Tadahiro Asada

Rheology and Rheo-Optics of Polymer Liquid Crystals

The rheological and optical properties are most important properties to characterize the liquid crystalline state, and therefore studies on the viscosity have been performed before 1900 (1–3).

Deformation and Structural Re-formation of Lyotropic Cholesteric Liquid Crystal of Hydroxypropyl Cellulose + Water System

Abstract Flow properties and optical properties in applying and stopping shear on a lyotropic cholesteric liquid crystalline system of concentrated aqueous solutions of hydroxypropyl cellulose have been studied. The wave length dependence of transmitted light intensity through a sample subjected to steady shear have been measured quantitatively at various shear rates. The spectra of absorbance after the sudden cessation of steady shear flow are also observed as function of time. The shape of the spectrum at a steady state changes very much with shear rate. The shape of spectrum after the sudden cessation of steady shear always recovers quickly. A theoretical model including orientation distribution of Bragg reflection elements is proposed, which is useful to interpret observed spectra-data. Flow situations and also structural formation processes change markedly above and below a certain critical shear rate.

The diffusion coefficient for the nylon 6 and water system

Abstract The diffusion of water vapor in nylon 6 film has been measured by means of quartz microbalance and weighing bottle methods at penetrant concentrations ranging from about 1 to 8 (wt. %) or (%) and at temperatures ranging from 15° to 60°C. From the sorption-desorption data the average diffusion coefficient D a as a function of penetrant concentration, and the apparent activation energy for diffusion processes as a function of temperature have been determined. The mutual diffusion coefficient D as a function of penetrant concentration has been determined from the steady-state behavior, and compared with D a . D a is almost independent of the penetrant concentration, especially at higher temperatures, whereas D increases with increasing concentration, even at temperatures higher than the transition temperature of the sample. This difference might be attributed to the fact that chain molecules need a long time to change their configurations when the concentration changes.

Coexistence of two different side chain packing structures in a smectic phase of liquid-crystalline side chain polymers

Abstract Ten varieties of liquid-crystalline side chain polymers, poly(cholesteryl-ω-(methacryloyloxy)alkanoates) (pChMO-n, n = 1, 2, 3, 4, 5, 7, 9, 10, 11 and 15; the carbon number of the alkyl chain), were studied by differential scanning calorimetry and small angle X-ray scattering. On and after the first cooling run from the isotropic state, these polymethacrylates gave the same smectic phase. X-ray investigations showed that pChMO-n with short spacers (n = 1–7) has a two layer (bilayer) SA packing structure, and pChMO-n with a longer spacer (n= 15) has a single layer (monolayer) SA packing structure. However, these two types of packing structure appear simultaneously in pChMO-n (n = 9s−11) below their phase transition temperature. To clarify the manner of the coexistence of the two different structures the smectic layer spacing and X-ray diffraction patterns were examined by small angle X-ray scattering at various temperatures.

Optical Second-Harmonic Generations of Liquid Crystalline Main-Chain Polymers

Abstract Optical second-harmonic generation (SHG) of liquid crystalline main-chain polymers, which are the copolymers of 2-hydroxy-6-naphthoic acid with 4-hydroxybenzoic acid, and their application for SHG device have been studied. Varieties of copolyesters which have various composition-ratios were prepared. The SHG activities of each sample were evaluated by both the powder and Marker fringe methods. It was found that the double orientation processing was effective to obtain the sample of high SHG activity. At present, the effective nonlinear optical coefficient d(eff) of the sample with the composition PHB/HNA (60/40), which was prepared to be a plane-plane oriented (double orientation) film of thickness 10-30μm, is obtained to be 10 times that of quartz d11 value (0.50pm/V).

Rheology of A Lyotropic Polymer Liquid Crystal of Rodlike Polymers and Main-Chain Thermotropic Liquid-Crystalline Polymers

Abstract Dynamic viscoelastic properties of main-chain thermotropic liquid crystalline copolymers random copolyesters (PHB/PET) at different temperatures have been investigated. The form of the viscoelastic functions depends on both temperature and the composition ratio of copolymers. It was cleared that in certain temperature region, the viscoelastic behaviors for random copolyesters with optimum composition ratio were quite similar to those for a lyotropic polymer liquid crystals of PBG.

Electro-Optical Properties of Cholesteric Liquid Crystals and Polymer Complex

Abstract A set of liquid crystals and polymer complex (LCPC) films which have different polydomain focal conic textures and different polymer wall were prepared. The electro-optical properties of cholesteric liquid crystals and polymer complex were investigated using OS - 6411C Digital Storagescope with He-Ne laser and candescent light. These LCPC films may have various threshold-voltage, electro-optical response time and contrast ratio which depend on LCPCs composition, especially the focal conic liquid crystal textures in polymer matrix and polymer wall effect. Among these, the best LCPC film was developed which has a very low driving-voltage, quick response time and high contrast ratio. The results reveal that the cholesteric twisting power and polymer wall effect are most important factors for electro-optics of LCPC films.

The packing structure of side chains of liquid-crystalline side-chain polymers before and during heat treatment

Abstract Six varieties of liquid-crystalline side-chain polymers, poly (cholesteryl ω-(methacryloyloxy)alkanoates) (p-ChMO-n, n = 1,2,3,4,5,7, the carbon number of the alkyl chain), were studied by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). On and after the first cooling run from the isotropic state, these polymethacrylates gave the same smectic phase. However, on the first heating run for virgin samples, unique phenomena were observed, similar to those frequently observed on the first heating run for thermotropic liquidcrystalline polymers. The thermal properties of the first heating run for these six polymers showed different tendencies between pChMO-n (n-1–3) and pChMO-n (4–7). Although the DSC curve of pChMO-n (n = 4, 5 and 7) exhibited the melting and clearing points on the first heating run, the DSC curve of pChMO-n (n = 1,2 and 3) exhibited an exothermal peak between the glass transition and the clearing point on the first heating run. This difference, probably...

Nonlinear optical properties of the thermotropic liquid-crystalline main-chain polymers (aromatic polyesters)

Abstract The second harmonic generatign (SHG) of the liquid crystalline main-chain type copolymers of 2-hydroxy-6-naphthoic acid (HNA) with 4-hydroxybenzoic acid (PHB), in various composition ratios were investigated. The SHG of the films was greatly affected not only by the polymerization conditions but also by the processing conditions of the films. The nonlinear optical coefficient dexp of the electrically oriented sample is 3–5 times larger than that of the mechanically oriented sample (5pm/V). The relationship between molecular compositions and the hyperpolarizability (β) examined by the molecular orbital method clearly indicated that the high SHG of the main-chain polymer mainly originates from the additivity of β value of individual unit due to head to tail connection.

Spatial Light Modulator by Using Polymer Cell-Wall Type Liquid Crystal Optical Shutter

Abstract Polymer Cell-Wall Type Liquid Crystal (PCW-LC) light shutter has been developed. This is a kind of liquid crystal-polymer complexes (LCPCs), utilizing the light scattering of cholesteric focal conic texture. However, its abilities are superior to other LCPCs reported. As the cholesteric liquid crystal grains are covered with thin polymer films, the polymer content is very small, around 10 wt%. Consequently, the driving voltage is very low (Ca. 5–6V). This type of LC light shutter has the great advantage of non-polarizer usage. Therefore, this type of light shutter can be useful for not only liquid crystal display devices but also other applications, for example, spatial light modulator (SLM). In this work, PCW-LC is introduced at first, and then the applications of PCW-LC light shutter to SLM is described. Non-polarizer usage makes it easier to combine it with the other component parts for producing a SLM.