two series of mesogenic dicarboxylic esters have been prepared and studied, one having an olefinic and the other a trans-l, 4-cyclohexane central group. The compounds are mainly nematic; however a few also exhibit smectic phases. Twisted-nematic mesophases are observed for for the esters having chiral alcohol groups. Comparisons of nematic behavior for compounds with trans-, cis-, and α-methyl-substituted double bonds indicate the mesophase-destabilizing effects of increases in intermolecular separation and the lesser importance of molecular symmetry. Dicholesteryl trans-1, 4-cyclohexanedicarboxylate, which contains no aromatic groups, was found to possess the second highest mesophase-isotropic point in either series, surpassed only by the corresponding p-methoxyphenyl ester. Several of the nematogenic fumaric acid derivatives exhibited dynamic scattering, indicating that these materials possess a negative dielectric anisotropy. The trans-1, 4-cyclohexane diesters did not show the dynamic scattering effect.
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Verbit et al. (1975) studied this question.
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