The Applications Of Selenium-containing Dynamic Covalent Bonds In Light-responsive Self-assembly And Self-healing Materials

Dynamic covalent bonds are special kinds of covalent bonds that can break,form and recombine reversibly under external stimulations.The bond energy of the dynamic covalent bond is between the covalent bond and non-covalent bond,so it has unique stability and reversibility,and has been widely used in the construction of stimulusresponsive systems and the preparation of dynamic covalent materials.Seleniumcontaining dynamic covalent bonds consist of diselenide bonds(Se-Se),selenium-sulfur bonds(Se-S)and selenium-tellurium bonds(Se-Te).Their exchange reactions all show light wavelength dependence.Although the selenium-containing dynamic materials have been reported progressively in the past five years,achieving dynamic,mild and remote regulations to the properties of materials is still in its infancy when using the response to the visible light of selenium-containing dynamic bonds.This thesis studied the optical wavelength response of selenium-containing dynamic bonds in macromolecular assemblies,and then applied the characteristic of selenium-containing bonds in the remote self-healing materials.The main achievements of this paper are as follows:1)The selenium-sulfur(Se-S)bond containing photoresponsive polymeric assemblies were prepared and their controllable assembly and disassembly induced by different wavelengths of light were achieved.UV light was used to induce seleniumsulfur exchange reaction between polymers to prepare Se-S bond containing polymeric assemblies.The reaction process was characterized by the UV-VIS absorption spectrum and the gel permeation chromatography(GPC).Through the study of the mechanism,it could be confirmed that the exchange reaction between polymers go through free radical mechanism.In addition,visible light could induce the breaking of the selenium-sulfur(Se-S)bonds in the polymer vesicles,and then the vesicles therefore disassembled,which gave the potential for developing light-wavelength responsive dynamic materials.2)The selenium-containing composite materials with carbon nanotubes were prepared.Using a laser as a visible light source,the remote and rapid healing of conductive functions of selenium-containing polymeric composie materials was realized.Based on the dynamic exchange reaction of diselenide bonds under visible light,we have studied the conductivity healing process of composite materials under visible light by introducing diselenide bonds into crosslinked polyurethane materials.A remotely controlled conductivity self-healing process could be achieved by utilizing the blue laser as the light source.The gentleness of visible light sources could reduce the damage of polymer materials caused by ultraviolet light or heating induced self-healing.At the same time,the remote transmission characteristics of laser light sources also provide numerous possibilities for material applications.3)The remote and underwater self-healing of selenium-containing polymeric materials was achieved based on the characteristic that the optical response wavelength of diselenide bonds is consistent with the corresponding wavelength of the underwater blue window.Introducing diselenide bonds into the hydrophobic polymer backbone endowed the material with a remote healing function induced by underwater laser irradiation.This material was applied in the emergency healing scenario,simulating the accidental leakage of the underwater oil pipeline which could be contactlessly and rapidly repaired at a distance.