Imidization induced structural changes of 6FDA-ODA poly(amic acid) by two-dimensional (2D) infrared correlation spectroscopy

Two-dimensional (2D) gradient mapping method and 2D correlation analysis of in situ FTIR spectra were used to probe the thermal imidization-induced spectral changes in 6FDA-ODA poly(amic acid) (PAA) films prepared by a reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′-oxydianiline (ODA) in N,N′-dimethylacetamide. Large spectral changes in the in situ FTIR spectra of 6FDA-ODA PAA film were observed in the range, 130–230 °C. The thermal imidization of 6FDA-ODA PAA films strongly affects the spectral changes in amic acid groups in the PAA unit. The spectral change in the amic acid groups occurred before those of the imide ring. The cyclic anhydrides, isoimdes and intermolecular links are present together with the imide ring in the thermally-cured 6FDA-ODA PAA films.