Preparation And Properties Of Self-healing Silicone Elastomer Crosslinked By Reversible Bonds

Polysiloxane macromolecular materials are widely used in aerospace,conductive devices,special coatings,medical devices,energy materials,intelligent skin,robots and other fields due to their diverse functional groups.However,in the process of use,the material will inevitably be damaged by external physical damage,resulting in shortened service life and potential safety hazards.Therefore,the development of self-healing silicone elastomer has a long-term application prospect.In this paper,reversible crosslinking was introduced into the polysiloxane system through a variety of dynamic chemical bonds to form a self-curing crosslinking network with a variety of dynamic reversible bonds.The self-healing elastomer was endowed with antibacterial ability by introducing antibacterial active compounds.In addition,by introducing the modified conductive nano materials,a variety of self-curing strain sensors were successfully prepared.The mechanical properties,self-healing properties,thermal stability and dynamic mechanical properties of self-healing silicone elastomers and self-healing composites,as well as the sterilization ability of antibacterial elastomers and the sensing performance of composites as strain sensors were systematically discussed.The contents of this paper are as follows:1.Using?,?-aminopropyl polydimethylsiloxane(PDMS),p-benzaldehyde(TA)and3-aminophenylboronic acid(APB)as raw materials,a silicone self-healing elastomer was prepared by Schiff base reaction and dehydration reaction.The elastomer had good mechanical properties,with tensile strength of 2.54 MPa and elongation at break of 275.3%.Due to the existence of various reversible bonds,the material can complete the self-healing process under various conditions.The repair efficiency was 91.6%at room temperature,95.1%at high temperature and 85.5%in water.In addition,multi walled carbon nanotubes(MWCNTs)were compounded with polymer system to prepare repairable conductive composites,and their application potential as strain sensors was further explored.2.The MXene and the amino functionalized polysiloxane(PDMS)were modified by esterification and Schiff base reaction with asparagine(Asn)and 3,4-dihydroxybenzaldehyde(DHBA)as raw materials,respectively.A-MXene and D-PDMS were then composite to prepar a self-repairing conductive composite(A-MXene/D-PDMS).The reversibility of imine bonds and various hydrogen bonds in A-MXenes/D-PDMS made it have good tensile properties and high self-healing ability without external stimulation.The elongation of the composite with 10wt%A-MXenes was 81%,and its mechanical strength reached 1.81 MPa.After repair,the tensile properties and conductivity of the composites were 98.4%and 97.6%respectively.In addition,the practical value of conductive composite as strain sensor was further evaluated.Even after the process of disconnection and healing,conductive composite detected the tiny human movement accurately,including speech,swallowing and pressing.3.PDMS-DHBA and MWCNTs-DHBA were prepared by reaction of 3,4-dihydroxybenzaldehyde(DHBA)with aminofunctionalized polysiloxane(PDMS-NH₂)and aminofunctionalized multi wall carbon nanotubes(MWCNTs-NH₂)by Schiff base reaction.Then,the conductive nano materials were compounded with polymer system,and zinc ions were introduced by adding zinc chloride to develop self-healing silicone conductive nanocomposite elastomer(PDMS/MWCNTs-Zn²⁺).The elastic body can spontaneously achieve effective self-healing behavior through the reversibility of hydrogen bond,metal ligand bond and imine bond.The elongation at break of PDMS/10wt%MWCNTs-Zn²⁺was 169%,and the mechanical strength reached 4.39 MPa.After 24 hours of repair,the tensile properties of the composites can be restored to 92.9%.In addition,the reliability and sensitivity of PDMS/MWCNTs as strain sensor were evaluated.The GF value of the strain is 3.7673 at 0%?160%.Before and after self-healing,the elastomer can be successfully used to monitor the subtle movements of the human body,including smile and speaking.4.A self-repairing silicone elastomer(PDMS-TA-DAF-Zn)with antibacterial ability was prepared by Schiff base reaction and metal-ligand bond with p-benzenedioxaldehyde(TA),3,4-diaminofuran(DAF),?,?-aminopropyl polydimethylsiloxane(PDMS)and zinc chloride as raw materials.The first recovery rate of the silicone antibacterial material was89.5%.After repeated repair,the mechanical properties of the system were not significantly reduced.The antibacterial properties of PDMS-TA-DAF-Zn were evaluated by Escherichia coli and Staphylococcus aureus.The antibacterial efficiency was 99.9993%and 99.9997%respectively.5.The organosilicon network with disulfide bond was prepared by dehydration reaction between amino group and carboxyl group from thiooctanoic acid(TA)and amino functionalized polysiloxane(PDMS-NH₂).By introducing gold nanoparticles,self-curing conductive composite materials based on S-Au interaction were constructed.The dynamic S-Au bond effectively dissipated the energy generated by external forces and improved the tensile property of conductive elastomers.In addition,S-Au interaction had good photothermal effect,which made the elastomer heal rapidly under near infrared radiation,and the repair efficiency reached 92%.We further evaluated the performance of the conductive elastomer as a strain sensor.The sample can accurately monitor the bending of human joints and the changes of muscle state.