Synthesis of Polyimides With Acetic Acid and Quaternary Ammonium Salt‐Based Deep Eutectic Solvents

Traditional polyimide (PI) synthesis relies extensively on hazardous dipolar aprotic solvents, posing significant health and environmental risks. To address this challenge and expand the green solvent library for PI synthesis, this study investigates a series of deep eutectic solvents (DESs) comprising acetic acid and tetraalkylammonium chloride as sustainable reaction solvents. Using a fluorinated poly(amic acid) (PAA) model system as an example, the optimized DES formulation demonstrated excellent chemoselectivity and solubility which yield PAA precursors with inherent viscosities and molecular weights comparable to those of the control samples synthesized in the common polar aprotic solvent dimethylacetamide (DMAc). The PAA precursors were subsequently thermally imidized to form PI films with thermomechanical and dielectric properties comparable to those from DMAc, confirming the substitutability of the DES solvent. To further demonstrate the universality of the proposed platform, the investigation is extended to synthesize a series of fluorinated PIs with distinct structural features to reduce water and solvent residues in the PAA precursors. This improvement results in more transparent PI films after thermal imidization. These findings demonstrate that the proposed DES platform serves as both a viable green alternative and a multifunctional processing tool for high‐performance polymers.