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The chemical oxidation of polyaniline is carried out at constant acidity, investigating six separate pH levels (pH = 1, 2, 3, 4, 5, and 6). All prior studies on polyaniline self-assembly used a falling-pH or a temporarily buffered falling-pH method, making this the first application of pH-stat techniques to the study of polymer nanostructure formation. This allows us to isolate with improved precision the various nanostructures formed at different stages of polyaniline self-assembly, which include spheres, flakes and ribbons at neutral pH, fibers and tubes at mildly acidic pH, and grains at highly acidic pH. The evolution of these structures is investigated as a function of both pH and time. This approach results in the observation of two previously unnoticed phenomena: the morphology is found to evolve as a function of time even when pH is kept constant, and polyaniline nanotubes are formed at a constant acidity. Both of these results have important implications for existing self-assembly theories. Fourier transform infrared spectroscopy is used to investigate the polyaniline compositional and structural evolution underlying the visible morphological changes and shows that as pH falls there is increased protonation, decreased ortho-coupling, lower phenazine presence, and less sulfonation. The time evolution, on the other hand, shows increased sulfonation and decreased oxidation. Ultraviolet−visible spectroscopy shows a mixture of delocalized and localized polaron behavior for the pH-1-stat to pH-3-stat products, and insulating characteristics for the higher pH structures. This is confirmed by four-point conductivity measurements. [ABSTRACT FROM AUTHOR]

Highly ordered mesoporous carbon−titania nanocomposites with nanocrystal-glass frameworks have been synthesized via the organic−inorganic−amphiphilic coassembly followed by the in situ crystallization technology. A soluble resol polymer was used as a carbon precursor, prehydrolyzed TiCl 4as an inorganic precursor, and triblock copolymer F127 as a template. The carbon−titania nanocomposites with controllable texture properties and composition can be obtained in a wide range from 20 to 80 wt% TiO 2by adjusting the initial mass ratios. The C−TiO 2nanocomposites with “bricked-mortar”frameworks exhibit highly ordered 2D hexagonal mesostructure and high thermal stability up to 700 °C. The nanocomposites have high surface area (465 m 2g −1) and large pore size (∼4.1 nm). Additionally, the nanocomposites show good performance in degradation of Rhodamine B due to the photocatalytic activity of the titania nanocrystals and the strong adsorptive capacity of the glasslike carbon. [ABSTRACT FROM AUTHOR]

A facile dual-templating approach is demonstrated to prepare hierarchically ordered macro-/mesoporous carbons. Monodispersed silica colloidal crystals are used as a hard template, amphiphilic triblock copolymer PEO−PPO−PEO as a soft template, and soluble resols as a carbon source. The procedure involves packing and aging of silica microspheres, evaporation-induced organic−organic assembly of mesostructures in the void of microspheres, thermosetting and carbonization of phenolic formaldehyde (PF), and removal of silica scaffolds by HF. The obtained porous carbons have a highly ordered face-centered cubic macrostructure with tunable pore sizes of 230−430 nm and interconnected windows with a size of 30−65 nm. The rigid silica hard templates can prevent the shrinkage of the mesostructure during the thermosetting and carbonization process, resulting in large cell parameters (∼18 nm) and pore sizes (∼11 nm). The bimodal porous carbon materials have large BET surface areas (up to 760 m2/g), large pore volumes (∼1.25 cm3/g), and partially graphitized frameworks. With the increase in the silica sphere diameter, the BET surface areas and the window sizes increase. The hierarchically ordered carbon structures show strong diffraction at wavelengths of 500−690 nm depending on the treatment used. [ABSTRACT FROM AUTHOR]