Preparation And Properties Of Dual Self-healing Microcapsules

During the transportation and employ,the materials will inevitably be cracked,damaged and broken due to external forces,lights and heat for a long time,which seriously affects its normal use.Inspired by the self-healing phenomenon of natural organisms,self-healing materials can successfully sense and repair damage through the interaction of internal structure or composition of materials.The introduction of self-healing properties not only extends the life of the material,but also significantly increases the level of safety and intelligence.According to whether the healing agents are implanted into the material,the self-healing materials can be divided into two categories:extrinsic-type and intrinsic-type.At present,the two self-healing methodological studies have gradually become clear,and the single repair mechanism and their respective problems are insufficient to meet the dual requirements of material self-healing ability and self-performance enhancement.In order to solve the defects of single repair,synchronously optimize the self-heal and strength of materials,and use the dual heal mechanism to synergistically strengthen the self-healing properties and mechanical strength of materials will become a research hotspot in the future.In this paper,we mainly cooperate with the two heal mechanisms of intrinsic and extrinsic,and use microcapsules with dual self-heal function by means of“Mussel-Inspired Chemistry”and“Click”chemistry.It is used as an additive to prepare polymer-based composite materials with excellent self-healing and mechanical properties.The content of this paper is mainly divided into the following three parts:1.Stellate mesoporous silica?STMS?was used as the reservoir of healing agent;Ethylene Glycol Dimethacrylate?EGDA?and Benzoin Isobutyl Ether?BIE?were used as the healing agent and photoinitiator,respectively.After that,STMS was loaded with EGDA and BIE,microcapsules were prepared based on the basic principle of mussel-inspired chemistry using polydopamine?PDA?coated STMS loaded with heal agentandphotoinitiator.Hydrogen-bondedpolymer poly?methyl-2-ureido-4-pyrimidinone-butyl acrylate??P?MAUPy-co-nBA??was prepared by atom transfer radical polymerization?ATRP?and it is modified on the surface of the microcapsules by“Clicking”chemistry.Microcapsules with dual self-healing properties were prepared by internal healing agent and external hydrogen bonding synergistically and complexed into polyacrylic acid?PAA?hydrogels.Through the characterization methods such as stretching,rheology and electron microscopy,the hydrogel material has excellent mechanical properties and self-healing performance,and the self-healing efficiency can reach more than 85%.2.Using acrylonitrile?AN?and butyl acrylate?nBA?as comonomer,azodiisobutyl?AIBN?and N,N-dimethylformamide?DMF?as initiator and solvent,respectively.The copolymer P?AN-co-nBA?of AN and nBA was synthesized by one-pot two-step method.Because of the nitrile group?-C?N?on the side chain of AN,the part of-C?N groups on the copolymer were modified to tetrazole group by the catalysis of sodium azide?NaN₃?and zinc chloride?ZnCl₂?.Based on the coordination between tetrazole group and Zn?II?,the self-healing material?Metallopolymers,MPs?with good self-healing properties was prepared at ambient temperature.After compounding the PDA-coated STMS microcapsules loaded with the biomass healing agent linseed oil?LO?,the self-healing and mechanical properties are further enhanced by the dual action of the coordination of catechol groups on the surface of PDA with Zn?II?and the internal healing agent.3.The LO was used as the biomass healing agent,and the STMS was loaded with LO.After that,the surface functionalization of the STMS was performed using a silane coupling agent?-methacryloxypropyl trimethoxyl silane?MPTS?with a double bond.Bifunctional microcapsules were prepared by chemical oxidation of polypyrrole?PPy?on their surface.The microcapsules and metal iron ions?Fe?III??are compounded into the PAA hydrogel,and the hydrogel materials with excellent self-healing properties were prepared by the synergistic action of the biomass healing agent inside the microcapsules and the coordination action of PPy and Fe?III?on the surface of the microcapsules.At the same time,the prepared double self-healing PAA hydrogel material has strong mechanical and electrical properties,and successfully realizes the effective detection of human body motion by the hydrogel flexible sensor.