Thermal Conversion of Polyamic Acid Gel to Polyimide Solution Having Amino Group Side chains

Shiina Y , Ohnuki S and Morikawa A

Published on: 2022-03-23


Deformation of a polyamic acid gel was observed upon heating. The gel prepared from 1,1-bis[4-(aminophenoxy) phenyl]-1-[4-(4-amino-2-trifluoromethylphenoxy) phenyl] ethane (triamine-CF3), 4,4’-oxydianiline (ODA) and benzohenonetetracarboxylic dianhydride (BTDA) in N-methyl-2-pyrrolidone (NMP) at 20 o C was heated to 180 o C. The swelling became weak upon increasing the temperature, and the gel turned into a solution that could be stirred easily above 80 o C. The solution heated to 180 o C did not returned to the gel state even upon cooling to 20 o C. IR measurements of the heated gel showed that the deformation was due to an amide exchange reaction, which proceeded through scission of the amide linkage into anhydride and amine end groups. The viscosity barely changed upon heating. The amide exchange and imidation reactions proceeded simultaneously upon heating the polyamic acid gel, and formed a soluble polyimide containing amino side chains.