Preparation and dielectric properties of polyimide/silica nanocomposite films prepared from sol-gel and blending process

Using poly(amic acid) (PAA) as a precursor followed by thermal imidization, the polyimide/silica nanocomposite films were prepared via an improved sol-gel process and a blending process, respectively. FT-IR, TEM and TGA measurements were used to characterize the structure and properties of the obtained films. The results confirmed that the introduction of silica did not yield negative effects on the conversion of the PAA precursor to the polyimide. With the increase of silica content, the aggregation of silica appeared in the polyimide matrix, and the thermal stability decreased slightly for both kinds of films. The dielectric constant (epsilon) of both films increased slowly with the increase of the silica concentration. The dielectric constant of the obtained polyimide/silica nanocomposite films displayed good stability within a wide range of temperatures or frequency. Based on modeling relation between epsilon and silica content, the difference in dielectric properties for two kinds of nanocomposites are discussed. Copyright (c) 2007 John Wiley & Sons, Ltd.