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Abstract
Nematic-isotropic transition temperature was determined for 4-(4-X-benzylideneamino)phenyl 4-Y-benzoates, where X and Y were chosen from methoxy, nitro, chloro, bromo, dimethylamino, methyl, fluoro, trifluoromethyl groups. The order of group (X or Y) efficiency in promoting the nematic-isotropic transition temperature is markedly affected by the nature of the group (Y or X) located at the other end. For example, the methoxy and methyl series give NO2 > CH3O > N (CH3)2 > Cl ≒ Br > CH3 > F > CF3, whereas the trifluoromethyl series gives N(CH3)2 > CH3O > CH3 > Cl ≒ Br > NO2 > F, suggesting that the dipole-dipole interaction contributes significantly to the stabilization of the nematic phase.