Seiji Ujiie

Self-assembly of thermotropic liquid-crystalline folic acid derivatives: hydrogen-bonded complexes forming layers and columns

Folic acid derivatives having 2-(3,4-dialkoxyphenyl)ethyl moieties have been found to exhibit thermotropic liquid-crystalline behavior. Smectic and discotic phases are observed for these compounds over wide temperature ranges. X-Ray diffraction and infrared measurements show that the formation of the smectic and discotic phases is due to the ribbon- and disk-like structures of the pterin rings of folic acid, respectively. The smectic phase is changed to a hexagonal columnar phase by the addition of alkali metal salts. This behavior is attributed to the change of the hydrogen-bonded structures from ribbon to disk induced by the ion–dipolar interactions.

Supramolecular ferroelectric liquid crystals. Hydrogen-bonded complexes between benzoic acids and chiral stilbazoles

Abstract Supramolecular ferroelectric liquid crystalline complexes have been obtained from 4-alkoxybenzoic acids and optically active trans-4-substituted-4′-stilbazoles. Chiral smectic C phases are induced by the formation of supramolecular mesogenic structure through the selective intermolecular hydrogen bond between the achiral benzoic acids and the chiral non-mesogenic stilbazoles.

Lamellar Mesophases Formed by Thermotropic Liquid Crystalline Ionic Polymer Systems without Mesogenic Units

Mixtures consisting of polyamine (branched polyethyleneimine (PEI) and polyallylamine (PAA)) and n-alkanoic acid (Cn: n = the carbon number of alkanoic acid) were prepared and their thermal and liquid crystalline properties were examined. The occurrence of proton transfer from the carboxylic acid to the amine groups was found by IR measurement of the mixtures. The polyamines and Cn exhibited no mesophase. Also, PEI/Cn with n = 3, 4, 5, which are mixtures of PEI and Cn, did not show a liquid crystalline phase. However, PEI/Cn with n> 5 clearly displayed a lamellar fluid liquid crystal phase having a layer structure with low order inside the layer, due to ion–ion interactions. In the lamellar mesophase, PEI/Cn showed a focal-conic fan texture which resembles the fan-shaped textures in smectic A and C phases. PEI/Cn with 5 < n < 13 formed a bilayer structure in the lamellar mesophase. On the other hand, a tilted bilayer structure is proposed as a packing model of PEI/Cn with 13 < n< 19. PAA/C18 consisting of polyallylamine and C18 also showed a lamellar fluid mesophase and formed a similar layer structure to PEI/C18.

A new ionic liquid crystal compound with viologen group in the principal structure

Abstract A new ionic liquid crystal system, based on compounds with the viologen group (for example, 1–2: Cr 190 SA 280 dec.) has been synthesized, and is found to exhibit the smectic A phase.

Ion-conductive liquid crystals: Formation of stable smectic semi-bilayers by the introduction of perfluoroalkyl moieties†

Liquid-crystalline compounds 1 and 3 having perfluoroalkyl-terminated mesogens at both ends of poly(ethylene oxide) chains have been prepared. These compounds show smectic A (S A ) and C phases over 100 °C. The S A -Iso (isotropic) transition temperatures are higher by about 70 °C than those of the corresponding alkyl-substituted compounds 2 and 4. The incorporation of lithium triflate into 1 and 3 widens the temperature ranges of the S A phases for the resulting complexes. The complexes of 1 and 3 containing 50 mol-% of lithium triflate exhibit columnar phases. The ionic conductivities of the homotropically aligned complexes based on 1 along the direction perpendicular to the molecular director of the S A phases are higher than those of the corresponding compound of 2. The increase of the ionic conductivities as well as the stabilization of the smectic phases for these perfluoroalkyl-terminated compounds may be due to the formation of more stabilized layered structures through the intermolecular interactions among the perfluoroalkyl moieties.

Liquid-Crystalline Branched Polymers having Ionic Moieties

Ionic LC-dendrimers were obtained by proton-transfer reaction of alkanoic acid and primary amino groups of poly(amidoamine) dendrimer in a 1:1 molar ratio. The ion complexes containing stearate, palmitate or myristate ions showed a smectic A phase. However, the ion complexes containing laurate and decanoate ions exhibited no liquid-crystalline phase. Oilystreak, maltese, and homeotropic textures were observed in the smectic A phase. The formation of the homeotropic structure is characterized by conoscopic observation. The X-ray diffraction pattern in the smectic A temperatures consists of sharp inner reflections at the small angles and the wide-angle diffuse halo. Mixtures of the dendrimer and stearic acid [a molar ratio (x) of stearic acid against the primary amino groups of the dendrimer] were prepared; mixtures with x = 0.11–1.5 showed a smectic A phase. However, the mixture with x = 2.33 formed a disordered hexagonal columnar mesophase, characterized by an optical texture and X-ray diffraction measurement.

Induction of mesophases through the complexation between benzoic acids with lateral groups and polyamides containing a 2,6-diaminopyridine moiety

Supramolecular liquid crystalline polymeric complexes have been prepared by the complexation of 4-alkyloxybenzoic acid derivatives and polyamides containing a 2,6-diaminopyridine moiety. 4-Alkyloxybenzoic acids substituted by methoxy, methyl, and nitro groups at the 3-position are used for the complexation. These polymeric complexes behave as single component liquid crystalline polymers and exhibit stable and enantiotropic mesophases. In contrast, simple 4-alkyloxybenzoic acids having no substituent at the 3-position, do not form stable complexes with the polymers. For low molecular mass complexes derived from 2,6-bis(acylamino)pyridine and 4-alkyloxybenzoic acid derivatives, substituent effects are different from those for the polymeric system. In these cases, mesomorphic behaviour is observed only for the complexes based on the simple 4-alkyloxybenzoic acid and 4-alkyloxy-3-methylbenzoic acid.

Liquid crystalline properties and molecular packing of semifluorinated n-alkanes F(CF2)10(CH2)mH

The phase transitions for a homologous series of semifluorinated n-alkanes, F(CF 2 ) 10 (CH 2 ) m H, with 2 ≤ m ≤ 19 (FlOHm), have been characterized using a polarizing microscope, DSC, X-ray diffraction, and dilatometry. Thermal analysis and optical textures indicate the presence of the smectic-smectic phase transition when the number of methylene units ranges from 6 to 12. The phase-transition temperature depends on the length (m) of the hydrocarbon segment. The density decreases with increases in the carbon number of the hydrogen segment. The data for both the thermal properties and the density suggest that the smectic-smectic phase transition is significantly first-order, which is primarily caused by a change in the molecular packing for the molecular rearrangement, while a transition for the clearing point is related to disordering of the entire molecule. The volume jump shows that FlOHm have the same molecular packing in the high-temperature mesophase and that their magnitude is greater than that of the conventional liquid crystalline compounds having an aromatic-mesogenic core. The effects of the fluorinated segment for the phase transitions are also discussed herein.

New pyridinium type ionic liquid crystal compounds with a 1,3-dioxane ring in the principal structure

Abstract A new pyridinium type ionic thermotropic liquid crystal system having two rings in its central core has been synthesized. These compounds exhibited a smectic A phase over a very wide range including room temperature (for example 5-1: Cr -24 SA 150I).

Cubic Mesophase Formed by Thermotropic Liquid Crystalline Ionic Systems – Effects of Polymeric Counter Ion

ABSTRACT Thermotropic ionic liquid crystals with a pyridinium skeleton were synthesized and the effects of counter ions for the liquid crystal formation were examined. The liquid crystal formation depended on the counter anions. The pyridinium liquid crystal, having chloride counter ion, showed columnar, cubic, and smectic A phases. The pyridinium liquid crystals with polymeric counter ions formed columnar and cubic phases. However, they did not show a smectic A phase. The polymeric counter ions enhanced the thermal stability of the cubic phase when compared to chloride counter ion.