Influence of Molecular Structural Changes on the Mesomorphic Behavior of Benzylideneanilines

Abstract

Since the discovery by Heilmeier, Zanoni and Barton¹ that liquid crystals with negative dielectric anisotropy exhibit dynamic scattering, there has been considerable interest in this class of materials. The Schiff Bases resulting from the reaction between para-substituted anilines and para-substituted benzaldehydes have been of particular interest, especially since the report² that N-(4-methoxybenzylidene)-4′-n-butylaniline is nematogenic at room temperature. The research reported here is the result of a detailed study of the effects of small changes in structure on the transition temperatures of benzylideneanilines. Specifically, two series of compounds (I) and (II) are described. In both series the alkoxy group is systematically varied from methoxy to heptyloxy. In series I, the alkyl groups used were n-C₄H₉, n-C₅H₁₁, n-C₆H₁₃, n-C₇H₁₅ and n-C₈H₁₇ while in series II, the alkyl groups were C₂H₅, n-C₄H₉, n-C₆H₁₃ and n-C₈H₁₇.