CONICET | Buscador de Institutos y Recursos Humanos

The development of self-healing thermosetting polymers started some years ago with the aim to extend the service life of structural and functional polymers. These materials are capable of mending cracks upon the application of an external stimulus, restoring the original (or at least similar) mechanical properties. Great efforts have been devoted to find new approaches, allowing more efficient healing processes, among which the thermal activation of dynamic covalent bonds present in the polymeric network seem to be a very promising alternative. The polymer networks based on epoxidized soybean oil (ESO) and citric acid (CA) used in the present work constitute an example of this strategy. The β-hydroxyester links produced by the epoxy-acid reaction can be rearranged through transesterification reactions, changing the network topology, what can be used to induce healing at a macroscopic level. The inclusion of metallic nanoparticles in polymers gives the possibility to remotely promote the healing by using the heat generated by photothermal effect. It consists in the heat generation by metal nanostructures when they are exposed to electromagnetic radiation with a specific frequency matching its surface plasmon resonance. The figure presented below shows the healing sequence, starting with a fractured sample of the ESO-CA network with embedded Au nanoparticles, which is depicted in picture A. Picture B shows the sample being subjected with two clamps between a glass and a steel ring, and the subsequent irradiation process with a green laser (λ=532 nm) is showed in C. The final healed sample after 1h of irradiation is seen in D and E. Although the welding line is still visible, these preliminary results demonstrated that healing can be achieved by photothermal activation. Current work is being focused in finding the optimal parameters to obtain a higher degree of reparation.