Synthesis of aromatic polyimide film by vacuum deposition polymerization

A new method for preparing the polymer films directly in the reduced atmosphere has been developed. In this process the polymerization can be carried out through depositing the component monomer vapors. Both pyromellitic dianhydride and 4,4’‐diaminodiphenyl ether (oxydianiline) were evaporated at a molar ratio in terms of stoichiometry by controlling the heating power for each evaporation source. From the infrared absorption spectrum observation, it was found that the as‐deposited film was the mixture of the polyamic acid and both nonreacted monomers. After having been heated to 200 °C for 60 min, the deposited film was finally transformed into the polyimide film through the condensation reaction. The obtained polyimide film had good adhesion to the glass and metal substrate and showed excellent chemical resistance, heat resistance, and electrical insulation characteristics. By selecting the appropriate combination of monomers, other polymer films could be obtained through the vacuum deposition polymeriza...