Tailored Polyurethanes via Amine‐Terminated <scp>PPO</scp> Chain Extension: Synergistic Enhancement of Mechanical, Thermal, and Dielectric Properties

ABSTRACT An amino‐terminated low‐molecular weight poly(2,6‐dimethylphenylene oxide) (APPO), was prepared and employed as a macromolecular chain extender to enhance the performance of toluene diisocyanate (TDI)‐based polyurethanes (PUs). Dynamic mechanical analysis (DMA) showed that incorporating APPO progressively increased the soft‐segment glass transition temperature ( T g ), with 10% APPO raising T g by 21°C (from 14°C to 35°C) in PPG‐TDI systems and 15°C (from −9°C to 6°C) in PTMEG‐TDI systems. Tensile tests revealed optimal mechanical performance at 6% APPO, where tensile strength increased by 183% (from 8.8 to 25.1 MPa) and 94% (from 21.2 to 42 MPa) for the two PUs, respectively, while Shore A hardness rose by approximately 15 points. The dielectric constants were reduced by 12% and 10%, respectively, owing to the low polarity of PPO segments. Immersion‐compression tests in diesel fuel at 100°C demonstrated exceptional fuel resistance, with storage modulus retention rates reaching 92%–94%. These findings highlight the potential applications of APPO‐modified PUs in critical automotive components, such as gaskets and seals, for high‐temperature fuel environments.