Self-healing processes in ionomeric elastomers

The use of dynamic bonds in self-healing polymeric systems allows restoring of the chemical structure and mechanical properties multiple times. In this respect, the use of ionomers represents a promising approach. The strong interaction between ionic moieties within a non-polar matrix leads to microphase separation and a behavior similar to covalent crosslinks in a thermally reversible network. The implementation and parameter optimization, however, requires a profound understanding of the structure-property relationships. Motivated by recent findings on the excellent self-healing behavior of ionomeric NBRbased systems, we report on an ionomer model system designed to explore the thermal and viscoelastic properties of these materials by varying the ionic content, neutralization degree and nature of counter-ions. The dynamic mechanical properties of the materials are investigated by rheological oscillation measurements in dependence on the ionic content and the nature of cation. The temperature-reversible formation of ionic cross-links, an essential feature for the ability of extrinsic self-healing by thermal activation, is shown to be possible by incorporation of magnetic nanoparticles. The transfer of the basic results to NBR elastomers is successfully demonstrated.