Study On The Synthesis And Properties Of Cholesteryl Group-containing Double Mesogen Compounds

The molecular structure of cholesterol contains asymmetric carbon atomsand exhibit a layered helical arrangement,which has motivated many researchers to use them to synthesize liquid crystals(LC)compounds.The helical supramolecular structure of cholesteryl-based LC can impart some unique optical properties,Such as selective reflection of circular polarised light,high optical rotatory power and electro-optic effect.So far,the cholesteric LC have had a wide application for medical diagnosis,gas test electromagnetic detectation and liquid crystalline anti-couterfeiting trademark.In this paper,four series of dimesognic compounds withing cholesteryl were synthesized,and their LC properties and luminescence properties were studied.Among them,both the thioether-containing end group and the cinnamic acid-containing derivative exhibit strong optical properties and rainbow colors.The cholesteric helical pitch decreased with increasing temperature.It shows a lower transition temperature and a narrower cholesteric phase compared to analogues with alkoxy groups.The dimesognic compounds having cinnamic acid derivatives was shown a cholesteric phase.For 12-TC and 14-TC,the SmA phase and Ch phase were shown.As the terminal chain length increases,the thermal stability of the smectic mesophase increases.By changing the shape of cholesteryl dimesognic compounds,the temperature ranges of the mesophase varies.The change of length of the spacer chain causes a change in the thermal behavior and liquid crystal behavior of the target product,and a significant odd-even effect occurs in the Lc-I transition temperature.The molecular structures of the intermediates and target compounds were confirmed by Fourier transform infrared and proton nuclear magnetic resonance spectroscopy.The thermal phase behaviour of the synthesised dimesognic compounds were investigated by polarizing optical microscopy coupled with hot stage and differential scanning calorimetry.All of these dimesognic compounds showed cholesteric or smectic phases,while also exhibiting a higher clearing point temperature and a wider mesophase temperature range.