123974-97-0Relevant academic research and scientific papers
Molecular mechanism of anomalous increase in the helical pitch of cholesteric liquid crystals induced by achiral dopants
Kidowaki, Masatoshi,Moriyama, Masaya,Wada, Momoyo,Tamaoki, Nobuyuki
, p. 12054 - 12061 (2007/10/03)
A dopant-induced anomalous increase in the helical pitch of dicholesteryl 10,12-docosadiynedioate 1 is explained by generation of smectic clusters in the cholesteric phase where the dopants act as promoters of smectic domains. The dopants, having a mesogenic core and the proper length of alkyl chains on both their molecular sides, such as 4,4′-dialkylazobenzenes, 4,4′-dialkylazoxybenzenes and 4,4′-dialkylbiphenyls, considerably increase the pitch. However, dopants having benzene or a binaphthyl structure in the molecular center, and alkyl chain at one side of the molecules and Z-isomers of azobenzene and azoxybenzene derivatives slightly decrease the pitch by acting as impurities that decrease the transition temperature of the host. At X-ray diffraction study of the cholesterics revealed that the pitch increases with an increase in size and amount of the smectic domains induced by the appropriate dopants.
Aryliminodimagnesium Reagents. XV. Condensation with Nitrobenzene. Formation of Unsymmetrical Azobenzenes Favored By Long-Chain p-Alkoxy-Substituted Reagents
Okubo, Masao,Matsuo, Koji,Yamauchi, Akira
, p. 915 - 918 (2007/10/02)
In the reaction of p-MeC6H4N(MgBr)2 with p-alkoxynitrobenzene, no effect of alkoxy chain length on the relative yields of azoxy and azo products was observed.In contrast, in the reaction of p-alkoxy-C6H4N(MgBr)2 with p-nitrotoluene, C12- and C18-alkoxyl chains led to the corresponding unsymmetrical azobenzenes in unexpectedly high yields.This result, arising from efficient condensation and deoxygenation processes, was explained in terms of cooperation of reagent molecules through their aggregation assisted by a novel tying effect of their long chains.
