Enhanced conductivity and dielectric absorption in discotic liquid crystalline columnar phases of a vanadyl complex

Haase, Wolfgang; Kilian, D.; Athanassopoulou, M. A.; Knawby, D.; Swager, Timothy M.; Wróbel, S.

doi:10.1080/02678290110093741

Cited by 37 publications

(17 citation statements)

References 7 publications

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“…Despite this spontaneous inversion, it is possible to use non-covalent interactions (for example, metal coordination to the calixarene, or hydrogen bonding with a guest molecule) to limit the motion, although doing so can prevent polarization reversal 85,86 . Once the core is fixed, the polarization can only be switched by rotating the mesogens or the entire assembly, which are both sterically unfavourable mechanisms 87,88 . Other systems, such as a tribenzocyclononene core with chiral side chains (Fig.…”

Section: Organization Of Molecular Dipolesmentioning

confidence: 99%

Supramolecular ferroelectrics

et al. 2015

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Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics - materials with a spontaneous and electrically reversible polarization - are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

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Section: Organization Of Molecular Dipolesmentioning

confidence: 99%

Supramolecular ferroelectrics

et al. 2015

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“…In a ferroelectric columnar phase, the direction of the macroscopic polarity can be switched by applying an electric field and can be kept after switching off the electric field as shown in Figure 1. Though it was attempted by using conical and bowlic molecular shapes [1][2][3][4][5][6][7][8][9][10][11], the switching behavior was not observed so far. Recently, two examples which indicated ferroelectrical switching behaviors are reported by Gorecka's and our groups [12].…”

Section: Introductionmentioning

confidence: 98%

Ferroelectrically Switchable Columnar Liquid Crystalline Ureas

Kishikawa

Nakahara

Nishikawa

et al. 2009

Molecular Crystals and Liquid Crystals

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The phase behavior of N, N 0 -bis(3,4,5-trihexadecyloxyphenyl)urea (1) was investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. It was found that 1 exhibited two columnar phases, rectangular columnar and hexagonal columnar phases. The switching current peak ðPs % 600 nC=cm 2 Þ was observed under applying a triangular voltage with maintaining the homeotropic (dark) texture, which suggested that the polarities of the columns were changed by the applied triangular voltage without changing the directions of the column axes. The mechanism for the ferroelectric switching behavior was explained by the conformational isomerization of the urea moiety.

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“…[25] Thanks to the dipole forces half disc molecules, bend core polycatenares or bowl-like vanadyl complexes can create columnar phases. [14,26,27] A permanent dipole moment appears in molecules of low symmetry and can be created thanks to electron-withdrawing fragments like carbonyl, cyano, chloride or other groups contained in the molecule. Thus, the molecules with inserted electron-accepting moiety give increased temperature range of LC phases.…”

Section: Introductionmentioning

confidence: 99%

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

et al. 2015

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2015): Influence of mesogenic core polarity and position of chains attachment on columnar phase stability, Liquid Crystals, Series of new Ni(II) metalomesogens of triangular molecular shape and forming Col h liquid crystalline (LC) phase were synthesised and described. Using in the molecular core the barbituric moieties that contain carbonyl or thiocarbonyl groups causes strong polarisation of the molecules and creates a permanent dipole moment μ, which was confirmed by quantum mechanical calculations. The relationship between molecular dipole moment and selforganisation of molecules into the columnar phase was considered. The position of alkyl and alkoxy chains substituted at phenyl ring that affects LC phase formation seems to be connected with planar conformation of the attached chains. These can broaden the mesogenic core and stabilise the Col h mesophase.

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Enhanced conductivity and dielectric absorption in discotic liquid crystalline columnar phases of a vanadyl complex

Cited by 37 publications

References 7 publications

Supramolecular ferroelectrics

Supramolecular ferroelectrics

Ferroelectrically Switchable Columnar Liquid Crystalline Ureas

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

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