Control of the homeotropic order of discotic hexa-peri-hexabenzocoronenes

The thermal properties and self-organization of hexa-peri-hexabenzocoronene (HBC) derivatives with dove-tailed alkyl chains of various lengths have been investigated using polarized optical microscopy and wide-angle X-ray scattering. It is shown that the size-related increase of steric interactions among the peripheral side chains substituted to the aromatic core leads to a dramatically lowered isotropization temperature, allowing thermal processing at practical temperatures. Additionally, the introduction of ether linkages within the side chains enhances the affinity of the discotic molecules towards polar surfaces, resulting in homeotropic self-assembly when the compounds are processed from the isotropic state between two surfaces and, for the first time, as a thin film on a single surface. It is established that the degree of homeotropic order is influenced by the phase behavior, the supramolecular order in the bulk, and the surface affinity of the corresponding derivatives. These results are important for the design of photovoltaic cells based on HBC derivatives

Prise en charge chirurgicale des malformations artério-veineuses (12 années d'expérience dans le cadre de la consultation multidisciplinaire des angiomes du CHRU de Lille)

LILLE2-BU Santé-Recherche (593502101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Solid-state pyrolysis of polyphenylene-metal complexes: A facile approach toward carbon nanoparticles

Novel polyphenylene-metal complexes with discotic, linear, and dendritic geometries are synthesized by using a facile approach consisting of reactions between Co2(CO)8 and ethynyl functionalities in dichloromethane. Various carbon nanoparticles (CNPs), including graphitic carbon nanotubes (CNTs), graphitic carbon rods, and carbon-metal hybrid particles are obtained from the solid-state pyrolysis of these complexes. The ultimate structures of the CNPs are found to be dependant on the structure and composition of the starting compounds. Precursors containing graphenes always result in graphitic CNTs in high yield, whereas dendritic precursors give rodlike carbon materials. Alternatively, linear oligo(arylethylene) precursors afford mostly carbon-metal hybrids with large amounts of amorphous carbon. Furthermore, the CNP structures could be controlled by adjusting the carbon/metal ratio, the type and position of the metal incorporated into the precursor, and the mode of pyrolysis. These results provide further chances toward understanding the mechanism of CNP formation