Preparation and properties of new photosensitive polyimides from bis(4-aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides

New photosensitive polymides containing photosensitive disilane unit were synthesised from 1,2-bis(4-aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides by the usual two-step procedure that includes ring-opening polyaddition to yield the precursor polyamic acids, followed by cyclodehydration giving the respective polyimides. The polymaic acids had inherent viscosities between 0.63 and 0.85 dL/g depending on the tetracarboxylic dianhydride used. Excepting the polyimide obtained from pyromellitic dianhydride, all other polyimides were soluble in N-methyl-2-pyrrolidone, m-cresol, and pyridine. While the polyimide containing diphenyl sulfone unit was amorphous, the other polyimides were semi-crystalline polymers based on their x-ray diffractograms. The polyimides had glass transition temperatures between 235 and 304°C. They were thermally stable up to 380°C in both air and nitrogen atmospheres. All the polyamic acids showed a drastic decrease in the inherent viscosity upon UV light irradiation, implying the inherent photosensitivity of the polymers containing the disilane moiety.