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Keywords:

  • liquid crystals;
  • organogels;
  • self-assembly;
  • supramolecular polymers;
  • ureas

Abstract

Bis- and monoureas hybridized with the oligo(p-phenylene vinylene) (OPV) π-electronic segment and 3,4,5-tridodecyloxyphenyl wedge were synthesized and their supramolecular polymerization in diluted solution, gel formation in concentrated solution, and liquid crystallinity in bulk state were investigated. Bisurea 1 a featuring a hexamethylene linker showed the highest supramolecular polymerization ability and formed tapelike nanofibers that can gelate various organic solvents. On the other hand, bisurea 1 b featuring a dodecamethylene linker and monourea 2 showed a lower degree of supramolecular polymerization, resulting in gel formations in a smaller variety of solvents. These results clearly reflect a high level of cooperativity between the two urea sites and the two OPV segments of 1 a upon hydrogen-bonding and π–π stacking interactions, respectively. When the gels of 1 a, 1 b, and 2 were dried, all the compounds self-organized into multilamellar superstructures. Thermal treatment of these lamellae at high temperatures induces columnar liquid-crystalline mesophases as a result of microsegregation between the rigid OPV parts and the molten aliphatic wedges. These results demonstrate that the present molecular constituent is very useful for fabricating dye-based functional assemblies providing nanoscale π-electronic fibers, and solvent-incorporated and bulk soft materials.