Preparation And Properties Of Self-healing Polymer Materials Based On Borate Ester Bonds

Self-healing materials with self-regulation,self-detection,and self-healing have been widely studied for their ability to achieve self-healing after material damage,which could reduce material loss and environmental pollution,and are currently widely used in biomedicine,tissue engineering,medical engineering,sensors,flexible electronics,etc.As a novel dynamic covalent bond,borate ester bond can achieve rapid repair of damaged materials without external stimulation at room temperature.However,current selfhealing materials based on borate ester bonds still have problems such as the need for additional p H adjusters and weak mechanical strength.In this thesis,self-healing polymer materials based on borate ester bonds were prepared by introducing basic monomers.By adjusting the monomer composition,the mechanical properties and self-healing efficiency of self-healing materials based on borate bonds were studied.The main research contents are as follows:1.Dimethylaminoethyl methacrylate(DMAEMA)was used as the basic monomer,N-hydroxymethyl acrylamide(NAM)was used as the hydroxyl donor,and 1,4-benzenediboronic acid(BDBA)was used as the boron source.Self-healing hydrogel based on borate ester bonds was prepared by free radical polymerization in one step.The test results show that with the addition of DMAEMA,the fracture strain of the hydrogel firstly increased(BH-2.5-1.0-0.4,201%)and then decreased(BH-6.5-1.0-0.4,470%).Among them,the fracture strain of BH-5.5-1.0-0.4 hydrogel was 542%,and the fracture stress reached 179 k Pa.After healing at room temperature for 3 min,BH-5.5-1.0-0.4hydrogel can bear its weight without breaking;and after 24 h of repair,the fracture strain of BH-5.5-1.0-0.4 can be restored to 100%.Finally,the structure,thermal stability,cyclic stability,healing mechanism of hydrogel and the effects on the overall properties of the material under acidic,neutral and alkaline conditions were studied.2.The polymer structure was adjusted by introducing the second basic monomer-N,N-dimethylacrylamide(DMA)into the research system in order to further improve the mechanical properties of materials while maintaining the polymer's intrinsic alkaline environment.The result show that with the increase of DMA content,the fracture stress of H-10-5 elastomer can be significantly reached to 801 k Pa and the fracture strain reaches 821%;the fracture strain of H-10-7 elastomer reaches 700% and the fracture stress reaches as high as 982 k Pa.It is proved that the mechanical properties of the material are significantly improved.In addition,H-10-7 elastomer shows excellent fatigue resistance in a 400% stress-strain cyclic tensile test.Finally,H-10-5 and H-10-7elastomers were repaired at room temperature for 24 h after being completely cut off,and the self-healing efficiency reached 97.2% and 98.6%,respectively,which showing excellent self-healing performance.