PMDA was added in several times, with an interval of 20 minutes each time, and fully stirred for 2H to completely dissolve to obtain a golden yellow viscous liquid that is a polyamic acid solution.
PMDA was added in several times with an interval of 20 min. the solution was thoroughly stirred for 2 h. After the solution was completely dissolved, a golden viscous liquid, namely polyamide acid solution, was obtained.<br>