Controllable Preparation And Properties Of Supramolecular Extrinsic Self-healing Materials

Epoxy resins have been widely applied in the fields such as aerospace,automotive,and power systems due to their excellent mechanical properties,dimensional stability,ease of processing,and so on.However,the inevitable occurrence of microcracks during processing or service has a serious impact on service life of epoxy resins.Introducing extrinsic self-healing materials such as microcapsules into epoxy resins can repair cracks under external stimuli and improve its service life.However,these externally assisted self-healing materials generally have the drawbacks of complex preparation processes and difficulty in multiple self-healing.Therefore,the development of extrinsic self-healing materials with multiple self-healing ability through simple preparation processes are desirable for the long-term use of epoxy resins.In this thesis,extrinsic supramolecular self-healing materials were prepared by non-covalent modification of hydrogen bonded supramolecules with amphiphilic polymers using a simple mixing method.The microcracks in epoxy resin could be thermally initiated to achieve multiple self-healing by utilizing the reversible hydrogen bonds in the supramolecular structure.The compatibility of self-healing agents with epoxy resin and their impact on the thermal stability of epoxy resin were investigated,and the self-healing and mechanical properties of epoxy resins embedded with supramolecular self-healing materials were explored.Firstly,a supramolecular self-healing material consisting of amphiphilic polymers and deep eutectic supramolecular polymers,namely F-127/DESPs,was prepared.By utilizing the interactions between the polyoxyethylene and polyoxypropylene blocks in the amphiphilic polymers with DESPs and epoxy resin,respectively,the supramolecular self-healing material was endowed with good compatibility in epoxy resin.By utilizing thermal activation,hydrogen bonds in DESPs are reversibly broken and regenerated,resulting in the formation of shorter polymer fragments with higher migration rates during hydrogen bond breakage,thereby achieving rapid multiple self-healing behaviors of epoxy resins.The epoxy resin embedded with an extrinsic supramolecular self-healing material,F-127/DESPs,could achieve almost 100%self-healing efficiency for both primary and secondary scratches after heating at 60^oC for 2 hours,and the mechanical properties of epoxy resin were also restored after self-healing.In order to improve the mechanical properties and water-resistant self-healing performance of epoxy resin embedded with supramolecular self-healing materials,an extrinsic supramolecular self-healing material(F-127/C₁₂TAB/DESs)well compatible with epoxy resin was also prepared by modifying hydrophobic supramolecular adhesives,C₁₂TAB/DESs,with amphiphilic polymers.The epoxy resin coating embedded with F-127/C₁₂TAB/DESs exhibited good multiple morphology self-healing ability for primary and secondary damages after being heated at 60^oC for 2 hours,and even the scratches in the coating could be also healed after water resistance for 60 hours.When the scratches were generated on the epoxy resin embedded with F-127/C₁₂TAB/DESs,its mechanical properties can also achieve primary and secondary self-healing processes through thermal initiation.