A comparative study of the liquid‐crystalline behavior of three homologous series of 1,2‐propanediol derivatives

Abstract

Abstract Homologous series (R = n ‐hexyl to n ‐tetradecyl) of 3‐(alkylamino)‐, 3‐(alkylthio)‐ and 3‐alkoxy‐1,2‐propanediols have been synthesized and their thermal behavior studied by thermomicroscopy and differential‐scanning calorimetry. The occurrence of liquid‐crystalline behavior was found to be strongly dependent on both the alkyl‐chain length and the hetero‐atom that links the alkyl chain to the 1,2‐propanediol moiety. No thermotropic liquid‐crystalline behavior could be observed for 3‐alkoxy‐1,2‐propanediols; 3‐(heptylamino)‐ through 3‐(nonylamino)‐1,2‐propanediol exhibit a transient smectic A phase on supercooling of the isotropic liquid, whereas 3‐(hexylthio)‐1,2‐propanediol through 3‐(nonylthio)‐1,2‐propanediol form smectic phases that are quite stable. Although the thermal behavior in the pure form differs considerably, all three classes of compounds are capable of lyotropic mesophase formation in the presence of water.