Sakumitsu Sakagami

Liquid Crystalline Compounds Exhibiting Two Smectic B Modifications

Abstract Four liquid crystalline compounds, i.e., three terephthal-bis-4-n-alkylanilines (TBAA; alkyl = pentyl, hexyl, and heptyl) and N-(4-n-heptyloxybenzylidene)-4-n-hexylaniline (HBHA) were synthesized and the phase transitions were studied by means of optical microscope, differential scanning calorimeter and miscibility relationships. It is indicated that all the compounds exhibit a smectic B-smectic B phase transition of which the transition heat is very small. Furthermore, a brief description is given of a smectic phase of TBAA which occurs only monotropically.

Liquid crystalline properties and photochromism of 4-alkyl-N-(4-alkloxysalicylidene)anilines

Eight new homologous series of 4-alkyl-N-(4-alkloxysalicylidene)anilines were synthesized. The phase transitions of these homologues were determined using differential scanning calorimetry and polarizing optical microscopy. The homologues began to exhibit liquid crystalline phases as the terminal alkyl or alkoxyl chains were lengthened. In addition, some members of these homologues series exhibited photochromism in the solid state.

Spectroscopic study of liquid crystalline N-[4-(4-n-alkoxybenzoyloxy)2-hydroxybenzylidene]hydroxyanilines

New homologous series of N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]hydroxyanilines were synthesized. All 4-hydroxyaniline derivatives exhibited a nematic phase, while 3-hydroxyaniline and 2-hydroxyaniline derivatives exhibited only a nematic phase as the terminal alkoxy group was lengthened. Infrared spectra suggest that the 4-hydroxyaniline derivatives form intermolecular hydrogen bonding of the single bridge type, while the 3-hydroxy and 2-hydroxy derivatives form the polymer type. The Raman band at around 1360 cm-1 exhibited large differences in intensity among these derivatives. This can be explained by the effect of intermolecular or hydrogen bonding molecular conformation.

Electro-optic effects in smectic C liquid crystals

Abstract Electro-optic effects are observed in the smectic C states of 4- n -heptyloxybenzoic acid, 4- n -octyloxybenzoic acid. 4,4′-bis- n -heptyloxyazoxybenzene, and 4- n -decyloxy cinnamic acid under the application of an external ac electric field. The stripe domain pattern is observed for all the compounds studied above the first threshold. In the smectic C state there exists a second threshold at which the direction of the domain lines changes.

Microscopic Study on the Molecular Arrangements in the Smectic A, B and C Modifications

Abstract The molecular arrangements in three smectic modifications, i.e., the smectic A, B and C states are discussed on the basis of optical observations of smectic spherulites, which were fixed in a very viscous polymer matrix. The observed microscopic patterns for the smectic A state support the conventional idea that the smectic A state has a molecular arrangement such that the long molecular axis lies perpendicular to the layers. In the smectic B state, similar patterns to the smectic A were observed, suggesting a similar molecular arrangement to the smectic A state. On the other hand, the smectic C state exhibits strikingly different patterns from those of the smectic A and B states. Twisted smectic layers are proposed for the molecular arrangement of the smectic C state in order to reasonably explain all the observed microscopic patterns.

Infrared Spectroscopic Study of Liquid Crystalline N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-cyanoanilines

Abstract A homologous series of N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-cyanoanilines [AHC(n; n = 1–8, 10, 12)] was synthesized. AHC(4–8, 10) exhibit a monotropic nematic phase. The temperature dependence of infrared (IR) spectra of AHC(4–8) has been observed in the spectral range of 2300–600cm−1. On cooling, the intensity of the IR band at 2230cm−1 remained unchanged through the phase-transition of isotropic-nematic and increased gradually toward room temperature (solid phase). This band can be assigned to the C ≡ N stretching vibrational mode. The wavenumber of the band increased slightly (about 1 cm−1) during the temperature from isotropic to solid. In mela-CN substituted AHC, it is suggested that the CN group may not play a dominant role in the intermolecular interaction.

Raman Spectroscopic Study of Liquid Crystalline N-[4-(4-n-Alkoxybenzoyloxy)-2-Hydroxybenzylidene]-Chloroanilines

Abstract N-[4-(4-n-Alkoxybenzoyloxy)-2-hydroxy-benzylidene]-chloroanilines[nAHmC(n; n=1-8, m; m=2: ortho, m=3: meta, m=4: para)] were synthesized. They exhibited a nematic phase. In addition, 8AH4C exhibited the smectic C and A phases. The temperature dependence of their Raman spectra has been observed in the spectral range of 20–1800 cm−1. In a group of nAHmC, the Raman band at about 980 cm−1 decreased in intensity and wavenumber through the solid-liquid crystal phase transition. In the other group, the corresponding band increased through the phase transition. The bands have been assigned to the CH out-of-plane vibration(980 cm−1) of the benzene ring. Such a behavior can be explained by the molecular conformations with different twist angles of the aniline ring to the salicylaldimino part of the molecule in conjunction with information gained in the photochromic studies of N-2-hydroxy-benzylidenanilines. The temperature dependence of the 1190 cm−1 band ascribed to the ring-N bond stretching vibration gave support to the result of the CH deformation vibration.

Catalytic gasification activity of iron enhanced by spilt-over hydrogen

Abstract Gasification rate increases remarkably by mechanical mixing of iron loaded carbon with supported hydrogenation catalyst, when the carbon is gasified in hydrogen or steam-hydrogen mixture. It is concluded that the catalytic activity of iron is enhanced by atomic hydrogen which is produced by adsorption and dissociation of the molecular hydrogen on the supported hydrogenation catalyst and spills-over to the iron through the support and the carbon.

Light Diffraction and Light Scattering in Nematic Liquid Crystals with a Positive Dielectric Anisotropy

A light diffraction pattern is observed in nematic liquid crystals with a positive dielectric anisotropy and is found to agree with that of a grating consisting of periodic slits spaced at nearly equal intervals. The sequence of diffraction spots extends along a direction perpendicular to the rubbing direction of the glass electrode surfaces. At a higher electric field, the characteristic light scattering pattern is observed, the shape of which is the well-known four-leaf-clover with a weak scattered light intensity indicating the existence of domains with a shape similar to that of polymer spherulites.

Light Scattering Study on Orientations in the Smectic Modifications

Abstract The scattering of light by smectic liquid crystals is discussed in terms of theories which have been applied to the scattering from crystalline polymers. The I ⊥ patterns observed from the smectic A and B states are of the four leaf clover form in which the scattering intensity increases continuously in going toward the center, while the smectic C gives circularly symmetric patterns for both I∥ and I⊥. These indicate that the scattering, at least in the smectic A and B mesophases is due to an assembly of anisotropic rods having random-orientation. Some new experimental facts observed for the cholesteric and pseudo-isotropic nematic states are described.