Synthesis of poly[(amic acid)-co-(amic ester)] precursors and studies of their imidization using FT-IR and FT-Raman spectroscopy

A pollyimide precursor, poly[(amic acid)-co-(amic ester)] (PAAE), was prepared by partial esterification of poly(amic acid) (PAA). To investigate the thermal imidization behavior of PAAE, several different PAAEs were synthesized by varying the fraction of the amic ester moiety. They were then imidized using a stepwise heating process. The conversion of PAAE to polyimide was investigated as a function of ester fraction and temperature by monitoring the changes in the imide II (1374 cm−1) and CH stretching vibrational modes (2935 cm−1) using FT-IR and FT-Raman spectroscopy, respectively. The degree of imidization for a given temperature was compared with expected values.