Tough self-healing elastomers by molecular enforced integration of covalent and reversible networks

The work starts from a limitation of self-healing polymers: networks made only from reversible bonds tend to be mechanically weaker than networks with permanent covalent crosslinks. The authors propose a hybrid strategy—combine reversible hydrogen-bond crosslinks with permanent covalent crosslinks—to improve toughness while retaining self-healing. A key challenge is that hydrogen-bond (often polar) motifs and covalent (often non-polar) motifs can be immiscible without co-solvents. To address this, they design randomly branched polymers that carry both types of bonding motifs. These branched linkers are intended to force covalent and reversible bonds to mix at the molecular level in a dry elastomer network without co-solvents. They report that the resulting hybrid dry elastomer is very tough (fracture energy 13,500 J/m², comparable to natural rubber) and can self-heal at room temperature, recovering tensile strength around 4 MPa similar to existing self-healing elastomers.