ABSTRACT
Abstract-Poly(ester-amine salt) (PEAS) is a salt-like precursor that can be converted into a polyimide. In the imidization process, a 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA)/4,4'- oxydianiline (ODA)-based PEAS precursor was synthesized and its thermal imidization was investigated. By examining the degree of imidization and the characteristic absorption bands in the FT-IR spectra, the imidization mechanism and the effects of heating temperature and time were studied. Based on the reactions of model compounds, it was found that an imide structure could be formed from PEAS via two pathways. The first pathway proceeded via an amic acid intermediate when the imidization temperature was low. In this pathway, amic-acid structures formed through ammonolysis of ester units, and then these converted into imide units. The second pathway was an anhydride intermediate process occurring at high imidization temperature. In this pathway, the ammonium salt structure dissociated to an ester-acid and an amine unit, then the elimination of methanol from esteracid structure yielded an anhydride unit, and lastly the condensation between an anhydride and an amine unit resulted in an imide unit.
