Design,Synthesis And Properties Of Polyurethane Functional Materials Based On Dynamic Reversible Bonds

Polyurethane material has excellent performance,is widely used in military,tire,construction,leather and other fields.However,in the process of using materials,damage will inevitably occur.In order to improve the service life and safety of materials,researchers have invented self-repairing materials by imitating the repair behavior of natural organisms,which has greatly reduced the safety accidents caused by damage in the process of using materials.Therefore,in view of the incompatibility between intrinsic self-repairing mechanical strength and repairing performance,this paper designed self-repairing polyurethane elastomers with excellent mechanical properties by introducing non-covalent hydrogen bonds and covalent disulfide bonds,and carried out functional design of the materials.The main research contents are as follows:A self-healing polyurethane elastomer(IPAD)with high mechanical properties and high efficiency was designed and synthesized by using isophorone diisocyanate,polypropylene glycol,hydrazine adipate(ADD)and diazonium alkyl urea(DU)as raw materials.By changing the molecular structure,the mechanical strength and repair properties of the elastomer were regulated,and the influence of the molecular structure on its mechanical properties and self-healing properties was studied.The results showed that with the increase of chain extender,the orientation of the elastomer was enhanced,and the mechanical strength of the elastomer was 38.3 MPa by adjusting the covalent cross-linking network of the polymer reasonably.When the cut dumbbell splines were repaired at 100℃ for 24 h,the material repair efficiency reached 102.77% under the synergistic action of hydrogen bond and loose structure.In addition,the antibacterial properties of the elastomer were studied.With the increase of DU component,the antibacterial efficiency of the elastomer gradually increased.The antibacterial efficiency of the elastomer against Escherichia coli and Staphylococcus aureus was 82.62% and69.08%,respectively.At the same time,a flexible conductive sensing material was prepared by physical deposition of Ag NPS on the bottom layer of the elastomers.The conductive material not only showed the antibacterial efficiency of 98.53% and 99.56%against Escherichia coli and gluconococcus aureus,but also realized the sensitive perception of finger bending,fist clenching and other movements.In order to achieve the preparation of high mechanical strength,mild,efficient and rapid self-healing polyurethane elastomers(SPUs),a unique molecular structure design was adopted in this paper.4,4’-dichloryhexyl methane diisocyanate,hexamethylene diisocyanate and isophorone diisocyanate were used as hard segments,polycarbonate with different molecular weights was used as soft segments,and 4,4’-diaminodiphenyl disulfide was used as chain extender.Four different polyurethane elastomers were designed by self-assembly strategies of different soft segments,and the effects of molecular structure and type of isocyanate on polymer mechanical properties,repair efficiency and rate were studied.The results showed that the self-assembly of polycarbonate with different molecular weights increased the degree of loose and disordered polyurethane network.It not only gives the elastic body excellent mechanical strength(47 MPa),but also can realize efficient self-healing(95%)within 100 min at60℃.The strain-induced crystallization phenomenon of the material during tension is a key factor for the material to achieve high mechanical properties.Through comparative study of self-healing performance,it is found that loose hard domain packing and dynamic bonds with low bond energy are the key points to realize efficient and fast selfhealing.In this paper,the recovery effect of SPU elastomer is explored by solvent and hot pressing.After three times of hot-pressing recovery,the material can still maintain the mechanical strength of 41 MPa.The results of Pseudomonas aeruginosa degradation showed that the weight loss of the elastomer on the 35 th day of degradation was 30.4%.In addition,through the surface of the elastomer structure raised,contact point and spraying uniform carbon nanotubes,constructs the simple strain sensor,the sensor can not only detect the big body movements(for example: hand clenched,his leg),and can realize monitoring of small amplitude pulse such action.The above synthetic polyurethane elastomers have excellent mechanical strength and repair properties,and the insights into multiple hydrogen bond assembly strategy,stretch-induced crystallization strategy and self-healing mechanism also provide good insights into the design of high strength and self-healing materials,which have great application prospects in advanced durable electronic skin matrix and other fields.