Synthesis and mesogenic properties of three- and four-ring compounds with a fluoroisothiocyanatobiphenyl moiety

Dąbrowski, R.; Dziaduszek, Jerzy; Garbat, K.; Filipowicz, M.; Urban, S.; Gauza, Sebastian; Sasnouski, Genadź

doi:10.1080/02678292.2010.521983

Cited by 35 publications

(19 citation statements)

References 25 publications

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“…The high thermal stability of the smectic A phase is also seen for the members with a shorter propyl chain [78]. Its cyclohexyl analogue 29 already has a low melting nematic compound [101]. The shift of the fluorine atom to the central position (compound 30) decreases both the melting point and the stability of smectic A phase.…”

Section: Therphenyl Derivativesmentioning

confidence: 99%

“…Shortly, they are very useful components for formulation of the medium birefringence mixtures with high photochemical stability. Total depression of the smectic phase is obtained through the exchange of biphenyl unit for bicyclohexyl unit, see isothiocyanato compounds 105c and 105 [101]. With this move, low melting compounds with an extremely broad range of nematic only phase are obtained with high Δn ~ 0.35-0.4, which is involved by way of the high order parameter of these compounds.…”

Section: Four-ring Compounds: Quaterphenyls Phenylethynyl Terphenylsmentioning

confidence: 99%

“…Many such mixtures with Δn values in the range 0.3-0.7 have been demonstrated so far [49,50,91,93,94,101,111,122,124,128]. Mixtures with a broad range of nematic phases and birefringence values of Δn = 0.3-0.45 are now available with an acceptable level of viscosity (γ < 300 mPa· s), see example Mixtures 1791 and 1825 composed of fluoro-substituted alkyltolane and alkylphenyl tolane isothiocyanates have the highest birefringence among those presented in Table 17.…”

Section: Mixture Formulationmentioning

confidence: 99%

“…Many mono-, di-, tri-and tetrafluoro-substituted isothiocyanatoterphenyls have been prepared in our laboratory during the last decade [78,[101][102][103]. They were tested as mixture components in cooperation with Wu, S.T.…”

Section: Therphenyl Derivativesmentioning

confidence: 99%

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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: Therphenyl Derivativesmentioning

confidence: 99%

Section: Four-ring Compounds: Quaterphenyls Phenylethynyl Terphenylsmentioning

confidence: 99%

Section: Mixture Formulationmentioning

confidence: 99%

Section: Therphenyl Derivativesmentioning

confidence: 99%

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High Birefringence Liquid Crystals

2013

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“…Unsubstituted cyclohexylbenzene and bicyclohexyl benzene isotiocyanates, biphenyl-, fluorosubstituted terphenyl-, tolane-, and phenyl tolane isothiocyanates are very useful liquid crystalline compounds for diverse applications because of their high polarity, low viscosity, and high birefringence. [13][14][15] Electric characterization of the new notch filter is shown and discussed. Filter frequency response has been characterized by measuring the transmission coefficient S 21 of the scattering matrix vs. microwave frequency.…”

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confidence: 99%

Note: Tunable notch filter based on liquid crystal technology for microwave applications

Urruchi

Marcos

Torrecilla

et al. 2013

Review of Scientific Instruments

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In this work, a compact design of an electrically tunable notch filter, based on liquid crystal (LC) technology, has been designed, manufactured, and characterized. The proposal has been achieved through particular configuration schemes with low cost inverted-microstrip structures and conventional spurlines structures due to its ease of integration. Central frequency tunability has been induced by applying low ac voltages, thus involving low power consumption. For these devices, filter responses have been approached specifically at microwave C-band frequency allocated for many satellite communications applications. Also, it has taken advantage of new highly anisotropic nematic LC mixtures at those frequency ranges. Recently, liquid crystal (LC) technology has begun to be used in nonoptical applications due to its promising features in further electronic applications ranging from kilohertz to megahertz frequencies. Intrinsic anisotropy of some LC properties, which implies different properties depending of the direction in which they are measured, allows new advanced devices to be designed with tunable features, by using these materials.The use of LC to design tunable devices at microwave frequency bands is not a new conception; nevertheless there has been an increasing interest in improving their performance, particularly in the last decade. Liquid crystals were recognized as candidates for microwave dielectric substrates in the early 1990s. 1 Although first approaches to LC devices in waveguides led to bulky and large consumption designs (due to strong magnetic fields for switching LC molecules), most of the recent prototypes, such as tunable phase shifters, 2, 3 capacitors, 4 filters, 5,6 or antennas, 7 have reported practical functions involving electric fields for orienting LC at those frequencies.Filters are very valuable devices because they represent a powerful tool for frequency response processing. They are designed in order to select or to remove bands of frequency. A band-rejection filter or band-stop filter is a filter that attenuates a frequency band, while the other frequencies remain unchanged. A notch filter is a band-rejection filter with a narrow stopband, with a high quality factor, that is mainly used to remove spurious frequencies and to filter noise signals.In this work, the design of a notch filter for about 5 GHz rejection frequency (f 0 ), based on the electric field switching of a LC, has been proposed and its feasibility has been demonstrated. Filters working at this frequency, allocated in the C-band, are intended to be used in satellite telecommunication systems or, for example, to avoid the interference a) Author to whom correspondence should be addressed. Electronic mail:vurruchi@ing.uc3m.es.between the UWB (Ultra Wide-Band) and WLAN (Wireless Local Area Networks) systems. 8 UWB systems are particularly promising for short-range high-throughput wireless communications. Multiple solutions have been proposed for providing tunability in microwave devices, such as varactors based on sem...

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