Some Effects of Small Changes in Molecular Framework on the Incidence of Smectic C and Other Smectic Liquid Crystal Phases in Esters

Abstract

The smectic properties are discussed for several series of esters which have the same “central core” molecular structure, i.e.,

The effects of just extending the carbon chain in a series of n-alkyl esters are discussed for the methyl to n-decyl esters of 4′n-decyloxybiphenyl-4-carboxylic acid. The effect on the inicidence of the smectic C Phase is quite striking. The butyl to hexyl esters inclusive exhibit this phase, while the heptyl to decyl esters show latent smectic C properties for which “virtual” transition temperatures can be obtained. The temperatures of S_A to S_c transition lie on two parabolic curves, the even members lying on the curve representing higher S_c thermal stabilities than those of the odd members. The earlier homologues of the series show S_A, S_B, or S_E or S_AB properties. The effect on the incidence of the smectic phases was also investigated for molecules containing longer carbon chains. Here the incidence of the smectic C phase is discussed for the methyl to n-nonadecyl esters of 4′-n-octyloxybiphenyl-4-carboxylic acid. This series is roughly divided into three types, with the earlier homologues (methyl to propyl) showing S_A, S_B, S_E, or S_AB phases, the middle homologues (butyl to octyl) S_A, S_c or Sc “virtual” and the later members (nonyl to nonadecyl) only S_A phases.