Preparation and properties of polyimide-polysiloxane hybrid materials by the sol-gel process

Abstract

Polyimide-poly(methylsiloxane) hybrid films were successfully prepared by the sol-gel process with methyltriethoxysilane (MTES) and/or dimethyldiethoxysilane (DMDES) in the polymer solution. Two methods were used for making hybrid films. First, MTES and/or DMDES were dissolved in the N,N-dimethylacetamide (DMAc) solution of the polyamic acid (polyimide precursor) prepared from 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300°C the polyamic acid was converted to polyimide and the sol-gel reaction, which consists of hydrolysis and condensation of MTES and/or DMDES, proceeded simultaneously. Second, methanol was used as the solvent to make the hybrid films by using the triethylamine salt of polyamic acid. The IR spectra proved that the sol-gel reactions started from MTES and DMDES readily proceeded in the polymer matrix. The hybrid films prepared in methanol were more transparent than those prepared in DMAc. Measurement by dynamic mechanical analysis indicated that the polystloxane was dispersed homogeneously in the polyimide matrix even after the heat treatment at 300°C, in the case of both DMAc and methanol solution methods. With respect to the tensile properties, the tensile strength and the elongation at break of the hybrid films prepared by the methanol solution method were higher than those by the DMAc solution method. The modulus of the obtained hybrid films decreasing with increasing DMDES ratio in the silicone unit in both cases.