Abstract. Homologous series (R = n-hexyl to n-tetradecyl) of 3-(alky1amino)-, 3-(a1kylthio)-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-(hepty1amino)-through 3-(nonylamino)-l,2-propanediol exhibit a transient smectic A phase on supercooling of the isotropic liquid, whereas 3-(hexy1thio)-1,2-propanediol through 3-( nonylthi0)--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.
1989) Synthesis and mesogenic properties of several homologous series of aldose dialkyl dithioacetals. A model for their behaviour, Liquid Crystals, 5:1, 265-283, Ten homologous series (n-butyl through n-decyl) of aldose S,S-acetals (D-glucose, D-galactose, D-mannose, L-rhamnose, 2-deoxy-~-glucose, D-XylOSe, D-lyxose, D-or L-arabinose, D-ribose and 2-deoxy-~-ribose) have been prepared. Most of these compounds form thermotropic liquid crystals, the exceptions being the entire L-rhamnose series and some of the derivatives with the shortest alkyl chains. All of the compounds have been investigated with differential scanning calorimetry and polarization microscopy. Some temperature dependent powder X-ray data are also presented. A model is proposed which correlates the carbohydrate configuration with the melting behaviour. On the basis of now available behaviourial characteristics, visual inspection, mixing experiments and precedent, the mesophase is identified as smectic Ad, the partially overlapping carbohydrate moieties being in the centre and the aliphatic chains pointing outward at an angle of about 62". Despite the intrinsic chirality of all the carbohydrate mesogens, no evidence for chiral mesophases was found, not even after introduction of a homochiral branched alkyl chain.
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