Thermally reprocessable bio-based polymethacrylate vitrimers and nanocomposites

Vitrimers are covalently cross-linked polymeric materials that can be processed upon heating wherein triggerable polymer networks shuffle chemical bonds through exchange reactions without losing their network integrity. In this work, we apply vitrimers to develop recyclable thermosets derived from materials with relatively high biosource content. We explore the reaction between p-ketoesters derived from commercially available (2-acetoacetoxy) ethyl methacrylate (AAEMA) incorporated within isobornyl methacrylate (IBOMA, from pine sap), and a bi-functional amine (Priamine, derived from vegetable oils) to synthesize catalyst-free vitrimers. Controlled radical miniemulsion polymerization was also used to synthesize the water-borne copolymer analogs. Vitrimer nanocomposites were obtained by the incorporation of amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH2) at different loadings (0, 5, 10 and 20 wt%). Incorporation of 20 wt% POSS-NH2 improved tensile modulus (from 96 to 176 MPa), tensile strength (from 2.5 to 5 MPa) and decomposition temperature (225-255 degrees C), and slowed down the relaxation rate and increased apparent activation energy of stress relaxation compared to the neat vitrimer. We further show that the vitrimers studied here and the nanocomposites containing vinylogous urethane cross-linking networks can be un-cross-linked by dissolving in excess monofunctional amine at 65 degrees C or recycled by grinding and remolding at 125 degrees C without compromising the mechanical properties.

Automated summary

Vitrimers are covalently cross-linked polymeric materials that can be processed upon heating. This study developed recyclable thermosets with relatively high biosource content using catalyst-free vitrimers. The incorporation of amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH2) improved the mechanical properties of vitrimers.