Dimesogenic compounds consisting of cholesterol and azobenzene‐based moieties: dependence of liquid crystal properties on spacer length and fluorination of the terminal chain

Abstract

The liquid crystalline (LC) properties of two series of non‐symmetric dimesogenic compounds consisting of cholesterol and azobenzene‐based moieties interconnected by ω‐oxyalkanoyl spacers of varying length are compared: one series (AOC‐n) has an octyloxy chain attached to the azobenzene mesogen unit while the other (AOCF‐n) has a perfluoroheptylmethyloxy chain. In general, compounds bearing the fluorinated alkoxy chain exhibited LC properties over a much broader temperature range than those with the alkoxy chain. In addition, the AOC‐n series exhibited the chiral smectic C (SmC*), smectic A (SmA) and cholesteric (N*) phases depending on the length of the central spacer, whereas the AOCF‐n series favoured the formation of only the SmA phase with the N* phase completely suppressed. Both series showed an odd–even dependence of the isotropization temperature on spacer length.

Acknowledgement

This work was supported by the Korea Science and Engineering Foundation through the Center for Electro‐ and Photo‐Responsive Molecules, Korea University. K.‐N. K., E.‐D. D. and Y.‐W. K. are recipients of the BK 21 fellowship from the Ministry of Education and Human Resources of the Republic of Korea.