Multi-level Reversible Interaction Synergistically Enhances Self-healing Polymer Materials

With the development of polymer science,polymer materials play an irreplaceable role in industrial production and daily life.However,polymer materials will inevitably suffer damage during molded and used,threatening the safety of life and property,so it is particularly important to develop polymer materials with self-healing functions.The intrinsic self-healing material can repair its own damage through various internal dynamic reversible interactions,without the need for external repair agents.However,the mechanical properties of intrinsic self-healing materials are usually poor,and the repair of their damage often requires the input of external energy(such as thermal energy)to promote the movement of polymer segments and the reconstruction of reversible interactions.Therefore,the development of polymer materials with high strength and mild condition self-healing is very challenging but have practical application value.In this paper,to address this problem,by introducing a variety of reversible interactions with different binding energies into polymer materials,and utilizing the synergy between various dynamic interactions,the material not only has many excellent mechanical properties,such as high strength,toughness and excellent stretchability,etc.,can also achieve efficient self-healing under mild conditions.1.Through reasonable design,dynamic covalent bonds and graded hydrogen bonds are simultaneously introduced into the polyurea material,and through the synergistic enhancement of different dynamic forces,the polyurea material with high-strength,excellent toughness and room temperature self-healing is prepared.Among them,the relatively weak hydrogen bond between isophorone diisocyanate urea groups(IPU)gives the material a higher energy dissipation and large stretchability.The relatively strong hydrogen bond between 4,4'-methylene bis(phenyl isocyanate)urea group(MPU)gives the material temporary physical cross-linking sites to obtain high strength.The crosslinking of the dynamic imine bond makes the material have good recoverability.The synergy of multiple reversible interactions gives the material ultra-high strength(44.2 MPa)and toughness(127 MJ/m~3).At the same time,due to the stimulus response of the hydrogen bond and the imine bond to water,the material can be repaired at room temperature.2.After a simple chemical reaction,two polymers(polyethylene-vinyl acetate-vinyl alcohol)containing hydrogen bonds between hydroxyl groups and phenylboronic acid-terminated polyurea containing IPU hydrogen bonds are obtained.The self-healing composite material with high strength,excellent toughness and large stretchability is obtained by compounding two kinds of polymers.Among them,multiple hydrogen bonds endow the material with energy dissipation,and the boronate bond cross-linked structure formed by phenylboronic acid and hydroxyl can increase the strength of the composite material.Doped with 25 wt%of PIU-BOH composite material,its strength is increased by 5 times compared with the original material,and the toughness is increased by 15 times,which fully shows that the synergy of multiple reversible interactions can effectively improve the strength and toughness of the material,at the same time the composite material can be recycled by hot pressing.