Control of the Homeotropic Order of Discotic Hexa-peri-hexabenzocoronenes

Abstract

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.

Organometallic Ferrocene- and Phosphorus-Containing Polymers: Synthesis and Characterization

“…The resulting compounds have considerable application in variable fields such as: organic light emitting diode [182], photovoltaic [172,[183][184][185][186] and other technologies. Moreover, compounds that have liquid crystalline behaviour were found to be a suitable medium for photovoltaic applications [187,188]. The properties of liquid crystalline dyads based on ferrocene and C 60 come from electrons flow presented a dendritic-like ferrocene architecture.…”

Unconventional nanotubes self-assembled in alumina channels: morphology and surface potential of isolated nanostructures at surfaces

“…Molecule 2 adsorbed edge-on to the alumina, yielding (after pyrolytic cross-link) tubes with the graphitic layer oriented perpendicular to tube axis (figure 1; Zhi et al 2005a,b). Molecule 3 was expected to be adsorbed face-on to the alumina (Pisula et al 2005); however, after high-temperature pyrolysis, only carbon nanotubes with different graphene layer orientations were obtained. We deposited these different nanotubes on an atomically flat substrate from solution and studied their morphology using scanning force microscopy (SFM; Samorì 2005).…”

Nanoscale assembly into extended and continuous structures and hybrid materials

“…Slow crystallization from an isotropic state gave homeotropic (face-on) arrangement of HBC columns between two polar surfaces, as characterized by 2D wide-angle X-ray scattering, though film thickness was limited owing to competing column assembly in solution. 51 This organization of HBC columns is preferred thermodynamically, and growth was likely nucleated by organized face-on monolayers. Furthermore, an ester linkage in the side chain facilitated homeotropic alignment on aluminum or glass surfaces due to affinity of the HBC face for the surface.…”