Photocurable comb polyamic acid for solvent-free direct ink writing with low dimensional shrinkage

Polyimides are high-performance organic polymers with excellent insulation, high-temperature resistance, and mechanical properties. However, their poor solubility makes it challenging to use them to prepare solvent-free high-performance photocurable polyimide inks with low dimensional shrinkage. In this study, photocurable comb polyamic acid resins were synthesized, and their solubility was examined based on density functional theory (DFT) calculations. Experiments showed that polyamic acid resins with specific topologies could be dissolved in photocurable monomers to prepare solvent-free photocured polyimide inks. A custom-made UV-assisted direct ink writing 3D printer was used to fabricate complex three-dimensional devices. Further heat treatment caused the polyamic acids to undergo dehydration and cyclization into rigid polyimide structures, and this process exhibited less than 6% dimensional shrinkage. The final material had a maximum storage modulus of 3.1 GPa (40 ℃) and a glass transition temperature of 204 ℃. The good comprehensive performance suggests great potential for aerospace applications.