Four series of unsymmetrical 1,4-phenylene-bis-(4-substituted benzoates) were prepared in which one substituent is a terminal alkoxy group with a number of carbon atoms kept constant (at n = 6, 8, 14, and 16) while the other substituent (X) alternatively changed from CH3O, CH3, Cl, NO2, CN, and CnH2n+1O. Compounds prepared were characterized by infrared spectroscopy and their mesophase stabilities investigated by differential scanning calorimeter (DSC) and polarized-light microscope. The results were discussed in terms of mesomeric and polarizability effects. In all the four series, the mesophase-isotropic transition temperatures (T-c) were successfully related to the polarizability anisotropy of bonds to the small compact substituent, X.