Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant (original) (raw)
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V-shaped electro-optic response observed in a chiral ferroelectric smectic liquid crystal
Applied Physics Letters, 2008
We report on the observation of V-shaped switching in a ferroelectric liquid crystal cell over a wide range of temperatures. Results of the optical transmittance in the visible region give us the helical pitch for various temperatures of the ferroelectric liquid crystalline compound used. We show that the helical pitch, in addition to the spontaneous polarization ͑P S ͒ and thickness of the alignment layer of the cell, is an important factor in giving V-shaped switching. A longer or helical compensated mixture gives a better V-shaped switching.
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Physical Review E, 2004
Ferroelectric ordering, the electroclinic effect and chiral smectic C (SmC*) -smectic A (SmA*) phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electrooptic and second harmonic generation techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied DC-electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the switching behavior in reflection and transmission allows to distinguish the contributions from the bulk and the sub-surface layers of the cell. The analysis of temperature dependence shows the existence of a strong surface coupling. The temperature dependent nonlinear polarization shows a critical behavior corresponding to the superfluid model.
A novel nematic liquid crystal phase with ferroelectric response
A novel nematic liquid crystal phase with ferroelectric response Ferroelectric switching was observed for a nematic liquid crystal consisting of bentcore polar molecules. X-ray diffraction shows that this originates from the cooperative alignment of nanometric size polar and biaxial cybotactic groups present in the nematic phase. This discovery discloses the way toward ferroelectric fluids that can be aligned using a simple electric field.
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The European Physical Journal Applied Physics, 2011
We have experimentally investigated the unwinding process of the ferroelectric Sm-C * phase of a chiral AFLC smectic liquid crystal compound 12OF1M7 using the electro-optic properties, microscopic observations and constant current method. We found that this process occurs via two steps through an intermediate phase. Furthermore, we have established the (E-T) phase diagram of the studied compound by combining the experimental results.
Physical Review E, 2004
We describe an analog electro-optic (EO) switching mechanism occurring in thin cells filled with a lowpolarization ferroelectric liquid crystal mixture with positive dielectric anisotropy. The mixture is composed of an achiral nonpolar smectic-C ͑Sm-C͒ host doped with a small amount of a commercially available unichiral compound. The switching mechanism provides analog EO behavior, and thus could be attractive for information display applications. The process is polarization-driven for weak fields, while for higher field strength the dielectric coupling dominates the process.
Development of novel chiral dopants to be used in ferroelectric liquid crystal system
The study of chiral dopant and its application in liquid crystal system is one of the largest area of research in fluids leading to technological application in the field of display devices. Chiral dopant when mixed with achiral host mixture forms ferroelectric liquid crystal to be used in surface stabilised liquid crystal devices. 4-(pentyl, heptyl, nonyl)-2, 3 difluoro terphenyl nitriles and (S)-(−)-1-cyno-2-methylbutyl-4-pentyldifluoroterphenyl-4′-carboxylate were synthesised and mixed with achiral host mixture HM1 with the percentage of 3 and 7. Ferroelectric properties of synthesised FLC 1 were studied.
Liquid Crystals, 1991
The switching characteristics and the electro-optic response due to the electroclinic effect in chiral smectic A liquid crystals are analysed theoretically. We give an exact analytic solution to the dynamic equation of the tilt angle (8) up to the O4 term in the Landau expansion of the free energy. The non-linear behaviour of B and the characteristic. time under an applied electric field are described near the S2-S; transition. They both have a finite value at the transition which depends on the field. The characteristic time (to) exhibits a critical slowing down at sufficiently low fields, which occurs only in the early stages of the switching. At late stages, the switching time exhibits a maximum at a particular temperature which depends on the field, and then decreases in a very narrow temperature range near the transition. The U4 term is important in explainingcertain properties even for very small 6, and it becomes essential for B > 5". The optical response of an electroclinic liquid crystal cell is considered in detail. We derive an expression for the output intensity of light passing through an electroclinic cell. The delay and rise times for the optical signal are shown to a first approximation to be 0.379 to and 2.577 to, respectively.
New electromechanical effect in chiral smectic C* liquid crystals
1985
Re~u le 29 mars 1985, revise le 22 mai, accepte le 17 juin 1985) Résumé. 2014 Un nouvel effet électromécanique a été trouvé dans des cristaux liquides S*C orientés planairement, sous l'influence d'un champ électrique alternatif appliqué. En plus du phénomène électrooptique bien connu, des vibrations mécaniques ont été observées dans la direction parallèle aux couches smectiques et perpendiculaire au champ électrique. Abstract. 2014 A new electromechanical effect has been found in planar oriented S*C liquid crystals under the influence of an applied alternating electric field. Apart from the well-known electrooptical effects a mechanical vibration has been observed in a direction parallel to the smectic layers and perpendicular to the electric field. J. Physique Lett. 46 (1985) L-759 -L-761 15 AOÛT 1985, Classification
Smectic-A*–smectic-C*transition in a ferroelectric liquid crystal without smectic layer shrinkage
Physical Review E, 1999
The smectic layer spacing of a nonfluorinated ferroelectric liquid crystal ͑FLC͒ compound with almost no shrinkage and only minor tendency to form zigzag defects was characterized by small angle x-ray diffraction. The material lacks a nematic phase. The smectic-A*-smectic-C* phase transition was studied by measuring the thermal and electric field response of the optical tilt and the electric polarization. These properties are described very well by a Landau expansion even without introduction of a higher-order ⌰ 6 term. This result suggests a pure second-order phase transition far from tricriticality and differs considerably from the typical behavior of the A*-C* transition in most FLC materials. ͓S1063-651X͑99͒01907-8͔