Masahito Hosino

Nematic-Smectic Transition in an Aligned Rod System

The nematic-smectic transition in the system of completely aligned hard cylindrical rods is investigated, by making use of the method of symmetry breaking potential. In the second virial approximation the transition is found to occur in the 3-dimensional system but not in the 1- and 2-dimensional systems, in contrast with the result obtained by Wadati and Isihara that the 2-dimensional system also exhibits such a transition. It is shown that the transition is very like the second order one. A shape effect is also studied. Furthermore, by introducing an isotropic attractive intermolecular force, the dependence of the transition on the strength of that force as well as the length and diameter of the rod molecule is investigated.

Statistical Theory of Cholesteric Ordering in Hard-Rod Fluids and Liquid Crystalline Properties of Polypeptide Solutions

A statistical theory of lyotropic cholesteric phase in the system of long coiled rod molecules is presented. Effects of molecular exclusion and of attractive intermolecular force are both taken into consideration. On the basis of the theoretical results, experiments on the cholesteric solutions of polypeptide are investigated, where use is made of the scaled particle theory on the fluid of hard rod molecules. It is thus found that the experimental dependences of cholesteric twisting power on temperature, concentration and molecular weight of the polymer and also the experimental curvature elasticity are explained satisfactorily.

Effect of Orientational Fluctuation on Nematic-Smectic A Transition in the System of Hard Rod Molecules

By applying the method of symmetry breaking potential to Zwanzigs three direction model for liquid crystal, the nematic-smectic as well as isotropic-nematic transitions are investigated. Particular attention is paid to the effect of orientational fluctuation on the nematic-smectic A transition. It is shown that the nematic-smectic A transition is reduced to the one of first order owing to that kind of fluctuation for the case of short molecule.

Molecular Statistical Theory of the Frank Elastic Constants of Liquid Crystals

The Frank elastic constants K 1, K 2, K 3 are calculated in the mean field approximation by assuming that the intermolecular force is the sum of hard rod repulsion (length L and width D) and Maier-...

Phase Transitions in the Systems of Identical Rigid Molecules in Perfect Alignment-Relations of the Smectic A and Columnar Orderings in Liquid Crystals and the Crystalline Ordering to the Molecular Shape

The method of symmetry breaking potential is applied to the system of identical rigid molecules with simple typical shapes (rod with square cross-section, square plate and cube), which are perfectly aligned, to examine the occurrences of such various types of spatial ordering as in smectic, columnar and crystalline phases in relation to the molecular shape. A smectic A phase occurs in the system of rigid rod molecules much more easily than the close packed crystal structure does in the system of rigid sphere molecules. Columnar and crystalline phases do also similarly in the system of molecules of square plate and cube, respectively. It is also shown that the nematic-smectic A transition in the case of rigid rod molecules in perfect alignment is the second order one, in contrast with those in the others of typical first order transitions. The effect of orientational fluctuation is discussed in short.

Theory of Phase Transitions in the Assembly of Biaxial Molecules Interacting via Dispersion Forces

Abstract The ordering in the assembly of biaxial molecules which interact pairwise via the dispersion force is investigated statistical-mechanically, where four kinds of liquid crystalline phase and phase transitions between some pairs of those phases are discussed in comparison with the existing theoretical results from the model of uniaxial molecules. There appear one uniaxial nematic phase, two kinds of biaxial nematic phase and one discotic phase. The phase diagram of temperature versus interaction strength are obtained, where the four phases mentioned above appear in different regions depending on the molecular shape. Some advantages of the present method in investigating the orientational ordering in biaxial liquid crystals, including the discotic phases, are discussed.

Theory of phase transition in assemblies of rigid-body rectangles

ABSTRACT The ordering in assemblies of rigid-body rectangles is investigated statistical-mechanically, and the four kinds of liquid crystalline phases that appear as well as the transitions between some of the pairs of these phases are discussed. There appears one uniaxial nematic phase, two biaxial nematic phases, and one discotic phase. The phase diagram of the density versus the breadth-to-depth ratio of the rectangles is obtained; the four phases mentioned above appear in different regions depending on their molecular shape. Finally, the differences between the phase diagram of a system consisting of an assembly of rigid-body rectangles and that of a system of an assembly of biaxial molecules interacting via a dispersive force are discussed.

Chiral phases in a system of biaxial molecules

ABSTRACT Chiral phases in a system of biaxial molecules are investigated based on a theory of biaxial liquid crystals, which we have presented in past work. Four chiral phases are identified, corresponding to a uniaxial nematic phase, two biaxial nematic phases, and a discotic phase, respectively. We find that in the chiral uniaxial nematic phase, the pitch of the chiral structures does not depend on temperature. In contrast, in the two chiral biaxial nematic phases, as well as in the chiral discotic phase, the pitch is temperature-dependent.

Competing Orders in the System of Perfectly Aligned Rigid Square Pillars

SmecticA (SmA) and columnar orders competing with each other in the system of many identical rigid square pillars in perfect alignment are theoretically investigated by applying the method of symmetry breaking potential. It is found that SmA and crystalline phases appear but no columnar phase. With the increase of density the SmA ordering falls down abruptly at a certain density being accompanied with a columnar ordering, where a first order phase transition from the SmA to crystalline phases occur. Such effects as orientational fluctuation, diversity in molecular length and small system size that suppress the SmA ordering more than the columnar one are discussed to compare the present result and those previously obtained either theoretically, experimentally or computationally by other authors.