Hemisilicone (PM 2 E) Elastomers: Assessing Prepolymer Synthetic Strategies

Hemisilicone, −(SiMe 2 –O–SiMe 2 –CH 2 CH 2 ) n –(PM 2 E), represents a promising alternative to conventional silicone, polydimethylsiloxane (PDMS), for elastomer applications. In this study, we address a key challenge in PM 2 E synthesis by developing an anionic ring-opening polymerization (AROP) method that ensures precise control over both α- and ω-chain end functionalities through the in situ preparation of lithium silanolate-based initiators, generated by the reaction of disiloxanes with methyllithium. The propagation proceeds cleanly, without backbiting or chain transfer side reactions, resulting in a narrow molecular weight distribution. We compare the mechanical properties of elastomers prepared from PM 2 E prepolymers synthesized via different polymerization methods. Notably, PM 2 E synthesized by the AROP method enables the formation of elastomers with outstanding mechanical properties, including exceptional stretchability (>1000% strain) and excellent tear resistance. In contrast, elastomers prepared from equilibrated polydisperse PM 2 E exhibit comparable stretchability but significantly lower tear resistance. Overall, this polymerization approach offers a robust platform for producing high-performance, impurity-free silicone materials with well-defined architectures.