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Designing and self-assembly of unconventional star-shaped mesogens or 'hekates' are of interest to materials science and molecular electronics. This work presents the synthesis of several symmetric trimeric liquid crystalline compounds comprising 1,3,5-trihydroxybenzene (phloroglucinol) as central core. The liquid crystalline behaviour was induced by attaching three rod-like azo-aromatic semi-flexible units to the central core via esteric linkages. Based on differential scanning calorimetry and polarising optical microscopy, the mesophase stability mainly depends on the alkyl chain length. The compounds showed monotropic or enantiotropic behaviour, except the compound with nine atoms on the chain end which is non-mesomorphic. In addition to the synthesis and mesophase characterisation, the self-assembled structures and individual properties have been characterised by molecular simulations. [ABSTRACT FROM AUTHOR]

The article describes the liquid-crystalline properties of some 2,5-asymmetric disubstituted [1,3,4]oxadiazole derivatives containing an azo and an ester linkage obtained through esterification of 2-(4-methoxyphenyl)-5-(4-hydroxyphenyl)-[1,3,4]oxadiazole with a series of 4-(4-alkoxyphenyl)-benzoic acids containing 6-10 and 18 aliphatic carbon atoms. All reported compounds present liquid-crystalline properties, evidenced by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), with nematic and smectic C type structures, with very large range of stability of mesophases (between 130°C and 198°C on heating and 134°C and 214°C on cooling). [ABSTRACT FROM AUTHOR]