Thirteen 4'-n-alkoxydiphenyl-4-carboxylic acids have been prepared and their mesomorphic behaviour is compared with that of the 4-n-alkoxybenzoic acids. They exhibit mesophases of much greater relative thermal stability than the simpler benzoic acids; this is attributed to the enhanced intermolecular cohesion arising from the second aromatic ring and to the greater molecular length of the diphenyl compounds. The high relative thermal stability of the mesophases is emphasised by the mesomorphic behaviour of the methyl, ethyl, and n-propyl alkoxydiphenylcarboxylates, and the absence of anisotropic melts in the analogous alkoxybenzoates.

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