Synthesis and characteristics of polyimide/titania nano hybrid films

Polyimide/titania (PI/TiO2) nano hybrid films are synthesized by sol–gel technology. [4,4′-(4,4′-Isopropylidenediphenoxy) bis (phthalic anhydride)] (IDPA), 4,4′-diaminodiphenyl ether (ODA) and 3-aminopropyltrimethoxysilane (APrTMOS) mixed entirely and reacted at room temperature to form the polyamic acid (PAA). Tetraethyl orthotitanate (Ti(OEt)4) and actylacetone, the latter one is used as chelating agent, are then added to the polyamic acid. After imidization at high temperature, PI/TiO2 hybrid films with different block chain length, 5000 of PAA and 15000 g mol− 1, and a cross-linked structure are formed. The resulting hybrid films, containing relatively small amounts of titania, exhibit higher transparency and flexibility. Moreover, as compared with pure PI, the hybrid film formed from APrTMOS has better ability to form a film with a higher titania content. Due to the high and low refractive index (RI) of TiO2 and APrTMOS, their introduction may lead to the change of the RI of hybrid films. From the transmission electron microscope (TEM) images; the particle size of titania decreases with increasing APrTMOS content. Thermal decomposition temperatures (Td), with a 5% weight loss, are in the range of 400–540 °C. The dynamic mechanical thermal analysis showed a systematic increase of glass transition temperature, along with a broader and weaker tan δ peak with increasing titania content.