Self-assembly of columnar mesophases from diaminotriazines

Abstract

Diaminotriazines are known to self-associate in solution, in the solid state, and on surfaces via characteristic hydrogen bonding motifs. Although complementary hydrogen bonding between diaminotriazine derivatives and carboxylic acids has been shown to induce mesomorphic properties, the hydrogen-bonded self-association of diaminotriazines to form liquid crystalline phases has not been reported. Here, we describe the synthesis and mesophase characterization of biphenyldiaminotriazines bearing one alkoxy side-chain (compound 3) or two alkoxy side-chains (compound 2). Although compound 3 does not show any mesomorphism, derivatives of compound 2 exhibit thermotropic columnar mesophases as shown by polarized optical microscopy, differential scanning calorimetry, and variable-temperature X-ray powder diffraction. The results are consistent with self-assembly of a hexameric hydrogen-bonded rosette that can stack to form columnar mesophases, suggesting that the association of diaminotriazines by hydrogen bonding can play an important role in directing molecular organization in liquid crystalline phases.