Research On The Preparation And Properties Of Self-healing Materials Based On Transesterification And Disulfide Exchange

Self-healing function can effectively prolong the lifetime of materials and improve the availability of resource,which has been a research hotspot of material science.However,costly healing agents,complicated process,and cycle of healing of the traditional external self-healing material limited its application.It cannot achieve truly self-healing.For this reason,materials scientists began to design and develop intrinsic self-healing material.The healing mechanism of the intrinsic self-healing material is the dynamic interaction of the material body,which can achieve infinite self-healing in principle.In this thesis,we explored the possibility of preparing intrinsic self-healing material through ring-opening condensation reaction using inexpensive industrial raw materials,and prepared a self-healing material based on transesterification.Meanwhile,we explored the possibility of preparing intrinsic self-healing material through efficient and green thiol-ene click reaction and synthesized a kind of self-healing material based on disulfide bond exchange.On this basis,we extended moderately and explored the possibility of preparing self-healing functional material through thiol-epoxy click reaction and synthesized a magnetic self-healing functional material based on disulfide bond exchange.The main contents are as follows:Tetrabutyl titanate?TBT?catalyzed triethanolamine?TEA?to initiate ring-opening polymerization of glycolide to synthesize a polyglycolide-based polyol?HTPG?intermediate product,which subsequently reacted with hexamethylene diisocyanate trimer?HDIT?to synthesize a self-healing crosslinked network polymer?ICSPG?based on dynamic transesterification.The structures of the intermediate product HTPG and the final product ICSPG were identified using ¹H-NMR and FTIR.DSC,TGA,DMA and tensile testing were utilized to identify the thermal stability,mechanical properties and self-healing performance,respectively.The experimental results show that ICSPG has good thermal stability,the decomposition temperature is 280??420?,Tensile strength is above 12.4MPa,And with the increase of the-NCO content,the stability and mechanical properties of ICSPG are improved.ICSPG can successfully achieve self-healing under hot pressing.The effects of the healing temperature,healing hours and healing cycles on self-healing efficiency were studied.In addition,a possible ring-opening mechanism of glycolide as well as ICSPG self-healing mechanism was also proposed.Dibutyltin dilaurate?DBTDL?catalyzed the reaction of diisocyanate trimer?HDIT?with pentaerythritol triallyl ether?PTTAE?to prepare a nine-functional ene-terminated dendritic intermediate?NETD?.And then NETD was reacted with Polydisulfide dithiol?PSDT?via thiol-ene click reaction under ultraviolet?UV?radiation to form a self-healing polyurethane?PSPN?based on disulfide exchange.¹H-NMR,FTIR,Raman and UV/Vis spectroscopy,TG-DSC analysis,DMA,rheometer and tensile test were used for the identification of structure,thermal stability,mechanical properties,rheological properties and self-healing performance.The experimental results show that PSPN has good thermal stability,and the thermally decomposing temperature is about 300?,and it exhibits special rheological properties.PSPN also exhibits elastic rheological behavior and viscous rheological behavior in the high-frequency region at the same time.And it shows more than 80%self-healing efficiency while healed under UV light and heating.Finally,the PSPN self-healing mechanism was proposed.Dimethylbenzylamine?BDMA?catalyzed the thiol-epoxy addition reaction of pentaerythritol glycidyl ether?PTEGE?and PSDT to form a disulfide crosslinked epoxy resin network?PSEN?.The self-healing magnetic epoxy resin composite?PSEN-Fe₃O₄?based on disulfide bond exchange was prepared by one-pot method.The composite material,also as a magnetic self-healing functional material,can achieve self-healing at room temperature.FTIR,Raman spectroscopy,TG-DSC analysis,DMA,tensile test and other methods were used to identify and analyze the structure,thermal stability,mechanical properties and self-healing performance.The experimental results show that PSEN has good thermal stability.The thermal decomposition temperature is above 300?.Fe₃O₄ nanoparticles can enhance the thermal stability and mechanical strength of PSEN composites.The self-healing efficiency at room temperature is 88%,which can still reach 62%after the doping of Fe₃O₄particles.Finally,the possible BDMA-catalyzed disulfide bond metathesis mechanism was proposed.