聚酰胺酸结构及其亚胺化的红外光谱分析

利用变温透射红外光谱方法，通过跟踪聚酰胺酸（PAA）的亚胺化过程，对由均苯四酸二酐和4,4′-二氨基二苯醚合成的聚酰胺酸及经过加热亚胺化后生成的聚酰亚胺(PI)的红外吸收光谱进行分析，对聚酰胺酸和聚酰亚胺的红外谱峰进行合理的归属，发现聚酰胺酸在亚胺化过程中有-COO-和-NH+2存在，-COO-中羰基的对称与反对称伸缩振动分别位于1607和1406 cm-1，NH+2的伸缩振动则有3200、3133、2938、2880、2820和2610 cm-1等多个精细谱带。 并根据对-COO-和-NH+2谱峰的归属，提出聚酰胺酸生成聚酰亚胺的机理为聚酰胺酸中COOH的H+转移到聚酰胺酸中的NH上，形成NH+2，然后脱水环化生成聚酰亚胺。

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 C=O 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.