Synthesis and Characterization of Polymethylphenylsiloxane With Arbitrarily Tunable Phenylsiloxane Contents via Phosphazenium Salt/<scp>KOH</scp> Catalyzed Ring‐Opening Polymerization

ABSTRACT Poly(dimethylsiloxane‐ co ‐methylphenylsiloxane) (P(DMS‐ co ‐MPS)) is an important polysiloxane with good thermal stability, low‐temperature resistance, and damping properties due to the phenyl groups in the polymer chain. However, there were limited studies on the synthesis and performance study of high molecular weight P(DMS‐ co ‐MPS) copolymers with different MPS contents. In this contribution, a series of P(DMS‐ co ‐MPS) copolymers with molecular weight up to 468.4 kg/mol and MPS contents varying by 10 mol% (9–92 mol%) were successfully synthesized by P 5 Cl/KOH catalyzed ring‐opening copolymerization (ROCP) of octamethylcyclotetrasiloxane (D 4 ) and tetraphenyltetramethylcyclotetrasiloxane (D 4 Ph ). The good random characteristic of the resulting P(DMS‐ co ‐MPS)s was fully verified by the 29 Si NMR, predictable T g s, and good high‐temperature resistance. The low T g s between −115.7°C and −26.8°C and the good damping performance at low temperature enabled P(DMS‐ co ‐MPS) copolymers as good candidates for applications as elastic materials under extreme conditions.