Force-induced fluorescence response of functional two-photon micro-nanofabrication photosensitive materials based on dynamic C–N bonds†

Epoxy acrylate (EA) has excellent thermal performance, mechanical properties, and chemical stability, making it a typical representative of thermosetting resins. Dynamic C–N bonds were introduced through chemical click reactions between triazolinedione (TAD) and indole, resulting in EA polymers with different mass ratios. Among them, the 80 wt% EA-10 : 3 had the strongest tensile strength of 71.03 MPa with an elongation at break of 7%, while the 90 wt% EA-10 : 2.5 had a relatively excellent modulus and hardness of 5.21 GPa and 223 MPa by nanoindentation testing, respectively. In addition, the 90 wt% EA-10 : 3 polymer exhibited good two-photon polymerization printing performance with scanning speeds of 100 μm s⁻¹–100 000 μm s⁻¹ and laser powers of 5 mW–50 mW. Simultaneously, the sample block exhibited mechanical properties with a modulus and hardness of 5.12 GPa and 230 MPa under the laser power of 30 mW. In situ relaxation fluorescence spectroscopy was used to characterize the dynamic behavior of the C–N bonds in force reversible polymer networks. This work proposes a valuable strategy to enhance the functionality of EA polymers in various special performance material applications, while maintaining their strength and toughness.