Physical properties of laterally fluorinated isothiocyanato phenyl‐tolane liquid crystals

Gauza, Sebastian; Parish, Amanda; Wu, Shin‐Tson; Spadło, A.; Dąbrowski, R.

doi:10.1080/02678290801956321

Cited by 40 publications

(20 citation statements)

References 25 publications

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“…They have a birefringence reaching up to 0.45 at room temperature in the case of isothiocyanates for pentyl terminal chain, and furthermore, they also reach Δn values up to 0.6 for the ethyl chain [110,111]. Their FoM 1 values are about 40 at room temperature and reach maximum value ~240 at 150 °C .…”

Section: Phenyl Tolanesmentioning

confidence: 87%

High Birefringence Liquid Crystals

2013

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Liquid crystals, compounds and mixtures with positive dielectric anisotropies are reviewed. The mesogenic properties and physical chemical properties (viscosity, birefringence, refractive indices, dielectric anisotropy and elastic constants) of compounds being cyano, fluoro, isothiocyanato derivatives of biphenyl, terphenyl, quaterphenyl, tolane, phenyl tolane, phenyl ethynyl tolane, and biphenyl tolane are compared. The question of how to obtain liquid crystal with a broad range of nematic phases is discussed in detail. Influence of lateral substituent of different kinds of mesogenic and physicochemical properties is presented (demonstrated). Examples of mixtures with birefringence ∆n in the range of 0.2-0.5 are given.

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Section: Phenyl Tolanesmentioning

confidence: 87%

High Birefringence Liquid Crystals

2013

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“…Assuming that the internal field in a crystal is the same in all directions, Vuks [26] derived the equation for an anisotropic medium which relates the ordinary and extraordinary refrac− tive indices with the molecular polarizabilities for aniso− tropic materials as Opto−Electron. Rev., 22, no.…”

Section: Theory (Four-parameter Model)mentioning

confidence: 99%

“…Quite a few molecular structures with high Dn values have been investigated by using different methods [2][3][4]25]. However, most of the studies on high Dn liquid crystals have only been carried out in their eutectic mixtures [4,26,27]. In our study, we have taken pure samples of two NCS nematic liquid crystalline compounds: 4'−butylcyclohe− xyl−3, 5−difluoro−4−isothiocyanatobiphenyl and 4'−pentyl− cyclohexyl−3, 5−difluoro−4−isothiocynatobiphenyl.…”

Section: Introductionmentioning

confidence: 99%

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

Devi

Choudhury

Bhattacharjee

et al. 2014

Opto-Electronics Review

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Optical studies have been carried out on two fluorinated isothiocyanato nematic liquid crystal (LC) compounds 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl. Transition temperatures of the two samples were confirmed using a polarizing microscope. The two LC compounds were found to exhibit fairly high clearing temperatures. Measurements of refractive indices of the two compounds were done by using thin prism method with He-Ne laser beam of wavelength 630 nm. Birefringence of the two LC compounds was calculated from the measured refractive indices. Both the compounds are found to display fairly high values of birefringence. Validation of a modified four-parameter model, based on Vuks equation describing the temperature dependence of refractive indices of the two liquid crystals, is also presented in this paper. The model is validated by fitting the experimentally measured values of refractive indices, birefringence and average refractive indices of the two nematic LCs with the theoretical values. In this paper, the calculation of order parameters of the LCs is presented by using two methods: direct extrapolation method based solely on the birefringence data and by using modified Vuks method based on Haller’s extrapolation. As observed from the obtained results, this procedure of calculating order parameter gives very reasonable results.

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“…As expected [22] the melting temperature of the complex is higher than for the corresponding ligands, according to the higher core rigidity and molecular size obtained upon coordination. A similar behaviour is expected also for the isotropization temperature, provided that coordination extends the rigid core without affecting its planarity.…”

Section: Introductionmentioning

confidence: 73%