Studies On Preparation And Properties Of Self-healing Meterials Based On Multiple Hydrogen Bonds

As a kind of smart materials,self-healing materials has been researched in extensive fields due to its unique spontaneously self-healing properties with external stimuli.Hydrogen bond is reversible and thus it can generally be used to fabricate self-healing hydrogels.However,the hydrogels based on a kind of hydrogen bond have poor mechanical properties and self-healing properties.Multiple hydrogen bonds have been confirmed to have the capacity of improving the materials with ideal mechanical properties and self-repairing properties.Therefore,self-healing hydrogels with multiple hydrogen bonds were widely prepared.However,there is few self-healing elastomers composed of the multiple hydrogen bonds.In this paper,multiple hydrogen bonds are introduced into polyurethane elastomers,and their properties were studied and adjusted in order to obtain the required composite polyurethane elastomers.In order to prepare the self-healing polyurethane elastomers,acryl glycinamide?NAGA?with bisamide grouphas that can form multiple hydrogen bonds had been prepared by the reaction between acryl chloride and glycine hydrochloride.The structure of NAGA was characterized by ¹H NMR and FTIR spectra,which showed successful preparation of NAGA.Polyurethane?PU?elastomers were then prepared by polyglycols as soft segments and MDI and IPDI as co-hard segments.Changing the types of polyglycol with different molecular weights and ratios between MDI and IPDI can prepare different PU elastomers.PNAGA/PU elastomers were prepared by in-situ polymerization of NAGA in the polyurethane matrix using photo-initiation.The structures of the elastomer before and after NAGA polymerization were confirmed by FTIR,and the results showed that the peak of the C=C special absorbance disappeared after NAGA polymerizationt.By testing the mechanical properties of PU and PNAGA/PU elastomers,it is obvious that the ratio of the soft segment and the isocyanate had an effect on the performance of elastomers.The strength of PNAGA/PU_PTMG-2000-3:1elastomer obtained by compounding PU_PTMG-2000-3:1 and PNAGA reached 17.83 MPa,which is nearly 6 times higher than that of PU_PTMG-2000-3:1.The self-healing properties and mechanisms of the different elastomers were studied.Elastomers mainly used dynamic reversible hydrogen bonds to achieve the self-healing,and the more dynamic reversible hydrogen bonds in elastomers,the higher self-repairing performance.The healing efficiency of the elastomer could reach 90%in 24 h.The loss energies for the one cycle of PNAGA/PU_PTMG-2000-3:1,PNAGA/PU_PTMG-2000-4:1,PNAGA/PU_PTMG-1000-3:1 and PNAGA/PU_PTMG-1000-4:1 were 0.2461 MJ/m³,0.1429 MJ/m³,0.3662 MJ/m³,and 0.3803 MJ/m³,respectively,when the strain is fixed at 250%.In addition,it could be obtained from cyclic stretching experiments on polyurethane elastomers that the elastomers had better fatigue resistance after rearrangement of the segments.In order to further study the effects of the type and ratio of the hydrogen bonds on the properties of elastomers,a self-healing polyurethane PUPAI was prepared by combining the copolymer of ACG and itaconic acid and polyurethane,and the elastomers PUPNI and PUPUI were prepared and compared with PUPAI.N-acryloylglycine?ACG?with an amide group and a carboxyl group that can form multiple hydrogen bonds was prepared and characterized.The polymer of ACG and itaconic acid was prepared using AIBN as an initiator.The molar ratio of ACG to itaconic acid was adjusted to prepare different PUPAI elastomers.PUPNI and PUPUI were prepared according to the same method,and their performance was compared with PUPAI.It was found that PUPAI11 has more excellent mechanical properties,and its fracture stress is10.6 MPa,and its Young's modulus is 1.97 MPa.For PUPAI,with the increase of ACG content in the copolymer,the repair efficiency of the obtained PUPAI improved,which could reach above 90%.