Supermolecular self organization via molecular aggregation II. Electro-optical studies on structure formation processes in associated liquid-crystalline diols

Abstract

Abstract Orientational correlations are investigated in the isotropic phase for mesogens formed by diols which exhibit a columnar discotic or smectic phase at lower temperatures. These compounds consist of a central part to which either three or only one aliphatic chains of various length (n = 4–14) are attached at one end and two hydroxy groups at the other. The electro-optical studies reveal that associations are formed in the isotropic phase due to hydrogen bonding and that the stability is controlled by the collective association of a number of molecules giving rise to disclike or layer-like aggregates. It seems that these aggregates are responsible for the formation of the columnar phase which is stable at a lower temperature as far as the three chain diols with long aliphatic chains are concerned. The same situation holds for the formation of a smectic phase for the single chain diols. Structure formation in this new class of compounds is thus a function of the shape of the aggregates rather than of the shapes of the individual molecules.