Synthesis and mechanical properties of advanced polyimide/silicon dioxide nanocomposites

Hybrid inorganic-organic materials based on a polyimide (PI) and silicon dioxide (SiO2) were prepared previously only via sol-gel approach. However, sol-gel processes have some critical limitations. The primary drawback is that the resultant gel is extremely fragile and sol-get process is complicated and costly. In this study, using SiO2 nanoparticles polyimide/SiO2 nanocomposites were synthesized from 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-benzophenone-tetracarboxylic dianhydride (BTDA). A coupling agent, 3-glycidyloxyporpl trimethoxysilane (GTMOS), was used to functionalize the SiO2 nanoparticles which enhanced the compatibility between polyimide and SiO2 nanoparticles. The microstructures of polyimide/SiO2 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray diffraction (WAXD). All the polyimides show typical noncrystalline X-ray diffraction. The frequent occurrence of particular interatomic distances (R) denoted by the noncrystalline WAXD maxima were determined. All the modulus, strength and fracture strain of polyimide were improved with 5 wt% SiO2 modified with the coupling agent.