RESUMEN
Mechanically strong supramolecular hydrogels (up to 98.9% water content) were obtained by the combination of a rigid, fully π-conjugated polymer backbone and zwitterionic side chains. The gels were characterized by SAXS, SEM and rheology measurements and are fluorescent, stimuli responsive (temperature, salts) and bind DNA.
Asunto(s)
Fluorenos/química , Hidrogeles/química , Polímeros/química , ADN/química , Fluorescencia , Microscopía Electrónica de Rastreo , Reología , Dispersión del Ángulo Pequeño , Temperatura , Difracción de Rayos XRESUMEN
We present a fast and efficient in situ synthetic approach to obtain fully π-conjugated polymers with degrees of polymerization up to 23 and near quantitative (>95%) heterobis-functionalization. The synthesis relies on the key advantages of controlled Suzuki chain-growth polymerization: control over molecular weight, narrow polydispersity, and ability to define polymer end groups. The first end group is introduced through the initiator metal complex tBu(3)PPd(X)Br, while the second end group is added by quenching of the chain-growth polymerization with the desired boronic esters. In all cases, polymers obtained at 50% conversion showed excellent end group fidelity and high purity following a simple workup procedure, as determined by MALDI-TOF, GPC, and (1)H and 2D NMR. End group functionalization altered the optoelectronic properties of the bridge polymer. Building on a common fluorene backbone, and guided by DFT calculations, we introduced donor and acceptor end groups to create polymeric molecular wires exhibiting charge transfer and energy transfer as characterized by fluorescence, absorption, and transient absorption spectroscopy as well as by fluorescence lifetime measurements.
Asunto(s)
Polímeros/síntesis química , Estructura Molecular , Peso Molecular , Procesos Fotoquímicos , Polimerizacion , Polímeros/química , Teoría CuánticaRESUMEN
Supramolecular complexation of perylene bis(diimide) (PDI) dyes with the macrocyclic host cucurbit[8]uril (CB[8]) prevents self-aggregation of the dye molecules and enables their use as highly (photo)chemically stable, strongly-emitting fluorophores in water. The complexes are stimuli-responsive to binders and can be electrochemically cycled, leading to reversible on-off fluorescence switching and access to noncovalent formation of higher-order architectures in water.
Asunto(s)
Hidrocarburos Aromáticos con Puentes/química , Fluorescencia , Colorantes Fluorescentes/química , Imidazoles/química , Imidas/química , Perileno/análogos & derivados , Agua/química , Animales , Bovinos , Colorantes Fluorescentes/síntesis química , Modelos Moleculares , Estructura Molecular , Perileno/química , Albúmina Sérica Bovina/químicaRESUMEN
Visible light photocatalysis is a promising route for harnessing of solar energy to perform useful chemical reactions and to convert light to chemical energy. Nanoscale photocatalytic systems used to date were based mostly on oxide semiconductors aided by metal deposition and were operational only under UV illumination. Additionally, the degree of control over particle size and shape was limited. We report visible light photocatalysis using highly controlled hybrid gold-tipped CdSe nanorods (nanodumbbells). Under visible light irradiation, charge separation takes place between the semiconductor and metal parts of the hybrid particles. The charge-separated state was then utilized for direct photoreduction of a model acceptor molecule, methylene blue, or alternatively, retained for later use to perform the reduction reaction in the dark.