Tailoring Backbone Rigidity and Cross-Linking of Photosensitive Polyimides for 3D Printing with Ultralow Dielectric Loss at High Frequencies

Abstract Additive manufacturing represents a versatile platform for the development of high-frequency communication electronics. However, existing dielectric polymer inks often fail to simultaneously meet the requirements of low dielectric loss, high thermal stability, and high mechanical robustness. In this work, a photosensitive polyimide (PSPI) was synthesized via an acrylate-grafting acyl chlorination route, incorporating trifluoromethyl, bulky fluorene, and asymmetric diphenyl ether moieties. This molecular architecture facilitates the formation of a highly cross-linked network (with a gel content of up to 94%) and enables solvent-free 3D printing while ensuring ultralow dielectric loss and high thermal stability. The cured PSPI ink exhibits a glass transition temperature of 170 °C and a tensile strength of 71.42 MPa. Benefiting from the rigid polymer backbone and optimized crosslinking network, the cured polymer ink achieves a dielectric loss as low as 0.0070 at 20 GHz, outperforming that of state-of-the-art PSPI polymer inks. Furthermore, the successful fabrication of heterogeneous circuit structures via UV-assisted direct ink writing demonstrates the reliability of this synergistic molecular and network design. Overall, this study provides a robust molecular strategy for the development of photosensitive polymer inks in 3D printing and high-frequency electronics.