Metathesis

Organic chemistry

Polymer chemistry

Dynamic covalent chemistry

Thermal stability

Catalysis

Thermosetting polymer

Chemistry

Silyl ether

Molecule

Polymerization

Ether

Supramolecular chemistry

Polymer

Silylation

Journal of the American Chemical Society

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.

Direct Silyl Ether Metathesis for Vitrimers with Exceptional Thermal Stability