Masato Nanasawa

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.

Photochromism of Viologens Included in Crown Ether Cavity

Abstract The effect of a π-electron–donating macrocyclic molecule on the photochromic behavior of viologen derivatives was investigated in a thin polymer film. The intermolecular interactions between the viologens and the macrocyclic molecule were investigated in a solution before photoirradiation. In acetone, benzylviologens, N,N′-dibenzyl-4,4′-bipyridinium hexafluorophosphate (1) and N,N′-dibenzyl-trans-1,2-bis(4-pyridinium)ethylene hexafluorophosphate (2) each derived from 4,4′-bipiyridine and trans-1,2-bis(4-pyridyl)ethylene, respectively, form an inclusion complex with p-benzocrown ether (3) with binding constants of ca 200 M−1, which was driven by a charge transfer interaction. The peak wavelength of the charge transfer absorption band was at 453 and 421 nm for the inclusion complexes of 1 and 2 with 3, respectively. Upon photoirradiation to the polymer film containing 1, the film changed color from colorless to blue, associated with the reduction of 1 from the dication to the radical cation. The original dication was recovered after 120 min. The addition of 3 into the film containing 1 caused not only the color change from colorless to yellow, associated with the charge transfer interaction between 1 and 3 before photoirradiation, but also an acceleration in the bleaching rate of the photoreduced 1. When p-dimethoxybenzene (4) was used as an acyclic analog of 3, a negligible change in the photochromic behavior of 1 was observed. Similar effect of 3 on the photochromic behavior of 2 was observed. These results imply that the π-electron–donating macrocyclic molecule causes a faster bleaching of photoreduced viologens by forming the inclusion complex.

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).

Liquid crystal properties of new ionic liquid crystal compounds having a 1,3-dioxane ring

New pyridinium type chiral ionic liquid crystal materials having a 1,3-dioxane ring in the central core, (+)- N -2-methylbutyl-4-(5-alkyl-1,3-dioxan-2-yl)pyridinium bromides (6), were synthesized. Mixture A was made by adding 5.9 wt % of compound 6−3 to the ferroelectric liquid crystal mixture Merck 4655-100; its phase transitions and some liquid crystal properties were measured. In spite of a large decrease of Ps for mixture A, its response time A was the same as that of Merck 4655-100. The dielectric constants perpendicular to the molecular axis for the smectic C* and smectic A phases were measured for the mixture and Merck 4655−100: in the smectic C phase, these dielectric constants were almost the same (4.5∼5.5), but in the smectic A phase, the perpendicular dielectric constant of the mixture was 47.0 and that of Merck 4655−100 was 4.5.

New 1,3-oxathiane type ionic liquid crystal compounds

New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-oxathiane ring in the central core,N-ethyl-4-(5-alkyl-1,3-oxathian-2-yl)pyridinium bromides 8, were synthesized. These compounds exhibited a smectic A phase over a very wide range including room temperature (for example 8c: G –30 SA 21 I).

Redox photochromism of viologen in organized solid state

Abstract N,N′-Diphenylbipyridinium(viologen) having alkylbenzene sulfonate with long alkyl chains (C6-C15) was synthesized by three reaction sequences. The viologens with alkyl chains of C10-C15 exhibit a liquid crystal phase and display smectic-A type. Upon irradiation with near-UV light, viologen films change from pale yellow to blue-green, whose absorption maxima shift remarkably to red and the shapes differ with the length of the alkyl chain of the counter anions. The colour induced by light is maintained above 95% at 30° C and can be bleached at higher temperature. This has made possible, for the first time, the colour development by light and bleaching by heat of transparent anisotropic thin films.

Color-modulation by Additives for Photochromism of Cyclic Viologen Derivatives

Abstract Two cyclic viologen derivatives were prepared in order to investigate their photochromic properties in a thin polymer film. The absorption peaks of photoreduced cyclic viologen units were shifted to the red side by the inclusion of indole or 1,4-dimethoxybenzene, although those of photoreduced acyclic analogues were not shifted in the presence of the guests.

New possibility for an organic semiconductor: a smectic liquid crystalline semiconductor having a long conjugated core and two long alkyl chains

We report a new possibility for liquid crystalline organic semiconductors. These materials exhibit smectic liquid crystalline phases, in which the molecules assume a smectic molecular order by self‐assembly. Because of the strong dispersion force among long alkyl chains, on cooling, smectic molecular order was retained at room temperature. A charge transport ability was also retained. The conductivity of a device having smectic liquid crystalline order is about 5×107 that of a device with no smectic order. The current – voltage characteristic of the device has a very sharp increase at low threshold voltage (5 V). A high carrier mobility of 1.8×10‐2 was observed in the smectic phase of one of the compounds studied (e).

Side chain type ionic liquid crystalline polymers having high Preliminary communication molecular weight

Side chain type ionic liquid crystalline polymers having a 4-(1,3-dioxan-2-yl)pyridinium structure in their mesogenic side chain were synthesized. These polymers exhibited the smectic A phase. The molecular weights of these ionic liquid crystalline polymers are very high, e.g. for compound 7 - 2 M w = 486 000.

New 1,3-Dioxane Type Ionic Liquid Crystal Compounds Having a Different Counter Anion

Abstract New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-dioxane ring in their central core: N-substituted-4-(5-alkyl-1,3-dioxan-2-yl)pyridinium halides (6) were synthesized. These componds exhibited a smectic A phase over a very wide temperature range including room temperature [for example 6–5: G –24 SmA 152 I (°C)]. The size of the counter anion affected the transition temperatures between the isotropic state and the smectic A phase.