This research describes liquid-crystalline polymorphism of two series of Schiff bases differ in the type of terminal group, where one of them has a carboxyl us terminal group while the other contains methoxy as a terminal group 4-(-alkoxybenzylideneamino) benzoic acid and 4-methoxy-N-(4-alkoxybenzylidene) aniline. Based on the polarized optical microscopy (POM) and the differential scanning calorimetry (DSC); Influence of the alkyl chain length (and the type of terminal group) on the type of mesophases and entropic effects of phase transition are discussed. Extraordinary results have been found and not expected, where five of the ten synthesis compound has a liquid-crystalline properties and the other not.