Preparation And Characterization Of Self-healing Polyurethane Based On Dynamic Non Covalent Bond

Polymer materials inevitably suffer mechanical damage during use,thereby shortening their service life and even posing safety hazards.Empowering materials with self-healing ability can repair and restore damaged areas,in order to r educe maintenance costs,extend service life,and improve reliability and safety.Due to the conflicting requirements of polymer self-healing ability and mechanical properties,the preparation of polymer materials with excellent self-healing and mechanical properties has always been a huge challenge.Polyurethane has become one of the most widely used polymer materials due to its strong designability,diverse preparation methods,and excellent comprehensive performance.This project involves the structural design of polyurethane molecular chains,introducing a large number of dynamic bonds between the molecular chains to achieve cross-linking,enabling the material to have good mechanical properties in the usage environment.At the same time,under certain conditions,the dynamic bond fracture reconstruction can generate self-healing function,ultimately achieving the goal of high strength and high repair rate.The specific work content is as follows:（1）A self-healing polyurethane elastomer with multi-level hydrogen bonds was prepared by introducing both 2-urea-4[1H]pyrimidinone（UPy）and carboxyl groups,which can form quadruple hydrogen bonds,into the polyurethane molecular chain.Research has found that changing the content of UPy and carboxyl groups can adjust the hydrogen bonding crosslinking density.When the UPy content of the quadruple hydrogen bonding module is50%,the tensile strength of the polyurethane is 50.8 MPa,and the repair rate is 72.0%after 24 hours of repair at 80℃.（2）Polyurethane elastomers with carboxyl groups in their molecular chains were prepared,and carboxyl groups acted as ligands to form coordination bonds with Fe³⁺.Polyurethane without the introduction of Fe³⁺is in a viscous state with poor mechanical properties.After the formation of coordination bonds,the mechanical strength is significantly improved.By adjusting the Fe³⁺content,polyurethane with different mechanical properties can be obtained.When the molar ratio of Fe³⁺to carboxyl group is 1:4,the comprehensive performance of the material is the best,with a tensile strength of 37.6 MPa.At the same time,the repair rate reaches 86.7%after 12 hours of repair at 80℃.（3）Carboxyl groups can form coordination bonds with metal ions,as well as ion pairs with strong electrostatic interactions with amino groups.Therefore,based on the study of polyurethane molecular chains in Chapter 2,a self-healing polyurethane based on a dual network of strong ion bonds and weak hydrogen bonds was successfully prepared by adding small molecules containing amine groups.Relying on the synergistic enhancement effect of the dual dynamic network,the prepared polyurethane exhibits ultra-high strength of 59.4 MPa,high elongation at break of 1043%,high fracture energy of 207.1MJ/m³,and self-healing efficiency of 80.0%.