Thermal, mechanical and optical transport properties of nanocomposite materials based on triethoxysilane-terminated polyimide and TiO2 nanoparticles

Abstract

In the preparation of polymer based nanocomposites (NCs), compatibility between the organic phase and inorganic nanoparticles as the filler can be improved by a variety of methods, such as functionalizing polymer chains at their ends, adding a coupling agent to bond the polymer chains and inorganic network etc. In this study, several novel polyimide/titanium dioxide nanocomposites (PI/TiO2 NCs) were prepared by the incorporation of TiO2 nanoparticles into silane terminated PI. To this point, 3-(bis(4-aminophenyl)amino)benzonitrile as a diamine monomer was first synthesized and then it was reacted with an excess amount of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride. The triethoxysilane terminal groups were introduced by reacting the anhydride end-groups of the polymer with (3-aminopropyl)-triethoxysilane. Different hybrid materials based on the silane-terminated PI with inorganic TiO2 network were successfully fabricated by thermal imidization. The resulting materials were characterized by different techniques. According to the transmission electron microscopy images, the TiO2 nanoparticles were well dispersed into the PI matrix with a particle size around 20-40 nm. The resulting composite's mechanical, optical and thermal properties are effectively enhanced by the incorporation of 8 wt TiO2 nanoparticles. According to the thermogravimetric analysis curves, the T-5 of the NC was increased with the TiO2 loading and approximately a 63 degrees C improvement in T-5 is found. The tensile strength of the hybrid films is significantly increased compared with the pure PI.