Origin of the Complex Molecular Dynamics in Functionalized Discotic Liquid Crystals

Elmahdy, Mahdy M.; Floudas, George; Mondeshki, Mihail; Spiess, Hans Wolfgang; Dou, Xiaohui; Müllen, Kläus

doi:10.1103/physrevlett.100.107801

Cited by 57 publications

(89 citation statements)

References 32 publications

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“…Recent investigations on a series of dipole functionalized HBCs (11a-d) showed that the presence of dipole substituents enhances intermolecular interactions, crucial for a uniform alignment of their columnar superstructures. [74,75] Furthermore, the crystalline phase was stabilized at elevated pressures (up to 600 MPa at temperature up to 450 K).…”

Section: Chemical Modification Of the Periphery Of Pahsmentioning

confidence: 99%

“…Soluble HBC (9a-c) can form liquid crystalline phases, in which the molecules align into ordered columns. [73][74][75] Moreover, the so-called discotic species can lie with their aromatic core on the surface in a ''faceon'' arrangement or stand with the edge of the aromatic cores in an ''edge-on'' fashion. For FETs, an ''edge-on'' organization of discotics in uniaxially oriented columns is required (Fig.…”

Section: Chemical Modification Of the Periphery Of Pahsmentioning

confidence: 99%

See 1 more Smart Citation

Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity

2009

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Organic electronics is one of the hottest and most exciting research topics today. However, its performance still lags behind that of inorganic‐based electronics. This Progress Report demonstrates that by controlling the complexity of organic molecules at the molecular and at the supramolecular level as well as by choosing suitable processing techniques, the desired function for applications in electronics can be achieved. Our main focus is on polyphenylene‐based nanomaterials, versatile organic molecules that allow access to novel intricate materials. We emphasize the molecular complexity as well as the supramolecular organization and the interfacing of novel organic materials as key guidelines.

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Section: Chemical Modification Of the Periphery Of Pahsmentioning

confidence: 99%

Section: Chemical Modification Of the Periphery Of Pahsmentioning

confidence: 99%

Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity

2009

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“…[43][44][45] Discotic liquid crystals also display a "double" primary relaxation with similar temperature dependence as found in PCNB. In other words, the two systems, PCNB and discotic liquid crystal, share both the same degree of anisotropy and a similar phenomenology.…”

Section: Resultsmentioning

confidence: 63%

“…19 It is worth noting that a relaxation phenomenology similar to PCNB has been reported in related molecular systems, namely discotic liquid crystals consisting of phenyl-based, rigid disk-shaped aromatic flat cores functionalized with flexible polar sidegroups. [43][44][45] These materials, whose constituent molecules can be considered to be larger "cousins" of the hexasubstituted benzenes, display in fact two dielectric relaxations with different characteristic times but virtually identical temperature dependencies. 44 Also in the case of discotic liquid crystals, the lower-frequency relaxation corresponds to the main α process, as discernible from the position of the loss maximum at the corresponding T g (determined from calorimetry measurements), and the second (α ) process at higher frequency displays lower dielectric strength than the first one.…”

Section: Resultsmentioning

confidence: 99%

Double Primary Relaxation in a Highly Anisotropic Orientational Glass-Former with Low-Dimensional Disorder

et al. 2016

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The freezing of the cooperative reorientational motions in orientationally disordered (OD) molecular crystals marks the so-called "glassy" transition, which may be considered a lower-dimensional version of the structural glass transition. While structural glasses display both positional and orientational disorder, in fact, in orientational glasses the disorder involves exclusively the orientational degrees of freedom of the constituent molecules, while the molecular centres of mass form an ordered lattice. We report here on a glass-forming system with even less degrees of freedom, namely the OD phase of a dipolar benzene derivative, pentachloronitrobenzene (C 6 Cl 5 N O 2 ). We probe the orientational dynamics of PCNB as a function of temperature and pressure * To whom correspondence should be addressed † Universitat Politècnica de Catalunya ‡ Università di Pisa 1 by means of dielectric spectroscopy at normal and high pressure and high-pressure density measurements, and show that the system exhibits a double primary relaxation feature associated with two distinct motions of the molecular dipole moment. After ruling out an interpretation in terms of primitive or intramolecular relaxations, we discuss an assignment of the double relaxation feature based on the material's anisotropy and on the comparison with discotic liquid crystals.

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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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Origin of the Complex Molecular Dynamics in Functionalized Discotic Liquid Crystals

Cited by 57 publications

References 32 publications

Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity

Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity

Double Primary Relaxation in a Highly Anisotropic Orientational Glass-Former with Low-Dimensional Disorder

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

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