Synthesis and Dielectric Properties of Polyimide-Titania Hybrid Composites

A new class of polyimide-titania (TiO2) composites with chemical bonds between the polyimide and titania system has been synthesized by the sol–gel reaction and characterized. The hybrid composite films were obtained by the reaction of lysine-organotitane monomer, which is formulated as [(EtO)3Ti (lysinate)]2, followed by polycondensation with dianhyride in N-methyl-2-pyrrolidone (NMP) solution, followed by heating at 100, 200, and 300 °C. The presence of chemical bonds between polyimide (PI) and titania has great effect on the properties of polyimide films, especially on their thermal and dielectric properties. The dielectric constants of the resultant nanocomposites are lower than the usual polyimide films due to the increased free volume and less polar Ti–O–Ti groups, and can be tuned by varying the molar ratio of tetraethoxysilane (TEOT) in the feed. The polyimide units offer additional advantages of imparting thermal and mechanical strength.