Main-chain liquid-crystalline dendrimers based on amido-core moieties – effect of the core structure

Abstract

New main-chain liquid-crystalline dendrimers based on the same heterolithic dendritic branch but attached to various multivalent amido-cores have been synthesized in order to investigate the evolution of the mesomorphic properties with the variation of the chemical nature and structure of the core. The connectivity of the core has been varied from 2 to 4, and in one case its chemical nature changed in order to increase the number of hydrogen bonds for studying their influence on the mesomorphism. All these supermolecules possess mesomorphism, which was characterized by polarized-light optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray diffraction (XRD). They exhibit solely a hexagonal columnar mesophase, whatever the core nature. These measurements show that decreasing the core connectivity or increasing the amount of intra- and inter-molecular hydrogen-bonding slightly affects the thermal stability of the mesophase. The supramolecular organization within the Col_h phase is described.