The reaction was conducted in a two-necked round-bottom flask equipped with a nitrogen gas inlet and a condenser and purged with dry-nitrogen gas. A desired amount of TPO pellets and MAH was added to the vessel, followed by injecting toluene into the flask and immersing the apparatus into an oil bath at 140 °C in sequence. After TPO and MAH were completely dissolved, BPO was added to the solution in an atmosphere of nitrogen. After the reaction mixture had been stirred for approximately 4 h, the reaction solution was poured into acetone to precipitate the functionalized polymer (TPO–MAH). TPO–MAH was further purified by HPLC-grade acetone by Soxhlet extraction overnight and was then dried at 80 °C at reduced pressure for 18 h