Preparations And Properties Of Self-healing Elastomers Crosslinked By Metal-ligand Coordination

Materials such as elastomers produce some damages inevitably during use,which can seriously shorten their lifetime.Self-healing materials become new class of smart materials that possess the ability to recover its properties when broken.It depends on the responsible ability of non-convalent crosslink or the dynamic properties of special covalent bond.Our work is mainly introduced at three aspects as follows:1.Silicone elastomers with high self-healing efficiency based on metal coordination and hydrogen bonding.Firsly,amino end methyl vinyl silicone oil was synthesized with 2,6-pyridinedicarbonyl dichloride,and then grafted silicone elastomer was prepared with the synthetic sulfhydramide on the side chain by thiol-ene click reaction.A network of poly(dimethylsiloxane)polymer chains crosslinked by pydidyl-iron coordination and hydrogen bond was formed.The thermo-reversibility of hydrogen bond is strongly illustrated by the variable temperature infrared spectrum,and the structure of metal coordination was analyzed by the Raman spectrum.We also investigated the influences of the density of metal coordination and hydrogen bond on the tensile properties and self-healing properties.The research revealed that the self-healing properties of silicone elastomer derive from the thermally reversible hydrogen bonds and metal coordinations.The self-healing efficiency of elastomers prepared is as high as 95.3%at room temperature after 8 h without any external stimulus.2.Preparation of self-healing polyurethane elastomers based on metal coordination and hydrogen bonding.Polyurethane elastomers were prepared by 2,6-Diaminopyridine and polyurethane prepolymer synthesized by Poly(tetrahydrofuran)and HDI trimers.A network of polyurethane polymer chains crosslinked by pydidyl-iron coordination and hydrogen bond was formed.The results show that the maximum tensile strength of polyurethane elastomers is 4.2 MPa.The healing strength is 3.87 MPa and the broken elongation is up to 1050%.The self-healing efficiency of elastomers prepared is as high as 92.2%at 50℃ after 6 h.3.Preparation of self-healing SBS based on metal coordination.Firstly,the SBS-MT with different grafting ratios were obtained with 2-Mercaptoethanol on the side chain by thiol-ene click reaction,and then SBS-AE was prepared by the esterification reaction.FT-IR and ’H-NMR were used to characterize the polymer and revealed the products were pure enough.All in all,the synthetic steps are simple enough and the reaction speed is fast enough.Next,the modified SBS elastomers with imidazole was prepared by Michael addition reaction,and the ligand was provided for the coordination network.