Yuji Sasaki

Liquid crystalline amorphous blue phase and its large electrooptical Kerr effect

An amorphous blue phase III with low and wide thermal range (∼20 °C) including room temperature is induced by doping a bent-core nematic with a strong chiral material. We confirm that the electrooptical response is due to the Kerr effect, with the Kerr constant being up to two orders of magnitude larger than conventional Kerr materials such as nitrobenzene.

Discrete and sequential formation of helical nanofilaments in mixtures consisting of bent- and rod-shaped molecules

We have studied the phase transition from the isotropic to B4 phase in a mixture of bent- and rod-shaped molecules. Highly sensitive DSC showed many heat-capacity anomaly peaks upon cooling, strongly suggesting the discrete and sequential growth of helical nanofilaments or their assemblies. Such growth process of the B4 phase was confirmed by IR and UV-Vis absorption spectra.

Gluconic Acid Fermentation by Pullularia pullulans :Part I. Screening of Gluconic Acid-producing Strains and Some Conditions for Its Production

INTRODUCTION Pullularia pullulans, one of the imperfect fungi, is a widely distributed species in nature. How ever, very little has been reported about valua ble metabolic products or physiological charac teristics of this mold. It is objectionable, being responsible for the blackening of sake lees and also as a contaminant in breweries. Therefore, P. pullulans has been considered to be a quite useless mold. During the study on the sugar metabolism of molds, several strains of P. pullulans seemed to produce great amounts of gluconic acid from glucose in shake cultures in the presence of CaCO3. Since 1880, when Boutroux1) discovered the gluconic acid production by acetic acid bacteria, not only Acetobacter and the related Gluconobacter2), but also other different kinds of bacteria, such as Pseudomonas3,4), Phytomonas4), Achromobacter5), Aerobacter6), Neisseria7) and Moraxellae8) have been studied for their gluconic acid-producing capa bilities. It has also been indicated that some molds belonging to the genera, Aspergillus9), Peni cillium10), Mucor11), Fusarium12) and Polyporus11) and yeasts, such as Mycodermal3) and Candida14),

Blue Phase III—Isotropic Phase Transition in a Bent-Core Liquid Crystal with Chiral Dopant

Calorimetric measurements and optical observations have been performed to investigate the effect of chirality on a bent-core nematic (BCN) material which can exhibit an amorphous blue phase (BPIII) over a wide temperature range by mixing with a highly chiral dopant. It was found that the first-order character of the nematic (N)–isotropic (I) phase transition of the host BCN sample was clearly weakened by increasing the chiral dopant concentration and eventually moved into the supercritical evolution. The colors of the textures also showed a blue shift when increasing the chiral concentration.

Critical Behavior at the SmC*α−SmC* Phase Transition Studied by High Sensitivity DSC

Calorimetric measurements have been done to investigate the smectic-C*α(SmC*α)- smectic-C*(SmC*) transition using high sensitivity differential scanning calorimetry. It was found that the SmC*α−SmC* transition for a liquid crystalline compound 11OHFBBB1M7 shows a first-order transition with a clear thermal hysteresis while other two compounds, LN36 and 12OTBBB1M7, exhibit continuous behaviors which support the existence of the critical point and also the slow relaxation dynamics encountered with the change in the helical pitch.

Polymer-Stabilized Micropixelated Liquid Crystals with Tunable Optical Properties Fabricated by Double Templating

Self-organized nano- and microstructures of soft materials are attracting considerable attention because most of them are stimuli-responsive due to their soft nature. In this regard, topological defects in liquid crystals (LCs) are promising not only for self-assembling colloids and molecules but also for electro-optical applications such as optical vortex generation. However, there are currently few bottom-up methods for patterning a large number of defects periodically over a large area. It would be highly desirable to develop more effective techniques for high-throughput and low-cost fabrication. Here, a micropixelated LC structure consisting of a square array of topological defects is stabilized by photopolymerization. A polymer network is formed on the structure of a self-organized template of a nematic liquid crystal (NLC), and this in turn imprints other nonpolymerizable NLC molecules, which maintains their responses to electric field and temperature. Photocuring of specific local regions is used to create a designable template for the reproducible self-organization of defects. Moreover, a highly diluted polymer network (≈0.1 wt% monomer) exhibits instant on-off switching of the patterns. Beyond the mere stabilization of patterns, these results demonstrate that the incorporation of self-organized NLC patterns offers some unique and unconventional applications for anisotropic polymer networks.

High-resolution calorimetric study of critical behaviour at the smectic-C*–smectic- phase transition

Precise heat-capacity measurements have been made around the smectic-–smectic- phase transition in the R–S mixture of liquid crystal MHPOBC ([1,1′-biphenyl]-4-carboxylic acid, 4′-(octyloxy)-, 4-[[(1-methylheptyl)oxy]carbonyl]phenyl ester) which exhibits ferro- and antiferroelectric phases. Ultra-low frequency ac calorimeter and high-sensitivity differential scanning calorimeter have been used. The measurements revealed the existence of quite slow relaxation near the transition. The heat-capacity anomaly accompanying the transition showed a significant increase as decreasing heat frequency in the ac method. The excess heat capacity observed for a mixture that is closest to the critical point has been analysed quantitatively.

Effect of Enantiomeric Excess on the Smectic- – Smectic-C* Phase Transition

Calorimetric investigation on the effect of enantiomeric excess on the smectic- (Sm ) – smectic-C* (SmC*) phase transition has been carried out using a high-sensitivity differential scanning calorimetry in an antiferroelectric liquid crystal compound. For highly optically pure samples, the Sm – SmC* transition is found to be first-order accompanying a thermal hysteresis, while the decrease in the optical purity weakens the first-order nature of the transition and eventually moves towards continuous behavior through the critical point. Our results indicate that the enantiomeric excess dramatically influences the nature of the Sm – SmC* transition.

Microscopic characterisation of self-assembled colloidal particles in electrohydrodynamic convection of a low-birefringence nematic liquid crystal

ABSTRACT Electrokinetics of small particles immersed in anisotropic fluids is attracting attention in recent years. Here we focus on microscopic appearance of single as well as self-assembled particles moving in the electrohydrodynamic convection (EHC) of a nematic liquid crystal with low birefringence. Characterisation of the birefringent properties is made by polarised light microscopy under different illumination conditions. Because of the small optical anisotropy, the director distortion around the particles clearly exhibits distinctive colours on both sides depending on the height in the cell. The observation can be explained as the change in the net phase retardation of the light. It is also found that a caterpillar-like motion is possible by tuning temperature, although the horizontal size of the EHC rolls is relatively narrow. GRAPHICAL ABSTRACT

Liquid crystal mesophases beyond commensurate four-layer periodicity

For more than one decade, were the only three confirmed commensurate SmC* variant phases with periodicities less than or equal four layers. In 2006, employing ellipsometry and resonant X-ray diffraction (RXRD), our research team first discovered a new liquid crystal mesophase having a six-layer periodicity in one ternary mixture which includes one sulfur-containing compound. From our ellipsometric results, this phase showed antiferroelectric-like optical response. This novel discovery inspired renewed interest to search for liquid crystal mesophases with commensurate periodicities greater than four layers. Soon after, another mesophase having a six-layer structure and showing a ferrielectric-like dielectric response, instead, was uncovered by RXRD measurements on a different binary mixture which has one bromine-containing compound. Meanwhile mesophases having a 5-, 8-, 12- or 15-layer periodicity were reported. However, numerous questions remain to be addressed associated with these unusual reported phases. Theoretical models giving rise to mesophases with periodicities greater than four layers have been developed; but, to date, none of them have provided satisfactory explanations of all the physical phenomena related to the mesophases exhibiting a six-layer structure. Moreover, the question “what is the source of long-range interactions between liquid-like smectic layers, which are responsible for establishing mesophases with long periodicities and mean-field behavior of the smectic-A–smectic-C transition?” remains unanswered for more than three decades.