Effects of meta and para diamines on the properties of polyetherimide nanocomposite films prepared by the sol-gel process

The effects of chemical structure of diamines on the properties of polyetherimide (PEI) nanocomposite films prepared by the sol-gel process were investigated. For meta diamine, nanocomposites with improved thermal, mechanical, and dielectric properties can be prepared by a sol-gel process from soluble PEI via chemical imiclization, with silica content up to 10%. However, for the PEI with pPDA as diamine and bisphenol A dianhydride, a two-stage sol-gel process via thermal imidization was necessary to prepare the nanocomposites. The thermal stability and mechanical properties were improved with the addition of up to 5 wt % of silica content. The variation could be attributed to the fact that differences in the compatibility between PEI and SiO2 for two kinds of PEI with the different meta and para structure of the diamine monomer. The morphology of the fracture surfaces investigated by SEM showed a finely interconnected or cocontinuous phase for PEI nanocomposites with the silica content of up to 10% and 5 wt % for mPDA and pPDA as diamine, respectively. At higher silica contents, thermal and mechanical properties were reduced due to the aggregation Of SiO2. (c) 2007 Wiley Periodicals, Inc.