Analysis of Structure and Imidization of Poly(amic acid) Using FTIR Spectroscopy

We monitored the imidization process of poly(amic acid) synthesized from pyromellitic dianhidride and 4,4′-oxydianiline,and analyzed the IR bands of the poly(amic acid) and the polyimide after thermal imidization using variable temperature FTIR spectroscopy in transmission mode.We investigated peak assignments of the poly(amic acid) and the polyimide and found —COO-and —NH+2 in the system.The CO symmetrical and asymmetrical stretching vibrations in —COO-locate at 1607 and 1406 cm-1 respectively,NH+2 stretching vibration locate at 3200,3133,2938,2880,2820,2610 cm-1.According to the identified IR absorption peaks of —COO-and —NH+2,we proposed the mechanism of the imidization process of poly(amic acid) that during the imidization H+ from COOH of the poly(amic acid) can move to NH of the poly(amic acid) and form —COO-and NH+2,then the intermediate cyclodehydrates to polyimide at last.