Structure-property relationships in D-glucitol derivatives with two geminal hydrocarbon chains. Part 1.—Thermotropic and lyotropic liquid-crystalline behaviour
Abstract
Two homologous series of N-acyl N-alkyl 1-amino-l-deoxy-D-glucitol derivatives were prepared. In the first series (2), the alkyl chain length was kept constant (n-dodecyl) and in the second series (3) the acyl chain length was kept constant (n-tetradecanoyl). A number of acid addition salts, 4 and 5, were also prepared. The thermotropic properties of the compounds in series 2 and 3 changed from enantiotropic smectic Ad(SAd)via monotropic SAd and non-mesogenic to monotropic disordered hexagonal columnar (Dhd) and finally enantiotropic Dhd. Clearly, this change in thermotropic behaviour corresponds to a change in molecular shape from rod-like to (inverted) wedge-like. The acid addition salt 4 was found to form a Dhd phase which is similar to a normal hexagonal (HI) phase. Several of the acid addition salts 5 showed an interesting polymorphism on heating. Initially, an SAd phase was formed which transformed to a Dhd phase before reaching the clearing point. The formation of lyotropic mesophases was studied qualitatively (contact preparation method) for all the compounds. The expected range of lyotropic phases in compounds 2 and 3, from normal hexagonal (HI) in the molecules with one long and one short apolar chain to inverted hexagonal (HII) for molecules with two long apolar chains, was indeed observed. Compounds 5 formed the so-called ‘myelin figures’ when heated in the presence of water.
- This article is part of the themed collection: Liquid Crystals