Naotake Nakamura

Polyelectrolyte effect in perfluorosulfonated ionomer solutions

Ubbelohde viscosity measurements were performed on dilute solutions of perfluorosulfonated ionomers (PFSI) in various solvents exhibiting quite different dielectric constants. With aliphatic alcohols as solvents an increase of the reduced viscosity with dilution is evident. This effect is analogous to the so-called ‘polyelectrolyte effect’ observed for highly charged ionic polymers in polar solvents. The polyelectrolyte effect increases with the dielectric constant for alcohols, is similar in water and in methanol solutions, and disappears for high polarity solvents. This evolution is discussed in terms of an increase of the electrostatic persistence length. The viscosimetric behaviour of PFSI solutions is shown to fit well with the Liberti-Stivala equation.

Syntheses and Physical Properties of Ferrocene Derivatives (I) Liquid Crystallinity of Ferrocene Derivatives Containing Cholesteryl Group

Abstract Nine kinds of ferrocene derivatives, [4-[ω-(cholesteryloxy carbonyl)alkoxy carbonyl]phenyl] ferrocene, were synthesized. Polarizing microscopy observations and differential scanning calorimetry measurements of these compounds were made in a wide temperature range. The liquid crystallinity was observed in the derivatives containing 2,4,6, 10, and 11 carbon atoms in the flexible alkyl chain of the compounds. An appearance of the liquid crystallinity was discussed with a conformation of the flexible alkyl chain which exerted a great influence on the molecular shape.

Syntheses and Physical Properties of Ferrocene Derivatives (II) Liquid Crystallinity and Multiple Melting Behavior of Ferrocene Derivatives

Abstract Nine kinds of monosubstituted ferrocene derivatives, ω-[4-(4-methoxyphenoxycarbonyl)phenoxycarbonyllalkyl 4-ferrocenylbenzoate, were prepared. The derivatives containing 4, 6, 10 and 11 carbon atoms in the flexible alkyl chain of the compounds showed liquid crystallinity, and multiple melting behavior was observed in the compounds containing 4, 6 and 11 carbom atoms. An appearance of the liquid crystallinity showed a carbon number dependence on the flexible alkyl chain.

Infrared studies on hydrogen bond interaction in a homologues series of triphenylene discotic liquid crystals having carboxylic acids at the peripheral chains

Abstract Temperature dependence of infrared spectra was measured in a hexagonal columnar (Col h ) mesophase for three homologues of a triphenylene mesogen with two terminal carboxylic acids. It was found for all homologues that the band intensity of hydrogen bonded C=O (approx. 1710 cm −1 ), as a carboxylic acid dimer, increases at the isotropic to Col h phase transition on cooling, while the monomeric C=O (approx. 1740 cm −1 ) band decreases. The results strongly indicate that the rotational and translational fluctuations in Col h mesophase is significantly suppressed by the hydrogen bonding interaction and the suppression depends on the spacer length connecting the triphenylene core and carboxylic acid group leading to the modification of mesomorphic thermal stability.

Syntheses and Physical Properties of Ferrocene Derivatives (III) Liquid Crystallinity of Disubstituted Ferrocene Derivatives

A new series of 1,1′-disubstituted ferrocene derivatives, 1,1′-bis[4-[ω-(4′-methoxyphenoxycarbonyl)phenoxy]-alkoxycarbonyl]ferrocene, incorporating a variable carbon number of methylene chain units...

Syntheses and Physical Properties of Ferrocene Derivatives (IV) A Study on the Smectic Structure of Ferrocene Derivatives Containing a Cholesteryl Group

Abstract The smectic structure of ferrocene derivatives, [4-[ω-(cholesteryloxycarbonyl)alkoxycarbonyl]phenyl]-ferrocene (abbreviated to CAPF-n, n = 2, 4, 6, 8, 9, 10, and 11, the carbon number of the frexible alkyl chain), was studied by X-ray diffraction. The structure of CAPF-n having a shorter alkyl chain (n < 9) was different from that of a longer one. The derivatives containing 2, 4, 6, 8, and 10 carbon atoms in the flexible alkyl chain have a double-layer structure, while the derivatives having 9, 10, and 11 carbon atoms in the alkyl chain showed a quasi single-layer structure. CAPF-10 indicated both the double-layer and the quasi single-layer structures.

Syntheses and Physical Properties of Ferrocene Derivatives (VII) PhaseTransition Behavior and Liquid Crystal Structure of 1,1′-Disubstituted Ferrocene Derivatives

Abstract Liquid crystalline 1,1′-disubstituted ferrocene derivatives, 1,1′-bis[ω-[4-(4′-methoxyphenoxycarbonyl)phenoxy]alkoxycarbonyl] ferrocene (abbreviated hereafter to bMAF-n, n = 2∼12, where n is a carbon number of the methylene chain units), were synthesized, and their phase transition behavior was studied using a differential scanning calorimeter and a polarizing microscope. The liquid crystal structures of the compounds were investigated by the X-ray diffraction method. Nine of eleven compounds of the samples showed liquid crystallinity. The liquid crystalline phases were identified as a nematic (n = 3 and 5∼12), a smectic C (n = 5∼12) and a smectic F or I (n = 11 and 12). As a model structure of the smectic phase, a tilted structure with an expanded substituent is presented.

Syntheses and Physical Properties of Ferrocene Derivatives (XV) Crystal Structure of a Liquid Crystalline Ferrocene Derivative, ω-[4-(4-Methoxyphenoxycarbonyl)Phenoxycarbonyl] Undecyl 4-Ferrocenyl-Benzoate

The crystal structure of a liquid crystalline monosubstituted ferrocene derivative, ω-[4-(4-methoxyphenoxycarbonyl)phenoxycarbonyl]-undecyl 4-ferrocenyl-benzoate was determined by the single-crystal X-ray structure analysis. The flexible spacer(undecyl chain) was an all-trans conformation. In order to form a rod-like structure, the molecule is slightly bent at the substituted group bonding the ferrocene. Two cyclopentadienyl rings made up an eclipsed type rather than a staggered one. The molecules are arranged in layers just like those in the smectic phase of the liquid crystals. The aspect of dipole-dipole interaction, however, was different from that of other homologues with even number of carbon atoms in the flexible spacer.

Syntheses and physical properties of ferrocene derivatives (IX) : Crystal structure of a ferrocene derivative, ω-[4-(4-methoxyphenoxycarbonyl)phenoxy carbonyl]propyl 4-ferrocenylbenzoate

Abstract The structure of a mono-substituted ferrocene derivative of which the flexible spacer is located between the ferrocenyl and mesogenic groups, ω-[4-(4-methoxyphenoxycarbonyl)phenoxycarbonyl]propyl 4-ferrocenylbenzoate was determined by the X-ray diffraction method. It was found that the two cyclopentadienyl rings in the ferrocene and the—C3H6—chain introduced as a flexible spacer exhibited a very interesting conformation. The two cyclopentadienyl rings are a staggered conformation rather than an eclipsed one. This staggered conformation is an unusual structure in mono-substituted ferrocene derivatives, in general. Also, the—C3H6—chain includes two gauche conformations and makes a bent molecular feature rather than a rod-like one. As a result, the title compound does not exhibit liquid crystallinity.

Electrorheological Effect of “Side-on” Liquid Crystalline Polysiloxane

Liquid crystals have attracted great attention in the field of engineering. Their application to the development of screens and displays is a representative example of their unique properties, because it demonstrates their excellent molecular-orientation ability. To develop further uses of liquid crystals, we have investigated the electrorheological (ER) effect, in which viscosity is controlled by the strength of an applied electric field. Since the discovery of the ER effect by Winslow in 1949, several ER fluids have been widely studied as smart materials for industrial uses. After extensive research on ER fluids, it has been found that side-chain liquid crystalline polymers (LCPs) show a relatively large change in shear stress upon applying an electric field, because the thermal motion of terminal mesogenic groups is independent from that of the polymer backbone. In addition, ER effects of the side-chain LCPs have been commonly observed at temperatures above the clearing point. This observation can be attributed to the enhanced order, which results from the formation of the liquid crystalline phase. From a practical viewpoint, side-chain LCPs exhibiting a smectic phase have a high viscosity in the phase, which causes a poor response to the application of an electric field. This limits the temperature range at which ER effects can be measured when LCPs showing a smectic phase are used as the ER fluids. It is widely known that the viscosity in the smectic phase is usually higher than that of the nematic phase, in accordance with the different order parameters of the various liquid crystalline phases. The generated shear stress is defined as the difference between the shear stress in the presence and that in the absence of an applied electric field. Therefore, a lower shear stress in the absence of an electric field is expected to enhance the ER effect. The shape of the constituent molecules in liquid crystals is a fundamental factor in determining the mesophase properties. Side-chain LCPs are generally classified into two kinds depending on whether the mesogenic groups are attached terminally or laterally to the polymer backbone via a flexible spacer, as shown in Figure 1. In “side-end” LCPs, in which the mesogenic groups are linked to the backbone through one of their end groups, the smectic phase is usually favored. In contrast, the nematic phase is favored in “side-on” LCPs, in which the mesogens are laterally attached. Although side-end LCPs have been widely used to investigate ER effects, there are no reports describing ER effects on side-on LCPs. In expectation of a large ER effect in the nematic phase, we synthesized a side-on liquid crystalline polysiloxane compound in this study. The phase-transition behavior of polysiloxane was determined by means of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), and its rheological properties were investigated in the nematic phase and the isotropic state. The synthetic route to the sideon liquid crystalline polysiloxane compound prepared herein is shown in Figure 2. Here, we describe the phase-transition behavior of a siloxane polymer. From POM observations we find that the siloxane poFigure 1. Structures of side-chain liquid crystalline polymers : a) side-end; b) side-on.