Schiff-based polymer covalent adaptable networks with excellent tunable mechanical properties

In dynamic covalent networks, the activation energy increases with the crosslink density of the network when the dynamic bond content is constant. In this study, only a small amount of N-[3-(trimethoxysilyl)propyl]ethylenediamine (ANN) was added to regulate the crosslink density of the dynamic crosslinked network without changing its activation energy. Biobased Schiff-based polymer networks, EAPA-X, were prepared using biodialdehyde (EAAP), Priamine 1071, and N-[3-(trimethoxysilyl)propyl]ethylenediamine (ANN). Comprehensive characterization, including nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), dynamic thermomechanical analysis (DMA), mechanical testing, and reprocessing measurements, was conducted on the prepared films. The results indicate that by varying the ANN content from 0 % to 10 %, EAPA-X films achieved tunable Young's modulus values ranging from 4 to 1034 MPa. This improvement can be attributed to the condensation behavior of methoxysilane groups in ANN, which enhances the crosslinking density of the polymer system due to its role as a hard chain segment. Interestingly, despite the significant difference in crosslinking density (340-1994 mol/m3) between EAPA-X films, the activation energies remained similar, showing low values around 50 kJ/mol. Additionally, the films demonstrated excellent self-healing and recyclability. These results highlight the significant potential of EAPA-X films for sustainable applications in smart materials, electronic packaging, and flexible semiconductor materials.