The size of the silica particles and morphology of hybrids were controlled in copolyimide based hybrids through amino-silane functionalization of silica particles prepared in situ through a self-catalyzed sol-gel process using atmospheric moisture. The particles were generated using tetraethoxysilane in the uncompatiblized (UPISH) system whereas a mixture of 3-aminopropyltrietoxysilane and tetraethoxysilane was used in the compatiblized Co-PI/silica hybrid (CPISH) system. The properties of resulting hybrid films were measured by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Thermogravimetirc Analysis, Dynamic Mechanical Analysis and Universal Testing Machine. FTIR results confirmed the formation of silica particles and Co-PI matrix. FE-SEM images revealed spherical silica particles with sharp boundaries in UPISH; whereas nano-sized coupled silica network structures with totally different morphologies were observed in CPISH system. The CPISH system exhibited better thermal stability, higher modulus and Tg values than UPISH system. The improvement in thermal and mechanical properties has been discussed with reference to morphological changes due to incorporation of 3-aminopropyltrietoxysilane in aerobic condition and in a self-catalyzed sol-gel process.

Farman Ali, Shaukat Saeed, Khaled M. Saoud and Syed Sakhawat Shah