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.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry