A series of polyimide／titania(PI／TiO2) nanocomposite membranes with different contents of TiO2 were fabricated by sol-gel process based on an organic soluble PI and the tetrabutyl titanate in the common solvent NMP．TEM was employed to observe the microstructure of the composite membrane．The solvent resistance was measured through extraction experiment in polar solvents such as NMP

DMF and THF et al

at 25℃ for 72 h．The thermal properties were investigated by DT-DTG and DSC．The result showed that the average size of TiO2 particles was about 10 nm in the composite membrane

which contained TiO2 22.3％ by weight．The solvent resistance and the thermal properties of the composites were greatly enhanced as compared with the pure PI．The residues of the extraction of the composites in NMP increased with the contents of TiO2

and so did the thermal decomposition temperatures and the glass transition temperatures．All of these changes showed that the molecular chains of PI were chemically attached to the three-dimension framework of TiO2 nano-particles in the composites．An assumption was promoted to explain the relationship between the properties and the structures of PI／TiO2 nano—composites．