An ellipsometric study of polymer film curing: 2,6-Bis(3-aminophenoxy) benzonitrile/4,4′oxidiphthalic anhydride poly(amic acid)

The curing of 2,6-bis(3-aminophenoxy)benzonitrile/4,4′oxidiphthalic anhydride ((β-CN) APB/ODPA) has been investigated using spectroscopic ellipsometry on films with various degrees of imidization. Results indicate that much of the film imidization is accomplished at 200 °C and above. Three absorption peaks have been observed (4.1, 5, and 6 eV) which correspond to intra- and inter-molecular optical transitions. A comparison of the film optical constants for the pristine poly(amic acid) and the fully cured polyimide shows film densification upon imidization. A curing timeline has been obtained using in situ real-time spectroscopic ellipsometry, and ellipsometry is shown to serve as a general technique for studying organic film curing.