Construction of a Dynamic Ultrastretchable Epoxy Network Based on Chemical–Physical Cross-Linking Transformation

Conventional epoxy resins have high cross-linking density and rigid molecular structures, which make them difficult to develop into flexible elastomers. Here, inspired by the cuticle of the marine mussel byssi, we incorporate reversible Fe3+–carboxyl cross-links into a cross-linked epoxy network through a transformation between chemical cross-links and physical cross-links to realize the construction of a dynamic cross-linked network in traditional epoxy resins. Dynamic cross-linking networks and long flexible chain segments endow the epoxy system with excellent stretchable properties. Carbon nanotubes coated with ferric oxide (Fe3O4) nanoparticles were synthesized and added to the epoxy system, reinforcing the epoxy system. The synergistic combination of the modified molecular structure and nanohybrid endows the epoxy system with 550% elongation at break, a tensile strength of 1.4 MPa, and the ability to respond quickly to an applied magnetic field. An ultrasensitive strain sensor was constructed from synthetic epoxy hybrid materials; the GF (strain coefficient) of the strain sensor was up to 344.32. This research will be beneficial in expanding the application range of traditional epoxy polymer materials in the emerging sensor field.