Abstract
Thirteen p-n-alkoxybenzylidene-p-aminobenzoic acids were prepared and their mesomorphic transition temperatures were determined. They exhibit mesophases of greater relative thermal stability than the p-n-alkoxybenzoic and p-n-alkoxycinnamic acids but 4′-n-alkoxydiphenyl-4-carboxylic acids exhibit greater thermal stability than the acids studied here though p-n-alkoxybenzylidene-p-aminobenzoic acids are longer by -CH+N- group in the monomer; this may be attributed to the stereochemistry of -CH+N- link causing the molecule to be broader than the 4′-n-alkoxydiphenyl-4-carboxylic acids. Comparatively higher thermal stability of mesophases of these acids is emphasized by the mesomorphic behaviour of methyl p-n-alkoxybenzylidene-p-aminobenzoates which are purely smectic and the absence of anisotropic melt in the analogous p-n-alkoxybenzoates.

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