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We report on the physical properties of swollen solutions of the amphiphilic molecules of cetylpyridinium chloride and hexanol in brine. A remarkable characteristic of this system is the existence of a crossover between dilute and less dilute solutions, in the lamellar phase and the sponge phase, with some interesting consequences for the theory of membranes.
Structures and functions of various biological macromolecules at cellular levels are controlled by electrostatic, excluded-volume, macromolecular topological connectivity, and hydrodynamic forces. Some aspects of these challenging issues will be addressed. Specifically we will focus our discussions on (a) pattern recognition by macromolecules and complexation, (b) coupling between conformational transitions...
We have studied the electrical conductivity of well aligned samples of hexahexylthiotriphenylene (HHTT) in the pure as well as doped states. The dopant used was a small concentration (0.62 mole %) of the electron acceptor trinitrofluorenone (TNF). In the columnar phases, doping causes the AC(1 kHz) conductivity along the columnar axis (σ‖) to increase by a factor of 107 or more relative to that in...
Optical activity of matter is related to the chirality of its constitutive molecules. In liquid crystals, chiral molecules can give rise to superstructures in which the local dielectric tensor rotates in space describing a helix, a fact which greatly enhances the optical activity of the medium. The structures and the optical properties of some helical phases are well-known, as for instance the cholesteric...
The bilayers of some typical biological membrane lipids such as PC and DGDG disintegrate in a large excess of water to form an optically invisible dispersive bilayer phase. ‘Dark bodies’ can be reversibly precipitated from it by raising the temperature. The dispersive phase probably consists of ‘knotted sticks’, i.e. very thin nodular tubes of bilayer. After reviewing pertinent experimental and theoretical...
We describe briefly some results obtained on both chiral and achiral compounds exhibiting chiral mesophases. We report the first example of a single component system exhibiting the undulated twist grain boundary C* or UTGBC* phase. Preliminary results concerning a few achiral compounds composed of banana-shaped molecules exhibiting a mesophase is reported. They have been investigated by polarized...
Phase separation of liquid crystals from a solution with polymers has long been studied and used to prepare polymer stabilized and polymer dispersed structures. They are formed by spatially isotropic phase separation. A new mode, in which the phase separation proceeds anisotropically, has recently been discovered. Known as phase separated composite films (PSCOF), the resultant structures are made...
The critical behaviour of surface adsorption and collapse transition of a flexible self-attracting self-avoiding polymer chain is examined. Depending upon the underlying lattice and space dimensionality, phase diagrams that exhibit many different universality domains of critical behavior are found. We discuss these phase diagrams and the values of the critical exponents found from different theoretical...
Although H2O has been the topic of considerable research since the beginning of the century, the peculiar physical properties are still not well understood. First we discuss some of the anomalies of this ‘complex fluid’. Then we describe a qualitative interpretation in terms of percolation concepts. Finally, we discuss recent experiments and simulations relating to the hyothesis that, in addition...
One discusses phenomenologically the statics and dynamics of surface anchoring of nematic liquid crystals. In statics, for symmetrical situations, one can induce, under the action of an external field, a surface breaking with a bifurcation between two opposite orientations of the director. In dynamics, one shows that the surface director relaxation is intrinsically fast, and accompanied by a transient...
Liquid crystal displays had a humble beginning with wrist watches in the seventies. Continued research and development in this multi-disciplinary field have resulted in displays with increased size and complexity. After three decades of growth in performance, LCDs now offer a formidable challenge to the cathode ray tubes (CRT). A major contribution to the growth of LCD technology has come from the...
We study the statistical properties and dynamics of flexible fluid membranes containing active transmembrane proteins and find that such active membranes can be either stable or unstable to small disturbances, depending on the signs of certain crucial parameters characterising the protein-membrane interaction. A major finding is that the shape-fluctuation spectrum in the stable case for a zero-tension...
Several surfactant molecules self-assemble in solution to form long, cylindrical, flexible wormlike micelles. These micelles can be entangled with each other leading to viscoelastic phases. The rheological properties of such phases are very interesting and have been the subject of a large number of experimental and theoretical studies in recent years. We shall report our recent work on the macrorheology,...
Some fatty acids, lipids, polymers and mesogenic molecules which are amphiphilic in nature spread at the air-water interface to form stable Langmuir monolayers. They exhibit a rich variety of two-dimensional (2D) phases. In this article, we briefly review some of the novel features we have found in these monolayers. For example, we find transition from a 2D monolayer to three-dimensional structures...
We give a short overview of three different aspects of the work done in our laboratory on the propulsion mechanism of the bacterium named ‘listeria’. They concern (1) the mechanical properties of the comet of the native bacterium, (2) the polymerization/crosslinking process of actin gels in spherical geometry, and (3) a theoretical analysis of the mesoscopic aspects of the propulsion.
Liquid crystal displays (LCDs) will be classified into miniature displays, reflective type, projection type, direct view type, and holography type. All of these LCDs will be widely utilized in the coming multimedia network era. Along with this trend, in the first part of this paper we will discuss the social background of this research. We will place an emphasis on a polymer stabilized (PS) FLCD that...
A trace formula for the oscillating part of the level density for a spherical billiard has been obtained in spherical polar coordinates. The Jacobian of stability and the length of the orbits are obtained from the classical mechanics of the problem. The same formula is applicable to both the planar and the diametric orbits. Numerical results have been obtained with this formula and compared with the...
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