RESUMEN
The size and shape of a surfactant aggregate could be altered by using supersaturation like in crystal growth, rather than applying common laws that drive surfactant aggregate formation.
Asunto(s)
Tensoactivos/química , Urea/química , Rastreo Diferencial de Calorimetría , Microscopía por Crioelectrón , Cristalización , Enlace de Hidrógeno , Cinética , Microscopía de Fuerza Atómica , Microscopía Electrónica de Transmisión , Propiedades de SuperficieRESUMEN
Three different pi-conjugated oligomers (a blue-emitting oligofluorene, a green-emitting oligo(phenylene vinylene), and a red-emitting perylene bisimide) have been functionalized with self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at both ends. The molecules self-assemble in solution and in the bulk, forming supramolecular polymers. When mixed together in solution, random noncovalent copolymers are formed that contain all three types of chromophores, resulting in energy transfer upon excitation of the oligofluorene energy donor. At a certain mixing ratio, a white emissive supramolecular polymer can be created in solution. In contrast to their unfunctionalized counterparts, bis-UPy-chromophores can easily be deposited as smooth thin films on surfaces by spin coating. No phase separation is observed in these films, and energy transfer is much more efficient than in solution, giving rise to white fluorescence at much lower ratios of energy acceptor to donor. Light emitting diodes based on these supramolecular polymers have been prepared from all three types of pure materials, yielding blue, green, and red devices, respectively. At appropriate mixing ratios of these three compounds, white electroluminescence is observed. This approach yields a toolbox of molecules that can be easily used to construct pi-conjugated supramolecular polymers with a variety of compositions, high solution viscosities, and tuneable emission colors.
RESUMEN
The layer-by-layer self-assembly of thin films consisting of alternating layers of DNA and bis-urea nanoribbons prevents diffusion of the components within the film and allows the anchoring of biotinylated molecules through molecular recognition in a predetermined layer of the film. Electron tomography demonstrates with nanometer precision the location of gold-labeled streptavidin bound to the incorporated biotinylated molecules.
