The Preparation And Properties Of Self-healing Conductive Composites

Taking the advantages of high stretchability and easy processing,conductive elastomers are widely used in conductive coatings,energy storage materials,electronic skins,and wearable sensors.While the polymer conductive material will inevitably suffer crack or break due to cyclic scratching or bending in practical application,resulting in the loss of its functionality.Introducing self-healing ability into polymer conductive material can effectively improve its use stability,safety and prolong its service life.In this thesis,conductive polymer polypyrrole(PPy),carbon nanotubes(CNT)and silver nanoparticles(Ag)were used as conductive fillers,and the self-healing polymers based on reversible hydrogen bonds were used as the matrix to prepare conductive composites materials with self-healing capability and their structure-property relationships were studied in details.The specific contents of this thesis are as follows:1.Poly(ethyl methoxyacrylate-co-N,N-dimethylacrylamide)(MD50)was swollen in pyrrole(Py)monomer solution,so that Py monomer was uniformly dispersed in MD50.The PPy conductive network was interspersed into the MD50 three-dimensional cross-linked network by in-situ polymerization method to form a conductive path,and the PPy/MD50 self-healing conductive composite was prepared.The elastomer has good mechanical properties with a tensile strength of 5.6 MPa and an elongation at break of750%.Due to the existence of reversible hydrogen bonds,the self-healing rate of PPy/MD50 can reach 90.18%at room temperature and 93.75%at high temperature.Furthermore,its application potential as a stretchable flexible sensor is further explored.2.Based on the highly hydrophilic self-healing polymer poly(methoxy polyethylene glycol acrylate-co-acryloyl morpholine)(MA)with reversible hydrogen bonding as the matrix in carbon nanotubes(CNT)dispersions swelling,the surface becomes sticky due to water absorption,so that CNT are uniformly attached to its surface,and a real-time self-healing stretchable conductive composite with a wrinkled structure is prepared(CNT₃₀/MA₃₀).The elongation at break of the CNT₃₀/MA₃₀ composite was717%,the breaking stress was 3.8 MPa,and the electrical conductivity was 1.78 S·cm^-1.At room temperature,after repairing for 30 s,the mechanical strength repair efficiency is 91.32%.After cutting the material and healing for 1 s,the electrical conductivity can be completely recovered.In addition,the practical value of CNT₃₀/MA₃₀ as a strain sensor and pressure sensor was further evaluated.After the disconnection-healing process,the CNT₃₀/MA₃₀ can still accurately detect tiny human movements,including pulse beating,eyebrow raising,and writing different letters.3.Using the fully swollen MA as the matrix,in-situ reduction of Ag nanoparticles on its surface,and using the effect of different concentrations of silver ammonia solution on the regulation of the folded structure,a stretchable self-healing conductive composite with a multi-layer pleated structure was prepared(Ag₄/MA).The elongation at break of the Ag₄/MA conductive composite was 700%,the breaking stress was 1.29 MPa,and the electrical conductivity was as high as 1900 S·cm^-1.At room temperature,after 1 min of healing,the mechanical strength repair efficiency was 98.44%.After cutting the material and healing for 2 s,the electrical conductivity can be fully recovered.The applications of Ag₄/MA as stretchable electrodes and strain sensors were further evaluated.Even after the disconnection-healing process,Ag₄/MA still has stable electrical conductivity in stretching,and can accurately detect tiny human movements,such as vocalization and muscle movements.