Direct Silyl Ether Metathesis for Vitrimers with Exceptional Thermal Stability

TLDR

Vitrimers combine the desirable physical properties of thermosets with the malleability and reprocessability of thermoplastics, yet robust dynamic covalent chemistries that yield strong, thermally stable materials remain needed. This work introduces a new silyl ether metathesis reaction to produce vitrimers with exceptional thermal stability. Small‑molecule studies showed that silyl ether motifs exchange anhydrously under Brønsted or Lewis acid catalysis, and the authors silylated poly(ethylene‑co‑vinyl alcohol) with trimethylsilyl groups before cross‑linking with a bis‑silyl ether cross‑linker to form the vitrimer. The resulting vitrimer displayed exceptional thermal stability, reprocessability at 150 °C, and good creep resistance below its melting transition, proving the silyl ether metathesis as a robust dynamic covalent chemistry for thermosets.

Abstract

Vitrimers are a new class of polymeric materials that simultaneously offer the desired physical properties of thermosets and malleability/reprocessability of thermoplastics. Despite significant progress being made in the field of vitrimers, there exists a critical need for the development of robust dynamic covalent chemistries for the production of strong and thermally stable vitrimers. In this work, we discovered a new silyl ether metathesis reaction and used it for the preparation of vitrimers with exceptional thermal stability. In small-molecule model studies, we observed that silyl ether motifs directly exchange under anhydrous conditions catalyzed by a Brønsted or Lewis acid catalyst. For initial vitrimer demonstration, a commodity polymer, poly(ethylene-co-vinyl alcohol) (PEOH), was silylated with trimethylsilyl (TMS) groups followed by cross-linking with a bis-silyl ether cross-linker. The resulting thermoset showed exceptional thermal stability while maintaining malleability/reprocessability at elevated temperatures. The vitrimer properties such as recyclability and stress relaxation at various temperatures were carefully investigated. The material was reprocessable at 150 °C while also exhibiting good creep resistance at temperatures below its melting transition (Tm). This work demonstrates the silyl ether metathesis reaction as a new, robust dynamic covalent chemistry to introduce plasticity, reprocessability, and recyclability to thermosets.