Spironaphthooxazine (SNO) was attached to a three-dimensional network of polysiloxane through the allyloxy group on C-7 of the naphthalene ring of SNO, and the photochemical coloration and thermal decoloration behaviors of this material (Film-P) were examined by comparing their properties with those of model SNO having a 7-propyloxynaphthyl group in solution, in a doped polysiloxane film (Film-D), and in a doped PMMA film. For Film-P, the SNO units were connected to a part of the vinyl groups on the Si atoms of a linear polysiloxane by hydrosilylation, and the remaining vinyl groups were bridged by the bifunctional linear polysiloxane possessing two hydrosilyl groups at both ends of the chain. While Film-P containing 1.7 x 10(-3) mol dm(-3) of the SNO unit formed a transparent film, Film-D containing more than 1.2 x 10(-3) mol dm(-3) could not form a transparent film but segregation of SNO occurred. A transparent Film-D was prepared at 0.54 x 10(-3) mol dm(-3) SNO concentration. The decoloration reaction rate of Film-D was faster than those for Film-P, solutions, and PMMA. However, due to the low concentration, the coloration of Film-D was weak. When the concentration of SNO in Film-P was increased 5.7 times, the decoloration rate became 3.6 times faster. Its half-life time was 0.9 s, which is 3.1 times as fast as that of corresponding solution in hexamethyldisiloxane.
Eleven novel thermotropic rod-shaped liquid crystals composed of alkoxyphenyl (methoxy to decyloxy) or hexanoyloxyphenyl groups on both ends of the diamantane core have been synthesized and their liquid crystalline properties investigated. All of them behaved as liquid crystals at considerably high temperatures. When the alkoxy side chains are propyloxy or shorter, the clearing points are over 300°C. The clearing point of a liquid crystalline compound with two hexanoyloxy groups also exceeds 300°C. When the alkoxy groups on both ends of the molecule are octyloxy or longer, they showed only smectic phases as the mesophase. When they are shorter than octyloxy, the compounds showed nematic phases just below their clearing points. A nematic phase was also observed for the hexanoyloxy compound as well as the smectic A and B phases. However, as the bent-shaped adamantane-derived hexyloxyphenyl molecule did not show any liquid crystalline properties, the linear structures of the diamantane-derived molecules were crucial in generating liquid crystalline phases.Currently, liquid crystal displays (LCDs) are the major display devices for TVs, PCs, mobile phones, and other useful products. The liquid crystalline (LC) compounds for such devices should exhibit various significant properties before they are adopted for widespread use.1 The required physical properties for any type of display are: 1) a wide nematic-phase temperature range, 2) high chemical and thermal stability, and 3) low viscosity to attain short switching times. Although numerous molecules have been synthesized and studied to improve performance, the development of a single compound that satisfies all of the required properties has not yet been achieved. Therefore, most liquid crystals (LCs) for LCDs are a mixture of several different LC compounds, however, the mixing of multiple LCs lowers the nematicisotropic (NI) phase-transition temperature. In order to maintain a practical LC temperature range which is as wide as possible, it is necessary that LCs which have high NI phase transition temperatures be mixed together. 2Most rod-like LC compounds have a rigid but flat core structure and one or two flexible side chains, and may also have a polar functional group. 3 The rigid core is made up of one or more hydrocarbon rings and heterocycles such as 1,4-disubstituted benzene, trans-1,4-disubstituted cyclohexane, 2,5-disubstituted pyrimidine, and trans-2,5-disubstituted 1,3-dioxane rings. However, some liquid crystalline compounds possessing barrel-like thick core structures, such as bicyclo[2. Recently, much attention has focused on the molecular nanodiamond family called diamondoids, 8 which was first discovered in the pitch of crude petroleum.9 Diamondoids have a diamond-like saturated hydrocarbon skeleton based on threedimensionally fused cyclohexanes whose smallest member is adamantane. They have been studied extensively because of their interesting structural as well as physical properties. 1013A number of their chemical modifications have also been repo...
Diamantane, one of the diamondoid family molecules, was introduced to thermally reversible photochromic heliofulgides. They exhibited good thermally reversible photochromism. A chiral photochromic indolylfulgide derivative was used to control the pitch length of cholesteric liquid crystalline state by photoirradiation. However, as the indolylfulgide derivative has absorption in the visible light region, it is not a suitable agent to control the selective reflection wavelength. Chiral benzofurylfulgide derivative, possessing shorter absorption maximum wavelength, was employed for this purpose. Diamantane has a long barrel-like C 3 -symmetric structure with the corresponding symmetric axis. Several derivatives, with long alkyl or related substituents on the carbon atoms at both ends of the molecule, showed liquid crystalline properties. Thus, diamantane worked as a thread stitching up photochromism and liquid crystals.
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