Synthesis and Liquid Crystalline Properties of Dimesogenic Compounds Containing Trifluoromethyl Substituents at Terminal Phenylene Rings and Central Decamethylene Spacer

Synthesis and Liquid Crystalline Properties of Dimesogenic Compounds Containing Trifluoromethyl Substituents at Terminal Phenylene Rings and Central Decamethylene Spacer

A series of new dimesogenic compounds whose mesogens are of aromatic ester or amide type having a trifluoromethyl $(CF_3)$ substituent at the para-position of each terminal phenolic rings were prepared and their liquid crystalline properties were studied by differential scanning calorimetry (DSC) and on a cross-polarizing microscope. The compounds have two identical mesogenic units bracketing a central decamethylene spacer. Trifluoromethyl group appears to favor the formation of smectic phases when it is attached to a phenoxy or anilide terminal. Its group efficiency for mesophase formation seems to be inferior to other common substituents. A thermodynamic analysis of the phase transitions was made and the results were explained in relation to the structures of the compounds.