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Showing papers on "Liquid crystal published in 1988"



Journal ArticleDOI
TL;DR: Computer simulation of buckled defects confirms predictions of the disclination energies and gives evidence for a finite dislocation energy.
Abstract: We study isolated dislocations and disclinations in flexible membranes with internal crystalline order, using continuum elasticity theory and zero-temperature numerical simulation. These defects are relevant, for instance, to lipid bilayers in vesicles or in the ${L}_{\ensuremath{\beta}}$ phase of lyotropic smectic liquid crystals. We first simulate defects in flat membranes, obtaining numerical results in good agreement with plane elasticity theory. Disclinations and dislocations eventually exhibit a buckling transition with increasing membrane radius. We generalize the continuum theory to include such buckled defects, and solve the disclination equations in the inextensional limit. The critical radius at which buckling starts to screen out internal elastic stresses is determined numerically. Computer simulation of buckled defects confirms predictions of the disclination energies and gives evidence for a finite dislocation energy.

459 citations


Journal ArticleDOI
TL;DR: In this article, the de Gennes free energy of the twist-grain boundary (TGB) state was used to calculate the x-ray scattering intensities in the cholesteric phase near the TGB phase boundary.
Abstract: The nematic--to--smectic-A transition in liquid crystals is analogous to the normal to superconducting transition in metals with the Frank director n in liquid crystals playing the role of the vector potential A in metals. The liquid-crystal analog of an external magnetic field is a field, arising, for example, from molecular chirality, leading to a nonzero \ensuremath{ abla}\ifmmode\times\else\texttimes\fi{}n in the equilibrium nematic phase. The cholesteric (twisted nematic) phase is the analog of a normal metal in an external magnetic field. In type-II superconductors in an external magnetic field, the Abrikosov flux lattice phase with partial flux penetration intervenes between the low-temperature Meissner phase and the high-temperature normal-metal phase. In this paper we study the analog in liquid crystals containing chiral molecules of the Abrikosov phase in superconductors. Using a covariant form of the de Gennes free energy, we find that in mean-field theory a state, which we call the twist-grain-boundary (TGB) state, with regularly spaced grain boundaries consisting of parallel screw dislocations, intervenes between the smectic and cholesteric phases. We calculate the liquid-crystal analogs of the upper and lower critical fields ${H}_{c2}$ and ${H}_{c1}$. The properties of the TGB phase depend on the angle 2\ensuremath{\pi}\ensuremath{\alpha} between axes of dislocations in adjacent grain boundaries. \ensuremath{\alpha} can be rational or irrational. When \ensuremath{\alpha}=p/q for mutually prime integers p and q, the TGB state has a q-fold screw axis and quasicrystalline symmetry for crystallographically forbidden q. Our calculations ignore exponentially small terms favoring lock in at rational \ensuremath{\alpha}. We calculate the x-ray scattering intensities in the cholesteric phase near the TGB phase boundary and in the TGB phase for rational and irrational \ensuremath{\alpha}. We also discuss experimental difficulties in observing the TGB state and the possible effects fluctuations not included in mean-field theory might have on its existence.

432 citations


Journal ArticleDOI
J. W. Doane1, A. Golemme1, John L. West1, Joe B. Whitehead1, B.-G. Wu1 
TL;DR: An overview of polymer dispersed liquid crystal (PDLC) materials, their physical properties, and potential applications in the optic and electrooptic industry is presented in this article, with a focus on optical and optical properties.
Abstract: An overview of polymer dispersed liquid crystal (PDLC) materials, their physical properties, and potential applications in the optic and electrooptic industry is presented. These optoelectronic materials have unique properties which are expected to expand liquid crystal technology into new display and light shutter applications. Recent research by small and large industrial and university laboratories on device physics and chemistry has provided substantial progress towards the commercialization of these materials. Work to date on such features as response times, switching voltage, and contrast as well as material preparation procedures and unique optical characteristics will be reviewed. These materials are also of interest to basic physics because of new kinds of physical phenomena brought on by the confinement of a nematic liquid crystal to small submicron-size droplets. Enhanced surface-to-volume ratio, large nematic deformations and problems associated with molecular anchoring at a polymer w...

431 citations


Journal ArticleDOI
TL;DR: In this paper, a new switching process was observed in surface stabilized ferroelectric liquid crystals, associated with a third stable state in addition to the well-known bistable states.
Abstract: A new switching process was observed in surface stabilized ferroelectric liquid crystals. The switching is associated with a third stable state in addition to the well-known bistable states. The appearance of the third state is characteristic of materials with a large spontaneous polarization and is caused by minimizing induced polarization charges. The switching between each bistable state and the third state exhibits a sharp dc-threshold and hysteresis, suggesting a possible application for a switching device.

380 citations


BookDOI
01 Jan 1988
TL;DR: Theoretical and experimental results of second-order nonlinear optical properties of poly(p-Phenylene Vinylene)-Holes,Electrons,Polarons, and Bibpolarons and the Thermodynamics of electrically active Dopants in Conduting Polymers are discussed in this article.
Abstract: Nonlinear Optical and Electroactive Polymers: An Overview- Nonlinear Optical Polymers- Microscopic Origin of Second Order Nonlinear Optical Properties of Organic Structures- Design, Ultrastructure, and Dynamics of Nonlinear Optical Effects in Polymeric Thin Films- New Nonlinear Organic Crystals for Ultrafast Infra-Red Optical Processing- Electric-Field Poling of Nonlinear Optical Polymers- Frequency and Temperature Variations of Cubic Susceptibility in Polydiacetylesnes- Femtosecond Studies of Dephasing and Conjugation with Incoherent Light- Studies of Monomer and Polymer Monolayers Using Optical Second and Third Harmonic Generation- Development of Polymer Nonlinear Optical Materials- Orientationally Ordered Electro-Optic Materials- Conformation Transition in Polydiacetylene Solution- Molecular Engineering Approaches to Molecular and Macromolecular Nonlinear Optical Materials: Recent Theoretical and Exprimental Result- Poled Copoly(Vinylidene Flouride-Triflouroethylene) As A Host for Guest Nonlinear Optical Molecules- Electroactive Polymers- Electroactive Polymers:Consequences of Electron Delocalization- Optical Properties of Poly(p-Phenylene Vinylene)- Holes,Electrons,Polarons, and Bibpolarons and the Thermodynamics of electrically Active Dopants in Conduting Polymers- Transient Current Spectroscopy in Polymeric Films- Electrochemistry of Polyaniline:Consderation of a Dimer Model- Theory- A PPP Variational-Perturbation Calculating of Hyperplarizabilities of Conjudated Chains- Optical Spectra of Flexible Conjugated Polymers- Excitation in Conjugated Polymers- Synthesis- Towards New Electronic Structures in Crytallographically Ordered Conjugated Polymers- Side Chain Liquid Crystalline Copolymers for NLO Response- Synthesis of Certain Specific Electroactive Polymers- Rigid Aromatic Heterocyclic Polymers:Synthesis of Ploymers and Oligomers Containing Benzazole Units for Electrooptic Application- Devices- Nonlinear and Electro-Optic Organic Devices- Nonlinear and Optical processes in Optical Fibers- Nonlinear Optical Processes and Application in the Infrared with Nematic Liquid Crystals

372 citations


Journal ArticleDOI
28 Apr 1988-Nature
TL;DR: In this article, it was shown that hard spherocylinders with both translational and orientational freedom can form a thermodynamically stable smectic phase in a fluid of hard rod-like particles.
Abstract: One of the most remarkable phenomena exhibited by colloidal suspensions of monodisperse rod-like particles is the spontaneous formation of smectic liquid crystals1–5. In these smectic phases, the particles order in periodic layers; on average, the axes of the rods are perpendicular to the layers. Smectics are distinct from crystals in that there is no long-range positional order within the layers. Because the spacing of the smectic layers is of the order of optical wavelengths, white light is separated into colours when scattered, giving rise to beautiful iridescence as in the colour photographs of ref. 2. As early as 1949, Onsager6 showed that nematic ordering may arise from hard-core repulsions between anisometric particles. However, it appears to have been generally accepted in the literature that smectic liquid crystalline ordering demands that attractive forces also operate7. There is nevertheless experimental evidence that smectic ordering does occur in colloidal systems where the particles interact predominantly through repulsive electrostatic interactions. This observation raises the fundamental question of whether smectic ordering can occur in a system of particles with purely repulsive interactions. Inspired by the seminal work of Alder and Wainwright8 on the freezing of a system of hard spheres, we have explored the possibility that smectic ordering occurs in a fluid of hard rod-like particles. Earlier computer simulations on hard parallel spherocylinders9,10 (cylinders with length L and diameter D, capped at each end with hemispheres of the same diameter) indicated that, in this somewhat artificial system, smectic order was indeed possible. Here we present numerical evidence that hard spherocylinders with both translational and orientational freedom can form a thermodynamically stable smectic phase.

344 citations


Journal ArticleDOI
TL;DR: The micromechanical tests to measure the thermoelastic properties of the liquid and gel phases of dimyristoylphosphatidylcholine have found that the rippled P beta' phase is only formed when a vesicle is cooled to temperatures below the main acyl chain crystallization transition, Tc, under zero or very low membrane tension.
Abstract: We have used micromechanical tests to measure the thermoelastic properties of the liquid and gel phases of dimyristoylphosphatidylcholine (DMPC). We have found that the rippled P beta' phase is only formed when a vesicle is cooled to temperatures below the main acyl chain crystallization transition, Tc, under zero or very low membrane tension. We also found that the P beta' surface ripple or superlattice can be pulled flat under high membrane tension into a planar structure. For a ripple structure formed by acyl chains perpendicular to the projected plane, the projected area change that results from a flattening process is a direct measure of the molecular crystal angle. As such, the crystal angle was found to increase from about 24 degrees just below Tc to about 33 degrees below the pretransition. It was also observed that the P beta' superlattice did not form when annealed L beta' phase vesicles were heated from 5 degrees C to Tc; likewise, ripples did not form when the membrane was held under large tension during freezing from the L alpha phase. Each of these three procedures could be used to create a metastable planar structure which we have termed L*beta' since it is lamellar and plane-crystalline with acyl chains tilted to the bilayer plane. However, we show that this structure is not as condensed as the L beta' phase below 10 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

303 citations


Journal ArticleDOI
J. S. Foster1, Jane Frommer1
01 Jun 1988-Nature
TL;DR: In this paper, the first use of the scanning tunnelling microscope (STM) to unambiguously image well defined organic adsorbates on surfaces was reported, and a two-dimensional order in 4-n-octyl-4n-4′-cyanobiphenyl, a smectic in the bulk, confirming and embellishing literature models.
Abstract: Since its conception1, the scanning tunnelling microscope (STM) has been used principally to explore surfaces of well ordered inorganic solids and graphite2,3. We now report the first use of the STM to unambiguously image well defined organic adsorbates on surfaces. We have imaged individual organic molecules in a liquid crystal array on a graphite surface with the STM with nearly atomic resolution. Liquid crystals have previously been analysed by X-ray diffraction, neutron scattering, dilatometry and other means to determine molecular order. Here we identify a two-dimensional order in 4-n-octyl-4′-cyanobiphenyl, a smectic in the bulk, confirming and embellishing literature models. We have also imaged 4-(trans-4n-pentylcyclohexyl)benzonitrile, a nematic liquid crystal in the bulk at room temperature. We observe an increase in order in both liquid crystals with respect to their bulk phases. The bulk smectic appears crystalline on the graphite surface, as the smectic planes are perfectly registered with one another. The structure of the bulk nematic at the interface with the surface shows a strong conformity to the graphite substrate. In both cases the molecular axes lie parallel to the substrate, and the STM images a cross-section along the direction of the molecular axes of the classical bulk phases (Fig. 1).

301 citations


Journal ArticleDOI
TL;DR: In this paper, a molecular dynamics simulation of a sodium-decanoate/decanol/water system is presented, with the exception of CH2 and CH3 groups that are considered to be "united atoms".
Abstract: A molecular dynamics simulation of a sodium–decanoate/decanol/water system is reported. The system is treated in full atomic detail, with the exception of CH2 and CH3 groups that are considered to be ‘‘united atoms,’’ and is a refinement of a previous model membrane [Mol. Phys. 11, 1 (1983)]. The long‐range Coulomb interactions were included specifically. The order parameters of the chain units of the lipids and diffusion constants of components in the system calculated from the simulation agree well with those reported in experiments on this model membrane. The overall structure of the membrane shows considerable disorder, with a broad lipid–water interface, extending over approximately 1 nm. The distribution of the components is such that an almost complete charge cancellation occurs throughout the system, which is in contradiction with the generally assumed electrical double layer structure for membranes. A counterion condensation of 70% is observed. Both the translational and the rotational motions of water are slowed down compared to bulk water. The penetration of water into the hydrocarbon region of the membrane is substantial. Pair correlations of various atom pairs, and dihedral statistics and transition rates of the dihedrals in the lipids are reported. The distributions of chain segments of the lipids, of water molecules, and of sodium ions are compared with theoretical predictions.

285 citations


Journal ArticleDOI
04 Feb 1988-Nature
TL;DR: It is found that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration.
Abstract: DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids1–3. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions4–8. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to lOμm. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.

Journal ArticleDOI
TL;DR: It is shown that twisted nematic liquid-crystal spatial light modulators behave as phase-only modulators when operated below the conventional optical threshold and behave as spatial amplitude modulator when used between crossed polarizers above the optical threshold.
Abstract: It is shown that twisted nematic liquid-crystal spatial light modulators behave as phase-only modulators when operated below the conventional optical threshold. Thus such devices, when operated in a reflection mode, behave as spatial amplitude modulators when used between crossed polarizers above the optical threshold; they behave as phase modulators when used between parallel polarizers and operated below that threshold.

Journal ArticleDOI
TL;DR: In this article, the authors report liquid crystal, termoset or thermoplastic materials, and demonstrate how the droplet morphology and density, and thus device performance, can be controlled by each method.
Abstract: New optoelectronic materials based on polymer dispersed liquid crystals (PDLC) show great potential for application in displays, temperature sensors, optical computing and for solar energy control. We report liquid crystal, termoset or thermoplastic materials. PDLC materials may be formed by several different processes. The liquid crystal may be dissolved in low molecular weight polymer precursors, in a thermoplastic melt or with a thermoplastic in a common solvent. Subsequent polymerization, cooling of the polymer melt or solvent evaporation lead to liquid crystal immiscibility, droplet formation and growth, and polymer gelation. The optoelectronic properties of these materials are affected by the droplet morphology. Specific examples are presented for each of these processes and it is demonstrated how the droplet morphology and density, and thus device performance, can be controlled by each method. The thermoplestics are suitable for forming films by a variety of techniques. A range of polymers...

Journal ArticleDOI
TL;DR: A linear term linked to molecular chirality occurs in the bending energy of membranes with C/ sub 2/ or D/sub 2/ symmetry and is found to alternate in sign, depending on the direction of a cylindrical curvature.
Abstract: A linear term linked to molecular chirality occurs in the bending energy of membranes with C/sub 2/ or D/sub 2/ symmetry. We find it to alternate in sign, depending on the direction of a cylindrical curvature, and discuss consequences for anisotropic solid membranes, tilted fluid bilayers, and ferroelectric smectic liquid crystals.

Journal ArticleDOI
TL;DR: In this article, the electro-optical dynamics, hysteresis effects, and microscopic structure of polymer-dispersed films of nematic liquid crystal are probed in order to gain insight into the operation of this new class of liquid crystal light valves.
Abstract: The electro-optical dynamics, hysteresis effects, and microscopic structure of polymer-dispersed films of nematic liquid crystal are probed in order to gain insight into the operation of this new class of liquid crystal light valves In tracking the rise and decay response times of these devices, it appears that there are both ‘fast’ (0·1·l0ms) and ‘slow’ (10-1000ms) processes that occur in the film A model is proposed which explains these results, in which the reorientation of the nematic droplets takes place in two stages: a fast reorientation by the nematic within the bulk of the droplet, followed by a slower rotation of the nematic nearer the droplet surface (including the point disclinations) This model agrees with a similar proposal made by Doane et al in a previous study of related films This model is also used to explain both the behaviour of the films in response to short voltage pulses and hysteresis effects present in the film The response time of these films can be tailored by ad

Journal ArticleDOI
TL;DR: The scattering matrix, differential cross section, and total cross section for supramicrometer-size nematic droplets in a polymeric matrix are derived in the anomalous-diffraction approach and indicate strong dependence of the diffraction patterns on wavelength and droplet structure.
Abstract: The scattering matrix, differential cross section, and total cross section for supramicrometer-size nematic droplets in a polymeric matrix are derived in the anomalous-diffraction approach. Scattering patterns are calculated in detail for three different nematic-director configurations: one characteristic of a droplet in a strong external field, the other characteristic of a droplet outside the field in the case of normal surface anchoring, and the third characteristic of an isotropic droplet with a surface-induced nematic layer. The results, which are presented graphically, indicate strong dependence of the diffraction patterns on wavelength and droplet structure. The possibilities of determining droplet size and nematic-director structure from experimental light scattering data are discussed. Special attention is paid to the possibility of the detection of the surface-induced nematic ordering.

Patent
19 Sep 1988
TL;DR: In this paper, a horizontal electric field drive type liquid crystal electro-optic device where a liquid crystal material is driven by controlling the strength of an electric field parallel to a substrate, noncontinuity of the electric field strength around each pixel electrode is minimized and a construction having improved display characteristics and a method of manufacturing the same are provided.
Abstract: In a horizontal electric field drive type liquid crystal electro-optic device wherein a liquid crystal material is driven by controlling the strength of an electric field parallel to a substrate, noncontinuity of the electric field strength around each pixel electrode is minimized and thereby the occurrence of flaws in the orientation of the liquid crystal material and dispersion in operation are reduced and a construction having improved display characteristics and a method of manufacturing the same are provided. In a horizontal electric field drive type liquid crystal electro-optic device wherein a gate electrode 403, a source electrode 407, a drain electrode 408, a semiconductor film 406 and a common electrode 404 are formed on a glass substrate and a liquid crystal material is driven by controlling the strength of an electric field substantially parallel to the glass substrate, the electrodes and the semiconductor film are made curved, for example semi-circular or semi-elliptical, in sectional profile. These curved sectional profiles can be formed by suitably selecting and combining various patterning and etching methods.

Journal ArticleDOI
TL;DR: This scenario, closely analogous to the one that explains the origin of the hexagonal phases, is investigated here by means of simple geometrical calculations and can be smaller for the cubic phase than for the lamellar and hexagonal structures.
Abstract: Bicontinuous cubic phases, composed of bilayers arranged in the geometries of periodic minimal surfaces, are found in a variety of different lipid/water systems. It has been suggested recently that these cubic structures arrive as the result of competition between two free-energy terms: the curvature energy of each monolayer and the stretching energy of the lipid chains. This scenario, closely analogous to the one that explains the origin of the hexagonal phases, is investigated here by means of simple geometrical calculations. It is first assumed that the lipid bilayer is of constant thickness and the distribution of the (local) mean curvature of the phospholipid-water interfaces is calculated. Then, assuming the mean curvature of these interfaces is constant, the distribution of the bilayer's thickness is calculated. Both calculations quantify the fact that the two energy terms are frustrated and cannot be satisfied simultaneously. However, the amount of the frustration can be smaller for the cubic phase than for the lamellar and hexagonal structures. Therefore, this phase can appear in the phase diagram between the other two, as observed in many recent experiments.

Journal ArticleDOI
TL;DR: A short review of the state of the liquid crystal chemistry, divided in conventional (rod-like) and non-conventional (deviating more or less from the rod-like shape) molecular species is given in this article.
Abstract: This review article presents a short description of the historical development of the chemistry of thermotropic liquid crystals and the modern molecular-statistical interpretation of the liquid crystalline state A short survey on the present state of the liquid crystal chemistry, divided in conventional (rod-like) and non-conventional (deviating more or less from the rod-like shape) molecular species is given Liquid crystalline compounds for applications and their mixtures are treated from the chemical standpoint emphasizing the connections between molecular structure and properties

Patent
28 Jul 1988
TL;DR: In this article, a liquid crystal device including a ferroelectric liquid crystal disposed between plates treated to enforce a particular magnetometer orientation to the plates is described. But the plates are spaced by a distance sufficiently small to ensure unwinding of the helix typical in a bulk of the material to form either monostable, bistable or multistable states which exhibit novel electrooptic properties.
Abstract: A liquid crystal device including a ferroelectric liquid crystal disposed between plates treated to enforce a particular ferroelectric molecular orientation to the plates. The devices employ alone or in combination non-planar boundary conditions, polar boundary conditions, boundaries with multiple physical states, intrinsic spontaneous splay distortion of the polarization orientation field, combined ferroelectric and dielectric torques, layers tilted with respect to the plates. The plates are spaced by a distance sufficiently small to ensure unwinding of the helix typical in a bulk of the material to form either monostable, bistable or multistable states which exhibit novel electro-optic properties. The liquid crystal is responsive to an externally applied electric field, temperature or the like to make a light valve or other electro-optical device.

Journal ArticleDOI
TL;DR: The fundamental concepts of the homotopy theory of defects in liquid crystals and the results of experimental studies in this field are presented in this article and a set of fundamentally new effects that can occur in studying the topological properties of defects of liquid crystals is discussed.
Abstract: The fundamental concepts of the homotopy theory of defects in liquid crystals and the results of experimental studies in this field are presented. The concepts of degeneracy space, homotopy groups, and topological charge, which are used for classifying the topologically stable inhomogeneous distributions in different liquid-crystalline phases are examined (uni and biaxial nematics, cholesterics, smectics, and columnar phases). Experimental data are given for the different mesophases on the structure and properties of dislocations, disclinations, point defects in the volume (hedgehogs) and on the surface of the medium (boojums), monopoles, domain formations, and solitons. Special attention is paid to the results of studies of defects in closed volumes (spherical drops, cylindrical capillaries), and to the connection between the topological charges of these defects and the character of the orientation of the molecules of the liquid crystal at the surface. A set of fundamentally new effects that can occur in studying the topological properties of defects in liquid crystals is discussed.

Journal ArticleDOI
TL;DR: In this paper, the structure and dynamics of a system of hard spherocylinders with length-to-width ratio LID = 5 were discussed. But the results of these simulations were limited to the case of nonspherical hard core particles.
Abstract: The results of recent computer simulations on fluids of nonspherical hard-core particles are discussed. New data are presented on the structure and dynamics of a system of hard spherocylinders with length-to-width ratio LID = 5. These data show that such spherocylinders can occur in at least four stable phases, viz., isotropic fluid, nematic liquid crystal, crystalline solid, and, surprisingly, a smectic A phase.

Journal ArticleDOI
TL;DR: In this paper, the authors show that cross-linking in the isotropic state lowers the nematic-isotropic phase transition temperature compared with the unlinked case and the application of suitable stress raises it again.
Abstract: Using classical elasticity theory, the rise in free energy upon crosslinking nematogenic polymers into a network is calculated for the isotropic and nematic phases. Spontaneous strains are allowed for in the network. The consequence of network formation upon nematic–isotropic equilibria is calculated by adding these elastic contributions to a conventional Landau theory. Memory of the crosslinking conditions yields quartic and quadratic additions to the standard Landau theory. We find that crosslinking in the isotropic state lowers the nematic–isotropic phase transition temperature compared with the unlinked case and the application of suitable stress raises it again. Crosslinking in the nematic state raises the transition temperature. We recover the mechanical critical point proposed long ago by de Gennes. Our Gaussian theory encompasses both main‐ and side‐chain polymers. The hairpin limit for main chain networks yields a modulus varying exponentially with temperature. The Landau–de Gennes free energy for comb polymers is presented for the first time.

PatentDOI
TL;DR: Fast switching displays with memory properties are provided, which can display digits, symbols, and images, and which contain as chemically and thermally stable ferroelectric liquid crystalline substances.
Abstract: Fast-switching displays with memory properties are provided, which can display digits, symbols, and images, and which contain as chemically and thermally stable ferroelectric liquid crystalline substances, according to the invention, liquid crystalline derivatives which contain a chiral alkyl halide residue corresponding to the general formula ##STR1## are used in mixtures of one another as well as in conjunction with other liquid crystalline or non-crystalline liquid substances.

Patent
23 Feb 1988
TL;DR: In this article, a light modulating material comprising phase-separated microdroplets of liquid crystal in a light transmissive, synthetic resin matrix is matched or mismatched to an index of refraction N o of the liquid crystal optical axis of the micro-droplets so that when the microdroplet director is aligned relative to a surface of the material, maximum transmission of light occurs at a selected oblique angle relative to the surface of a material or at a a selected narrow angle about the perpendicular to the material.
Abstract: A light modulating material comprising phase-separated microdroplets of liquid crystal in a light transmissive, synthetic resin matrix wherein the index of refraction n p of the matrix is matched or mismatched to an index of refraction N o of the liquid crystal optical axis of the microdroplets so that when the microdroplet director is aligned relative to a surface of the material, maximum transmission of light occurs at a selected oblique angle relative to the surface of the material or at a selected narrow angle about the perpendicular to the surface of the material. Such matching or mismatching of indices of refraction may be accompanied by phase separation in an external magnetic or electric field, or by shaping the liquid crystal microdroplet into an ovoid or the like during or after phase separation to align the microdroplet directors thereby endowing the material with a permanent and movable viewing angle. One or more sheets of the improved light modulating material may be incorporated into a window or an electrooptic display device to provide angularly discriminating windows or displays that are transparent or visible only at selected angles of view and that are opague at other angles of view.



Book
01 Aug 1988
TL;DR: In this article, P S Pershan explains the connection between these two separate areas and gives some examples of problems where the understanding is still not complete, such as the second order phase transition between the nematic and smectic-A phase, and the relation between the several hexatic phases that have been observed and the first order restacking transitions between phases that should more properly be identified as crystalline-B.
Abstract: Current understanding of different phases as well as the phase transitions between them has only been achieved following recent theoretical advances on the effects of dimensionality in statistical physics. P S Pershan explains the connection between these two separate areas and gives some examples of problems where the understanding is still not complete. The most important example is the second order phase transition between the nematic and smectic-A phase. Others include the relation between the several hexatic phases that have been observed and the first order restacking transitions between phases that were all previously identified as smectic-B, but which should more properly be identified as crystalline-B. Some relatively recent experimental developments on the discotic phase, liquid crystal surfaces and lyotropic phases are also included. The book includes 41 major reprints of some of the recent seminal work on the structure of liquid crystals. They are introduced by a brief review of the symmetries and other properties of liquid crystalline phases. In addition, there is a discussion of the differences between true liquid crystalline phases and others that were described as liquid crystalline in the early literature, but which have since been shown to be true three-dimensional crystals. The progression from the isotropic fluid, through the nematic, smectic, and various crystalline phases can be understood in terms of a systematic decrease in symmetry, together with an accompanying variation in structure is explained. A guide to the selected reprints and a sort of "Rosetta Stone" for these various phases is provided. The goal of this book is to explain the systematics of this progression to students and others that are new to this field, as well as to provide a useful handbook for people already working in the field.

Journal ArticleDOI
TL;DR: Micelles formed from sodium glycocholate and dimyristoylphosphatidylcholine are demonstrated to form a magnetic field orientable liquid crystal within narrow ranges of composition and temperature.