Polyurea composite coating based on MXene carbon dots as well as preparation method and application of polyurea composite coating

Abstract

The invention discloses a polyurea composite coating based on MXene at carbon dots. The composite coating is prepared by heating and curing a polyurea composite elastomer based on MXene at carbon dots and an organic solvent, the polyurea composite elastomer based on the MXene (at) carbon dots is prepared by mixing a polyurea elastomer and MXene (at) carbon dot powder; the polyurea elastomer is prepared from the following raw materials: isophorone diisocyanate, poly (propylene glycol) bis (2-aminopropyl ether), isophthaloyl hydrazine and 4, 4 '-diaminodiphenyl disulfide through a two-step condensation polymerization reaction. Based on the synergistic effect of dynamic hydrogen bonds and flexible disulfide bonds of a self-repairing polyurea elastomer structure in the composite coating, the self-repairing characteristic of the composite coating is remarkably enhanced, meanwhile, a brick mud structure is formed through uniform embedding of MXene at carbon dots, and the mechanical strength, corrosion resistance, heat stability and rapid self-repairing capacity of the composite coating are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-functional materials, and in particular to a polyurea composite coating based on MXene@carbon dots, and a preparation method and application thereof. Background Art

[0002] Traditional anticorrosion coatings utilize physical or chemical barriers to isolate the corrosive medium from the substrate, achieving substrate corrosion protection. While these coatings can mitigate substrate corrosion to a certain extent, they often have limitations, such as fragility, high maintenance costs, and environmental impact. Self-healing materials mimic the self-repair properties of living organisms, capable of self-healing and restoring the coating's original properties. After damage, they rely on endogenous repair mechanisms to repair the damage and restore its original strength and functionality, thereby extending the material's service life, reducing maintenance costs, and improving its environmental friendliness. Self-healing coatings hold great promise and offer significant economic value in applications such as deep-sea construction sites and large-scale chemical plants. Polyurea elastomers, due to their outstanding mechanical properties, rapid curing speed, chemical resistance, and wear resistance, are widely used in anticorrosion coatings for marine engineering, chemical equipment, bridge construction, and other fields. In recent years, research on self-healing polyurea elastomers has become a hot topic, incorporating self-healing technology into the development and application of polyurea elastomer materials, enabling them to restore their original properties upon damage. To further improve polyurea elastomer materials, researchers have conducted extensive modification studies. Single organic coatings often have deficiencies in corrosion resistance and mechanical properties. To improve the overall performance of the coating, various fillers are usually added to enhance the barrier and protective properties of the coating. The addition of fillers can effectively fill gaps and defects in the coating, reducing the possibility of penetration by corrosive media, thereby improving the protective effect of the coating. For example, by adding organic or inorganic materials, such as nano-modified silica and carbon nanotubes, and functional modifying groups such as flame retardants and fungicides, polyurea materials can be endowed with special functional properties, further meeting the application requirements of polyurea materials. However, high-performance polyurea materials have a short curing time, high construction performance and construction technology requirements, and high cost. In addition, the long-term performance stability in high temperature, high humidity or highly corrosive environments is poor.

[0003] Therefore, there is an urgent need to develop a new type of self-healing anti-corrosion elastomer that can enhance its self-healing properties while also having high mechanical strength, corrosion resistance, and photothermal conversion performance. Summary of the Invention

[0004] This invention discloses a polyurea composite coating based on MXene@carbon dots, its preparation method, and its application. The synergistic effect of the dynamic hydrogen bonds and flexible disulfide bonds within the self-healing polyurea elastomer structure significantly enhances the self-healing properties of the composite coating. Furthermore, the uniform embedding of MXene@carbon dots optimizes the composite's microstructure, forming a "brick-and-mortar" structure that significantly improves its mechanical strength, corrosion resistance, and thermal stability, giving the composite coating excellent overall performance.

[0005] The first object of the present invention is to provide a MXene@carbon dot-based polyurea composite coating, which is prepared by heating and curing a MXene@carbon dot-based polyurea composite elastomer and an organic solvent; the MXene@carbon dot-based polyurea composite elastomer is prepared by mixing a polyurea elastomer and MXene@carbon dot powder; the polyurea elastomer is prepared by a two-step polycondensation reaction using isophorone diisocyanate, poly(propylene glycol) bis(2-aminopropyl ether), isophthalic acid hydrazide and 4,4'-diaminodiphenyl disulfide as raw materials.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned MXene@carbon dot-based polyurea composite coating, the preparation method comprising:

[0007] S1: preparing a polyurea prepolymer: dissolving isophorone diisocyanate in N,N-dimethylacetamide to obtain a first solution; dissolving poly(propylene glycol) bis(2-aminopropyl ether) in N,N-dimethylacetamide to obtain a second solution; and dropwise adding the second solution to the first solution while continuously stirring to perform a first polycondensation reaction to obtain a polyurea prepolymer;

[0008] S2: preparing a polyurea elastomer by dissolving isophthalic acid hydrazide in N,N-dimethylacetamide and stirring uniformly to obtain a third solution; dissolving 4,4'-diaminodiphenyl disulfide in N,N-dimethylacetamide and stirring uniformly to obtain a fourth solution; and sequentially adding the third solution and the fourth solution to a polyurea prepolymer to carry out a second polycondensation reaction to obtain a polyurea elastomer;

[0009] S3 preparation of MXene@carbon dot-based polyurea composite elastomer: a single layer of MXene and carbon dot powder are mixed and dissolved in deionized water, stirred evenly, and freeze-dried to obtain MXene@carbon dot powder; the MXene@carbon dot powder is added to the polyurea elastomer for mixing reaction to obtain a MXene@carbon dot-based polyurea solution; the MXene@carbon dot-based polyurea solution is then poured into a mold and dried to obtain a MXene@carbon dot-based polyurea composite elastomer;

[0010] S4 prepares a polyurea composite coating based on MXene@carbon dots: adds a polyurea elastomer based on MXene@carbon dots to an organic solvent, stirs it evenly at a high temperature, and prepares it into a coating; the coating is preheated and evenly coated on a substrate, and a polyurea composite coating based on MXene@carbon dots is formed on the substrate through a heat curing treatment.

[0011] Specifically, the mass ratio of isophorone diisocyanate and poly(propylene glycol) bis(2-aminopropyl ether) in step S1 is (1-2):(5-6); the temperature of the first polycondensation reaction is 25-30° C., and the time is 2-4 hours.

[0012] Specifically, the mass ratio of isophthalic acid hydrazide, 4,4'-diaminodiphenyl disulfide and polyurea prepolymer in step S2 is (1-5):1:(50-55); the temperature of the first polycondensation reaction is 50-60° C., and the time is 16-22 hours.

[0013] Specifically, the preparation method of the single-layer MXene in step S3 includes: adding lithium fluoride to a hydrochloric acid solution and then adding titanium aluminum carbide powder to perform an etching reaction to obtain a multilayer MXene; washing, centrifuging and oscillating the multilayer MXene to obtain a single-layer MXene.

[0014] Specifically, the mass ratio of lithium fluoride to titanium aluminum carbide in step S3 is (1.3-1.8):1; the temperature of the etching reaction is 50-60° C., and the time is 28-32 hours.

[0015] Specifically, the method for preparing the carbon dot powder in step S3 includes: adding citric acid and urea to N,N-dimethylformamide in sequence to obtain a fifth solution; and heat-insulating the fifth solution, followed by cooling, dialyzing, and drying to obtain the carbon dot powder.

[0016] Specifically, the mass ratio of citric acid to urea in step S3 is 1:2; the temperature of the heat preservation treatment is 150-180° C., and the time is 4-8 hours.

[0017] Specifically, in step S3, the mass ratio of the single-layer MXene to the carbon dot powder is 1:1; the freeze-drying time is 22 to 26 hours; and the mass ratio of the polyurea elastomer to the MXene@carbon dot powder is (10:50):0.1.

[0018] Specifically, the reaction temperature of the mixing reaction in step S3 is 50-60°C, and the reaction time is 30-60 min. The drying treatment includes: first placing the MXene@carbon dot-based polyurea solution in a vacuum drying oven at 80-90°C for 10-12 hours, and then placing it in a forced air drying oven at 80-90°C for 40-48 hours.

[0019] Specifically, the organic solvent in step S4 is xylene; the concentration of the coating is 300-400 mg@mL; the temperature of the heating and curing treatment is 50-60° C., and the time is 20-24 hours.

[0020] The third object of the present invention is to provide a polyurea composite coating based on MXene@carbon dots as described above for use in marine devices and equipment.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] (1) The present invention develops a novel self-healing polyurea composite elastomer, which synergistically introduces disulfide bonds and triple hydrogen bonds into the polymer hard segment. Under the synergistic effect of disulfide bonds and hydrogen bonds, the composite elastomer has both high mechanical properties and self-healing ability. At the same time, the uniform embedding of MXene@carbon dot nanomaterials forms a "brick-and-mortar" structure, which greatly improves its mechanical strength, corrosion resistance, and thermal stability. This gives the MXene@carbon dot-based polyurea composite coating excellent comprehensive performance.

[0023] (2) The present invention uses a solution polymerization method to prepare a polypropylene glycol bis (2-aminopropyl ether) (ED2000), isophorone diisocyanate (IPDI), isophthalic acid hydrazide (IPDH) and 4,4'-diaminodiphenyl disulfide (ASD) based on disulfide bonds (PU S ) and hydrogen bonds (PU H ) synergistic self-healing polyurea elastomer; triple hydrogen bonds in the polyurea composite elastomer enhance the interaction between molecular chains, thereby improving the strength of the material; disulfide bonds can break and reform under heating conditions, while hydrogen bonds provide additional dynamic interactions, facilitating the repair process; by optimizing the optimal ratio of hard segment chain extenders, the synergistic effect of disulfide bonds and hydrogen bonds enables the polyurea elastomer to have both good mechanical properties and self-healing ability;

[0024] (3) Monolayer MXene (Ti3C2T x ) and carbon dots (CD) were compounded and added into the prepared polyurea elastomer as fillers. By optimizing the best ratio, the polyurea composite elastomer (CD@Ti3C2T x -PU HS ) has both high thermal stability, tensile strength and toughness; MXene@carbon dot composite filler (CD@Ti3C2T x) enables the polyurea composite elastomer to maintain excellent self-healing properties while also having recyclability; and the excellent photothermal conversion performance of MXene@carbon dot composite filler can enable the polyurea composite elastomer to quickly repair in a short time; when applied to the coating, the carbon dots self-assemble onto the single-layer MXene through non-covalent bonds, and the presence of free carbon dots in the coating also promotes the formation of a denser protective layer in the coating, further improving the corrosion resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 (a) Transmission electron microscopy image of CD@Ti3C2Tx prepared in Example 2 of the present invention; Figure 1 (b) Transmission electron microscopy image of Ti3C2Tx prepared in Example 2 of the present invention; Figure 1 (c) is a transmission electron micrograph of the CD prepared in Example 2 of the present invention;

[0026] Figure 2 (a) is the 3-101H NMR spectrum of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 2 (b) 3-101H NMR spectrum of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 2 (c) 3-101H NMR spectrum of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 2 (d) 3-101H NMR spectrum of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention;

[0027] Figure 3 (a) Comparison of stress-strain curves of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention; Figure 3 (b) Toughness diagrams of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention;

[0028] Figure 4 (a) is an AFM image of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 4 (b) AFM image of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 4 (c) AFM image of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 4 (d) AFM image of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention;

[0029] Figure 5 (a) is a comparison of the TGA curves of CD@Ti3C2Tx-PUHS2.5 prepared in Examples 1-3 of the present invention; Figure 5 (b) is a comparison of the DTG curves of CD@Ti3C2Tx-PUHS2.5 prepared in Examples 1-3 of the present invention;

[0030] Figure 6 (a) is a graph showing the elastic storage modulus of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention; Figure 6 (b) Elastic loss modulus curves of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention; Figure 6 (c) Loss tangent temperature curves of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention;

[0031] Figure 7 (a) Stress-strain curve of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention after solvent recovery; Figure 7 (b) is a stress-strain curve of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention after hot pressing and recovery;

[0032] Figure 8 (a) is a tensile graph of 0.5%-CD@Ti3C2Tx-PUHS2.5 after self-repair prepared in Example 2 of the present invention; Figure 8 (b) is the stress-strain diagram of the self-healed 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 8 (c) Repair efficiency of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention at 80°C for 12 h;

[0033] Figure 9 (a) is a microscopic image of the scratch healing of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 9 (b) is a microscopic image of the scratch healing of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 9 (c) Scratch healing microscopy image of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 9 (d) Scratch healing microscopy image of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention;

[0034] Figure 10 (a) Stress-strain diagram of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention under infrared light irradiation for 10s; Figure 10 (b) Healing efficiency of UHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention under infrared light irradiation for 10 s;

[0035] Figure 11 The water absorption test graphs of different MXene@carbon dot-based polyurea composite coatings prepared in Comparative Example 1 and Examples 1-3 of the present invention are shown;

[0036] Figure 12 (a) is the Nyquist plot of the polyurea coating prepared in Comparative Example 1 of the present invention; Figure 12 (b) Nyquist plot of the MXene@carbon dot-based polyurea composite coating prepared in Example 2 of the present invention. Specific implementation plan

[0037] The following will combine the contents in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not used to limit the present invention.

[0038] Example 1

[0039] S1: 2.989 g of isophorone diisocyanate (IPDI) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) to obtain a first solution; 16 g of poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was dropwise added to the first solution, and the mixture was continuously stirred at 25° C. and subjected to a first polycondensation reaction for 3 h to obtain a polyurea prepolymer a;

[0040] S2: 0.669 g of isophthalic acid hydrazide (IPDH) was dissolved in 10 mL of DMAc and stirred to obtain a third solution; 0.342 g of 4,4'-diaminodiphenyl disulfide (ASD) was dissolved in 5 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer a in sequence to carry out a second polycondensation reaction at 50°C for 20 h to obtain a polyurea elastomer a, which was recorded as a-PU HS2.5 ;

[0041] S3MXene is synthesized by etching the Al atomic layer in the Ti3AlC2 phase; 1.6 g of lithium fluoride (LiF) is added to 20 mL of 9 mol / L hydrochloric acid solution (HCl), stirred for 5 min, and then 1 g of titanium aluminum carbide (Ti3AlC) powder (particle size <38 μm) is added to etch the reaction at 50 ° C for 30 h to obtain multilayer MXene; then, the multilayer MXene is rinsed with deionized water and centrifuged multiple times (3500 rpm, 5 min) until the pH of the supernatant reaches 6; the multilayer MXene is peeled off by oscillating with an oscillator for 10 min, and then centrifuged at 3500 rpm for 30 min. The supernatant is collected and freeze-dried for 24 h to obtain a single-layer MXene powder, which is recorded as a-Ti3C2T x 2 g of anhydrous citric acid (CA) and 4 g of urea were added to 20 ml of N,N-dimethylformamide (DMF) in sequence and stirred magnetically until dissolved to obtain a fifth solution. The fifth solution was then transferred to a polytetrafluoroethylene autoclave and kept at 160°C for 6 h, cooled at room temperature, and dialyzed in deionized water for 24 h (membrane cutoff: 1000 kDa). The black carbon dot powder was obtained by freeze-drying, which was designated as a-CD. 4 g of a-Ti3C2T x The mixture was mixed with 4 g of a-CD powder and dissolved in 60 mL of deionized water. The mixture was ultrasonicated for 15 min, mechanically stirred at 25 °C for 6 h (1000 rpm), and freeze-dried for 24 h to obtain MXene@carbon dot powder a, which was designated as a-CD@Ti3C2T x ; 0.04g of a-CD@Ti3C2T x Add 20g of a-PU HS2.5 The mixture was mixed and reacted at 50 °C for 30 min to obtain a polyurea solution a based on MXene@carbon dots. The polyurea solution a based on MXene@carbon dots was then poured into a polytetrafluoroethylene mold and dried in a vacuum drying oven at 80 °C for 12 h. The mixture was then placed in a forced air drying oven and dried at 80 °C for 48 h to obtain a polyurea composite elastomer based on MXene@carbon dots, which was designated as 0.2-CD@Ti3C2T x -PU HS2.5 ;

[0042] S4 will 0.2-CD@Ti3C2T x -PU HS2.5 Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating a with a concentration of 300 mg / mL; preheat coating a at 50°C for 30 minutes, evenly coat it on the working electrode after preheating, and heat and cure it in a vacuum drying oven at 50°C for 24 hours to form a polyurea composite coating based on MXene@carbon dots on the working electrode.

[0043] Example 2

[0044] S1: 2.989 g of isophorone diisocyanate (IPDI) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) to obtain a first solution; 16 g of poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was dropwise added to the first solution, and the mixture was continuously stirred at 25° C. and subjected to a first polycondensation reaction for 3 h to obtain a polyurea prepolymer b;

[0045] S2: 0.669 g of isophthalic acid hydrazide (IPDH) was dissolved in 10 mL of DMAc and stirred to obtain a third solution; 0.342 g of 4,4'-diaminodiphenyl disulfide (ASD) was dissolved in 5 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer b in sequence to carry out a second polycondensation reaction at 50°C for 20 h to obtain a polyurea elastomer b, which was recorded as b-PU HS2.5 ;

[0046] S3: 1.6 g of LiF was added to 20 mL of 9 mol / L HCl, stirred for 5 min, and then 1 g of Ti3AlC powder (particle size < 38 μm) was added and etched at 50 °C for 30 h to obtain multilayer MXene. Then, the multilayer MXene was rinsed with deionized water and centrifuged several times (3500 rpm, 5 min) until the pH of the supernatant reached 6. The multilayer MXene was peeled off by oscillating with an oscillator for 10 min, and then centrifuged at 3500 rpm for 30 min. The supernatant was collected and freeze-dried for 24 h to obtain a single-layer MXene powder, which was recorded as b-Ti3C2T x 2 g of CA and 4 g of urea were added to 20 ml of DMF in sequence and stirred magnetically until dissolved to obtain a fifth solution. The fifth solution was then transferred to a polytetrafluoroethylene autoclave and kept at 160°C for 4 h, cooled at room temperature, and dialyzed in deionized water for 24 h (membrane cutoff: 1000 kDa). The black carbon dot powder was obtained by freeze-drying, which was designated as b-CD. 4 g of b-Ti3C2T xThe mixture was mixed with 4 g of b-CD powder and dissolved in 60 mL of deionized water. The mixture was ultrasonicated for 15 min, mechanically stirred at 25 °C for 6 h (1000 rpm), and freeze-dried for 24 h to obtain MXene@carbon dot powder b, which was designated as b-CD@Ti3C2T x ; 0.1g of b-CD@Ti3C2T x Add 20g of b-PU HS2.5 The mixture was mixed and reacted at 50 ° C for 30 min to obtain a polyurea solution b based on MXene@carbon dots. The polyurea solution b based on MXene@carbon dots was then poured into a polytetrafluoroethylene mold and dried in a vacuum drying oven at 90 ° C for 12 h, and then placed in a forced air drying oven at 80 ° C for 48 h to obtain a polyurea composite elastomer based on MXene@carbon dots, which was recorded as 0.5%-CD@Ti3C2T x -PU HS2.5 ;

[0047] S4 0.5%-CD@Ti3C2T x -PU HS2.5 Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating b with a concentration of 300 mg / mL; preheat coating b at 50°C for 30 minutes, evenly coat it on the working electrode after preheating, and heat and cure it in a vacuum drying oven at 60°C for 20 hours to form a polyurea composite coating based on MXene@carbon dots on the working electrode.

[0048] Example 3

[0049] S1: 2.989 g of isophorone diisocyanate (IPDI) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) to obtain a first solution; 16 g of poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was added dropwise to the first solution, and the mixture was continuously stirred at 25° C. and subjected to a first polycondensation reaction for 3 h to obtain a polyurea prepolymer c;

[0050] S2: 0.669 g of isophthalic acid hydrazide (IPDH) was dissolved in 10 mL of DMAc and stirred to obtain a third solution; 0.342 g of 4,4'-diaminodiphenyl disulfide (ASD) was dissolved in 5 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer c in sequence to carry out a second polycondensation reaction at 50°C for 20 h to obtain a polyurea elastomer c, which was recorded as c-PU HS2.5 ;

[0051] S3: 1.8 g of LiF was added to 20 mL of 9 mol / L HCl, stirred for 5 min, and then 1 g of Ti3AlC powder (particle size < 38 μm) was added and etched at 50 °C for 30 h to obtain multilayer MXene. Then, the multilayer MXene was rinsed with deionized water and centrifuged several times (3500 rpm, 5 min) until the pH of the supernatant reached 6. The multilayer MXene was peeled off by oscillating with an oscillator for 10 min, and then centrifuged at 3500 rpm for 30 min. The supernatant was collected and freeze-dried for 24 h to obtain a single-layer MXene powder, which was recorded as c-Ti3C2T x 2 g of CA and 4 g of urea were added to 20 ml of DMF in sequence and stirred magnetically until dissolved to obtain a fifth solution. The fifth solution was then transferred to a polytetrafluoroethylene autoclave and kept at 160°C for 4 h, cooled at room temperature, and dialyzed in deionized water for 24 h (membrane cutoff: 1000 kDa). The black carbon dot powder was obtained by freeze-drying, which was designated as c-CD. 4 g of c-Ti3C2T x The mixture was mixed with 4 g of c-CD powder and dissolved in 60 mL of deionized water. The mixture was ultrasonicated for 15 min, mechanically stirred at 25 °C for 6 h (1000 rpm), and freeze-dried for 26 h to obtain MXene@carbon dot powder c, which was designated as c-CD@Ti3C2T x ; 0.2g of c-CD@Ti3C2T x Add 20g of c-PU HS2.5 The mixture was mixed and reacted at 50 ° C for 30 min to obtain a polyurea solution c based on MXene@carbon dots. The polyurea solution c based on MXene@carbon dots was then poured into a polytetrafluoroethylene mold and dried in a vacuum drying oven at 80 ° C for 12 h. It was then placed in a forced air drying oven and dried at 80 ° C for 48 h to obtain a polyurea composite elastomer based on MXene@carbon dots, which was recorded as 1%-CD@Ti3C2T x -PU HS2.5 ;

[0052] S4 will 1%-CD@Ti3C2T x -PU HS2.5 Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating c with a concentration of 300 mg / mL; preheat coating c at 50°C for 30 minutes, evenly coat it on the working electrode after preheating, and heat and cure it in a vacuum drying oven at 55°C for 24 hours to form a polyurea composite coating based on MXene@carbon dots on the working electrode.

[0053] Example 4

[0054] S1: 5.876 g of IPDI was dissolved in 3 mL of MAc to obtain a first solution; 15 g of ED2000 was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was added dropwise to the first solution, and the mixture was continuously stirred at 30° C. and subjected to a first polycondensation reaction for 4 h to obtain a polyurea prepolymer d;

[0055] S2: 1.248 g of IPDH was dissolved in 12 mL of DMAc and stirred to obtain a third solution; 0.412 g of ASD was dissolved in 6 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer d in sequence to carry out a second polycondensation reaction at 60 ° C for 16 h to obtain a polyurea elastomer d, which was recorded as d-PU HS ;

[0056] S3MXene is synthesized by etching the Al atomic layer in the Ti3AlC2 phase; 1.3 g of LiF is added to 20 mL of 9 mol / L HCl, stirred for 5 min, and then 1 g of Ti3AlC powder (particle size <38 μm) is added and etched at 60 ° C for 30 h to obtain multilayer MXene; then, the multilayer MXene is rinsed with deionized water and centrifuged multiple times (3500 rpm, 5 min) until the pH of the supernatant reaches 6; the multilayer MXene is peeled off by oscillating with an oscillator for 10 min, and then centrifuged at 3500 rpm for 30 min. The supernatant is collected and freeze-dried for 24 h to obtain a single-layer MXene powder, which is recorded as d-Ti3C2T x 2 g of CA and 4 g of urea were added to 20 ml of DMF in sequence and stirred magnetically until dissolved to obtain a fifth solution. The fifth solution was then transferred to a polytetrafluoroethylene autoclave and kept at 160°C for 6 h, cooled at room temperature, and dialyzed in deionized water for 24 h (membrane cutoff: 1000 kDa). The black carbon dot powder was obtained by freeze-drying, which was designated as d-CD. 4 g of d-Ti3C2T x The mixture was mixed with 4 g of d-CD powder and dissolved in 60 mL of deionized water. The mixture was ultrasonicated for 15 min, mechanically stirred at 30 °C for 6 h (1000 rpm), and freeze-dried for 22 h to obtain MXene@carbon dot powder d, which was designated as d-CD@Ti3C2T x ; 0.1g of a-CD@Ti3C2T x Add 20g of a-PU HS2.5The mixture was mixed and reacted at 60 °C for 40 min to obtain a polyurea solution d based on MXene@carbon dots. The polyurea solution d based on MXene@carbon dots was then poured into a polytetrafluoroethylene mold and dried in a vacuum drying oven at 90 °C for 10 h. The polyurea composite elastomer based on MXene@carbon dots was obtained, which was recorded as d-CD@Ti3C2T x -PU HS2.5 ;

[0057] S4 d-CD@Ti3C2T x -PU HS2.5 Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating d with a concentration of 300 mg / mL; preheat coating d at 50°C for 30 minutes, evenly coat it on the working electrode after preheating, and heat and cure it in a vacuum drying oven at 50°C for 24 hours to form a polyurea composite coating based on MXene@carbon dots on the working electrode.

[0058] Example 5

[0059] S1: 3.457 g of IPDI was dissolved in 3 mL of MAc to obtain a first solution; 15 g of ED2000 was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was added dropwise to the first solution, and the mixture was continuously stirred at 25°C for 2 h to perform a first polycondensation reaction to obtain a polyurea prepolymer e;

[0060] S2: 4.065 g of IPDH was dissolved in 24 mL of DMAc and stirred to obtain a third solution; 0.832 g of ASD was dissolved in 12 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer e in sequence to carry out a second polycondensation reaction at 55°C for 22 h to obtain a polyurea elastomer e, which was recorded as e-PU HS ;

[0061] S3: 1.8 g of LiF was added to 20 mL of 9 mol / L HCl, stirred for 5 min, and then 1 g of Ti3AlC powder (particle size < 38 μm) was added and etched at 55 °C for 32 h to obtain multilayer MXene. Then, the multilayer MXene was rinsed with deionized water and centrifuged several times (3500 rpm, 5 min) until the pH of the supernatant reached 6. The multilayer MXene was peeled off by oscillating with an oscillator for 10 min, and then centrifuged at 3500 rpm for 30 min. The supernatant was collected and freeze-dried for 24 h to obtain a single-layer MXene powder, which was recorded as e-Ti3C2T x2 g of CA and 4 g of urea were added to 20 ml of DMF in sequence and stirred magnetically until dissolved to obtain a fifth solution. The fifth solution was then transferred to a polytetrafluoroethylene autoclave and kept at 180°C for 6 h, cooled at room temperature, and dialyzed in deionized water for 24 h (membrane cutoff: 1000 kDa). The black carbon dot powder was obtained by freeze-drying, which was designated as e-CD. 4 g of e-Ti3C2T x The mixture was mixed with 4 g of e-CD powder and dissolved in 60 mL of deionized water. The mixture was ultrasonicated for 15 min, mechanically stirred at 25 °C for 6 h (1000 rpm), and freeze-dried for 26 h to obtain MXene@carbon dot powder e, which was designated as e-CD@Ti3C2T x ; 0.04g of 0.2-CD@Ti3C2T x Add 20g of e-PU HS The mixture was mixed and reacted at 55 °C for 40 min to obtain a polyurea solution e based on MXene@carbon dots. The polyurea solution e based on MXene@carbon dots was then poured into a polytetrafluoroethylene mold and dried in a vacuum drying oven at 85 °C for 11 h. The mixture was then placed in a forced air drying oven and dried at 85 °C for 45 h to obtain a polyurea composite elastomer based on MXene@carbon dots, which was designated as e-CD@Ti3C2T x -PU HS ;

[0062] S4 will e-CD@Ti3C2T x -PU HS Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating e with a concentration of 300 mg / mL; preheat coating c at 50°C for 30 minutes, evenly coat it on the working electrode after preheating, and heat and cure it in a vacuum drying oven at 55°C for 24 hours to form a polyurea composite coating based on MXene@carbon dots on the working electrode.

[0063] Comparative Example 1

[0064] Preparation of CD-free @ Ti3C2T x Polyurea coating:

[0065] S1: 2.989 g of isophorone diisocyanate (IPDI) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) to obtain a first solution; 16 g of poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) was dissolved in 16 mL of DMAc to obtain a second solution; the second solution was dropwise added to the first solution, and the mixture was continuously stirred at 25° C. and subjected to a first polycondensation reaction for 3 h to obtain a polyurea prepolymer A;

[0066] S2: 0.669 g of isophthalic acid hydrazide (IPDH) was dissolved in 10 mL of DMAc and stirred to obtain a third solution; 0.342 g of 4,4'-diaminodiphenyl disulfide (ASD) was dissolved in 5 mL of DMAc and stirred to obtain a fourth solution; the third solution and the fourth solution were slowly added to the polyurea prepolymer A in sequence to carry out a second polycondensation reaction at 50°C for 20 hours to obtain polyurea elastomer A, which was recorded as PU HS2.5 ;

[0067] S3 will PU HS2.5 Add to xylene and heat at 50°C to ensure complete dissolution to prepare coating A with a concentration of 300 mg / mL; preheat coating A at 50°C for 30 minutes, evenly apply it on the substrate after preheating, and heat and cure it in a vacuum drying oven at 50°C for 24 hours to form a polyurea coating on the working electrode.

[0068] Performance Testing

[0069] Transmission electron microscopy images reveal that Ti3C2T x , CD and CD@Ti3C2T x The microstructure of Figure 1 (a) CD@Ti3C2T prepared in Example 2 of the present invention x Transmission electron micrograph of Figure 1 (b) Ti3C2T prepared in Example 2 of the present invention x Transmission electron micrograph of Figure 1 (c) is a transmission electron micrograph of a CD prepared in Example 2 of the present invention; Figure 1 It can be seen that Ti3C2T x It is a thin sheet with a large specific surface area. The carbon dots are in the shape of small spheres and are self-assembled into Ti3C2T x Ti3C2T did not change after x Layered structure. x Compared with nanosheets, CD@Ti3C2T x The surface of the nanosheets is enriched with nitrogen and evenly distributed, which confirms that the carbon dots are successfully attached to the Ti3C2T x The surface of the nanosheets.

[0070] In order to verify the CD@Ti3C2T x -PU HS2.5 The successful synthesis and chemical structure of the product were analyzed by 400MHz H NMR spectrum. Figure 2 (a) is the 3-101H NMR spectrum of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 2(b) 3-101H NMR spectrum of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 2 (c) 3-101H NMR spectrum of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention;

[0071] Figure 2 (d) is the 3-101H NMR spectrum of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention; 1 In the H NMR spectrum, the hydrogen atoms in the urea bond domain belong to the amino (-NH-) component, and their nuclear magnetic resonance signals are usually distributed in the higher chemical shift region, specifically in the range of about 7-10ppm. The peak shape in this region often shows broad and fuzzy characteristics. This phenomenon is mainly attributed to the hydrogen bond interaction formed between the hydrogen atoms in the urea bond and the adjacent carbonyl group (-C=O-). The presence of hydrogen bonds significantly disturbs the chemical environment of hydrogen atoms, resulting in broadening and blurring of their nuclear magnetic resonance signals. In addition, the electronic effect of the urea bond also has a significant effect on the chemical shift of hydrogen atoms, further exacerbating the broadening and blurring of the peak shape. The hydrogen atoms contained in the amide group are 1 The signals in the H NMR spectrum usually appear in the chemical shift range of 3-5ppm. Compared with the urea bond region, the signals in this range are clearer and accurately reflect the specific chemical environment of the hydrogen atoms in the amide group. It is particularly noteworthy that the strong peaks in the range of 3 to 4ppm mainly correspond to the hydrogen atoms on the methylene (-CH2-) structural unit. The signals of the methylene hydrogen atoms in this chemical shift range show strong intensity and sharp peak shape, which is related to their stable position in the molecular structure and relatively constant chemical environment. The above chemical structure analysis results show that the CD surface is rich in various functional groups, including amino (-NH2), hydroxyl (-OH) and carboxyl (-COOH). These functional groups are not only hydrophilic, but can also react chemically with isocyanate (-NCO), which may produce micro-crosslinking effects in the polyurea molecular chain, thereby improving the mechanical properties and chemical stability of the material. In addition, Ti3C2T x The surface contains oxygen, hydroxyl and other functional groups, and CD can interact with Ti3C2T through its amino functional groups. x The oxygen atoms or hydroxyl groups on the surface generate hydrogen bonding interactions, which promotes the CD in Ti3C2T x Uniform assembly of the surface.

[0072] In order to verify the CD@Ti3C2T xThe influence of nanosheets on the mechanical properties of polyurea composite elastomers was studied by tensile testing the polymers at room temperature using a universal tensile testing machine at a speed of 500 mm / min to obtain stress-strain curves and toughness values. Figure 3 (a) Comparison of stress-strain curves of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention; Figure 3 (b) Toughness diagram of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention; Figure 3 It can be seen that by adding CD@Ti3C2T x Nanosheets, the mechanical properties of the material are greatly improved. When the addition amount is only 0.5%, PU HS2.5 The tensile strength, toughness and elongation at break increased from 6.05MPa and 36.71MJ / m 3 Significantly increased to 23.8MPa, 93.0MJ / m 3 , while the elongation at break remains basically unchanged. Its tensile strength and toughness are PU HS2.5 3.9 times and 2.6 times of that of Ti3C2T after CD modification. x The nanosheets have better compatibility with the polyurea matrix.

[0073] The microphase separation structure of the polymer was detected by atomic force microscopy (AFM). Figure 4 (a) is an AFM image of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 4 (b) AFM image of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 4 (c) AFM image of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention;

[0074] Figure 4 (d) is an AFM image of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention; Figure 4 As shown, the AFM images show clear soft and hard domain boundaries, especially for 0.5%-CD@Ti3C2T x -PU HS2.5 Materials, hydrogen bonds, disulfide bonds and CD@Ti3C2T x The nanosheets form a special three-dimensional polymer network. It can be seen that the breaking of hydrogen bonds and disulfide bonds can dissipate energy. CD modified Ti3C2T x Enhanced nanosheets and PU HS2.5 The hydrogen bond density at the interface forms a specific phase separation microstructure, which restricts the mobility of the soft segment and improves the mechanical properties.

[0075] It can be observed from the thermogravimetric curves and the corresponding differential thermogravimetric curves that the addition of CD@Ti3C2T x A series of significant changes in polyurea composite elastomers. Figure 5 (a) is a comparison of the TGA curves of CD@Ti3C2Tx-PUHS2.5 prepared in Examples 1-3 of the present invention; Figure 5 (b) is a comparison of the DTG curves of CD@Ti3C2Tx-PUHS2.5 prepared in Examples 1-3 of the present invention; It can be seen from the TGA curve that as CD@Ti3C2T x As the amount of nanosheets added increases, the temperature at which the material begins to lose weight (T 5％ ) gradually increased (from 272.68℃ to 289.49℃). From the corresponding differential thermogravimetric analysis (DTG) curve, it can be seen that CD@Ti3C2T x -PU HS2.5 The thermal degradation process of the composite elastomer can be divided into two distinct stages. Before 270℃, it is mainly the decomposition of some surface moisture and residual solvents, and the thermal weight loss in this stage is relatively small; secondly, in the temperature range of 270-400℃, it is mainly the decomposition of CD@Ti3C2T x -PU HS2.5 The degradation of urea bonds and benzene rings in the molecular chain. The thermal weight loss at this stage is more significant, chemical bonds begin to break and the molecular structure is destroyed. The maximum decomposition temperature of the material (T max ) also with CD@Ti3C2T x The temperature increased with the addition amount (from 383.82℃ to 387.60℃), T 5％ and T max The increase of CD@Ti3C2T x The addition of nanosheets significantly improves the thermal stability of the material. x Nanosheets and PU HS2.5 More hydrogen bonds are formed between the matrices, which can provide additional thermal stability at high temperatures, effectively inhibiting the thermal motion and degradation of the molecular chains, thereby improving the thermal degradation resistance of the material; secondly, CD@Ti3C2T x The two-dimensional structure and large surface area of ​​the nanosheet act as a physical barrier, preventing the rapid transfer of heat, slowing down the thermal conduction rate within the material, and improving the thermal stability of the material. x The dispersion of nanosheets and interfacial interactions form heat conduction paths in the composite material, improving the overall thermal stability of the material.

[0076] The CD@Ti3C2T x -PUHS2.5 dynamic behavior. Figure 6 (a) is a graph showing the elastic storage modulus of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention; Figure 6 (b) Elastic loss modulus curves of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention; Figure 6 (c) is the loss tangent temperature curve of PUHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 2-3 of the present invention; Figure 6 From the storage modulus (G′) and loss modulus (G″) curves of (ab), it can be seen that PU HS2.5 , 0.5%-CD@Ti3C2T x -PU HS2.5 and 1%-CD@Ti3C2T x -PU HS2.5 The storage modulus (G′) of CD@Ti3C2T is higher than the loss modulus (G″), so the polymer is in a rubbery state. From the loss factor (tanδ) curve in 6(c), it can be seen that the three elastomers have peaks at around -35℃, and with the increase of CD@Ti3C2T x With the addition of CD@Ti3C2T x After the addition of CD@Ti3C2T, the peak value of tanδ increases greatly, and the increase in the peak area indicates that the dissipation capacity of the material has been improved, thereby enhancing the toughness. x The polyurea elastomer made from nanosheets not only shows significant improvement in mechanical properties, but also exhibits excellent recycling characteristics.

[0077] Figure 9 (a) 0.5%-CD@Ti3C2T prepared in Example 2 of the present invention x -PUHS 2.5 The stress-strain curve of the solvent recovery; Figure 7 (a) Stress-strain curve of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention after solvent recovery; Figure 7 (b) is a stress-strain curve of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention after hot pressing and recovery; Figure 7 As shown, after one recycling, 0.5%-CD@Ti3C2T x -PU HS2.5The fracture strength recovery rates of the elastomers by hot pressing and solution recovery were as high as 96.7% and 98.4%, respectively. This indicates that both recycling methods can effectively retain the mechanical properties of the material. After three recycling cycles, 0.5%-CD@Ti3C2T x -PU HS2.5 The mechanical properties of the recycled elastomer remain above 90% of the original. This recyclability reduces the cost of using the material and reduces the environmental pollution caused by waste materials, which is in line with the concept of sustainable development. x The introduction of nanosheets not only improves the HS2.5 The mechanical properties of the material also enhance its recyclability.

[0078] In order to study CD@Ti3C2T x Nanosheets on PU HS2.5 To investigate the effect of self-healing performance, a dumbbell-shaped sample of 4*75*2 mm was cut into two pieces. The two cut surfaces were allowed to naturally contact at a specific constant temperature for a specific time without applying any external force. Then a tensile test was performed. The experiment was repeated three times and the average value was taken. Figure 8 (a) is a tensile graph of 0.5%-CD@Ti3C2Tx-PUHS2.5 after self-repair prepared in Example 2 of the present invention; Figure 8 (b) is the stress-strain diagram of the self-healed 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 8 (c) Repair efficiency of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention at 80°C for 12 h; Figure 9 (a) is a microscopic image of the scratch healing of PUHS2.5 prepared in Comparative Example 1 of the present invention; Figure 9 (b) is a microscopic image of the scratch healing of 0.2%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 1 of the present invention; Figure 9 (c) Scratch healing microscopy image of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention; Figure 9 (d) Scratch healing micrograph of 1%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 3 of the present invention; x After nanosheets, CD@Ti3C2T x -PU HS2.5 The self-healing efficiency of the composite material showed a trend of increasing first and then decreasing. After repairing at 80℃ for 12h, 0.2%-CD@Ti3C2T x -PU HS2.5 and 0.5%-CD@Ti3C2T x -PU HS2.5The repair efficiencies of CD@Ti3C2T reached 95.9% and 95.2% respectively. x When the amount of nanosheets added is small, the self-healing efficiency of the composite material is improved by about 3%. After repair at 80℃ for 30min, 0.2%-CD@Ti3C2T x -PU HS2.5 and 0.5%-CD@Ti3C2T x -PU HS2.5 The surface scratches of CD@Ti3C2T are basically gone. x Nanosheets and PU HS2.5 A large number of interfacial hydrogen bonds are formed between the chains, and the hydrogen bonds and the synergistic effect with the disulfide bonds jointly promote the self-healing process. x When the content of nanosheets increases to 1wt%, the self-healing performance of the composite material begins to decline, and the repair efficiency drops to 90.1%. This phenomenon can be attributed to the large amount of CD@Ti3C2T x Nanosheets exist in PU HS2.5 The matrix increases the rigidity of the material, restricts the movement of the molecular chains, hinders the reformation of hydrogen bonds and disulfide bonds, and affects the rearrangement of molecular chains and the reconstruction of interfacial hydrogen bonds during the self-repair process.

[0079] The simulated damage of the material was irradiated with 808nm 0.5W near-infrared light, and CD@Ti3C2T was found. x Nanosheets can quickly absorb infrared light and convert it into heat energy, thereby significantly increasing the local temperature of the material in a short period of time. x -PU HS2.5 Near-infrared light repair ability, stress-strain curve and self-repair efficiency of the material. Figure 10 (a) Stress-strain diagram of 0.5%-CD@Ti3C2Tx-PUHS2.5 prepared in Example 2 of the present invention under infrared light irradiation for 10s; Figure 10 (b) Healing efficiency diagram of UHS2.5 and CD@Ti3C2Tx-PUHS2.5 prepared in Comparative Example 1 and Examples 1-3 of the present invention under infrared light irradiation for 10s; PU HS2.5 The repair efficiency of 0.5%-CD@Ti3C2T is only 16.31%, while x -PU HS2.5 After 10 seconds of infrared light exposure, the repair efficiency can reach 88.6%, which confirms our hypothesis. x The addition of CD@Ti3C2T makes the composite material show excellent performance in photothermal self-repair. xBy absorbing infrared light, the material provides rapid heat input to damaged areas, accelerating the breaking and remodeling of hydrogen and disulfide bonds, thereby promoting self-repair. Furthermore, the 10-second repair time is faster than most current light-induced healing materials, demonstrating the importance of infrared self-repair for materials requiring rapid performance recovery in practical applications.

[0080] Each elastomer was immersed in a 3.5 wt % NaCl aqueous solution, and the water absorption was calculated. Figure 11 The water absorption test graphs of different MXene@carbon dot-based polyurea composite coatings prepared in Comparative Example 1 and Examples 1-3 of the present invention are shown in FIG. Figure 11 It can be clearly seen that the elastomers all experienced a process of rapid water absorption followed by a steady state. In the first few days, the elastomers absorbed water rapidly due to physical adsorption on the surface of the material. Subsequently, the water absorption rate gradually slowed down and eventually reached a saturated state, indicating that the water molecules inside the material reached a dynamic equilibrium. x When the addition amount is less than 0.5%, the water absorption rate of the composite elastomer is generally lower than that of PU HS2.5 Elastomer. Because a small amount of CD@Ti3C2T x Nanosheets can fill the gaps in PU elastomers, thereby reducing the permeation path of water molecules and reducing water absorption. x As the amount of addition increases, the water absorption rate of the composite elastomer begins to increase. This may be due to the hydrophilicity of MXene. The addition of MXene increases the hydrophilic area of ​​the material and improves the water absorption capacity of the material. In addition, CD@Ti3C2T x The addition of nanosheets may also change the PU SH2.5 The microstructure of the elastomer affects the diffusion and adsorption behavior of water molecules.

[0081] Electrochemical impedance spectroscopy (EIS) is an effective technique for evaluating the corrosion resistance of coatings in solution. EIS tests were performed on the examples and comparative examples in 3.5 wt% NaCl solution. Figure 12 (a) is the Nyquist plot of the polyurea coating prepared in Comparative Example 1 of the present invention; Figure 12 (b) is the Nyquist plot of the polyurea composite coating based on MXene@carbon dots prepared in Example 2 of the present invention. Figure 12 It can be seen that 0.5%-CD@Ti3C2T x -PU HS2.5 The Nyquist semicircle diameter of the coating (2.22×10 8 ) is greater than PU HS2.5 The semicircular diameter of the coating (8.55×10 6 ), after immersion for 30 days, 0.5%-CD@Ti3C2Tx -PU HS2.5 The semicircular diameter of the coating is still larger than that of PU HS2.5 The coating is two orders of magnitude higher. x -PU HS2.5 The coating has better anti-corrosion performance. PU HS2.5 The coating is easily penetrated by corrosive media due to the presence of micropores and defects, resulting in a decrease in anti-corrosion performance. x The defect is effectively filled by the nanosheets. HS2.5 The synergistic effect between polymer chains improves the barrier effect of the coating. x The addition of nanosheets not only improves the coating's physical barrier properties but also strengthens its cohesive energy by forming additional chemical bonds. This chemical bond formation helps improve the coating's overall stability and durability, reduces the penetration of corrosive ions through the coating, and reduces the risk of corrosion to the substrate.

[0082] The self-repairing and anti-corrosion polyurea composite elastomer based on MXene@carbon dots prepared in the embodiment of the present invention relies on the synergistic effect of dynamic hydrogen bonds and flexible disulfide bonds. The introduction of flexible disulfide bonds and hydrogen bonds significantly enhances the self-repairing properties of the polyurea elastomer, enabling it to effectively restore its original performance after being damaged. At the same time, CD@Ti3C2T x The uniform embedding of the polyurea elastomer optimizes the microstructure of the polyurea elastomer, greatly improving its mechanical strength, corrosion resistance and thermal stability.

[0083] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A polyurea composite coating based on MXene@carbon dots, characterized in that: The composite coating is prepared by heating and curing a polyurea composite elastomer based on MXene@carbon dots and an organic solvent; the polyurea composite elastomer based on MXene@carbon dots is prepared by mixing a polyurea elastomer and MXene@carbon dot powder; the polyurea elastomer is prepared by a two-step polycondensation reaction using isophorone diisocyanate, poly(propylene glycol) bis(2-aminopropyl ether), isophthalic acid hydrazide and 4,4'-diaminodiphenyl disulfide as raw materials.

2. A method for preparing a polyurea composite coating based on MXene@carbon dots according to claim 1, characterized in that: The preparation method comprises: S1: preparing a polyurea prepolymer: dissolving isophorone diisocyanate in N,N-dimethylacetamide to obtain a first solution; dissolving poly(propylene glycol) bis(2-aminopropyl ether) in N,N-dimethylacetamide to obtain a second solution; and dropwise adding the second solution to the first solution while continuously stirring to perform a first polycondensation reaction to obtain a polyurea prepolymer; S2: preparing a polyurea elastomer by dissolving isophthalic acid hydrazide in N,N-dimethylacetamide and stirring uniformly to obtain a third solution; dissolving 4,4'-diaminodiphenyl disulfide in N,N-dimethylacetamide and stirring uniformly to obtain a fourth solution; and sequentially adding the third solution and the fourth solution to a polyurea prepolymer to carry out a second polycondensation reaction to obtain a polyurea elastomer; S3 preparation of MXene@carbon dot-based polyurea composite elastomer: a single layer of MXene and carbon dot powder are mixed and dissolved in deionized water, stirred evenly, and freeze-dried to obtain MXene@carbon dot powder; the MXene@carbon dot powder is added to the polyurea elastomer for mixing reaction to obtain a MXene@carbon dot-based polyurea solution; the MXene@carbon dot-based polyurea solution is then poured into a mold and dried to obtain a MXene@carbon dot-based polyurea composite elastomer; S4 prepares a polyurea composite coating based on MXene@carbon dots: adds a polyurea elastomer based on MXene@carbon dots to an organic solvent, stirs it evenly at a high temperature, and prepares it into a coating; the coating is preheated and evenly coated on a substrate, and a polyurea composite coating based on MXene@carbon dots is formed on the substrate through a heat curing treatment.

3. The preparation method according to claim 2, characterized in that The mass ratio of isophorone diisocyanate and poly(propylene glycol) bis(2-aminopropyl ether) in step S1 is (1-2):(5-6); the temperature of the first polycondensation reaction is 25-30° C., and the time is 2-4 hours.

4. The preparation method according to claim 2, characterized in that The mass ratio of isophthalic acid hydrazide, 4,4'-diaminodiphenyl disulfide and polyurea prepolymer in step S2 is (1-5):1:(50-55); the temperature of the first polycondensation reaction is 50-60° C., and the time is 16-22 hours.

5. The preparation method according to claim 2, characterized in that The preparation method of the single-layer MXene in step S3 includes: adding lithium fluoride to a hydrochloric acid solution and then adding titanium aluminum carbide powder to perform an etching reaction to obtain a multilayer MXene; washing, centrifuging and oscillating the multilayer MXene to obtain a single-layer MXene; the mass ratio of the lithium fluoride to titanium aluminum carbide is (1.3-1.8):1; the temperature of the etching reaction is 50-60°C, and the time is 28-32 hours.

6. The preparation method according to claim 2, characterized in that The method for preparing the carbon dot powder described in step S3 includes: adding citric acid and urea to N,N-dimethylformamide in sequence to obtain a fifth solution; after the fifth solution is heat-insulated, it is cooled, dialyzed and dried to obtain carbon dot powder; the mass ratio of the citric acid and urea is 1:2; the temperature of the heat-insulation treatment is 150-180°C, and the time is 4-8 hours.

7. The preparation method according to claim 2, characterized in that In step S3, the mass ratio of the monolayer MXene to the carbon dot powder is 1:1; the freeze-drying time is 22 to 26 hours; and the mass ratio of the polyurea elastomer to the MXene@carbon dot powder is (10:50):0.

1.

8. The preparation method according to claim 2, characterized in that The reaction temperature of the mixing reaction in step S3 is 50-60°C, and the reaction time is 30-60 min. The drying treatment includes: first placing the MXene@carbon dot-based polyurea solution in a vacuum drying oven at 80-90°C for 10-12 hours, and then placing it in a forced air drying oven at 80-90°C for 40-48 hours.

9. The preparation method according to claim 2, characterized in that In step S4, the organic solvent is xylene; the concentration of the coating is 300-400 mg@mL; the temperature of the heating and curing treatment is 50-60° C., and the time is 20-24 hours.

10. Application of the MXene@carbon dot-based polyurea composite coating according to claim 1 in marine devices and equipment.

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