A self-healing and recyclable poly(urea-imine) thermoset synthesized from CO2

Abstract

The synthesis of self-healing and recyclable polymeric materials from renewable CO₂ is of great importance in the fields of functional materials and sustainable chemistry. In this work, mechanically robust poly(urea-imine) (PUI) thermosets were prepared from CO₂-sourced oligourea (OUa), terephthalaldehyde (TA) and tri(2-aminoethyl)amine (TAEA) through condensation between equimolar amino and aldehyde groups. The synthesized PUIs have satisfactory mechanical performance, seal-healing and recyclable properties as they contain cross-linked dynamic imine bonds and reversible hydrogen bonds. These properties can be adjusted by changing the ratio of TAEA to OUa, thus varying the chemical bonds and chain structure. The highest values for the mechanical properties tensile stress (10.2 MPa) and Young's modulus (79 MPa) were obtained in a PUI thermoset synthesized from a molar ratio of TAEA to OUa of 3 : 2 (OUa₂-T₃). In addition, this thermoset can be healed at 80 °C with a healing efficiency over 92% owing to the high reversibility of imine and hydrogen bonds and the flexibility of CO₂-sourced OUa chains. Moreover, it can also be reprocessed and recycled by physical and/or chemical means without change in its chemical structure, glass transition temperature and original mechanical properties. Additionally, this PUI thermoset can be easily degraded into its original reagents OUa, TA and TAEA under acid conditions. Therefore, as novel sustainable materials, the PUI thermosets reported in this article have great potential to replace conventional non-degradable thermosets over a wide field.