SEMIFLUORINATED LIQUID-CRYSTALLINE DIBLOCK AND TRIBLOCK ESTER MOLECULES

A series of ester molecules based on rigid fluoroalkyl mesogenic units instead of the classical linked-ring systems has been synthesized and investigated for liquid crystallinity. Aliphatic hydrocarbon chains or substituted single phenyl rings were linked to various perfluoroalkyl segments. The mesophases were investigated by optical microscopy, DSC, and X-ray diffraction. In these compounds smectic A or B phases were observed and identified optically or by X-ray diffraction. The 3,5-dihydroxyphenyl compounds were also found to be lyotropic. Differences in the mesophase transition temperatures were observed which are discussed in terms of the structure. The smectic layer spacings found from X-ray data show monolayers or bilayers. This type of layer ordering is discussed with reference to the structure and considering the molecules as models of main-chain and side-chain polymers.