Covalent adaptable networks through dynamic N,S-acetal chemistry: toward recyclable CO2-based thermosets

Designing easily recyclable polymers with customized properties is a key challenge to face up environmental concerns and the growing plastics demand. Here, we report a dynamic chemistry between CO2-sourced alkylidene oxazolidones and thiols that delivers circular non-isocyanate polyurethane networks embedding N,S-acetal bonds. Oxazolidones are synthesized from cheap reagents and carbon dioxide. The polymer structure is tuned by monomer design, translating in a wide panel of mechanical properties, ranging from PDMS-like elastomers (Young’s modulus (E) = 2.9 MPa and elongation at break (Ebreak) = 159%) to polystyrene-like rigid plastics (E = 2800 MPa, Ebreak = 2%). The dynamic nature of the N,S-acetal bond offers multiple closed- and open-loop recycling options, facilitating repeated thermoset reprocessing into the same material or the production of a different one of distinct properties. The versatility of this chemistry shows great potential for preparing materials (including composites) of tunable properties that can be recycled by multiple scenarios.