The purpose of the present investigation is to understand the relationship between smectic polymorphism and molecular structure. Reversal of the imine linkages (—CH = N—) between central and terminal benzene rings not only changes the mesophases thermal stabilities, but also their texture and/or number. Presence of a nitrogen in the ring decreases the stability and also changes the nature of the mesophases in many cases in contrast to the homocyclics. Carboxyl linkages instead of imines in comparable molecules changes both the number and stabilities of the smectic phases. These differences in the smectic phases due to structural changes are discussed in terms of molecular geometry and polarizability.