Alkoxyphenyl-substituted symmetric liquid crystalline diamantane derivatives

Abstract

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.© 2011 The Chemical Society of Japan.