Manipulating the Healing and Recycling Performance of Silicone Rubber by Synergetic Electronic and Steric Effects of Substituents

Silicone rubber is widely used in the insulation protection sleeve of cables. However, traditional cross-linked silicone rubber cannot repair the damage caused during transportation, installation, and service. When dynamic bonds are introduced, silicone rubber can repair these damages through the dissociation–association of dynamic bonds. Here, a self-healing silicone rubber material containing hindered urea bonds with different substituents was prepared, and its healing and recycling abilities by the synergistic electronic effect and steric effect of the substituents were studied. Among them, PDMS-TFM, which contains electron-withdrawing groups, not only has a 96% healing efficiency based on its tensile property and an 80% healing efficiency based on its insulation performance but also has a 99% recycling efficiency based on its tensile property and a 96% recycling efficiency based on its insulation performance, which makes it superior to other self-healing materials. The results indicate that substituents influence the activation energy and dynamics of the hindered urea bonds through their electronic effect by altering the bond length and bond energy. At the same time, due to steric effects, differences in molecular chain packing and free volume also lead to variations in the healing and recovery capabilities of silicone rubber. Moreover, silicone rubber was wrapped around copper wires and connected to a circuit containing LED lights, and its self-healing capability was further investigated by cutting the material with a knife and allowing it to heal at 90 °C for 24 h. In sum, the prepared self-healing silicone rubber material containing hindered urea bonds possesses excellent self-healing properties and holds potential application prospects in cable insulation materials.