Yoshihiko Onogi

Photo-induced phase transition of side chain liquid crystalline copolymers with photochromic group

Abstract Liquid crystalline copolymers containing 4′-cyanobiphenyl-4-oxyundecylacrylate (CBO-11-A) groups and phenylazophenyloxy-undecylacrylate (ABO-11-A) groups with various proportions were synthesized. The copolymers take a highly liquid crystalline state but the temperature range of liquid crystalline state was narrowed with increasing azobenzene content. Isothermal phase transition of copolymers was induced by the photoisomerization of the azobenzene moiety with irradiation of 365 nm light. The response time of this phase transition was measured using an excimer pulse laser (351 nm). It took from a few ms to several hundred ms at 70–80 °C to cause a phase transition in these liquid crystalline systems.

Temperature Effect on Dissipation of Triboelectric Charge into Air from Textile Surfaces

Triboelectric charges on textiles dissipate through a charge conduction mechanism and also by accompanying water molecules evaporating into air. The latter dissipation is less extensive than the former, but can be measured quantitatively under highly insulated experimental conditions. Rate constants of charge dissipation into the air at 20°C have been reported as a function of the ambient humidity and water content of fabrics. In this study, the rate constants are analyzed at temperatures above or below 20°C. Two kinds of water molecules, free and bound, are known to be present in the textile surface from charge dissipation analysis. Though free water is involved in atmospheric charge dissipation, the condition of water molecules in the fibers cannot be classified so simply. Rate constants of charge dissipation depend on the ambient absolute humidity and water content of sample fabrics for all the temperatures of these experiments.

Separation of simple ions by gel chromatography : I. simple model of separation for single-salt systems

Abstract The chromatographic separation of simple ions by a polymer gel in water was modelled as a liquid—liquid partition process. The model consists of two “homogeneous” phases, a mobile phase of pure eluent and a stationary (gel) phase of a structureless concentrated polymer solution with a few electric charges fixed within it. Thermodynamic considerations and a simplifying approximation yielded a simple description of single-salt systems, which accounted for the chromatographic behaviour of simple ions at low and high concentrations in a systematic fashion. The intoduced notion of “intrinsic distribution coefficients” of ions proved to be useful. The main mechanism of the separation ions is suggested to be the difference in the thermodynamic stabilities of individual ions in the two phases, rather than involving size-exclusion and adsorption effects.

Fiber densities measured by volume expansion method

Solid density has been measured using various methods, among which the volume expansion method is rather simple in principle. It has been extensively used for solid powder samples, but only for few polymer samples. We tried to use this method to measure the density of various dried polymer samples using helium and nitrogen as measuring gases. The densities obtained were comparable with those found by other methods. Considering the effect of the measuring gas size, the polymer microstructure is discussed based on the observed density of textile fibers The density of humid samples was calculated to be much larger than that of dried samples. Though the effect of water molecules on the density value could not be clearly explained, it is surmised to be the reason for the volume expansion method not being used for density measurement of polymeric materials