Self-healing siloxane elastomers constructed by hierarchical covalent crosslinked networks and reversible dynamic bonds for flexible electronics

The rapid development of flexible electronics brings forward more requirements for self-healing substrate materials. Siloxane elastomers as an ideal substrate is widely used in the flexible electronics. However, self-healing siloxane elastomers still need to be improved in terms of mechanical properties. Herein, methacrylate/epoxy groups terminated hyperbranched polysiloxanes (HPBSi) as core was prepared to improve the mechanical properties via providing hierarchical permanent chemical cross-linked networks. A series of room-temperature self-healing siloxane elastomers are constructed by HPBSi with a linear dual-epoxy siloxane monomer through an amino disulfide compound (AFD) with reversible dynamic bonds. Especially, the content of HPBSi and AFD is systematically researched and proved to play a key role in adjusting the mechanical and self-healing properties of the siloxane elastomers. For the P1-5 containing 5 wt% HPBSi, its tensile strength is as high as 0.87 MPa that is improved about 410% compared with an elastomer without HPBSi. P11-5 elastomer with more AFD can obtain the same healing efficiency at room temperature in a shorter time (12 h) compared with 48 h of P1-5 elastomer. Finally, the self-healing siloxane is used as a flexible substrate to fabricate a strain sensor for monitoring multiple human motions, demonstrating a promising potential use in the flexible electronics. Graphical Abstract