Yoshio Matsunaga

Mesomorphic behaviour of 1,3-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] and related compounds

Abstract DSC and X-ray diffraction studies on a series of 1,3-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] are presented. The only mesophase exhibited by the methoxy to hexadecyloxy homologues is of the smectic C type. The reversal of the iminomethyl linkage reduces drastically the incidence of a mesophase; that is, only the first five homologous members exhibit a smectic C phase in the series of 1,3-phenylene bis[4-(4-alkoxybenzylideneamino)benzoates]. Almost all the members in the second series become nematogenic by the chloro substitution at the 4-position of the 1,3-phenylene moiety. In addition, a smectic C phase is observable for the ethoxy to pentyloxy and also the tetradecyloxy and hexadecyloxy members. The second chloro-substituent introduced to the 6-position of the same central ring eliminates completely the smectic C phase and enhances the nematic thermal stability.

New mesogenic compounds with unconventional molecular structures 1,2-Phenylene and 2,3-naphthylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] and related compounds

Abstract DSC and X-ray studies on a series of 1,2-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] are presented. The phases were shown to be classical nematic and/or smectic by their continuous miscibilities with reference mesophases. The layer spacings in the smectic A phase measured as a function of the alkyl chain length revealed that the mean tilt angle of the linear three-ring part of the molecule to the layer normal is about 37° and that the molecular core is V-shaped with an angle of about 70° between the two out-stretched benzoate legs. This molecular model accounts for the effects of a methyl group introduced into the 3- or 4-position of the 1,2-phenylene moiety on the mesomorphic properties. Both the nematic and smectic A properties are markedly promoted by replacement of the 1,2-phenylene group by the 2,3-naphthylene group. The phases exhibited by the less-elongated series of 2,3-naphthylene bis(4-alkoxybenzoates) are also nematic and/or smectic A, but are now monotropic. The formation of...

Mesomorphic Behavior of 2,4-Bis-(4-alkoxybenzylidene)cyclopentanones and Related Compounds

Abstract The mesomorphic properties of homologous series of 2,5-bis(4-alkoxybenzylidene)cyclopentanones, 2,6-bis(4-alkoxybenzylidene)cyclohexanones, and 2,7-bis(4-alkoxybenzylidene)cycloheptanoneshave been compared with each other. The clearing point is markedly depressed by increasing the size of the cycloalkanone ring. The cyclopentanone derivatives carrying the methoxy to pentyloxy groups are purely nematogenic, the next member exhibits a smectic A phase as well as a nematic phase. Smectic A and C phases are observed for the heptyloxy and octyloxy homologues, and only a smectic C phase for the later members. In both the cyclohexanone and cycloheptanone derivatives, the methoxy to decyloxy homologues exhibit a nematic phase and the higher members exhibit a smectic C phase. In addition, a smectic A phase appears in the nonyloxy and decyloxy homologues of the cyclohexanone series.

Mesomorphic Behavior of 1,2-Phenylene Bis[4-(4-alkoxybenzylideneamino)benzoates

Abstract A series of 1,2-phenylene bis[4-(4-alkoxybenzylideneamino)benzoates has been prepared in order to establish that the nonlinear molecular structure is not necessarily incompatible with mesophase formation. The phases appearing in the methoxy and ethoxy derivatives are classical nematic. While the propoxy to octyloxy derivatives display a smectic A phase, as well as a nematic phase, the higher homologous members are purely smectogenic. Although the introduction of a methyl group to the 3-position of the central phenylene ring eliminates the nematic phase, the thermal stability of the smectic A phase is not much affected. The 4-methylation promotes both the nematic and smectic A phases. A metastable smectic B phase is observed in many members of these three series. The above-mentioned behavior closely resembles that given by the corresponding methyl derivative of phenyl 4-(4-alkoxybenzylideneamino)benzoate.

Mesophases Induced by Molecular Complexing

Abstract By mixing of potentially-mesomorphic electron donors and acceptors of the type N-(p-X-benzylidene)-p-Y-aniline, nematic and smectic liquid crystals could be induced. In the present work, the donor molecules with a dimethylamino group as X or Y and the acceptor molecule with a nitro group as X or Y were employed. The remaining terminal substituents were selected from short alkoxyl groups; namely, methoxyl, ethoxyl, and propoxyl groups. The effect of the replacement of ethoxyl group by propyl group was also studied. The induced mesophases are more deeply colored than the component compounds owing to the appearance of intermolecular charge-transfer absorption near 500 nm.

Liquid Crystal Phases Exhibited by N,N′,N″-Trialkyl-1,3,5-Benzenetricaboxamides

Abstract When crystals of N,N′,N″-trialkyl-1,3,5-benzenetricarboxamides with alkyl groups from pentyl to octadecyl are heated, viscous birefringent fluids are produced at temperatures between 40 and 120[ddot]C depending upon the alkyl chain length and they are transformed into optically isotropic liquids above 200[ddot]C. Transition to a liquid crystal phase is accompained by an enthalpy change of 10 to 68 kJ mol−1 and that to an isotropic liquid by that of 6 to 22 kJ mol−1. The X-ray diffraction pattern of the unoriented liquid crystal resembles that known for smectic A or B phase. A layer thickness given by a sharp inner peak is 1.40 nm for the pentyl derivative and increases up to 2.26 nm for the octadecyl derivative. The second moment of the broad-line proton NMR spectrum shows an abrupt decrease at the melting point from several G2 to a few hundredths G2.

Electrical Resistivities and the Type of Bonding in Some Quinone Complexes

MOST molecular complexes are essentially of the non-bonding type and their infra-red spectra are quite similar to the superposed spectra of the components1,2. However, the infrared, spectra of some diamine-quinone complexes and azine-quinone complexes have been found to show the pattern of the semiquinone ion instead of the quinone. Such complexes have been characterized as essentially of the dative type. Thus charge transfer molecular complexes may be classified into two groups, namely, the non-bonding type and the dative type, based on their infrared spectra. Using this method of classification, I have pointed out that most of the known complexes having resistivities of 105 ohm cm or less are of the dative type3.

Mesomorphic properties of orthopalladated complexes of laterally substituted azobenzene derivatives, 2-alkoxycarbonyl-4-(4-ethoxyphenylazo)phenyl 4-methoxybenzoates

Abstract Homologous series of 2-alkoxycarbonyl-4-(4-ethoxyphenylazo)phenyl 4-methoxybenzoates (L) and their orthopalladated μ-chloro dimers (Pd2Cl2L2) have been synthesized and their thermotropic phase transition behaviour has been characterized. The ligands, L, are three-ring nematogens with their central rings substituted in the 2-position by n-alkyl chains of varied length. The thermal stability of the nematic phases decreases rapidly with increasing side chain length and then levels off as the series is ascended. In every case the mesomorphic phase appears only over a small temperature range (less than 20° C). The orthopalladated species also proved to be nematogenic. Melting and clearing points rise on the average by 87° C and 126° C, respectively, and thus the temperature ranges of the nematic phases are enlarged considerably upon metallation. In relation to the observed stabilization of the nematic phases, particularly of higher homologues, a lath-like molecular structure, in which the side chains ...

Liquid Crystalline Properties of Mixtures Composed of N-[4-(Dimethylamino)phenyl]- and N-(4-Nitrophenyl)-α-(4-alkoxyphenyl) nitrones

Abstract Nematic and smectic liquid crystals induced in binary mixtures of electron donors and acceptors of the type 4-X-C6H4-CH=NO-C6H4,-Y-4 (nitrones) and those of the type 4-X-C6H4-CH=N-C6H4-Y-4 (Schiffs bases) were compared. The terminal substituent X is a dimethylamino group in the donors and is a nitro group in the acceptors. The other terminal substituent Y is a methoxyl, ethoxyl, propoxyl or butoxyl group. The nematic liquid crystals induced by the compounds of the former type are as stable as those by the compounds of the latter type. Even though a smectic liquid crystal is more often observable when the central linkage is -CH=NO-, its thermal stability is, in general, not much affected by the modification. The following mixtures are exceptional; the donor carrying a butoxyl group with the acceptor carrying a propoxyl or butoxyl group. In these two cases, the maximum temperatures of the smectic liquid crystals induced in the nitrones are lower as much as 35 to 40°C than those induced in the corr...

The Thermotropic Liquid-Crystalline Behavior of Alkylammonium Naphthalenesulfonates

Abstract A smectic A phase was observed for a number of alkylammonium naphthalene-1- and 2-sulfonates. The former series needs undecyl or longer alkyl groups to be mesogenic and the latter needs heptyl or longer ones. The clearing point is generally raised ascending the homologous series, but it is found within a rather narrow range; namely, 30°C in the case of 1-sulfonates and 21°C in the case of 2- sulfonates. The 1-naphthol-4-sulfonates are mesogenic only when the ammonium ion carries a tridecyl or longer alkyl group. The clearing point is rapidly promoted by the increase of the chain length.