Molecular Order and an Odd-Even Effect in an Homologous Series of Schiff-Base Nematic Liquid Crystals

Abstract

The orientational order parameters of an homologous series Schiff-base nematic liquid crystals, p-alkoxybenzylidenebutylaniline C_n, H_2n+1OC₆H₄CH=NC₆H₄C₄H₉ (n= 1 to 6), were obtained over a wide temperature range in 50-micron thick cells by means of optical anisotropy measurements. The ordering exhibits an odd-even alternation with respect to the number of carbon atoms n in the alkoxy C_nH_2n+1O⁻ end group. These results provide the first experimental evidence of the odd-even molecular ordering effect near the transitions of an homologous series of nematic liquid crystals with non-equivalent end groups.