Katsumichi Ono

A Novel Preparation Method of Organic Microcrystals

Organic microcrystals ranging from several tens nm to µm in size of several chromophores were successfully prepared by simply dispersing ethanol solutions of compounds into stirred water, i.e. by a reprecipitation method. The size of microcrystals was found to depend on concentration of ethanol solutions, dispersing conditions, temperature and so on.

Interaction and structure of PVA-Cu(II) complex: 1. Binding of a hydrophobic dye toward PVA-Cu(II) complex

Abstract The interaction between PVA-Cu(II) complex and a hydrophobic dye, p-aminoazobenzene, was investigated by means of absorption spectrometry. The binding behaviour of the dye could be analysed on the basis of the method proposed by Klotz et al.1. A structure model of the complex which was termed ‘cluster model’ was found to be consistent with the following experimental results: the binding affinity of the dye appeared only when the complex is formed, and the degree of binding is principally determined by the concentration of cupric ion.

Preparation of J-Aggregated Microcrystals of Pseudoisocyanine

Abstract J-aggregated microcrystals of 1,1′-diethyl-2,2′-cyanine bromide [pseudoisocyanine bromide (PIC)] was prepared by salting-out in saturated potasium bromide aqueous solution, reprecipitation in hexane and recrystallization in polymers at room temperature. J-band of microcrystals from aqueous conditions was sharp and blue-shifted compared with those from hydrophobic conditions. The size of the former microcrystals was smaller than that of the latter ones.

Effect of the Thickness of Alignment Layer on the Low-Frequency Dielectric Dispersion of a Nematic Liquid Crystal

The low-frequency dispersion of the complex dielectric constant of a nematic liquid crystal was measured as a function of the thickness of the polyimide alignment layer at 25 and 50° C. The dielectric relaxation strength of the low-frequency dispersion was strongly dependent on the thickness of the alignment layer and decreased with increasing thickness. A simple model assuming series combination of the alignment layer and liquid crystal phase was proposed to explain the frequency dependence of equivalent parallel capacitance of the liquid crystal cell. The experimental dispersion curves were excellently fitted by the equation based on the proposed model. This made possible the accurate determination of both the capacitive and conductive components of the alignment layer and the liquid crystal phase. The capacitive component of the alignment layer was proportional to the reciprocal of the thickness. The result indicated that the low-frequency dielectric dispersion of the cell is due to the Maxwell-Wagner effect of the alignment layer and the liquid crystal phase having different values of conductance. This made it possible to explain completely the quantitative aspect of the ionic effect in the nematic liquid crystal cell.

A Method for the Determination of the Internal Electric Field of Ion-Doped Ferroelectric Liquid Crystals

A new experimental method for the determination of the internal electric field in surface-stabilized ferroelectric crystal cells was proposed. The method is based on the simultaneous analysis of the current responses against square and triangular wave imposition of the voltage across the cell. From this method, the rotational viscosity coefficient and the ionic mobility of a ferroelectric liquid crystal doped with tetra-cyanoquinodimethane (TCNQ) can be estimated. Furthermore, two internal field components, i.e., the internal field due to depolarization and that due to ionic space charge, were calculated.

Complex formation and ionic association in methanol solutions of poly[ethylene oxide] and alkaline earth salts

Abstract Complex formation of poly(ethylene oxide) (PEO) with divalent barium and strontium salts was investigated in methanol. In these systems the complexation was accompanied by a considerable degree of ionic association. An analytical model for the polymer-ion complexation based on a one-dimensional lattice model was proposed. According to this model, the electrostatic effects between the bound ions were separated from the total free energy change of the binding. Three binding constants, i.e., the ionic association constant K A, the cation binding constant, K c, and the anion binding constant, K a, could be estimated. K A for barium and strontium salts was comparable, and the effect of counteranions on K A was not large. K c for barium salts was almost independent of the kind of counteranion and larger than that for corresponding strontium salts, indicating stronger polymer-ion interaction for barium salts. The anion binding constant, K a, was strongly dependent upon the kind of anion, and the order w...

Pseudo-homoepitaxial growth of diacetylene thin single crystals

Growth of thin single crystals from the melt of a diacetylene monomer, 2,4-hexadiynylene di-p-toluenesulphonate (PTS), between a substrate and a glass plate, has been investigated. Among five kinds of substrate examined, pseudo-homoepitaxy on poly-PTS substrate attained the best performance of growth control to give thin single crystals of PTS with a developed surface of over 1 mm2 as well as uniaxial orientation, whereas the other four substrates, e.g. KC single crystals and rubbed polyimide films, resulted in the formation of microcrystallites without any regular orientation under the same crystal growth conditions. The PTS crystals were successfully converted into the single-crystalline polymer, with a quality suitable for nonlinear optical device fabrication.

Network Structure of Polystyrene Microgels and Dispersion Mechanism in an Organic Solvent

Polystyrene microgels (PSMG) were prepared by soap-free emulsion co polymerization of styrene and divinylbenzene (DVB), and then dispersed in tetrahydrofuran (THF). The apparent diffusion constant D app and the intrinsic viscosity [η] for PSMG were determined in THF. D app was measured with dynamic light scattering technique, and the hydrodynamic radius Rh of PSMG swollen in THF was estimated using the Stokes-Einstein relation. The slope of plots of D app vs. concentration of PSMG changed from positive to negative with decreasing DVB content. This result was interpreted by a core-shell type network structure of swollen PSMG. Formation of the network structure is also supported by the difference in reactivity ratio between styrene and DVB. The swelling ratio of PSMG, which was calculated from the ratio of Rh and the diameter of dried PSMG, showed maximum at intermediate DVB content, while [η] showed minimum around the similar DVB content. This behavior was ascribed to the aggregation of PSMG. The dispersion mechanism could be qualitatively explained by considering both steric and topological repulsive forces, to which the network structure of the core-shell type may contribute.

Preparation of Thin Single Crystals of Diacetylene by Pseudo-Homo Epitaxy

Thin single-crystal growth of diacetylene monomer between a substrate and a glass plate has been investigated from the molten state. Among five different substrates examined, polydiacetylene single crystal, having the characteristics of pseudo-homo epitaxy, attained the best performance of growth control to give thin single crystals with the size of over one mm2 as well as uniaxial orientation. The crystals were successfully converted into polymer thin single crystals, which were usefull enough for nonlinear optical device fabrication.

Interaction and structure of PVA-Cu(ii) complex: 2. Effect of microstructure of PVA chain on binding affinity of p-aminoazobenzene

Abstract The effect of the content and distribution of the acetyl groups of partially acetylated poly(vinyl alcohol) (PVA) on the binding affinity of p -aminoazobenzene (AAB) to PVA-Cu( ii ) complex has been investigated. The binding affinity of the dye increased with increasing content of acetyl groups on the PVA chain. The enhancement of the binding affinity was larger for the PVA with a block-type distribution of the acetyl groups than for the PVA with a random distribution of the acetyl groups. Although the dye has a binding affinity to the partially acetylated PVA even in the uncomplexed state, this enhancement was far larger than the simple sum of the contributions from the Cu( ii ) complex of perfectly saponified PVA and from the uncomplexed acetylated PVA. The effects of pH and temperature on the binding affinity have been also investigated in connection with the hydrophobic character of the polymer chain.