Self-repairing coating for preventing biological fouling and preparation method and application thereof

Abstract

The invention belongs to the technical field of marine organism fouling protection, and particularly discloses a self-repairing coating for preventing biological fouling and a preparation method and application thereof, and the preparation method comprises the following steps: S1, adding polydimethylsiloxane and aliphatic diisocyanate into an organic solvent according to a molar ratio of 1: (1.0-3.0), continuously stirring for more than 0.5 h, and standing to prepare an organosilicon polymer solution; the polydimethylsiloxane is aminopropyl double end capped polydimethylsiloxane, and the polydimethylsiloxane is an aminopropyl double end capped polydimethylsiloxane; s2, adding methyl silicone oil into the organic silicon polymer solution, and continuously stirring for more than 0.5 hour to prepare a transparent organic silicon prepolymer; and S3, uniformly coating the surface of a substrate with the prepolymer prepared in the step S2, and standing to obtain the self-repairing coating for preventing biological fouling. Complete covering and damage self-repairing of a lubricating layer on the surface of the coating can be achieved, attachment and growth of fouling organisms are effectively prevented, and the coating is endowed with long-acting antifouling performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of biofouling protection, and in particular relates to the preparation and application of a smooth liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating. Background Art

[0002] Biofouling refers to the phenomenon in which microorganisms, algae, shellfish and other organisms attach, grow and reproduce on the surface of submerged objects. It is widely present in places such as ships, offshore platforms, underwater pipelines, and aquaculture facilities. In the marine economy, biofouling increases ship resistance, increases energy consumption, and affects shipping efficiency and the cost of sea passages. In marine resource development, biofouling organisms clog cooling water pipes, causing corrosion or failure of facilities, resulting in economic losses and safety hazards. In aquaculture, biofouling hinders water exchange, spreads diseases, and reduces aquaculture efficiency. In addition, biofouling also exacerbates carbon emissions in the shipping industry and hinders the large-scale application of marine renewable energy. At the same time, the treatment of fouling in infrastructure such as undersea tunnels and cross-sea bridges is directly related to their service life and safety.

[0003] The low surface energy anti-biofouling coating of silicone (PDMS) effectively hinders the stable attachment of fouling organisms (such as algae, barnacles, mussels, bacteria, etc.) by reducing the surface chemical activity and physical adhesion ability. Its molecular structure includes a flexible silicon-oxygen main chain (Si-O-Si) and a hydrophobic methyl side chain (-CH3). The Si-O bond has a high bond energy (about 444kJ / mol), which gives the main chain excellent flexibility and thermal stability. The molecular chain is highly rotatable, and a dynamic "flow layer" is easily formed on the surface. When fouling organisms try to attach, the surface molecular chains can release stress through local deformation, reducing the adhesion strength. The methyl groups are densely arranged on the surface of the coating to form a low-polarity, low-surface-energy hydrophobic layer, which hinders water molecules from forming a continuous film layer on the surface, reduces the interaction with the adhesion proteins secreted by the organisms, and inhibits the initial colonization of microorganisms such as bacteria. The surface energy of PDMS is extremely low (about 20-24mJ / m 2 ), close to hydrocarbons (such as polyethylene), and much lower than water (72mJ / m 2 ) and most bioadhesive substances (such as proteins with a surface energy of about 40-50 mJ / m 2), fouling organisms cannot be stably attached through hydrogen bonds or electrostatic effects, and only rely on weak van der Waals forces, and are easily peeled off by external forces. Although silicone coatings have many significant advantages, they still face challenges in practical applications, especially under static conditions (such as ships moored or equipment stationary), where there is a lack of water shear force, fouling organisms may still accumulate slowly. To address this problem, researchers have improved the hydrophobicity by grafting active groups / fluorocarbon segments on the ends of PDMS chains, and incorporated photocatalytic nanoparticles such as graphene into PDMS to give the coating photocatalytic antibacterial functions. At the same time, template methods, laser etching or self-assembly techniques are used to construct bionic micro-nanostructures on the PDMS surface to enhance self-cleaning ability and static antifouling efficiency. In addition, PDMS itself is soft and easily scratched. In complex marine environments, such as mud and sand scouring and mechanical collisions, it is easily damaged and fails. To solve this problem, researchers have adopted a variety of methods to enhance the mechanical properties of PDMS coatings. They incorporated nanoparticles such as SiO2, TiO2 and graphene into PDMS, which significantly improved the hardness and wear resistance of the coating. At the same time, by introducing dynamic chemical bonds or microencapsulated repair agents, researchers have also successfully endowed the coating with self-healing capabilities, allowing it to automatically restore its antifouling properties after damage. Therefore, it is crucial to prepare dual-functional coatings that have both antifouling and self-healing functions.

[0004] Chinese patent publication number CN 117304787 A discloses a self-healing marine antifouling coating that utilizes the characteristics of silicone in dynamic antifouling and the role of antifouling agents in static antifouling for antifouling. At the same time, alternating strong and weak bond structures are constructed in PU to achieve self-healing properties. However, its self-healing is temperature-dependent, and the self-healing effect is poor at room temperature. The room temperature self-healing efficiency of 48 hours is less than 85%, which is weaker than repairing at 80°C for 2 hours. In addition, the universality of silicone coatings is poor, and the addition of multifunctional reagents will reduce the self-healing effect. Moreover, during long-term use, the adsorption of oil or organic pollutants will increase the surface energy of the coating, resulting in a gradual decline in antifouling performance. In addition, residual water molecules on the substrate surface are a key factor in reducing the adhesion of the coating and affecting its long-term antifouling performance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the prior art and propose a method for preparing a self-repairing coating that is anti-biofouling, as well as the application of the anti-fouling coating prepared by the above method in the field of preventing marine biofouling.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0008] S1. Adding polydimethylsiloxane and diisocyanate in a molar ratio of 1:(1.0-3.0) to an organic solvent, stirring continuously for more than 0.5 h, and allowing to stand to obtain an organosilicon polymer solution; the polydimethylsiloxane is aminopropyl di-terminated polydimethylsiloxane; and the diisocyanate is an aliphatic diisocyanate;

[0009] S2. Add methyl silicone oil to the organosilicon polymer solution obtained in step S1, and continue stirring for more than 0.5 h to prepare a transparent organosilicon prepolymer;

[0010] S3. The prepolymer prepared in step S2 is evenly coated on the surface of the substrate, and after standing, an anti-biofouling self-repairing coating is obtained.

[0011] Preferably, the molar ratio of polydimethylsiloxane to diisocyanate is 1:(1-2).

[0012] Preferably, the number average molecular weight (Mn) of the polydimethylsiloxane is 1,000 to 27,000.

[0013] Preferably, the molar ratio of the polydimethylsiloxane to the diisocyanate is 1:(1.8±0.2); the number average molecular weight (Mn) of the polydimethylsiloxane is 2500±500; the diisocyanate is preferably a linear aliphatic diisocyanate; and the diisocyanate is hexamethylene diisocyanate.

[0014] Preferably, the mass ratio of methyl silicone oil to organosilicon polymer in S2 is (1-2):1.

[0015] Preferably, the mass ratio of methyl silicone oil to silicone polymer in S2 is (1.5-1.7):1.

[0016] Preferably, the organic solvent in S1 is tetrahydrofuran, and the mass volume ratio of polydimethylsiloxane to tetrahydrofuran is 0.05-0.5 g / mL; the mass volume ratio of polydimethylsiloxane to tetrahydrofuran in the organosilicon polymer solution in S2 is 0.1-0.2 g / mL; and the viscosity of the methyl silicone oil in S2 is 10-1000 CS.

[0017] Preferably, stirring is continued for 3 to 4 hours in S1 and allowed to stand for 96 to 120 hours; stirring is continued for 1 to 2 hours in S2 at a stirring speed of 500±300 rpm.

[0018] Preferably, in S3, the static environment is: temperature is 80±10° C., and relative humidity is 60% to 70%.

[0019] Figure 1 The diameter of the lubricating liquid droplets is 2 to 9 μm, and the thickness of the self-secreted liquid lubricating layer is 0.5 to 30 μm.

[0020] The substrate material is glass, 304 / 316 stainless steel, Q235 / Q345 carbon steel, ceramic sheet, plastic, rubber and other materials.

[0021] Application of the anti-biofouling self-repairing coating prepared by the method in marine environments.

[0022] The self-healing, anti-biofouling coating described in this invention controls the crosslinking rate of polymer molecular segments and their interactions, utilizing the molecular gaps between polymer coating chains to fix and confine the volume of lubricating droplets. This overcomes the internal structural defects of traditional smooth, porous, liquid-storage coatings, avoids the formation of "fisheye" structures on the coating surface, and achieves an optimal ratio of lubricant storage and loss. By combining the coating's molecular structure design, surface structure, and lubricant properties, the coating achieves complete coverage and self-repair of damage in the lubricating layer, effectively preventing the attachment and growth of fouling organisms on the surfaces of navigational and fixed submerged structures, and endowing the coating with long-lasting antifouling properties.

[0023] The application of the above antifouling coating as an anti-biofouling coating material.

[0024] Traditional silicone low surface energy coatings rely on hydrophobicity, low surface energy and elasticity to resist the attachment of fouling organisms. They require the impact of strong water flow to remove attached fouling organisms, and their anti-fouling effect under static conditions is very poor. The surface lubricating layer formed by adding silicone oil in the present invention constructs a dynamic hydrophobic surface on the surface of the silicone coating to inhibit the attachment of fouling organisms, thus achieving an anti-fouling effect under static conditions. Then, the lubricating liquid in the coating is fixed / locked by dynamic hydrogen bond cross-linking between the coating chain segments. Driven by external stimuli and surface tension, the continuous release of the lubricating liquid in the coating is controlled by the breaking and recombination of hydrogen bonds, maintaining the stability of the lubricating layer on the coating surface.

[0025] The mechanism of increased coating adhesion is as follows: (1) The amino group (-NH2) of PDMS-NH2 reacts with the isocyanate group (-NCO) of HDI to form urea bonds (-NHCONH-), forming a cross-linked network and improving the cohesive strength of the coating; (2) An excess of 80% HDI (molar ratio of 1.8) ensures that the remaining -NCO groups react with the hydroxyl groups (-OH) on the substrate surface to form covalent bonds (-NHCOO-), significantly enhancing the interfacial adhesion; (3) HDI reacts with interfacial water to generate amines and CO2, reducing the damage of water molecules to the interfacial bonds, and at the same time generating a polyurea structure to fill the interfacial micropores and improve the density.

[0026] The self-healing mechanism of the coating is as follows: (1) PDMS-NH2 reacts with HDI to form a polyurea structure (containing urea bonds: -NH-C(=O)-NH-). The NH and C=O in the urea bonds can form a strong hydrogen bond network. The dynamic characteristics of hydrogen bonds enable them to reversibly break and reassemble under heat or mechanical stress; (2) There is an excess of HDI in the coating (such as a molar ratio of PDMS-NH2:HDI = 1:1.8), which retains unreacted -NCO groups. When the coating is damaged, the -NCO exposed at the crack reacts with moisture in the environment (-NCO + H2O → -NH2 + CO2) to generate new urea bonds, forming a local cross-linked network and repairing the mechanical strength; (3) Methyl silicone oil (low surface energy, high fluidity) is used as a functional additive and is partially enriched on the coating surface to form a lubricating layer. Surface scratches damage the lubricating layer, and the methyl silicone oil migrates to the damaged area due to thermal motion or capillary action, reconstructing the hydrophobic lubricating layer.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention introduces reversible dynamic units to combine with interfacial water molecules, thereby blocking the negative impact of moisture on adhesion and enhancing the chemical bonding density between the coating and the substrate, so that the coating adhesion is ≥4.3MPa.

[0029] (2) The in-situ nucleation-confined flow maturation technology is used to precisely control the volume and distribution of lubricating droplets, optimize compatibility, achieve long-term lubricating layer coverage, and extend the anti-fouling cycle; dynamic chemical bonds are embedded, and the coating has loss-triggered self-repair capabilities. After repair, the anti-fouling performance recovery rate exceeds 90% under room temperature conditions, and it can be cycled multiple times, with a theoretical lifespan of over 10 years.

[0030] (3) No active substances are added, and it relies on physical antifouling mechanisms. The lubricating fluid is stabilized by the confinement effect between polymer chains, achieving continuous release of the lubricating fluid, complying with IMO environmental regulations. The coating is transparent and elastic, making it easy to inspect and monitor. The lubricating layer is combined with low surface energy characteristics, and the antifouling efficiency exceeds 95% under navigation and stationary conditions. The interface molecular design can be adapted to a variety of substrates and is widely used in ships, offshore platforms, underwater sensors, etc. The coating is resistant to ultraviolet light and salt spray, and can maintain stable performance in complex marine environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the mechanism of action of the antifouling coating of the present invention.

[0032] Figure 2 This is a diagram showing the self-repairing effect of the antifouling coating of the present invention.

[0033] Figure 3 These are transmission images of the substrates of the anti-fouling coatings of different embodiments of the present invention after the lubricating fluid is substantially completely removed; (a) Comparative Example 2, (b) Comparative Example 3, and (c) Example 5.

[0034] Figure 4 Schematic diagram of the transparency of the antifouling coating of the present invention.

[0035] Explanation of the accompanying symbols: 1-coating; 2-substrate; 3-lubricating liquid droplet; 4-lubricating layer; 5-hydrogen bond crosslinking point; 6-isocyanate group; 7-water molecule; 8-coating damage self-repair; 9-color card. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the equipment used in the present embodiment, comparative example and experimental example are conventional experimental equipment, the materials and reagents used are commercially available unless otherwise specified, and the experimental methods without special explanation are also conventional experimental methods.

[0037] Example 1

[0038] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0039] Aminopropyl di-terminated polydimethylsiloxane (average Mn ~ 2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.168g) stored at 2~5℃ were restored to room temperature, and 8mL of tetrahydrofuran (THF) solution was added at a molar ratio of 1:1. The mixture was stirred at room temperature for 4h to prepare a damage self-repairing low surface energy prepolymer based on molecular regulation mechanism. The obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and kept at 80°C (relative humidity of 60% to 70%) for 96 hours to obtain a damage self-repairing low surface energy antifouling coating based on a molecular regulation mechanism.

[0040] Example 2

[0041] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0042] Aminopropyl di-terminated polydimethylsiloxane (average Mn 2500, 2.650 g) and hexamethylene diisocyanate (HDI, 0.302 g) stored at 2-5°C were returned to room temperature, and 8 mL of tetrahydrofuran (THF) solution was added at a molar ratio of 1:1.8. The mixture was stirred at room temperature for 4 h to prepare a low surface energy prepolymer with self-repairing properties based on a molecular control mechanism. The obtained prepolymer was evenly coated on a substrate (2.5 × 7.6 cm 2 ) surface, and kept at 80°C (relative humidity of 60% to 70%) for 96 hours to obtain a damage self-repairing low surface energy antifouling coating based on a molecular regulation mechanism.

[0043] Example 3

[0044] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0045] The aminopropyl di-terminated polydimethylsiloxane (average Mn~2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.168g) stored at 2-5°C were restored to room temperature, mixed in a molar ratio of 1:1, and 8mL of tetrahydrofuran (THF) solution was added. The mixture was stirred continuously for 4h at room temperature and allowed to stand (at room temperature) for 96h to obtain a damage self-repairing low surface energy polymer based on a molecular regulation mechanism. Then, 0.25g of the above-prepared organic silicon polymer was weighed and completely dissolved in 2250μL of tetrahydrofuran solution at room temperature. 0.325g of methyl silicone oil (viscosity of 10CS) was injected, the rotation speed was maintained at 500rpm, and stirring was continued for 1h to prepare a smooth liquid-injected transparent low surface energy antifouling coating prepolymer. Finally, the obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and placed at 80℃ (relative humidity 60% to 70%) for 24h to prepare a smooth, liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating. Schematic diagram of the mechanism, self-repairing effect, stability and transparency are shown in Figure 2. Figures 1 to 4 As shown. The long-lasting antifouling performance of this coating system is due to its molecular-interface multi-level synergistic mechanism. First, the amino group (-NH2) of PDMS-NH2 reacts with the isocyanate group (-NCO) of HDI to construct a urea bond network (-NHCONH-), thereby improving the cohesive strength of the coating. The excess HDI has a dual effect: first, the remaining -NCO reacts with the hydroxyl group (-OH) on the surface of the glass substrate to form a carbamate covalent bond (-NHCOO-), thereby enhancing the interfacial binding energy; second, HDI reacts with interfacial water to form a polyurea structure, which effectively seals the nano-scale defects on the substrate surface and increases the coating / substrate contact area. Furthermore, the coating system exhibits dynamic self-healing control capabilities. First, the NH···O=C hydrogen bond network within the urea bonds reversibly breaks under external forces, dissipating over 90% of the impact energy through bond reorganization, maintaining the coating's structural integrity. Second, methyl silicone oil droplets are confined by this hydrogen bond network. When the surface lubricating layer is damaged, the droplets migrate along the polymer entanglement network driven by the chemical potential gradient and surface tension, reconstructing a low-surface-energy lubricating layer. Simultaneously, the reserved -NCO groups react with water via secondary kinetics to form new urea bonds, resulting in a 95% repair rate for cracked areas. Finally, the coating system achieves dual-pathway management of interfacial water molecules: First, the regenerated lubricating layer blocks water penetration through silicone oil-water repulsion, suppressing the weakening effect of interfacial hydrogen bond hydration. Second, water molecules that penetrate microcracks are captured by the -NCO groups, transforming them into reinforcing polyurea rather than destructive agents, achieving an intelligent transformation from "enemy molecule" to "friendly structure."

[0046] Example 4

[0047] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0048] The aminopropyl di-terminated polydimethylsiloxane (average Mn~2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.302g) stored at 2-5°C were restored to room temperature, and 8mL of tetrahydrofuran (THF) solution was added according to a molar ratio of 1:1.8. The mixture was stirred continuously for 4h at room temperature and allowed to stand (at room temperature) for 96h to obtain a damage self-repairing low surface energy polymer based on a molecular regulation mechanism. Then, 0.25g of the above-prepared organosilicon polymer was weighed and completely dissolved in 2250μL of tetrahydrofuran solution at room temperature. 0.275g of methyl silicone oil (viscosity of 10CS) was injected, the rotation speed was maintained at 500rpm, and stirring was continued for 1h to prepare a smooth liquid-injected transparent low surface energy antifouling coating prepolymer. Finally, the obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare a smooth, liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating.

[0049] Example 5

[0050] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0051] The aminopropyl di-terminated polydimethylsiloxane (average Mn~2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.302g) stored at 2-5°C were restored to room temperature, and 8mL of tetrahydrofuran (THF) solution was added according to a molar ratio of 1:1.8. The mixture was stirred continuously for 4h at room temperature and allowed to stand (at room temperature) for 96h to obtain a damage self-repairing low surface energy polymer based on a molecular regulation mechanism. Then, 0.25g of the above-prepared organic silicon polymer was weighed and completely dissolved in 2250μL of tetrahydrofuran solution at room temperature. 0.325g of methyl silicone oil (viscosity of 10CS) was injected, the rotation speed was maintained at 500rpm, and stirring was continued for 1h to prepare a smooth liquid-injected transparent low surface energy antifouling coating prepolymer. Finally, the obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare a smooth, liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating.

[0052] Example 6

[0053] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0054] The aminopropyl di-terminated polydimethylsiloxane (average Mn ~ 2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.302g) stored at 2-5°C were restored to room temperature, and 8mL of tetrahydrofuran (THF) solution was added according to a molar ratio of 1:1.8. The mixture was stirred continuously for 4h at room temperature and allowed to stand (at room temperature) for 96h to obtain a damage self-repairing low surface energy polymer based on a molecular regulation mechanism. Then, 0.25g of the above-prepared organosilicon polymer was weighed and completely dissolved in 2250μL of tetrahydrofuran solution at room temperature. 0.375g of methyl silicone oil (viscosity of 10CS) was injected, the rotation speed was maintained at 500rpm, and stirring was continued for 1h to prepare a smooth liquid-injected transparent low surface energy antifouling coating prepolymer. Finally, the obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare a smooth, liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating.

[0055] Example 7

[0056] A method for preparing a self-repairing coating that resists biofouling comprises the following steps:

[0057] The aminopropyl di-terminated polydimethylsiloxane (average Mn~2500, 2.650g) and hexamethylene diisocyanate (HDI, 0.504g) stored at 2-5°C were restored to room temperature, and 8mL of tetrahydrofuran (THF) solution was added according to a molar ratio of 1:3. The mixture was stirred continuously for 4h at room temperature and allowed to stand (at room temperature) for 96h to obtain a damage self-repairing low surface energy polymer based on a molecular regulation mechanism. Then, 0.25g of the above-prepared organic silicon polymer was weighed and completely dissolved in 2250μL of tetrahydrofuran solution at room temperature. 0.325g of methyl silicone oil (viscosity of 10CS) was injected, the rotation speed was maintained at 500rpm, and stirring was continued for 1h to prepare a smooth liquid-injected transparent low surface energy antifouling coating prepolymer. Finally, the obtained prepolymer was evenly coated on a substrate (2.5×7.6cm 2 ) surface, and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare a smooth, liquid-injected, transparent, low-surface-energy, long-lasting antifouling coating.

[0058] Comparative Example 1

[0059] As a control experiment, a method for preparing an antifouling coating comprises the following steps:

[0060] The polydimethylsiloxane base component and the curing agent were completely mixed in a weight ratio of 10:1 and evenly coated on the substrate (2.5×7.6cm 2 ) surface and placed at 65°C for 10 hours to prepare an antifouling coating.

[0061] Comparative Example 2

[0062] As a control experiment, a method for preparing an antifouling coating comprises the following steps:

[0063] The polydimethylsiloxane base component (0.25 g) and the curing agent were completely mixed in a weight ratio of 10:1, and 0.325 g of methyl silicone oil (viscosity of 10 CS) was injected and evenly coated on the substrate (2.5 × 7.6 cm 2 ) surface and placed at 65°C for 10 hours to prepare an antifouling coating.

[0064] Comparative Example 3

[0065] As a control experiment, a method for preparing an antifouling coating comprises the following steps:

[0066] Amino-terminated polydimethylsiloxane (0.25 g, average Mn 2500), trifunctional homopolymer of hexamethylene diisocyanate (THDI, 0.04 g), methyl silicone oil (0.325 g, viscosity 10 CS) and chloroform (10 mL) were mixed and added into a 25 mL round-bottom flask and stirred at room temperature for 4 h to obtain an antifouling coating prepolymer. The obtained prepolymer was evenly coated on a substrate (2.5 × 7.6 cm 2 ) surface and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare an antifouling coating. The coating material has too high a cross-linking density, resulting in poor fluidity of the fixed droplets in the matrix and inability to replenish the lubricating fluid lost on the coating surface in a timely manner.

[0067] Comparative Example 4

[0068] As a control experiment, a method for preparing an antifouling coating comprises the following steps:

[0069] Aminopropyl dicapped polydimethylsiloxane (0.265 g, average Mn ~ 2500) and toluene 2,4-diisocyanate (TDI, 0.311 g) were added to 8 mL of tetrahydrofuran (THF) solution, stirred continuously at room temperature for 4 h, and then allowed to stand. After standing (at room temperature) for 96 h, the solid polymer (0.25 g) was redissolved in 2250 μL of tetrahydrofuran solution, and methyl silicone oil (0.325 g, viscosity of 10 CS) was injected. The rotation speed was maintained at 500 rpm, and after stirring continuously for 1 h, it was evenly coated on a substrate (2.5 × 7.6 cm 2 ) surface and allowed to stand at 80°C (relative humidity 60% to 70%) for 24 hours to prepare an antifouling coating. The coating material had poor elasticity and unsaturated cavity structures appeared in the matrix, making it impossible to controllably replenish the lubricating fluid lost on the coating surface.

[0070] Experimental Example 8

[0071] See Table 1 for the adhesion (based on ASTM D4541 pull-off test standard) and damage self-repair performance of the antifouling coatings prepared in Examples 1 to 7 and the antifouling coating prepared in Comparative Example 1 on the glass substrate.

[0072] Table 1 Adhesion and self-healing performance tests of various coatings (at room temperature)

[0073]

[0074] Table 1 shows the adhesion (in MPa) and 60-minute self-repair rate of different antifouling coating examples (Comparative Example 1 and Examples 1-7). As can be seen from the table above, the adhesion of Comparative Example 1 is only 0.2±0.1 MPa and has no repair ability, while the adhesion of the examples is significantly improved with formulation optimization: Example 2 reaches a peak of 4.3±0.2 MPa, indicating that a reasonable ratio (such as PDMS-NH2:HDI = 1:1.8) can maximize the crosslinking density; Example 7's adhesion drops back to 3.0±0.2 MPa, which may be related to excessive crosslinking caused by excessive HDI (such as 1:3). In terms of self-repair rate, Examples 1-6 show an increasing trend, from 50% to 100% (Example 6), where the repair rate is positively correlated with the degree of HDI excess and the amount of silicone oil added; however, the repair rate of Example 7 drops to 95%, suggesting that excessive HDI at extreme ratios may inhibit the efficiency of dynamic bond recombination. In summary, Example 2 (adhesion 4.3 MPa + repair rate 80%) and Example 5 (adhesion 2.1 MPa + repair rate ~100%) represent the balance points of adhesion priority and optimal self-healing performance, respectively, verifying the synergistic regulatory effect of stoichiometric ratio and functional additives on coating performance.

[0075] Experimental Example 9

[0076] In this experiment, newly cultivated microscopic fouling organisms (E. coli and S. aureus) and macroscopic fouling organisms (Mytilus atrata) were used to test the antifouling performance of the antifouling coating. The antifouling coating prepared in Comparative Example 1 served as a control experimental group and was compared with the smooth, liquid-infused, transparent, low-surface-energy antifouling coatings prepared in Examples 1-7. Adhesion tests of both microscopic and macrofouling organisms were conducted. The test results are shown in Table 2.

[0077] Table 2 Statistics of fouling organism attachment on the coating surface by spectrophotometric quantitative analysis and counting method

[0078]

[0079] Note: Mussel attachment probability (%) = number of attachments / total number × 100%.

[0080] As can be seen from Table 2 above, the OD values ​​of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in Comparative Example 1 (unoptimized coating) are 1.796 and 1.721, respectively, and the probability of attachment of macrofouling organisms (V. atrata) is as high as 86-100%, indicating that its antifouling performance is poor. Examples 1 to 7 significantly improved performance by adjusting the PDMS-NH2:HDI stoichiometric ratio and the amount of silicone oil added: (1) Microbial inhibition: Example 5 (OD value 0.5) and Example 6 (OD value 0.5-0.6) performed best. It is speculated that they used a high cross-linking density (such as 1:1.8 HDI) and an appropriate amount of silicone oil (0.325g) to form a dense surface and a stable lubricating layer, which effectively blocked bacterial adhesion; (2) Macrobial antifouling: The V. atrata attachment probability of Examples 5 and 6 was reduced to 0-10%, which may be due to the silicone oil lubricating layer reducing the surface energy and maintaining the integrity of the coating in combination with the dynamic repair mechanism; while Example 7 (attachment probability 20-30%) was embrittled due to excessive HDI (such as 1:3), and the performance declined. The data verified that the synergistic optimization of the stoichiometric ratio (such as 1:1.8) and the amount of silicone oil added (such as 0.325g) can significantly improve the antifouling performance.

[0081] Experimental Example 10

[0082] Partial lubricant removal experiment: Use oil-absorbing paper to wipe away part of the lubricant on the surface of the antifouling coating, and compare the lubricant secretion status before and after wiping. See Table 3 for details.

[0083] Table 3 Lubricating fluid secretion status of antifouling coating surface in different embodiments

[0084]

[0085] As shown in Table 3, before wiping, the lubricating layers of Comparative Examples 2 and 4 were relatively thick (>50μm and >30μm, respectively), while Comparative Example 3 was the thinnest (<1μm). Example 5 ranged from 10-30μm. After wiping, the lubricating layers of Comparative Examples 2 and 4 were completely lost due to excessive lubricant secretion, indicating poor stability despite the initial thickness. Comparative Example 3 was unable to form a new lubricating layer due to poor lubricant re-secretion, reflecting a lack of recovery due to its excessively thin layer. However, after wiping, Example 5 was able to re-secrete lubricant and form a complete lubricating layer, demonstrating that its moderate thickness (10-30μm) offers a potential balance between preventing excessive lubricant loss and maintaining re-secretion capacity. This demonstrates that Example 5 offers advantages in terms of both lubrication performance and stability. The lubricating layer thickness should be controlled within a reasonable range; excessive thickness or thinness can lead to performance defects.

[0086] Experiment of almost completely removing lubricating fluid: Place the antifouling coating in the middle of the oil-absorbing paper, stack 3-5 layers of oil-absorbing paper on both sides, fix it with clips around the edges, and let it stand for a week. Figure 3, (a) the coating of Comparative Example 2 is whitish and opaque, (b) the coating of Comparative Example 3 is whitish and opaque, and (c) the coating of Example 5 is uniform and transparent. Silicone polymers can maintain an amorphous state under the plasticizing effect of lubricating oil, but once the oil is lost, their molecular chains will rearrange to form partially crystalline regions. Due to the increased difference in refractive index between the crystalline region and the amorphous region, a visual whitening effect is produced. In addition, the loss of lubricating oil causes micropores or cavities to appear inside the coatings of Comparative Examples 2 and 3, resulting in an increase in the porosity. When light is irradiated on the interface of these holes, Rayleigh scattering or Mie scattering occurs, and from a macroscopic perspective, the surface of the coating will appear whitish. The molecular cross-linking density of Comparative Example 3 is greater than that of Comparative Example 2, so white block spots appear in Comparative Example 3.

[0087] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a self-repairing coating that resists biofouling, characterized in that: The following steps are involved: S1. Adding polydimethylsiloxane and diisocyanate in a molar ratio of 1:(1.0-3.0) to an organic solvent, stirring continuously for more than 0.5 h, and allowing to stand to obtain an organosilicon polymer solution; the polydimethylsiloxane is aminopropyl di-terminated polydimethylsiloxane; and the diisocyanate is an aliphatic diisocyanate; S2. Add methyl silicone oil to the organosilicon polymer solution obtained in step S1, and continue stirring for more than 0.5 h to prepare a transparent organosilicon prepolymer; S3. The prepolymer prepared in step S2 is evenly coated on the surface of the substrate, and after standing, an anti-biofouling self-repairing coating is obtained.

2. The preparation method according to claim 1, characterized in that The molar ratio of polydimethylsiloxane to diisocyanate is 1:(1-2).

3. The preparation method according to claim 2, characterized in that The number average molecular weight (Mn) of the polydimethylsiloxane is 1,000 to 27,000.

4. The preparation method according to claim 3, characterized in that The molar ratio of the polydimethylsiloxane to the diisocyanate is 1:(1.8±0.2); the number average molecular weight (Mn) of the polydimethylsiloxane is 2500±500; and the diisocyanate is hexamethylene diisocyanate.

5. The preparation method according to any one of claims 1 to 4, characterized in that The mass ratio of methyl silicone oil to silicone polymer in S2 is (1-2):

1.

6. The preparation method according to claim 5, characterized in that The mass ratio of methyl silicone oil to silicone polymer in S2 is (1.5-1.7):

1.

7. The preparation method according to claim 6, characterized in that The organic solvent in S1 is tetrahydrofuran, and the mass volume ratio of polydimethylsiloxane to tetrahydrofuran is 0.05-0.5 g / mL; the mass volume ratio of polydimethylsiloxane to tetrahydrofuran in the organosilicon polymer solution in S2 is 0.1-0.2 g / mL; and the viscosity of the methyl silicone oil in S2 is 10-1000 CS.

8. The preparation method according to claim 5, characterized in that Stir continuously for 3 to 4 hours in S1 and let it stand for 96 to 120 hours; stir continuously for 1 to 2 hours in S2 at a stirring speed of 500 ± 300 rpm.

9. An anti-biofouling self-healing coating prepared according to the method of any one of claims 1 to 8.

10. Use of the anti-biofouling self-repairing coating according to claim 9 in a marine environment.

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