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 °C improvement in T_5% is found. The tensile strength of the hybrid films is significantly increased compared with the pure PI.