The development of a high-efficiency TiO 2 photocatalyst is of great importance to a variety of solar light conversion and application fields; the desired high efficiency can be achieved by employing well-controlled TiO 2 nanoarchitectures. In this study, we have successfully synthesized well-ordered and aligned high surface area mesoporous TiO 2 nanofibers (TiO 2 -NF) by electrospinning of TiO 2 powder dispersed in viscous polymer solution and subsequent calcination. For comparison, TiO 2 nanoparticles (TiO 2 -NP) are also prepared from calcination of the same TiO 2 powder. The TiO 2 -NF of ca. 500 nm in diameter and a few micrometers in length consist of compactly and densely packed spherical nanoparticles of ca. 20 nm in size and have mesopores of 3-4 nm in radius. Photocatalytic comparison between TiO 2 -NF and TiO 2 -NP indicated that the former had far higher photocatalytic activities in photocurrent generation by a factor of 3 and higher hydrogen production by a factor of 7. The photocatalytic superiority of TiO 2 -NF is attributed to effects of mesoporosity and nanoparticle alignment, which could cause efficient charge separation through interparticle charge transfer along the nanofiber framework. Finally, various surface characterization experiments were conducted and included to understand the photocatalytic behaviors of TiO 2 -NF and TiO 2 -NP.

A series of poly(ethylene oxide) (PEO)/organoclay nanocomposites have been prepared via a solvent casting method. Using three different organoclays modified with the alkylammonium salts, the effect of surfactants on organoclay surfaces in polymer/organoclay nanocomposites was investigated by focusing on two major aspects:  internal structure analysis and rheological measurement of the nanocomposites. The d spacings of both the pure PEO and intercalated organoclay were examined via X-ray diffraction analysis, and the microstructure of these nanocomposites was examined by transmission electron microscopy. Rheological properties of these nanocomposites exhibited different behavior with different modifier concentrations and surfactant sizes (chain lengths). To analyze the non-Newtonian flow behavior, we fitted shear viscosity data via the Carreau model, showing that steady shear viscosity and power-law behavior increase with organoclay content. Hysteresis phenomenon was also enhanced with organoclay content, and the increase in the storage/loss moduli and interactions among organoclay platelets were observed with organoclay content. The enhanced thermal stability of the nanocomposites by organoclay was also observed.

Biodegradable aliphatic polyesters (BAPs), synthesized from diols and dicarboxylic acids, and organophilic montmorillonite (OMMT) were intercalated by a solvent-casting method using chloroform as a cosolvent to produce nanocomposite (BAP/OMMT). The d spacings of both BAP and BAP/OMMT were examined by X-ray diffraction analysis, and the microstructure of BAP/OMMT was examined by transmission electron microscopy. Melting temperature changes and residuals were measured by thermal gravimetric analysis. Tensile strength and elongation were also examined with a universal testing machine. Increases in both the thermal stability and the mechanical strength of BAP/OMMT were observed for several different OMMT loadings. The rheological properties of the BAP/OMMTs were also examined with a rotational rheometer having a parallel-plate geometry. The shear viscosity at low shear rate exhibited a Newtonian plateau even at high loading and showed a higher degree of shear thinning at higher shear rate. Both the Newtonian plateau and the enhanced power-law behavior were correlated with a scaling function.