Rapid synthesis of polyimide precursors by solution polymerization using Continuous-flow microreactors

Abstract

Preparation method is of importance for development and application of polymers. Herein, we proposed a continuous-flow strategy for the preparation of polyimide precursors through solution polymerization in microreactors for the first time. The polymerization time was significantly reduced from several hours in a batch reactor to twenty minutes in a microreactor. Lower temperature, more appropriate molar ratio of monomers and longer residence time in the polymerization process resulted in poly(amic acid)s with higher molecular weights. Moreover, the relationship between the molecular weight and the residence time was used to discuss the polymerization kinetics. Meanwhile, the rapid preparation of poly(amic acid)s from pyromellitic dianhydride (PMDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), benzophenone-3,3′,4,4′- tetracarboxylic dianhydride (BTDA), 4,4′ - oxydiphthalic dianhydride (ODPA), or cyclobutane tetracarboxylic dianhydride (CBDA) was achieved in the microreactor. In particular, the number-average molecular weight of the PAA prepared by BTDA and 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl ether (6FODA) reached 36.3 kg / mol at the polymerization time of 19.6 min. This work demonstrated that microreactors would provide a promising and efficient pathway to prepare polyimide precursors with high molecular weights.