Studies on the Smectic Phase of Some Schiff's Bases With a Terminal Trifluoromethyl Group

Some terminally substituted trifluoromethylbenzylideneanilines have been synthesized with a view to investigate an unidentified smectic phase which exhibits an unusual texture as observed under the polarizing microscope. This phase was first reported by Griffin et al.² for the compound N-(4-n-decyloxybenzylidene)-4'-trifluoromethylaniline. In a comparable compound but with reversed imine linkage the nature of this smectic phase remains unchanged. Also if the terminal n-decyloxy group is replaced by an n-decyl group the nature of the smectic phase remains the same except that it is observed at a considerably lower temperature. We observe that this smectic phase has uniaxial symmetry when studied with a polarizing microscope as well as with NMR techniques; the latter showing an order parameter S = 0.8 for this phase. X-ray diffraction patterns show this phase to be crystal smectic B.