title: Supramolecular polymerization and polymorphs of oligo(p-phenylene vinylene)-functionalized bis- and monoureas.
abstract: Bis- and monoureas hybridized with the oligo(p-phenylene vinylene) (OPV) pi-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 1a 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 1b 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 1a upon hydrogen-bonding and pi-pi stacking interactions, respectively. When the gels of 1a, 1b, 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 pi-electronic fibers, and solvent-incorporated and bulk soft materials.
authors.affiliation: Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Chiba, Japan. yagai@faculty.chiba-u.jp
authors.forename: Shiki
authors.initials: S
authors.lastname: Yagai
authors.forename: Shun
authors.initials: S
authors.lastname: Kubota
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Iwashima
authors.forename: Keiki
authors.initials: K
authors.lastname: Kishikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Karatsu
authors.forename: Akihide
authors.initials: A
authors.lastname: Kitamura