Structure formation, phase behavior, and dynamics of mono-bromo hexa-peri-hexabenzocoronene (HBC-Br) are strongly affected by the confinement of cylindrical nanopores with rigid walls. Using self-ordered nanoporous anodic aluminum oxide (AAO)-containing arrays of aligned nanopores with narrow size distribution as a confining matrix, pronounced alignment of the HBC-Br columns along the nanopore axes was found to be independent of the pore diameter. Hence, arrays of one-dimensional supramolecular HBC-Br wires with the columns uniformly oriented along the wire axes on a macroscopic scale were obtained, unlike with discotics bearing smaller cores. The formation of the crystalline herringbone structure is shifted to lower temperatures in nanopores with diameters of a few hundred nanometers, whereas the formation of this low-temperature phase is completely suppressed when the pore diameter is below 20 lattice parameters. Moreover, the cylindrical confinement affects the disk axial dynamics as well as the distribution of relaxation times.

The surface of steel S235 was oxidized by Cl2 gas and checked for its electrocatalytic efficiency regarding oxygen formation in aqueous solution. If exposed to humid Cl2 gas for 110 min, steel S235 became an electrocatalyst that exhibits an overpotential for the oxygen evolution reaction (OER) of 462 mV at 1 mA cm(-2) at pH 7. The OER activity of the same sample at pH 13 was moderate (347 mV overpotential at 2.0 mA cm(-2) current density) in comparison with OER electrocatalysts developed recently. Potential versus time plots measured at a constant current demonstrate the sufficient stability of all samples under catalysis conditions at pH 7 and 13 for tens of hours. High-resolution X-ray photoelectron spectra could be reasonably resolved with the proviso that Fe2 O3 , FeO(OH), MnO(OH), and Mn2 O3 are the predominant Fe and Mn species on the surface of the oxidized steel S235.

Changes in large-scale polymer diffusivity along interfaces, arising from transient surface contacts at the nanometer scale, are not well understood. Using proton pulsed-gradient NMR, we here study the equilibrium micrometer-scale self-diffusion of poly(butadiene) chains along ∼100 μm long, 20 and 60 nm wide channels in alumina, which is a system without confinement-related changes in segmental relaxation time. Unlike previous reports on nonequilibrium start-up diffusion normal to an interface or into particulate nanocomposites, we find a reduction of the diffusivity that appears to depend only upon the pore diameter but not on the molecular weight in a range between 2 and 24 kg/mol. We rationalize this by a simple volume-average model for the monomeric friction coefficient, which suggests a 10-fold surfaceenhanced friction on the scale of a single molecular layer. Further support is provided by applying our model to the analysis of published data on large-scale diffusion in thin films.

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Even high amounts of gold nanoparticles (AuNPs) only moderately influence crystallization of bulk polyethylene (PE). However, under the rigid two-dimensional confinement of aligned cylindrical nanopores in anodic aluminum oxide (AAO) the presence of Au turns nucleation-dominated crystallization of PE at high supercooling into growth-dominated crystallization at lower supercooling. Transmission electron microscopy investigations revealed formation of larger Au crystals from AuNPs by Ostwald ripening. These larger Au crystals apparently acted as heterogeneous nucleation sites initiating PE crystallization in AAO nanopores. Thus, PE/Au composites in AAO exhibited significantly higher crystallization and melting onset temperatures as well as significantly weaker dependence of crystallization half-times on crystallization temperatures. X-ray texture analysis revealed for pure PE in AAO the existence of two copopulations of crystals with different orientations (indicative of nucleation-dominated crystal growth); PE/Au composites showed uniform alignment of the fastest growing PE crystal direction with the AAO nanopore axes (indicative of growth-dominated crystallization). The prevailing alignment of the [020] direction of orthorhombic PE with the AAO nanopore axes suggests that properly oriented crystals may form on pre-existing crystal surfaces by secondary nucleation. These secondary crystals grow along the AAO nanopores if, under the conditions of growth-dominated crystallization, competing crystals clogging the growth path are absent while the confinement of the AAO nanopore walls stabilizes the (020) growth faces.