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See detailElectrooptic and dielectric properties of new antiferroelectric liquid crystal mixtures
Andersson, G.; Dabrowski, R.; Drzewinski, W. et al

in Ferroelectrics (2000), 244

Two new antiferroelectric liquid crystal mixtures based on optically active hydroxyesters have been studied with respect to their electro-optic and dielectric behavior. The mixtures exhibit only a SmA ... [more ▼]

Two new antiferroelectric liquid crystal mixtures based on optically active hydroxyesters have been studied with respect to their electro-optic and dielectric behavior. The mixtures exhibit only a SmA* phase above SmCa* and show a stable antiferroelectric order over a broad temperature range (≈100°C). Electro-optic as well as dielectric studies suggest that the SmCa*-SmA* transition is second order. In thin cells signs of a sur- face-induced SmC* phase has also been observed. We present the rele- vant characteristics for three different electro-optic modes which could be exploited in these materials, including the very fast linear mode for sub-threshold voltages. [less ▲]

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See detailOptic, electrooptic and dielectric properties of novel antiferroelectric liquid crystal compounds
Jägemalm, P.; Lagerwall, Jan UL; Dahlgren, A et al

in Ferroelectrics (2000)

The optic, electrooptic and dielectric spectroscopy characterisation of novel four-ring thiophene-based chiral esters comprising suitably 5,5’-disubstituted 2,2’-bithiophene (antiferroelectrics) is ... [more ▼]

The optic, electrooptic and dielectric spectroscopy characterisation of novel four-ring thiophene-based chiral esters comprising suitably 5,5’-disubstituted 2,2’-bithiophene (antiferroelectrics) is reported. The two compounds exhibit interesting hysteresis in their phase sequences, and we show that even whole phases (e.g. their relatively wide ferri-phases) may be suppressed by the surface interactions in thin cells. [less ▲]

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See detailOn the coexistence of SmC* and SmCa* phases in binary chiral-dopant antiferroelectric mixtures
Lagerwall, Jan UL; Parghi, D. D.; Heppke, Gerd et al

in Ferroelectrics (2000), 244

We present the results from investigations on a series of binary chiral- dopant liquid-crystalline mixtures. The racemic host materials possess tilted smectic phases with varying strengths of synclinic ... [more ▼]

We present the results from investigations on a series of binary chiral- dopant liquid-crystalline mixtures. The racemic host materials possess tilted smectic phases with varying strengths of synclinic and anticlinic ordering (SmC and SmCalt phases respectively). The dopants used were either a strongly synclinic-favouring non liquid-crystalline chiral material (commonly used in FLC chiral-dopant mixtures) or a strongly anticlinic (antiferroelectric) material ((S)-MHPOBC). The electrooptic and dielectric properties of the mixtures were investigated in test cells of different thickness and the influence of each mixture component on the observed physical properties is discussed. [less ▲]

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See detailThe dependence on the helical pitch of the antiferroelectric dielectric modes
Lagerwall, Jan UL; Fütterer, T.; Moro, D. et al

in Ferroelectrics (1999), 244

In an attempt to determine the physical nature of the low-frequency dielectric mode in antiferroelectric liquid crystals, we have studied the dielectric response in thick planar-oriented samples of ... [more ▼]

In an attempt to determine the physical nature of the low-frequency dielectric mode in antiferroelectric liquid crystals, we have studied the dielectric response in thick planar-oriented samples of Smectic C/sub A/* compounds undergoing a helix inversion. If the mode is collective there ought to be a minimum in the dielectric absorption due to the mode, at the temperature at which the helical pitch diverges. Although the effect is not large, we find minima for both antiferroelectric modes at this point, indicating that both modes are related to the helical director structure. A corresponding experiment has also been performed on a binary mixture which shows a helix inversion for a certain mixing ratio. However, because the effect in this case is overshadowed by unavoidable variations in other parameters, no minimum was detected. [less ▲]

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