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The viscoelastic properties belong to the most important properties of chiral smectic liquid crystals. In this paper different methods for determination of viscoelastic properties of chiral smectic liquid crystals are compared. All of them belong to small deformation methods. The importance of the director alignment in the sample for determination of the bulk elasticity and viscosity coefficients is described. Using a typical ferroelectric in the chiral smectic C* phase we demonstrated that the correct bulk values of mentioned material constants can be determined using thick, homeotropically aligned samples only. [ABSTRACT FROM AUTHOR]

Three different Antiferroelectric Liquid Crystals, synthesized in Military University of Technology were investigated by dielectric means. Some of them are orthoconic. The structures of studied compounds are very similar. The only one difference is presented in rigid core. The position and number of Fluorine atoms in rigid core changes. Very rich dielectric modes are detected with frequencies from 50 Hz up to 40 MHz. In this paper, dielectric spectroscopy of investigated materials is presented. [ABSTRACT FROM AUTHOR]

Numerous methods of re-writable optical recordings using nematic mixtures for holographic media have been presented. A new approach to this problem is possible by using surface stabilized ferroelectric liquid crystal structures (SSFLC). This is very promising from the theoretical point of view because the surface stabilized the structure of ferroelectric smectic SmC* material inherently consists of a memory effect while driving by external electric field. Moreover, due to the layered structure of the surface stabilized ferroelectric liquid crystal there is a possibility of obtaining high resolution of the written gratings. In the paper, some theoretical basis regarding possibility of optical addressing of SSFCL cells are discussed. Methods of preparation of the optically addressed SSFLC cells in room temperature bistable SmC* structure are presented. Experiments with these cells in simple holographic two-beam set-up (DWTM) are described. [ABSTRACT FROM AUTHOR]

This paper focuses on the light transmission properties of Dye Guest-Host Polymer Dispersed Ferroelectric Liquid Crystal (DGHPDFLC). The DGHPDFLC samples were prepared by using various concentrations of UV curable polymer and 3 wt% blue dichroic dye under various intensities of ultraviolet irradiation. This system can remove a polarizer to achieve better brightness, and improve the transmission of Dye Guest-Host Ferroelectric Liquid Crystal and Polymer Dispersed Ferroelectric Liquid Crystal systems. The results show that the addition of polymer increases the ratio of transmitted light. The prepolymer (NOA65) become fully cured at a higher UV irradiation intensity, and it decreases the transmission of the system. [ABSTRACT FROM AUTHOR]

We propose a new voltage-transmittance (V-T) curve suitable to determine the driving pulse shapes. There are three alternating periods in the multiplex driving scheme; a selecting period, a holding period and a resetting period. Holding pulse shape and holding period affect the switching behavior of AFLCs. In this paper a new V-T characteristics of AFLCs applicable in the design of multiplex driving scheme is examined, where a square pulse is used for both selection and holding voltages. [ABSTRACT FROM AUTHOR]

This paper reports the results of the dielectric relaxation studies performed in the Smectic A (SmA) and Smectic C∗ (SmC∗) phases of the ferroelectric liquid crystal, 12CN5(R∗) in the frequency range 5  Hz to 13  MHz. Planar orientation used throughout the study was achieved by rubbed polyamide coating on the surfaces of the dielectric cell. Transition temperatures determined from the derivative of the dielectric permittivity agrees with that obtained using thermal polarizing microscopy. The dielectric spectrum in the SmA phase shows single relaxation, whereas the SmC∗ phase has two relaxations, viz., the low frequency Goldstone mode and the high frequency soft mode. Special attention was paid to the study of the low frequency Goldstone mode relaxation. From the Cole-Cole plots, the temperature dependence of dielectric strength (Δε), the relaxation frequency (fR) and the distribution parameter (α) relevant to the Goldstone mode have been estimated. The relaxation frequency follows the Arrhenius relation in the asymptotic regions far from the transition. Results of the bias-dependent dielectric measurements of the Goldstone mode relaxation have also been presented. [ABSTRACT FROM AUTHOR]

In search of the long pitch, orthoconic antiferroelectric liquid crystalline mixture (OAFLC), the high tilted host mixture with antiferroelectric smectic phase (AFLC) was formulated. The influence of the molecular dipole moment magnitude and orientation on physical properties of the AFLC was tested by doping of the host by three different dopants. The extensive study of the host material and obtained admixtures was done. Results are discussed in the context of the influence of the molecular dipole moment orientation and magnitude of the dopant on the tilt, helical pitch and spontaneous polarization of the [image omitted] phase of obtained mixtures. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a ferroelectric mixture with low eutectic point based on chiral and achiral thioesters. Nine ferroelectric mixtures of two thioesters have been studied by Dielectric Spectroscopy (DS) and Reversal Currents Method (RCM). DS and RCM measurements have been performed on the well aligned mono-domains by means AC electric field. Spontaneous polarization vs. temperature for each concentration has been measured to study the character of the transition between the para- and ferroelectric phases in view of the mean-field theory. The Influence of the chiral dopant on the nature of ferroelectric behaviour was also investigated. [ABSTRACT FROM AUTHOR]

This paper reviews several experimental studies of electric-field effects in liquid crystal devices containing ferroelectric, antiferroelectric and ferrielectric liquid crystals. Small-angle X-ray scattering has been employed to study both rapid, reversible layer flexing and irreversible, high-field deformations in surface stabilised ferroelectric devices. New antiferroelectric materials are also considered and the tilt angle and chevron angle adopted in devices are described. Generally, the chevron angle is found to compare well with the steric tilt angle (∼20°) and is considerably lower than the optical tilt angle (∼30°). Both conventional and resonant X-ray scattering experiments have been used to probe the layer and interlayer structure and field-induced deformations in antiferroelectric, ferrielectric and ferroelectric liquid crystal devices. It is found that the mechanism of the chevron to bookshelf transition is phase-dependant and is thresholdless in the ferroelectric phases of these materials. Further, resonant scattering reveals that the field-induced antiferroelectric or ferrielectric to ferroelectric transition can occur at field strengths that are similar to or higher than those required to deform the smectic layers. [ABSTRACT FROM AUTHOR]

Ferroelectric liquid crystal (FLC) liquid crystal over silicon (LCOS) devices can address large arrays of pixels at very high frame rates. They can also allow the phase of the light to be modulated in a manner that is independent of the state of polarisation of the incoming light. The optical versatility of the liquid crystal can now be matched by the electronic versatility of CMOS (complimentary metal oxide semiconductor) silicon backplanes as developments in very small feature sizes (sub micron) allows more and more complex electronic structures to be integrated into the device. In this paper, we briefly review some possible future applications of this technology in the area of displays, image processing and optical switching. In order to create these new device structures, we need suitable FLC materials. [ABSTRACT FROM AUTHOR]

The rubbing conditions are researched in terms of the rubbing cloth materials for ferroelectric liquid crystal (FLC) display application. Although cotton is generally used as the rubbing cloth, a good FLC molecular alignment can be obtained even in (semi) synthetic fiber clothes such as acetate, cellulose, and polyester. In order to obtain the good alignment without rubbing scratches, it is important to use a soft cloth. On the other hand, for a hard cloth, there is a possibility to obtain the good alignment by increasing the rubbing number and thus, polishing the alignment film surface. [ABSTRACT FROM AUTHOR]

Brief overview of polar liquid crystals (LCs) is given with a tutorial manner. They are chiral smectic C ferroelectric LCs (FLCs), chiral smectic CAantiferroelectric LCs (AFLCs), their ferrielectric subphase LCs, chiral columnar FLCs, chiral and nonchiral ferronematic LCs, various bent-shaped polar LCs such as B1, B2, B4, B7, twist-bend nematic, orthogonal polar smectic, and nonchiral columnar FLCs. After summarizing the definition of FLCs and AFLCs, and techniques to certify these polar LCs, their polar structures and characteristics are described together with important review articles. [ABSTRACT FROM AUTHOR]

Polymer-stabilized ferroelectric liquid crystals may show monostable and V-shaped electrooptical characteristics. We have investigated the dependence of their characteristics on the photocuring condition, especially ultraviolet light intensity. Furthermore, we offer a new scheme of the photocure being done under an electroclinic effect. The bistability of ferroelectric liquid crystals remains partially in the case of a weak ultraviolet light intensity and the saturation voltage increases as the ultraviolet light intensity increases. The tilt angle decreases as the ultraviolet light intensity increases. The decrease of tilt angle cannot be suppressed even in polymer-stabilized ferroelectric liquid crystals fabricated using the electroclinic effect. [ABSTRACT FROM AUTHOR]

A progress report on the synthesis and characterisation of a series of fluorinated chiral bi-mesogen low molar mass organosiloxane materials is presented. The mesogenic moiety is identical to that in the TSiKN65F mono-mesogen material reported by Naciri et al., which displays a de Vries-type SmA* phase. The parameter varied across the series is the length of the alkyl chain linking the mesogen moiety to the siloxane. The material with 10 carbon atoms in the chains displays a stable smectic phase with ferroelectric response at room temperature, whereas the materials with 6, 7 and 8 carbon atoms tend to crystallize. [ABSTRACT FROM AUTHOR]

The best chiral compounds for the design of shock-free ferroelectric liquid crystal compositions with a wide temperature range of the chiral smectic C phase have been developed. For these experiments about 70 different 4-ring chiral compounds were synthesized and investigated. The influence of the chiral fragment, the mixing ratio between chiral and non-chiral molecules, and the pretilt angle of the alignment materials on the quality and on the mechanical stability of the orientation were investigated. New optimized ferroelectric liquid crystal compositions for the fabrication of shock-free ferroelectric liquid crystal displays with high contrast ratio are presented. [ABSTRACT FROM AUTHOR]

A coplanar waveguide type microwave phase shifter using ferroelectric liquid crystal is constructed and its fundamental characteristics are measured. An analysis procedure of the effective permittivity of the phase shifter is explained. The decrease of the width of the center conductor in the phase shifter leads the increase of the dielectric permittivity change, consequently increasing the phase shift. The distance between the center conductor and ground plane needs the same as the width of the center conductor. Furthermore, it is confirmed that the arrangement of the dielectric substrate instead of the liquid crystal layer is useful technique. [ABSTRACT FROM AUTHOR]

We report the structural and relaxation investigations of an achiral bent-core compound in SmAPA phase. The studied material undergoes transition from one biaxial state to the other via a uniaxial state under electric field. These transformations are explained as successive transition from antiferroelectric to ferroelectric states, where, the intermediate uniaxial state has the molecular secondary directors in the neighbouring smectic layers perpendicular to each other. We also found that near SmAPR to SmAPA phase transition the second harmonic electro-optic response, induced polarization, and the dielectric behaviour hint softening behaviour in the material. [ABSTRACT FROM AUTHOR]

The present article is a study of the ferroelectric behavior in low-molar-mass organosiloxane liquid-crystal materials classed. A few novel compounds with large tilt angle and wide temperature range of the SmC* phase have been synthesized, and the mesophases exhibited by them have been compared. The mesophases under discussion were investigated by means of polarizing microscopy, differential scanning calorimetry, X-ray diffraction, as well as electro-optical experiments. The influence of the molecular structure on the occurrence of the SmC* phase was investigated. Finally, the electro-optical properties of the SmC* phase, such as tilt angle, dielectric permittivity, and switching behavior, were also measured. As a consequence, the correlation between their electro-optical properties and chemical structures of these compounds is investigated. [ABSTRACT FROM AUTHOR]

A new liquid crystal of siloxane dimer with an achiral swallow-tail, C11Si3C11, was synthesized and mixed with a chiral material of 4'-(1-butoxy-1-oxopropan-2-yloxy)biphenyl-4-yl 3-bromo-4-[9-(1,1,2,2,3,3,3-hepta-methyltrisiloxanyl)nonyloxy) benzoate, C9SiFLC, for the preparation of binary mixtures for the study. The mesophases under discussion were investigated by means of polarizing microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and electro-optical experiments. The influence of the mixture proportion of C9SiFLC on the occurrence of the chiral smectic C (SmC*) phase was investigated. Finally, the electro-optical properties of the SmC* phase, such as the tilt angle and switching behavior, were also measured. [ABSTRACT FROM AUTHOR]

Relation between the spontaneous polarization and alkyl chain length was investigated in ferroelectric switching of N,N'-bis(3,4,5-trialkoxyphenyl)urea (1-7) possessing n-C4H9, n-C8H17, n-C9H19, n-C10H21, n-C11H23, n-C12H25, and n-C16H33, respectively. The phase behaviors were investigated by differential scanning calorimetry, polarized optical microscopy, and the column diameters were obtained by X-ray diffraction. Compound 2-7 exhibited rectangular and hexagonal columnar phases. All of the hexagonal columnar phases showed ferroelectric switching under a triangular wave voltage. From the plot of the spontaneous polarization against the carbon atom number of the alkyl chains, correlation between them were clarified and it was strongly suggested that the switching current peaks originated in switching of the polar columns, not in the movement of ionic impurities. [ABSTRACT FROM AUTHOR]

Phase transitions temperatures and temperature dependence of helical pitch p for S-(+)-4'-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[(4,4,4,3,3,2,2-heptafluorobutoxy)alkoxy] benzoates, and 3-fluoro-, and 2-fluoro-, 2,3-difluoro-benzoates upon length of alkoxy spacer were tested. For etoxy and propoxy spacer the pitch p in antiferroelectric phase is increasing with temperature to maximal value of about 1000 nm in high temperatures region. For pentoxy, hexoxy, and heptoxy spacer the pitch p is longer and reverse temperature dependence is observed. The compounds convenient for formulation of antiferroelectric orthoconic mixture with pitch length of about 2000 nm were selected. [ABSTRACT FROM AUTHOR]

We have synthesized and investigated a new chiral dopant. It belongs to the derivatives of p-terphenyldicarboxylic acid and has twisting power in the smectic C* mixture much higher than any chiral compound of this series known before. The ferroelectric liquid crystal mixtures on the base of achiral SmC matrix and the new chiral dopant have been elaborated and there optical and electro-optical properties were investigated. [ABSTRACT FROM AUTHOR]

Polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which a photocurable mesogenic monomer is doped into a ferroelectric liquid crystal and a UV photocure is carried out in the SmA or the SmC* phase under the application of a bipolar AC electric field, show the monostable and V-shaped electrooptical characteristics, and thus are expected to be a newly developed materials for LC devices. In this study, in order to increase the thermal reliability of PSFLCs, we fabricate a new PSFLC photocured at the nematic (N) phase, and then investigate its characteristics in terms of the electrooptical effect and the X-ray diffraction. Results show that the PSFLC photocured at the N phase does not become monostable because the chevron angle does not coincide with the tilt angle. [ABSTRACT FROM AUTHOR]

Ferroelectric nanoparticle suspensions can enhance the properties of liquid crystals; increasing key parameters such as clearing point, birefringence and dielectric anisotropy. However, these suspensions are difficult to reliably prepare. The interaction between surfactant and ferroelectric particles plays a crucial role in determining the performance and stability of these suspensions. Here we focus on producing ferroelectric nanoparticles using a ball milling process. Using convenient Fourier Transform Infrared Spectroscopy (FTIR) we demonstrate an effective means to monitor the surfactant distribution during the milling process. We also found that the Curie transition from the ferroelectric to paraelectic state of the particles is dependent on both the milling time and surfactant concentrations. [ABSTRACT FROM AUTHOR]

We investigate the effects of rubbing on the surface free energies of polyimide thin films, and how the surface energetic properties influence the molecular alignment of ferroelectric liquid crystals and the formation of zigzag defects. Rubbing breaks the uniformity in free energy at the surface of polyimide thin film. By properly rubbing the polymer, a diminishment of the difference between the polar part of the surface energies along and against the rubbing direction, respectively, can be achieved, and will favour the formation of zigzag free ferroelectric liquid crystal layer. [ABSTRACT FROM AUTHOR]

A polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which photocurable mesogenic monomers are doped into an FLC and then a UV photocure is carried out in the SmC* phase under the application of a bipolar AC electric field, can exhibits monostable and V-shaped electrooptical characteristics. In this research, the time-resolved ellipsometry is applied to the PSFLCs, and we investigate the dependence of the molecular reorientational motion of the PSFLC on the photocuring condition such as the tilt angle which FLC molecules take in the photocure stage. The measurement results show that the dynamic behavior of PSFLC-molecular reorientation strongly depends on the photocuring condition of the tilt angle in addition to the concentration of polymer. Furthermore, the molecular reorientation of the PSFLC is 2-steps motion originated in the difference of the threshold voltage between near and far from polymer. [ABSTRACT FROM AUTHOR]

A series of N-triarylamine-based derivatives such as 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), 1,3,5-tris[4-(3-methylphenyl(phenyl)amino)phenyl]benzene (m-MTDAPB) and 1,3,5-tris-{4-[1-naphthyl(phenyl)amino]phenyl}benzene (1-TNAPB) were synthesized and characterized. Specially, 1-TNAPB was synthesized with high yield in 1 hr. The hole injecting/transporting properties of these materials were investigated by using double-layered organic light-emitting diodes (OLEDs) with the configuration of ITO/N-triarylamine/Alq3/LiF/Al, in which Alq3 was used as an emitting and electron transporting layer. A comparative study on EL performance of OLEDs fabricated with N-triarylamines as the hole injecting/transporting layer revealed that better results were observed in OLED with m-MTDAPB and α-NPD, respectively. OLED with m-MTDAPB (20 nm thickness) showed maximum luminescence of 15,970 cd/m2 at 10 V and turn-on voltage of 4 V. On the other hand, α-NPD (50 nm thickness) exhibited maximum luminescence of 17,650 cd/m2 at 17 V and turn-on voltage of 7 V. [ABSTRACT FROM AUTHOR]

The polymer-stabilized ferroelectric liquid crystal (PS-FLC) photocured under the application of an AC electric field shows a monostable V-shaped electrooptical characteristics. However, it is not clear how the V-shaped electrooptical characteristics can be realized in the PS-FLC. In this study, we have investigated in detail the elecrooptical characteristics, microscopic texture and X-ray diffraction of PS-FLC, and the effect of the polymer stabilization on the molecular alignment structure. As a result, it is guessed that two types of domain, in which there are two alignment directions monostabilized by the polymer photocured under the application of a bipolar electric field, would coexist. [ABSTRACT FROM AUTHOR]

The application of the LCD modeling and optimization system (MOUSE-LCD) for the design and development of the new advanced LCD configurations is demonstrated. The proposed new method of LCD optimization can be successfully applied for the design of the new advanced LCD configurations operating in various electrooptical nematic, cholesteric and ferroelectric LC modes, such as TN, STN, ECB, VAN, HAN, π-cell, book-shelf and others. We have found the conditions, which enable to realize perfect dark and bright states and wide viewing angles in LCDs for various LC physical characteritics, LC orientation in the cell and operating voltage as a function of the parameters of the phase compensators, anti-reflective layers, LC cell thickness and orientation of the polarizers. The optimization module allows for the spectral and angular averaging, thus enabling to produce LCD with wide viewing angles, achromatic (black/white) switching and fast response time. We have also shown, that some important LC elements of fiber optical systems, e.g., polarization controllers and polarization rotators can be designed and optimized. We demonstrate also 2D version, which enables to simulate the optical performance of LCD, as a function of the coordinate parallel to the LC layer. Liquid crystal (LC) structures in high resolution LCDs with a rapid lateral variation of optical parameters (microdisplays, multi-domain LCDs, IPS-LCDs) is characterized taking into account the effects of light diffraction. This software provides the simulation of various experimental tests with fine–structure LC cells. In particular, the simulation of LCD measurements with a polarizing microscope is performed. [ABSTRACT FROM AUTHOR]

A high speed phase modulator based on ferroelectric liquid crystal (FLC) is demonstrated. For uniform alignment and pure phase modulation, we propose a new FLC device using a short helical pitch material in a homeotropic alignment. This device is driven by periodic in-plane electrode stripes implemented on the surface of both cell substrates. As a result, we have obtained a large phase modulation (about 2.3π at λ = 1.55 μm under E = 2.5 V/μm) and fast response time ( [ABSTRACT FROM AUTHOR]

As part of our line of research into high resolution, video rate antiferroelectric displays we have studied the ferroelectric – antiferroelectric relaxation that follows the data pulse, in surface stabilised antiferroelectric liquid crystal (AFLC) displays, driven by biasless or low bias video frequency waveforms. This generally incomplete relaxation reduces the intensity of the light transmitted by a pixel in any partially ferroelectric (grey-level) state during a video frame, and hence limits the frame-averaged brightness of the AFLC display. The relaxation is a function of the surface stabilisation (i.e., the anchoring strength, pre-tilt and thickness of the device and the pitch of the AFLC), the rotational viscosity of the AFLC, the degree of relaxation of the AFLC between successive frames, the magnitude of the data pulse (grey level) and bias voltage. We have optimised the driving scheme for a number of symmetric and asymmetric (biasless) displays with different antiferroelectric materials and a variety of alignment surfaces, and present mathematical fits to the decaying transparency during single frames as functions of the data pulse. Finally we discuss the mechanisms governing the relaxation. [ABSTRACT FROM AUTHOR]

The induced antiferroelectric phase in bicomponent mixtures of fluorinated compound C 6 F 13 C 2 H 4 OPhPhCOOPhCOOC*H(CH 3 )C 6 H 13 and a member of homologous series of C n H 2n+1 COO(CH 2 ) 3 OPhCOOPhPhCOOC*H(CH 3 )C 6 H 13 (n = 1-7) are observed. In those systems also SmC* a phase was evidenced. The helical pitch was measured and it was found that helical pitch increases with the increase of concentration of fluorinated component in mixture. The pitch of SmC* A phase is longer than for SmC* phase. Additionally the pitch in induced SmC* A phase does not depend on temperature, while in single compounds with SmC* A phase strongly increases. [ABSTRACT FROM AUTHOR]

We performed Adiabatic Scanning Calorimetry (ASC) measurements on two ferroelectric liquid crystals: S-(-)-4-(2' -methylbutyloxy)phenyl 4-n-octyloxybenzoate and S-(-)-2-methylbutyl 4-n-nonanoyloxybiphenyl-4'-carboxylate. Our experiments showed that no latent heat was present for the smectic-A – smectic-C* (AC*) transition to within the experimental resolution. Therefore the AC* transition in both samples can be classified as a continuous one. By fitting the specific heat data we showed that this phase transition can be described by an extended mean-field model. [ABSTRACT FROM AUTHOR]

The changes of the helical pitch in antiferroelectric phase versus temperature were calculated based on measurements of selective reflection of the light in four homologous series C n F 2n+1 COO(CH 2 ) 6 O–A–COOC*H(CH 3 )C 6 H 13 (A-the rigid core- PhCOOPhPh, PhPhCOOPh, PhPhCOO(F)Ph or PhPhCOOPh(F), Ph – phenyl ring, n is changed from 1 to 7). The values of helical pitch do not change in monotonous way with increase of the chain length. The even members have shorter pitches. [ABSTRACT FROM AUTHOR]

Molecular design producing a strong chiral effect has been proposed and dichiral twin and monomeric materials have been prepared systematically based on this concept. A variety of superstructures are generated in the chiral smectic phases, including ferrielectric and antiferroelectric phases, a twist grain boundary phase and the variants, such as smectic blue and smectic Q phases, and mysterious isotropic phases exhibiting an anomalous electric-field induced phase transition. [ABSTRACT FROM AUTHOR]

The structures as well as the SmA*–SmC* transition of a ternary mixture that has ferroelectric phase in the range of room temperature have been investigated by means of both X-ray and optical microscopy methods. The low temperature ferroelectric mixture exhibits all typical spatial structural properties peculiar to layer-shrinking ferroelectric liquid crystal compounds. [ABSTRACT FROM AUTHOR]

In this contribution we describe a method of controlling the polarization dependence in holographically formed polymer dispersed liquid crystals using a ferroelectric liquid crystal mixture and a diacrylate monomer. By elevating the temperature of the prepolymer and liquid crystal mixture prior to the holographic exposure, we can control the polymer morphology and therefore the resulting alignment of the ferroelectric liquid crystal. The two distinct polymer morphologies that we manufacture and investigate are droplet and channel like. We investigate these grating structures using optical polarizing microscopy and scanning electron microscopy. We support our polarization dependence results with electro-optic characterization to see if ferroelectrics have added benefits of faster electro-optic response verses nematics in holographically formed polymer dispersed liquid crystal geometries. [ABSTRACT FROM AUTHOR]

The compounds from the fluorinated nF6B (n = 1,2,3,4,5,6,7) homologous series were investigated by means of optical, electrooptical, refractometrical, dielectric, densytometric, X-ray and IR spectroscopy methods. For some compounds being a subject of investigations a computer simulation of molecular properties were done. In our opinion high value of optical tilt Θ o angle in comparison with a tilt angle obtained from X-ray measurements can be interpreted in terms of de Vries model of SmA* phases as well as of dimers creation process. [ABSTRACT FROM AUTHOR]

The resolution and switching characteristics of two Bistable Optically Addressed Spatial Light Modulators (OASLMs) one with and one without a pixelated metal mirror (PMM) are compared. The two devices use amorphous hydrogenated silicon (a-Si:H) Schottky diode structures as their photosensitive layer, Indium Tin Oxide (ITO) layers for electrodes, Nylon-6 alignment layer and a ferroelectric Liquid Crystal (LC) material (ZLI-5014-100) as their modulating layer. Both devices exhibit bistability when driven by alternating monopolar pulses. The pixelated metal mirror OASLM has both higher resolution and better optical efficiency than the non-mirrored device. [ABSTRACT FROM AUTHOR]

Phase modulation using liquid crystals has wide-ranging applications including correlation [1] and telecommunications [2,3]. At present, relatively slow (order 5ms) nematic cells demonstrate the advantage of continuous phase modulation but are sensitive to polarisation of the input light [4,5]. The alternative is to use faster ferroelectric cells which exhibit polarisation insensitivity but show only binary phase modulation [2]. This work demonstrates a novel technique for measuring the phase response time, which allows evaluation of different cell topologies. Rise and fall times are calculated in the Fourier plane from a wave-front splitting interferometer. Phase modulation measurements of in-house cells have been made for planar and hybrid aligned liquid crystal cells using nematic liquid crystals. The results demonstrate the capabilities of in-house cells, and also show agreement with theoretical predictions of cell behaviour. [ABSTRACT FROM AUTHOR]

Two series of three ring esters with chiral chain (derivative of (S)-octanol-2) and achiral chain (the swallow type) with high tilted synclinic and anticlinic phases were chosen to studies. The aim of presented studies was to find how the changes of different molecule units influence the mesomorphic properties of the compounds (temperatures, enthalpies and the sequence of phase transitions) and to find members with the best properties for mixture formulation. The compounds were studied by polarising microscope, differential scanning calorimetry, miscibility and X-ray diffraction methods. [ABSTRACT FROM AUTHOR]

This work outlines a number of experimental techniques that can be used to determine some fundamental material constants in antiferroelectric liquid crystal materials, exemplified by results for the commercial AFLC mixture CS4001. The parameters measured range from the helical pitch of the material to the interlayer interaction coefficients, elastic constants and viscosities. The experimental methods employed include a variety of both optical and dielectric techniques. [ABSTRACT FROM AUTHOR]

Electrooptic characteristics based on the deformation of helical structure in a homeotropically aligned ferroelectric liquid crystal have been studied. In the voltage range below the threshold for the disappearance of the helix, no hysteresis was observed in the voltage dependence of the transmission intensity curve. Wide viewing angle characteristics can be obtained by improving an electrode configuration in a homeotropically aligned cell. [ABSTRACT FROM AUTHOR]

A chlorinated liquid crystalline compound, exhibiting paraelectric SmA, ferroelectric SmC∗, and antiferroelectric SmCA∗ phases as well as sub-phase alpha, has been studied by means of electrooptic and DSC calorimetry methods. The sub-phase alpha has been observed by reversal current method. To this end the response currents have been measured vs. temperature, electric flied strength and frequency of the driving voltage. It has been found that the reversal current exhibits one peak in the ferroelectric SmC∗ phase whereas the antiferroelectric phase shows two separated peaks. In the case of the sub-phase alpha (SmC∗α) a characteristic shape of the response current in the form of a doublet has been observed in a narrow temperature range between the SmA∗ and SmC∗ phases. Spontaneous polarisation and tilt angle have been evaluated as a function of temperature. The electrooptic measurements have been carried out on a single mono-domain grown under a strong electric field during slow cooling from the paraelectric SmA∗ to antiferroelectric phase. [ABSTRACT FROM AUTHOR]

Surface stabilisation of ferroelectric liquid crystals (SSFLC) shows interesting properties: in plane switching, high viewing angle and fast response. Liquid crystal on silicon (LCOS) devices have an active matrix fabricated onto a silicon buffer, which requires metallization of the inner surface to achieve reflectivity. In this work, the influence of the cell thickness on the device colour upon switching has been studied. Little variations of the cell thickness without damaging surface stabilisation change phase delays, selecting the reflected wavelength if the birefringence is unchanged. Light path is double than that in a transmissive cell, thus similar thickness variations cause higher colour deviations. [ABSTRACT FROM AUTHOR]

The structure of a ferroelectric liquid crystal mixture with an N∗  →  SmC∗ transition in skew aligned cells has been studied by X-ray diffraction measurements of the layer normal distribution. The rubbing directions of the cells were set parallel, and skewed at 9°, 18°and 40°. The cell with parallel alignment directions showed two sets of layers with normals twisted in-plane by ∼⃒±20°from the rubbing direction. The layer normal distribution of each set of layers was consistent with a chevron-like structure but with an additional untilted region, probably at the apex. It was also observed that the tilt of the chevron arms was weakly temperature dependent, with their normals tilting out of the plane of the device by an angle of 9°to 12°on cooling. The cells with alignment skewed by 9°and 18°also showed chevron-like structures which are probably developed in the middle of the cell with each arms tilted by ∼⃒20°and with normals slightly twisted in-plane by 4°with respect to the mean rubbing direction. However, there were additional components of the layer-normal distribution, which are believed to be a continuous distribution of layer orientations between the middle of the cell and layers near the substrate with normals twisted further away from the mean rubbing direction. The cell with alignment directions skewed by 40°showed only a chevron structure with the normals to its two arms twisted with respect to each other by 2°and tilted out of plane by ∼⃒17°. [ABSTRACT FROM AUTHOR]

The dielectric spectroscopy of an antiferroelectric liquid crystal (S)-4-(1-methylheptyloxycarbonyl)phenyl-4′-(6-pentanoyloxyhex-1-oxy)biphenyl-4-carboxylate for its homogeneous anchoring has been carried out for 10 μm and 4 μm cell thicknesses. This study suggests that the dielectric strength of Goldstone mode of the SmC* phase is significantly diminished from ∼195 to ∼69, whereas its relaxation frequency is increased from ∼2 kHz to ∼4 kHz from the higher to lower cell thickness. Alternatively, these parameters for the soft mode detected in the SmA* phase and for the two antiferroelectric relaxation modes detected in the phase do not show any appreciable change with the cell thickness. [ABSTRACT FROM AUTHOR]

Photosensitivity in ferroelectric liquid crystal (FLC) material has been developed by dispersing Cadmium Sulfide (CdS) nano-particles in FLC (CdS-FLC) host. The nematic (N*) – ferroelectric (SmC*) phase transition temperature for the CdS-FLC sample in absence and presence of white light excitation decreases by 6 and 14°C, respectively, compared to host material due to enhanced disorder. The anomalous behaviour in temperature dependent dielectric permittivity of CdS-FLC sample in presence of white light excitation in N* as well as SmC* phase has been explained on the basis of enhanced free charged density and self assembly of CdS-LC in the phases. [ABSTRACT FROM AUTHOR]

Molecular motion of a ferroelectric mixture has been studied by the dielectric spectroscopy in the frequency range of 1 Hz to 35 MHz in different mesophases viz. chiral nematic (N*), ferroelectric (SmC*) and hexatic (SmI*) phases. One soft like relaxation process in the N* phase and usual Goldstone mode in the SmC* phase have been found. A new mode has been detected at ∼50 Hz in the vicinity of SmC*- SmI* phase transition. The dielectric strength of this mode is highly temperature dependent and increases as temperature decreases. Two modes in different frequency ranges (kHz and few hundred Hz ranges) have been detected in the SmI* phase. [ABSTRACT FROM AUTHOR]

A key liquid crystalline property for electro-optic applications is the Fredericksz threshold electric field. There has been recent experimental interest in liquid crystal-based colloidal suspensions in which the colloidal nanoparticles both possess a permanent electric polarization and provide strong director anchoring on the particle surface. Such suspensions are sometimes known as Filled Liquid Crystals. Our calculations suggest, in qualitative agreement with experiment, that filling the nematic liquid crystal with ferroelectric nanoparticles can significantly decrease the electric Fredericksz transition threshold field. [ABSTRACT FROM AUTHOR]