Oxygen exchange at a highly oriented La0.5Sr0.5CoO3−δ thin film prepared on (100) surfaces of an yttria-stabilized zirconia single crystal by pulsed-laser deposition was studied with ac impedance spectroscopy under various temperatures and oxygen partial pressures. Three distinctive features observed in the impedance spectra were assigned to contributions from the ionic conduction of the electrolyte, oxide ion transfer across the electrode/electrolyte interface, and the oxygen exchange on the film surface. An equivalent circuit model was proposed to analyze the impedance results, from which the surface chemical exchange coefficients, kchem, were derived as a function of temperature and oxygen partial pressure.
A feasible processing of zwitterionic polymer-grafted anodic aluminum oxide (AAO) membranes by surface-initiated atom transfer radical polymerization (SI-ATRP) and the geometric effect were investigated.
Although one-dimensional polymer nanomaterials can be prepared by approaches such as the template method, the control over the morphologies of one-dimensional polymer nanomaterials containing multiple components is still a great challenge. In this work, we investigate the formation of polymer nanopeapods using a novel double-solution wetting method in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene (PS) solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then a second polymer solution of poly(methyl methacrylate) (PMMA) in acetic acid is infiltrated into the nanopores. Because of the stronger interaction between acetic acid and aluminum oxide than that between DMF and aluminum oxide, the PMMA solution preferentially wets the pore walls of the templates and the PS solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA nanostructures are obtained, where the shell and the core are composed of PMMA and PS, respectively. The compositions of the polymer nanopeapods are confirmed by removing PS or PMMA selectively. The formation mechanism of the nanostructures is related to the Rayleigh-instability-type transformation and further studied by changing experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only provides a simple approach to prepare multicomponent polymer nanomaterials with controlled morphologies and sizes, but also contributes to a deeper understanding of polymer−solvent interactions in confined geometries.
Capturing osmotic energy from a salinity gradient through an ion-selective membrane is regarded as one of the renewable clean energy resources to solve the increasing global energy demands. However, suffering...
We study the thermal annealing effect of poly(methyl methacrylate) (PMMA) nanofibers made from anodic aluminum oxide (AAO) templates and their transformation to PMMA nanospheres. The PMMA nanofibers are prepared by wetting an AAO template with a 30 wt % PMMA solution, followed by the evaporation of the solvent. After the AAO template is removed by a weak base, the PMMA nanofibers are thermally annealed in ethylene glycol, a nonsolvent for PMMA. The surfaces of the nanofibers undulate and transform into nanospheres, driven by the Rayleigh instability. The driving force for the transformation process is the minimization of the interfacial energy between PMMA nanofibers and ethylene glycol. The transformation times at higher annealing temperatures are shorter than those at lower annealing temperatures. This study provides a facile route to prepare polymer nanospheres which are not accessible by other traditional methods.
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