Takeyasu Tasaka

Liquid crystalline properties of dissymmetric molecules IV. The substituent effect on thermal properties of nematic and smectic A phases in three aromatic ring systems with ester linkages

This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH3, CH3, OC8H17, C8H17, halogens, CF3, OCF3, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis.

Liquid crystalline properties of dissymmetric molecules part 5: the effects of alkyl chain length and linkages on thermal properties of smectic A and C phases in three aromatic ring systems

Abstract This paper describes the effect of alkyl and alkoxy chain lengths on the thermal properties of four isomeric systems; 4-R-phenyl 4-(4-octyloxybenzoyloxy)benzoates ( 1 ), 4-octyloxyphenyl 4-(4-R-benzoyloxy)benzoates ( 2 ), 4-(4-R-benzoyloxy)phenyl 4-octyloxybenzoates ( 3 ), and 4-R-phenyl 4-octyloxyphenyl terephthalates ( 4 ) (R=alkoxy, alkyl). The smectic properties for 1 and 2 are fairly different when both terminal alkyl and alkoxyl groups are short, while both have the same liquid crystalline core. The homologs of 3 exhibit only a smectic C phase even in the higher homologs. The homologs of 4 preferentially exhibit smectic A and C phases from the earlier homologs. The difference in the smectic properties will be discussed in terms of their molecular characteristics.

Liquid crystalline properties of dissymmetric molecules part X: The effect of a terminal nitro group on molecular arrangement in smectic phases in three aromatic ring systems with two ester groups

The smectic A (SmA) layer structure has been examined by X-ray diffraction for four isomeric systems: 4-nitrophenyl 4-(4-alkoxybenzoyloxy)benzoates 1, 4-alkoxyphenyl 4-(4-nitrobenzoyloxy)benzoates 2, 4-(4-alkoxybenzoyloxy)phenyl 4-nitrobenzoates 3, and 4-alkoxyphenyl 4-nitrophenyl terephthalates 4. The phase transition behaviour and layer structure of the SmA phases are notably influenced by the relative orientation of the two ester groups to the terminal groups, by alkoxy chain length, and by temperature. The SmA phase for compounds 1 and 3 has a mainly ‘monolayer’ arrangement, where the layer spacing is 2-5 Å longer than the molecular length. The SmA phase for compounds 2 and 4 consists of a mixed layer structure having monolayer, bilayer, and partially bilayer arrangements, the distribution depending on the relative orientation of the ester groups, the alkoxy chain length, and temperature. It is supposed that the diversity of the SmA phase is related to the polar interaction around the nitro or the nitrobenzene moieties through the smectic layers and reversal of the ester groups causes a subtle change in the entire molecular shape.

Liquid crystalline properties of dissymmetric molecules VI. The effect of alkyl chain length on molecular arrangement in the smectic A phase in three-aromatic-ring systems with two ester groups

The effect of alkyl and alkoxy chain lengths on the layer structures of smectic A and C phases has been examined by X-ray diffraction measurements on three isomeric systems: 4-alkoxyphenyl and 4-n-alkylphenyl 4-[(4-octyloxyphenyl)carbonyloxy]benzoates (1); 4-octyloxyphenyl 4-[4-(octyloxyphenyl)carbonyloxy]benzoates (2); 4-octyloxyphenyl, 4-alkoxyphenyl and 4-n-alkylphenyl terephthalates (3); and p-phenylene 4-octyloxybenzoates, 4-alkoxybenzoate and 4-n-alkylbenzoate (4). Although all the derivatives exhibit smectic A and/or C phases having a monolayer arrangement of the molecules, the layer spacings are considerably affected by alternation of the ester linkages. The layer spacings for the homologues of 1 are a little shorter than the calculated molecular lengths, while those for 2 agree with the calculated molecular lengths. The layer spacings for 3 show a notable even-odd alternation in the higher homologues. The results are discussed in terms of a subtle change in the molecular structures due to replacement of the ester groups.

Smectic Phase Exhibited by Dissymmetric Liquid Crystals: Effect of a Terminal Fluoromethyl Group on Mesomorphic Properties

This paper describes smetic properties of some liquid crystal materials incorporating a terminal trifluoromethyl, a trifluoromethoxy, or a difluoromethoxy group. These groups tend to promote the appearance of smectic A phase with a characteristic molecular arrangement, and the layer structure is discussed in terms of the physical properties of the molecules.

Liquid crystalline properties of dissymmetric molecules IX. The effect of a terminal nitro group on the thermal properties of the smectic A phase in 4-nitrophenyl 4-(4-alkoxybenzoyloxyphenyl)benzoates

This paper describes the effect of alkoxy chain length on the physico-chemical properties of 4-nitrophenyl 4-(4-alkoxybenzoyloxyphenyl)benzoates. The homologous series shows a smectic A (SmA) phase commencing from the hexyloxy homologue. While the pentyloxy homologue shows only a nematic (N) phase under microscopic observation, X-ray diffraction shows that the N phase has a cybotactic domain with a layer structure of the SmA phase, where the layer spacings are longer than the calculated molecular lengths by c. Å. The layer spacings for the heptyloxy-nonyloxy homologues are longer than the calculated molecular lengths by 2.2-4.8 Å and are almost independent of temperature. The layer spacings are correlated with the calculated molecular lengths, and based on these results, a new molecular arrangement model for the SmA phase is proposed.

Physico-Chemical Properties of New Liquid Crystals Incorporating a Lactone Ring

ABSTRACT Synthesis and physico-chemical properties of 4-alkoxyphenyl and 4-alkoxybiphenyl-4′-yl 2H-pyran-2-one-5-carboxylates, 2H-chromen-2-one-6-yl 4-alkoxybenzoates and 4-alkoxybiphenyl-4′-carboxylates, and 2H-chromen-2-one-7-yl 4-alkoxybenzoates and 4-alkoxybiphenyl-4′-carboxylates are described. Terminal 2H-pyran-2-one and chromen-2-one cores are effective in enhancing liquid crystalline properties. The layer structure was examined by a small angle X-ray measurement, and the results are discussed in terms of the molecular structure. The polar effect of the terminal lactone group is recognized in the thermal properties and the layer structure of smectic A (SmA) phase.

The influence of lateral substitution of liquid crystals on the structure of their smectic Ad phases

Abstract The influence of lateral substitution of liquid crystals on the structure of their smectic Ad phases revealed by X-ray diffraction study is discussed.

Gelation of 1-Alkoxy-4-(2-Perfluoroalkyl)Ethoxybenzenes in Organic Solvents

ABSTRACT This paper describes preparation and physico-chemical properties of 1-alkoxy-4-(2-perfluoroalkyl)ethoxybenzenes (FmOOCn). For FmOOCn, 4-F(CF2)mCH2CH2O-phenyl-O-(CH2)nH, three homologues, m = 8 (n = 1, 2) and m = 10 (n = 1) reveal monotropic smectic A and unidentified smectic phases, respectively. Simultaneously, most of the homologous are possible to gelatinize various organic solvents such as octane, cyclohexane, DMF, ethanol, and so on. The gelation ability increases with increasing the carbon number of the perfluoroalkyl chain. The formed gel is transparent, semitransparent or opaque, and the phase transition between the gel phase and the isotropic fluid is thermally reversible. The images of gel observed with scanning electron microscope (SEM) show gathered fibrous aggregates.

A Comparative X-Ray Diffraction Study of Two Liquid Crystalline 2,5-Disubstituted 1,3,4-Oxadiazole and 1,3,4-Thiadiazole Derivatives in Their Smectic Phases

Abstract X-ray diffraction study of two liquid crystalline 2,5-disubstituted 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives reveals the existence of a partially bilayered smectic Ad phase in the terminally bromo substituted derivatives, with the lower level of molecular overlapping in the formation of the dimer and more pronounced smectic fluctuations on the dimeric density wave observed for the former compound.