A simple molecular theory of a nematic–nematic phase transition in highly polar compounds

Govind, A. S.; Madhusudana, N. V.

doi:10.1080/02678299308026466

Cited by 16 publications

(10 citation statements)

References 22 publications

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“…lower temperature). 20 As demonstrated by analysis of the Kirkwood factor the degree of antiparallel pairing is higher in the lower temperature nematic phase, and thus this model is not applicable to the present observation.…”

Section: Resultsmentioning

confidence: 71%

A nematic to nematic transformation exhibited by a rod-like liquid crystal

Mandle

Cowling

Goodby

2017

Phys. Chem. Chem. Phys.

198

145

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A novel, highly polar rod-like liquid crystal was found to exhibit two distinct nematic mesophases (N and N X ).When studied by microscopy and X-ray scattering experiments, and under applied electric fields, the nematic phases are practically identical. However, calorimetry experiments refute the possibility of an intervening smectic mesophase, and the transformation between the nematic phases was associated with a weak thermal event. Analysis of measured dielectric data, along with molecular properties obtained from DFT calculations, applying the Maier-Meier relationship allowed for the degree of antiparallel pairing of dipoles in both nematic phases to be quantified. Based on the results, we conclude that the onset of the lower temperature phase is driven by the formation of antiparallel molecular associations.

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Section: Resultsmentioning

confidence: 71%

A nematic to nematic transformation exhibited by a rod-like liquid crystal

Mandle

Cowling

Goodby

2017

Phys. Chem. Chem. Phys.

198

145

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“…1(b)), and this had been predicted by theoretical modelling. 3,4 The ferroelectric nematic, N F , phase was not observed experimentally, however, until 2017 when a new type of nematic phase exhibiting ferroelectric properties was independently reported by Mandle et al and Nishikawa et al in the materials RM734 and DIO, respectively. 5,6 This nematic phase was later assigned as the ferroelectric nematic phase, N F .…”

Section: Introductionmentioning

confidence: 99%

The effect of a lateral alkyloxy chain on the ferroelectric nematic phase

et al. 2022

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“…There are also some reports on new electrooptic effects in nematic liquid crystals with highly polar molecules [6]. Apart from applications, these compounds also exhibit several unusual features such as reentrant phase transitions, smectic-A polymorphism, nematic to nematic transition, and strong suppression of director fluctuation by fields [7][8][9][10][11][12][13]. When the nematic liquid crystals are sheared, they exhibit three different viscosities depending on the orientation of the director (the average molecular orientation direction) with respect to the flow and velocity gradient directions, and they are called Miesowicz viscosities [14].…”

Section: Introductionmentioning

confidence: 99%

Rheology of nematic liquid crystals with highly polar molecules

et al. 2014

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We report experimental studies on the rheology of a few nematic liquid crystals with highly polar molecules (CCH-7, PCH-7, CB-7). The selected molecules have the same alkyl chain (-C(7)H(15)) and cyano (-CN) end group. In the core part of the molecule, CCH-7 has two cyclohexane rings, PCH-7 has one cyclohexane and one aromatic ring, and CB-7 has two aromatic rings. Two viscosities were measured as a function of temperature, namely, η(2) (director parallel to the shear direction) and η(1) (director perpendicular to the shear direction). The orientation of the director was studied using small angle light scattering techniques. η(2) was measured in presheared sample, whereas the electrorheological technique was used to measure η(1). We show that both viscosities of the liquid crystals depend on the number of aromatic rings and Kirkwood correlation factor. The temperature dependent viscosities can be understood based on the intramolecular π-electron conjugation and intermolecular association of highly polar molecules.

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A simple molecular theory of a nematic–nematic phase transition in highly polar compounds

Cited by 16 publications

References 22 publications

A nematic to nematic transformation exhibited by a rod-like liquid crystal

A nematic to nematic transformation exhibited by a rod-like liquid crystal

The effect of a lateral alkyloxy chain on the ferroelectric nematic phase

Rheology of nematic liquid crystals with highly polar molecules

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