Hydrogen-bonding stabilized columnar mesophases in hexasubstituted triphenylene 2,3-Dicarboxamides

Abstract

A series of new mixed tail triphenylene derivatives having four β-alkoxy and two adjacent β-carboxamide side chains have been prepared and characterized. The synthesis was carried out by amidation of the triphenylene 2,3-dicarboxylic methyl ester with various primary amine. All the dicarboxamides exhibit an enantiotropic Colh phase, except compound TPC6-(CONHC6H13)2 bearing the shortest hexyloxy chains. Effects of variation in lengths of alkoxy and N-alkyl chains on mesogens were also studied and the pronounced influence of lengths of alkoxy chains turned out to be more important than that of N-alkyl chains. Furthermore, the intermolecular hydrogen bonding induced by amide functions in TPC8-(CONHC4H9)2 does indeed enhance the mesophase stability in comparison to the non-hydrogen bonding ester TPC8-(COOC4H9)2, as reflected by higher clearing temperatures and evidenced by temperature-dependent FT-IR studies. Although the compound TPC6-(CONHC6H13)2 was found to decompose to imide compound on the hot stage before clearing in the course of the POM experiment, only it shows good gelation property in single toluene, indicating that the intermolecular hydrogen bonding is not the only factor responsible for the formation of gel in these molecules.