Liquid Crystal Research Research Articles

Vorlander's wheel

In this short article, we draw attention to the pioneering studies of Daniel Vorlander, who lived from 1867 to 1941 and worked in Halle, Germany between 1890 and 1935. The number and range of compounds synthesized under his guidance are truly vast, but much of his work is hidden away in Doctoral theses. All of these data are collected in the LiqCryst [1] database and, therefore, now having access to the results of his life's work, we outline some of his achievements and pay tribute to his remarkable contribution to liquid crystal research.

Liquid Crystal Devices and Devices for Liquid Crystal Research

In this paper we focus on liquid crystal Fabry-Perot as a liquid crystal device which can also be used to obtain information about the liquid crystal materials used in these devices. The paper outlines the evolution form the simple need of such a device to the construction and testing which led to some unexpected results. Through analysis of these results a better insight in to the working of these devices further led to other interesting structures and eventually to the use of this structure to obtain information about liquid crystal materials in absence and presence of electric field.

Centre For Liquid Crystal Research, Bangalore

Centre For Liquid Crystal Research, Bangalore

Liquid Crystals Spanning the Globe

Abstract Liquid crystal research is increasingly an international activity, often involving collabrations between groups and laboratories separated by great distances and cultures. Bridging these gaps is an importanta part of scientific activity and below we report the experiences of two young scientists from the UK who travelled to Japan to further their research.

Proton channeling effect in the smectic liquid crystal

The planar channeling phenomenon in the smectic liquid crystal molten sodium oleate, has been investigated. A 2.0 MeV proton beam was used for the experiment. The angular distributions observed by proton backscattering show a typical channeling characteristics, indicating that the channeling technique may be used for the liquid crystal research.

The Glenn Brown Awards

Abstract Abstract The Planning and Steering Committee of the ILCS instituted a prize in honour of Professor Glenn Brown for an outstanding PhD thesis in the field of liquid crystal research. In 1992 the International Liquid Crystal Society decided to allow two prizes to be awarded in different areas of liquid crystal science. The laureates are selected prior to each conference in the biennial series of International Liquid Crystal Conferences and will deliver the Glenn Brown Lectures at the Conference.

Liquid Crystals in Education

Abstract The advancement of liquid crystal science and technology has been a truly interdisciplinary effort which combines basic principles of physics, chemistry, and engineering. The success of liquid crystal materials in flat panel displays and electro-optic applications can be attributed to the collaborations of scientists in various fields and the unique interface between academia and industry. Many scientists and engineers engaged in liquid crystal research are also educators in their respective disciplines andlor area of expertise. Those in academia routinely teach undergraduate and graduate courses in physics, chemistry, and engineering, and those in industry often find themselves teaching technical short courses and seminars. Many of us have visited elementary and high schools in the USA to speak to students about careers in science and engineering, and to present some eye-catching demonstrations that excite students about science and technology.

Annual Meeting of the American Chemical Society

Abstract Ordered Fluids and Liquid Crystals was the focus of the two-day symposium on April 5 and 6 in Anaheim, California that was sponsored by the Division of Colloid and Surface Chemistry, during the Annual Meeting of the American Chemical Society. The organizers were 5. Rananavare of the Oregon Graduate Institute and R. Shashidhar of the Naval Research Laboratory who did a magnificent job in arranging a program that was faithful to the title and addressed issues on nearly all topics of liquid crystals research and technology. Both days were packed with presentations that covered lyotropics, ferroelectrics, liquid crystal polymers, molecular theory, new materials, and, of course, applications.

Transient grating optical nonlinearities in nematic, cholesteric and smectic liquid crystals

The transients of Kerr-like optical nonlinearities in various liquid crystals observed with picosecond light-induced dynamic gratings are discussed. It is shown that relatively high intensities and strong optical fields of short laser pulses lead to rapid molecular reorientation, ultrasound generation, multiphoton absorption, cholesteric helix deformation and other new phenomena which are not only of interest for basic liquid-crystal research but also determine photonic switching times in liquid crystalline all-optical devices.

Sterically Stabilized Vesicles

AbstractAfter significant developments in liquid crystal and polymer research, scientists became interested in lyotropic systems containing polymers. These studies investigated, for instance, phase behavior and stability characteristics of suspensions of colloidal particles containing water‐soluble or surface‐adsorbed polymers or block copolymers. The most frequently studied were micelles, latex prticles, and lipid vesicles (liposomes). Liposomes aggregate and fuse in the presence of hydrophilic polymers but their properties were difficult to explain when block copolymers were adsorbed or surfactants with larger polymeric polar heads were inserted into the liposome membrane, because such systems are inherently ill defined. Liposomes containing diacyl surfactants with covalently linked, longer polymer chains display many new properties with very important consequences for both basic and applied research. They stimulate fundamental studies on phase behavior and polymer conformation, scaling laws, colloidal and surface properties, and cell function: applications deal predominantly with liposomes as drug delivery systems. While in basic research theory is currently more advanced than experiment, in medical applications theoretical understanding lags behind experimental achievements. It was discovered only relatively late that liposomes with an appropriate polymer coating are significantly more stable in a biological milieu, a necessary condition for their utility as drug carriers. In particular in medical applications, this practice has rejuvenated the field of anticancer therapy and targeted drug deliviery. All these advances were made possible by an effective and synergistic overlap of many different disciplines.

The Development of Liquid Crystal Research

Statistics and trends in liquid crystal (LC) research are presented, taken from the new “Liqcryst” database. Did you know that more than 50000 mesogenic compounds had been studied by 1990? Or that more than 2000 papers and 1500 patents are published in the field of liquid crystals each year? Some particular breakthroughs are highlighted and the current rate of development of chiral LCs, which exhibit ferroelectric, ferrielectric, and antiferroelectric phases, is compared with that of nematic displays some years ago.

SWAX — a dual-detector camera for simultaneous small- and wide-angle X-ray diffraction in polymer and liquid crystal research

The design, construction and performance of a new X-ray camera allowing simultaneous sampling of diffraction data both in the small- and in the wide-angle range are described. The instrument employs line collimation and contains two position-sensitive gas detectors covering distance ranges of 10–1000, and 3.4–4.9 Å, respectively, which are regions of strong interest in studies on polymer and liquid crystal structure. The detection system is time-multiplexed with free selection of the fractional live times in the two regions to adapt to signal intensity differences. The camera is specifically designed to study structural transitions and annealing phenomena where simultaneous measurement in both regions under identical conditions is essential.

Chirality in liquid crystals

Chirality has become arguably the most important and complex topic of research in liquid crystals today. The reduced symmetry in these organized phases leads to a variety of novel phase structures, properties, and applications. Molecular asymmetry imparts form chirality to liquid-crystalline phases, which is manifested in the formation of helical ordering of the constituent molecules of the phase. Similarly, molecular asymmetry imposes a reduction in the space symmetry, which leads to some phases having unusual non-linear properties, such as ferroelectricity and pyroelectricity. In the following article the various effects of chirality in liquid-crystalline systems are described in general terms.

The Cholesteric Blue Phases

In 1888, the year commonly taken as the birthdate of liquid crystal research, F. Reinitzer wrote to O. Lehmann to describe the curious properties of cholesteryl benzoate, a “substance [which] has two melting points, if it can be expressed in such a manner.” Throughout most of the 33°C interval between these two “melting points” this material is in the birefringent fluid state now known as the cholesteric liquid crystal. Today it is common to find compounds showing a whole cascade of liquid crystalline mesophases as the temperature is increased, but it is not customary to refer to any of the phase changes between them as “melting points” except for the lowest temperature transition where the crystalline lattice dissolves. In recent years, however, it has been discovered that many cholesteric liquid crystals, includin g cholesteryl benzoate, do something very strange in a temperature interval of only a degree or so just before they yield up their last bit of liquid crystalline order: they form complex structures having the symmetries of cubic lattices — they “freeze”! – and then “melt” at a higher temperature into either the ordinary amorphous liquid or else into a new kind of amorphous liquid which in turn undergoes a sharp transition into the ordinary amorphous liquid at still higher temperature.

Plenary Lecture. Smectic liquid crystals. A historical review

Abstract This paper is intended to reflect the development of liquid crystal research, rather than to present a detailed historical survey. The author has been involved in this field for some 30 years as a member of the Halle Liquid Crystal Group. There has been a remarkable continuity in liquid-crystal research at the University in Halle-almost from the beginning of scientific investigation of liquid crystals about a century ago. This continuity has been maintained by fruitful collaboration between teachers and students as well as by the accumulation of past experience, but all of this activity can be connected with one man-Daniel Vorlander (1867–1941), Professor of Chemistry and Director of the Chemical Institute of Halle University from 1908 to 1935. Vorlander and his co-workers published their first results on liquid crystals in 1902.

Plenary Lecture. Some pictures of the history of liquid crystals

Abstract A short review on the first 80 years of liquid crystal research has been given, beginning with the molecular theories of the 19th century, referring to the early work of Virchow and Mettenheimer, remembering the important pioneer Lehmann and his colleague Reinitzer. The struggle for truth against badly informed people like Tammann is also mentioned, as well as the final breakthrough and complete rehabilitation of Lehmann and Reinitzer. We apologize for having mentioned Vorlander only briefly but in the following review, Horst Sackmann will refer to him in great detail.

Specifically deuteriated intermediates for the synthesis of liquid crystals and liquid-crystalline polymers

Abstract The recent developments in solid state N.M.R. techniques have rendered deuterium a most attractive nucleus for use in the study of liquid crystals and other ordered systems. Its application often requires that the deuterium be positioned at specific sites in the molecule. Here, the preparation of such specifically labelled compounds for use in liquid crystal research is discussed. It is shown that many deuteriated liquid crystals can be prepared from a limited set of labelled intermediates. Strategies for the labelling of such intermediates in both aromatic and aliphatic sites based on experience gained in the author's laboratory during the last years are discussed. In the experimental section more than fifty procedures for obtaining specifically deuteriated intermediates and mesogens are described in detail.

ChemInform Abstract: Nematic Lyotropic Liquid Crystals as Media for Chemical Reactions

Abstract An old theme in liquid crystal research, first introduced by Svedberg in 1916, is the examination of how chemical reactivity is modulated by the anisotropy of the medium to result in changes in rates of reaction or structures of product. We have recently returned to this problem by examining reactions in aqueous lyotropic nematic media. One can identify systems in which phase transitions occur from rod to disc to spherical aggregates of amphiphiles as functions of either temperature or concentration of surfactant, cosurfactant, or electrolyte, and study model reactions occurring through these phase transitions. One can orient the lyotropic medium in a magnetic field and assess the degree of ordering of reactant and product and their penetration into the micellar media by spectroscopic methods.

Can <P4> be obtained from fluorescence depolarization in nematics? Disc-like probes

Abstract The determination of the fourth rank orientational order parameter, , is an important goal in liquid crystal research. Here we have looked at the feasibility of obtaining for a disc-like probe molecule from a time dependent fluorescence depolarization experiment. Simulated data at various temperatures have been prepared and then analyzed both individually and simultaneously using the global target deconvolution procedure. We have examined, in particular, the case of molecules subject to effective potentials containing a combination of second and fourth rank terms.

Methodical aspects in thermal analysis of liquid crystalline substances

On the basis of experience in liquid crystal research, the optimum conditions are presented for the use of thermo-microscopy and microcalorimetry (DSC) in preliminary investigations of the general chemical, thermodynamic and kinetic behaviour. In the second step, special measurements are necessary to obtain exact results on purities, phase types, temperatures, enthalpies, and kinetic parameters of transitions in stable and metastable states.