi] At 06:30 04 February 2015mentioning

confidence: 99%

Molecular dynamics simulations of alkyl substituted nanographene crystals

Ziogos

Theodorou

2015

Molecular Physics

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Discotic polyaromatic molecules, similar to nanometric graphene flakes, constitute an interesting class of materials for organic electronic applications. Grafting flexible side chains around the periphery of such molecules enhances their processability and gives rise to diverse behaviours, such as the manifestation of liquid-crystalline character and anisotropic mechanical response. In this work, we examine by means of molecular dynamics simulations the properties of molecular crystals comprised of alkyl-substituted hexa-peri-hexabenzocoronene mesogens. Pristine and mono-substituted systems by hydrogen or iodine atoms are modelled, with variable side chain length. A general structural and mechanical robustness to peripheral substitution is reported, with the mesogens forming tightly packed molecular wires even at elevated temperature and pressure. In their discotic ordering, the molecules present relatively low translational mobility, a beneficial phenomenon for charge transport. A thermotropic dependence of the mechanical response is identified, with the systems behaving differently in their room-temperature crystalline phase and in their liquid-crystalline phase at elevated temperatures. The melting process is also examined, elucidating an initial negative expansion along a high symmetry direction and the existence of a metastable state, before falling into the final liquid-crystalline state.

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Section: Downloaded By [Selcuk Universitesi] At 06:30 04 February 2015mentioning

confidence: 99%

Molecular dynamics simulations of alkyl substituted nanographene crystals

Ziogos

Theodorou

2015

Molecular Physics

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“…The dynamics of the discs is of particular interest with regard to optimization of the processing of these materials. Along these lines, we investigated a C 3 ‐symmetric HBC disk with alternating hydrophobic and hydrophilic side chains (Figure 6a) by NMR, X‐ray scattering, and rheology 60. In the solid (C r ) phase, the values for dynamic order parameter S CH of the HBC core (Figure 6a) indicate rigid columns, in agreement with wide angle X‐ray results.…”

Section: Applicationsmentioning

confidence: 99%

“…In the heterogeneous scenario, stacks of columns, in which the discs are inclined at an angle ±θ, are separated by disordered regions. (For details, see reference 60.) In such a structure, collective columnar rotation of the disks inclined at ±θ to the column axis is expected (Figure 6e).…”

Section: Applicationsmentioning

confidence: 99%

Magic Angle Spinning NMR of Macromolecular and Supramolecular Systems

Spiess¹

2013

Israel Journal of Chemistry

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Sideband patterns in single quantum and double quantum magic angle spinning NMR spectra are reviewed. Their use in elucidating non‐covalent interactions, such as hydrogen bonds or pi‐pi stacking, is demonstrated by studies of supramolecular systems of current interest. Moreover, the effects of local and collective motions are illustrated by examples from supramolecular and macromolecular science.

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“…The self-organization of disc-like molecules can result in liquid crystalline phases with remarkable structural and dynamical properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In particular, the electrical conductivity and the high photoconductivity typical of columnar phases make discotic liquid crystals (DLCs) promising candidates for numerous technological applications, for example in electroluminescent and photovoltaic devices [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores

et al. 2015

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We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasi-static case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and Xray scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC based nanocomposites.

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Fast and Slow Dynamics in a Discotic Liquid Crystal with Regions of Columnar Order and Disorder

Cited by 39 publications

References 27 publications

Molecular dynamics simulations of alkyl substituted nanographene crystals

Molecular dynamics simulations of alkyl substituted nanographene crystals

Magic Angle Spinning NMR of Macromolecular and Supramolecular Systems

High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores

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