No abstract

In this study, a commercially available nano-sized silica (SiO 2 ) was surface-modified via esterification with oleic acid (OA), a relatively inexpensive and hydrophobic modifier. The surface-modified silica (SiO 2 -OA) nanoparticles were used to disperse in the poly(amic acid) solutions of a commercial polyimide (PI), used for two-layer film, and thermally imidized to form a series of PI/silica nanocomposites. The effects of the addition of SiO 2 -OA nanoparticles on the properties of the as-prepared PI/ silica nanocomposites were studied. The results indicated that the as-prepared PI/silica nanocomposites exhibited improvements in the dynamic mechanical property, thermal stability, water resistance, and thermal expansion. POLYM. COMPOS., 28:575-581, 2007. © 2007 Society of Plastics Engineers pure SiO 2 has a higher dielectric constant (Ј ϭ 3.9) than the pristine PI (Ј ϭ 3.8), the dielectric constants are slightly decreased for the as-prepared PI nanocomposites. This is ascribed to the low moisture-uptake of the nanocomposites caused by hydrophobicity of the SiO 2 -OA as discussed earlier.

In this study, a commercially available nano-sized silica (SiO 2 ) was surface-modified via esterification with oleic acid (OA), a relatively inexpensive and hydrophobic modifier, and characterized by FTIR, NMR, SEM, EDS, and TGA measurements. Various amounts of the surface-modified silica nanoparticles (SiO 2 -OA) were dispersed in a poly(amic acid), which were then cyclized at high temperatures to form a series of PI/SiO 2 -OA nanocomposite films (PISA). The effect of the addition of the SiO 2 -OA nanoparticles on the properties of the as-prepared polyimide nanocomposite was studied. The results indicated that, comparing with pure PI and PI/pristineSiO 2 composite film (PISI), the as-prepared PISA films had enhanced dynamic mechanical properties and thermal stability, as well as reduced water absorption and thermal expansion. The as-prepared PI/SiO 2 -OA nanocomposites have potential for applications in high performance microelectronic devices.

Hierarchical nanosheet-based Bi2MoO6 microboxes are synthesized by a facile template-assisted strategy. MnCO3 microcubes are prepared as templates for the growth of Bi2MoO6 nanosheets and then etched by using HCl aqueous solution. In particular, the hierarchical Bi2MoO6 microboxes provide a large surface area, and facilitate visible-light absorption and charge separation, demonstrating efficient photocatalytic performance. This work highlights a new method to prepare hollow nanosheet-built Bi2MoO6 structures with high photocatalytic properties.