Precise Tailoring 3D Printed In Situ Toughening Low-k Microwave Transparent Structure via Thiol-acrylate Chain Transfer Behavior.

The unique electromagnetic properties of triazine resins have enabled their growing use in advanced low-dielectric (low-k) materials. However, their low printability and high brittleness severely restrict engineering applications. Conventional plasticization strategies that enhance printability often compromise dielectric and mechanical properties. Herein, an in situ thiol-acrylate chain transfer-mediated toughening strategy is introduced for Digital Light Processing (DLP) printing. A triazine-based resin system comprising THEICTA, isobornyl acrylate (IBOA), and polysulfide rubber (PSR) is formulated into a low-viscosity (η < 150 cP), highly photosensitive ink, enabling 50 µm resolution printing while preserving a low dielectric constant. Compared with the homopolymer of triazine resin, the topology-optimized molecular network simultaneously delivers a 462.4% increase in elongation at break, a 640.5% improvement in toughness, a high tensile strength (45.7 MPa), and a low dielectric constant (ε' = 2.66). Benefiting from its excellent printability, a printed gyroid lattice-filled plate (100 µm wall thickness) achieves 92% transmittance at 10 GHz under a 50° incidence angle following structural optimization.