Aging-Resistant, High-Strength, Reprocessable, and Recyclable Silicones through Dynamic Thiol–Maleimide Chemistry

Dynamic covalent cross-linked silicones have novel self-healing, reprocessing, and recycling capabilities. However, they are still challenged by weak mechanical properties and the deterioration of the intrinsic physicochemical properties, of silicones caused by the susceptibility of dynamic covalent bonds to external environmental factors. Herein, the aging-resistant, high-strength, reprocessable, and recyclable silicone and composite are developed by the facile thiol–maleimide click chemistry between thiol, phenyl-functionalized polysiloxane, and bismaleimide. The resultant silicones show a maximum tensile strength of about 38 MPa and a glass transition temperature of about 160 °C. Meanwhile, they also have excellent aging resistance to heat (150 °C), alkali (pH ≈ 14), acid (pH ≈ 1), humidity, and nonpolar organic solvents, where the tensile strength still remains about over 90% after being treated by these environmental factors for 84 h. Moreover, the pulverized silicone can be thermally compressed into new materials at 220 °C for 1 h due to the thermally activated dynamic reversibility of thiol–maleimide chemistry, and the tensile strength can completely recover, even after three reprocessing cycles. Furthermore, the fabricated carbon fiber/silicone composites with a tensile strength of 103 MPa can be recycled for matrix and carbon fiber when they are chemically degraded at 90 °C, and the recycled materials can be used to prepare new composites with the efficient recovery of mechanical properties. Therefore, this aging-resistant, high-strength, reprocessable, and recyclable silicone can simultaneously meet the requirements of mechanical properties and structural stability during future industrial applications.