High Performance, Reprocessable, and Degradable Biobased Polyhydroxyurethane Vitrimers from an Imine-Containing Vanillin Dicyclocarbonate.

Polyhydroxyurethane (PHU) is an emerging type of nonisocyanate polyurethane that is accessible by the aminolysis of cyclocarbonates (CCs) with amines. Biobased PHUs additionally conform to green, environmentally friendly, and sustainable development. Here, a five-membered vanillin di-CC with an imine group (VAI-5CC) was prepared through a cyclocarbonation of an imine-containing vanillin-tetraol with dimethyl carbonate under normal pressure, and the aminolysis of VAI-5CC with a triamine and hexanediamine or poly(propylene glycol) bis(2-aminopropyl ether) was explored. Several new biobased vanillin PHU vitrimers (CC-PHUs) with hydroxyurethane and imine (HU-IM) dual dynamic bonds were prepared successfully through this sustainable and green strategy. Aromatic vanillin units provide the CC-PHUs with excellent mechanical properties (storage modulus of 3.6-4.2 GPa and tensile strength of 74-106 MPa). HU-IM dual dynamic covalent bonds make the CC-PHUs easily reprocessed at a low temperature (110 °C). CC-PHUs were easily degraded under acidic conditions due to the presence of imine bonds.