High-Molecular-Weight Poly(fluorophenylsiloxane) Elastomers via Postpolymerization Macromolecular Chain Exchange Reaction for Optimized Comprehensive Properties

Designing polysiloxane elastomers for extreme environments requires a unique balance of mechanical robustness, environmental resistance, and low-temperature elasticity. Multicomponent copolymerization provides a powerful strategy to diversify siloxane architectures, yet conventional approaches often fail to achieve both compositional complexity and high molecular weight. Here, we present an optimized postpolymerization macromolecular chain exchange route to quaternary poly(fluorophenylsiloxane) (PMFPS) copolymers containing dimethyl (DiMe), diphenyl (DiPh), methyltrifluoropropyl (MeCF3), and methylvinyl (MeVi) repeating units. To our knowledge, this is the first demonstration of Mn as high as 441.1 kDa in polysiloxanes simultaneously incorporating four different siloxane units, achieved without sacrificing processability or structural integrity. The optimized PMFPS elastomers exhibit exceptional mechanical properties, including a tensile strength of 10.2 ± 0.4 MPa, elongation at break of 539.4 ± 5.6%, and toughness of 23.5 ± 0.7 MJ/m3. Furthermore, this work presents the first systematic evaluation of incorporating both DiPh and MeCF3 units within a single-polymer chain on comprehensive performance metrics, including low-temperature elasticity, thermal-oxidative aging resistance, oil resistance, and radiation resistance. Collectively, this study demonstrates that the postpolymerization macromolecular chain exchange reaction is a versatile and effective platform for the rational design of high-performance polysiloxane elastomers tailored for demanding environments.