Preparation And Characterization Of Anisotropic Self-healing Polymeric Materials

Polymeric materials have the characteristics of light weight,high strength,good toughness,and easy processing,and have been widely used in automobiles,electronic equipments,aerospace,construction,medical and other fields.However,due to the characteristics of the polymer itself,it is susceptible to irreversible damage from scratches,cuts,external impact and other factors during the usage,resulting in a significant decline in its mechanical properties and functions,thus limiting its application.The self-healing polymer can repair the damaged part spontaneously,which can effectively improve the safety,stability and service life of the material.However,the contradiction between mechanical strength and repair performance limits the development of self-healing polymers.In response to this problem,this paper aims to design and construct real-time self-healing polymers with both high strength and self-healing performance at room temperature.The real-time self-healing polymers at room temperature are constructed by using multiple weak hydrogen bonds in the polymer’s side chains strategy to construct high-strength,real-time repaired anisotropic polymers at room temperature,and an in-depth and systematic study of its formation mechanism.The main research areas of this paper are as follows:（1）Using methoxy polyethylene glycol acrylate（MPEG480）and acryloyl morpholine（ACMO）as the raw materials,a room temperature real-time self-healing polymer was prepared by free radical polymerization.Under the condition of repairing for 5s,the strength can reach 4.4MPa.On this basis,anisotropic polymers（MA）with both high strength and real-time repair at room temperature were prepared by the strategy of stretch-induced orientation.The anisotropic structure introduced by stretching endows the elastomer with excellent mechanical properties.The mechanical strength of the elastomer with a pre-tension strain of 200%can reach 8.4 MPa,and the elongation at break is 358%.Multiple weak hydrogen bonds in the polymer side chain enable the high-strength elastomer to be repaired rapidly at room temperature,with a self-healing efficiency of 87%.Secondly,the self-healing mechanism,the formation mechanism of anisotropic structure and the change of hydrogen bond formation during in-situ dehydration were systematically studied by means of FTIR,SEM,POM and small angle X-ray scattering（SAXS）.The results showed that hydrogen bonds were formed between the amide carbonyl group in the side chain of the polymer,the methylene group and the methoxy group;the SEM test confirmed the formation of the oriented structure in the polymer;SAXS and POM confirmed the in-situ water loss process.The anisotropy of the polymer became more and more obvious,and it was completed 2 h before the fixation and drying;2D infrared proved that the hydrogen bond in the polymer during the in-situ water loss process was formed after the water completely evaporated.In addition,the carbon nanotube（CNTs）dispersion is uniformly sprayed on the surface of the adhesive hydrogel and then pre-stretched.The obtained composite material can be used as a strain sensor with good conductivity and high sensitivity.Sensitive monitoring of movements such as muscle movement,elbow flexion and vocal cord development.（2）The anisotropic self-healing polymer prepared in（1）was soaked in zinc chloride（Zn Cl₂）solution for swelling treatment,and the anisotropic polymer was introduced into the anisotropic polymer by the coordination of Zn²⁺and amide carbonyl.The secondary directional cross-linked structure further improves the mechanical strength of the anisotropic self-healing polymer.The mechanical properties of the polymer can be easily controlled by adjusting the content of coordination bonds in the system.When the content of Zn²⁺is 3wt%,the mechanical strength of the polymer can reach 12.68 MPa,and the elongation at break is 265%.Multiple weak hydrogen bonds and coordination bonds endow the polymer with excellent repair performance.After repairing for 10 s at room temperature,the self-healing efficiency is 80%.In addition,the results of XPS confirmed the formation of a coordination bond between the amide carbonyl group and Zn²⁺in the polymer.In addition,the introduction of metal ions makes the elastomer have antibacterial properties.The antibacterial properties of metal materials can be detected by using Escherichia coli and Staphylococcus aureus.The results show that the elastomer has good antibacterial ability.