A composite marine antifouling coating with a multi-layered dynamic system of antifouling, self-healing, and structural stability synergistic regulation and its preparation method.

Abstract

This invention discloses a multilayer dynamic composite marine antifouling coating and its preparation method, belonging to the field of marine antifouling materials technology. Through the synergistic design of a polyurea crosslinking network, N→B coordination pH response, and disulfide bond self-repair, this invention prepares a GPTMS-PPMS-PU / GPM-Imine / CUR-CS composite system that combines high mechanical strength, precise pH-responsive antifouling, and self-repairing functions. The synergistic effect of the polyurea crosslinking network and polymethylphenylsiloxane enhances the coating's mechanical properties and resistance to extreme environments. The imine-phenylboronic acid ester bifunctional structure of GPM-Imine forms N→B internal coordination, enabling targeted release of CUR-CS under weakly acidic conditions. The disulfide bonds introduced by DSP endow the coating with self-repairing capabilities, while the low surface energy of HPPMS facilitates fouling desorption under high-speed water flow.

Description

Technical Field

[0001] This invention relates to the field of marine antifouling materials technology, and in particular to a composite marine antifouling coating with a multi-layer dynamic system of antifouling, self-healing, and structural stability synergistic regulation, and its preparation method. It is suitable for antifouling and corrosion protection of facilities in extreme marine environments such as deep-sea aquaculture cages, ship hulls, offshore platform legs, and subsea pipeline risers. Background Technology

[0002] Marine biofouling is a key issue restricting the development and utilization of marine resources. The attachment and growth of microorganisms, algae, and large organisms on the surface of marine facilities can lead to a 10-15% increase in ship drag, increased fuel consumption, accelerated corrosion of marine engineering facilities, and even induce leakage accidents, causing huge economic losses and ecological risks. Since the complete ban on organotin-based antifouling coatings in 2008, the development of efficient, environmentally friendly, and long-lasting marine antifouling materials has become an urgent need for the industry.

[0003] Organosilicon-based antifouling materials have become a research hotspot due to their low surface energy and good fouling desorption properties, with polydimethylsiloxane (PDMS) being the most widely used substrate. However, traditional organosilicon-based antifouling materials suffer from three major drawbacks: first, weak static antifouling ability, achieving fouling desorption only at specific ship speeds and failing to inhibit the attachment and reproduction of bacteria and diatoms in static environments; second, insufficient mechanical properties and adhesion, with low elastic modulus, easy tearing and detachment, and difficulty withstanding the impact of water currents and physical collisions in marine environments; and third, poor compatibility of antifouling agents, prone to explosive release leading to short antifouling duration, and some antifouling agents exhibiting environmental toxicity.

[0004] In existing technologies, polyurea modification can improve the mechanical properties of organosilicon materials, but it lacks targeted responsive antifouling designs. While the introduction of natural antifouling agents can improve environmental friendliness, their release rates are uncontrollable, resulting in limited static antifouling effects. Although some studies have attempted to introduce pH-responsive mechanisms, these often suffer from low response sensitivity, insufficient antifouling agent loading, and poor stability in neutral environments. Therefore, developing marine antifouling coatings that combine pH-responsive targeted release, high mechanical properties, and long-lasting environmental friendliness is key to addressing the pain points of traditional technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing organosilicon-based marine antifouling materials and provide a composite marine antifouling coating with a multi-layer dynamic system that synergistically regulates antifouling, self-healing, and structural stability, as well as its preparation method. Through the enhancement of polyurea crosslinking network, the pH response of N→B coordination and the self-healing of disulfide bonds are integrated into a three-in-one synergistic design to achieve the unity of dynamic and static antifouling synergy, mechanical property enhancement, damage self-healing and extreme environment adaptation.

[0006] This invention provides a method for preparing a composite marine antifouling coating with a multi-layered dynamic system that synergistically regulates antifouling, self-healing, and structural stability, comprising the following steps: (1) Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): CUR-CS was prepared by reacting chitosan, aqueous acetic acid solution, curcumin, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). (2) Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Using dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) and hexamethylene diisocyanate trimer (HDI trimer) as raw materials, a chain extension reaction was completed under nitrogen protection. Then, γ-glycidoxypropyltrimethoxysilane (GPTMS) was added, and the reaction was continued to complete the end-capping. After the reaction was completed, GPTMS-PPMS-PU was obtained by vacuum distillation. (3) Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): Using 3-aminopropylmethyldimethoxysilane (APMDS) and 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) as raw materials, p-toluenesulfonic acid was added as a catalyst and the reaction was carried out under nitrogen protection. After the reaction was completed, GPM-Imine was obtained by vacuum distillation, silica gel column chromatography purification, and vacuum drying. (4) Preparation of antifouling coatings GPTMS-PPMS-PU, GPM-Imine, CUR-CS and dithiodisuccinimide propionate (DSP) were mixed, acetic acid was added, and the mixture was stirred until the system was homogeneous to obtain an antifouling coating.

[0007] In one embodiment of the present invention, in step (1), the mass ratio of chitosan to curcumin is 5:4, the amount of EDC is 62.5% of the mass of curcumin, the mass concentration of acetic acid aqueous solution is 1%, the reaction temperature is 50 ℃, and the reaction time is 6 h to ensure that the grafting reaction is fully carried out.

[0008] In one embodiment of the present invention, in step (1), after the reaction is completed, the pH of the reaction solution is adjusted to 7.0 and then allowed to stand to precipitate. The solid is washed three times with deionized water and dried under vacuum at 60 °C for 12 h to ensure that the purity of the product is ≥ 98%.

[0009] In one embodiment of the present invention, in step (2), the chain extension reaction temperature is 40 °C and the stirring time is 4 h; the end-capping reaction temperature is 75 °C and the stirring time is 3 h, and the reaction is carried out under nitrogen protection to ensure that the polyurea main chain reacts completely with the silane end-capping reaction.

[0010] In one embodiment of the present invention, in step (2), the mass ratio of HDI trimer to HPPMS is 0.15~0.20:1, and it is dissolved in 30 mL of anhydrous propylene glycol methyl ether acetate; the amount of GPTMS is 8.5~11% of the mass of HPPMS; the vacuum distillation temperature is 60 ℃ and the pressure is 0.08 MPa, and the product is a pale yellow transparent viscous liquid.

[0011] In one embodiment of the present invention, in step (3), the molar ratio of APMDS to 3-FPBA is 1:1.0~1.4, more preferably 1:1.2; the reaction temperature is 40 °C, the stirring time is 7 h, and nitrogen protection is used to avoid oxidation.

[0012] In one embodiment of the present invention, in step (3), the solvent is removed by vacuum distillation (50 °C / 0.08 MPa), the mass ratio of the eluent for silica gel column chromatography is petroleum ether / ethyl acetate = 3:1, and the purity of the purified product is ≥ 97%.

[0013] In one embodiment of the present invention, in step (4), the amount of CUR-CS added is 10-14% of the mass of GPTMS-PPMS-PU, more preferably 12%; the amount of GPM-Imine is 12.0-16.0% of the mass of GPTMS-PPMS-PU; the amount of DSP is 6.5-9.0% of the mass of GPTMS-PPMS-PU; the amount of catalytic acetic acid is 0.10-0.15% of the mass of GPTMS-PPMS-PU; and the stirring time is 45 min at room temperature until the system is homogeneous and free of precipitation.

[0014] This invention provides a composite marine antifouling coating prepared by the method described above.

[0015] This invention provides the application of the above-mentioned antifouling coating in the antifouling and corrosion protection of facilities in marine environments.

[0016] The present invention provides an intelligent composite coating, wherein the above-mentioned antifouling coating is sprayed onto the surface of a substrate.

[0017] This invention provides a method for preparing a smart composite coating, comprising the following steps: Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was packaged in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer. A 10 wt% polyaniline ethanol solution was uniformly sprayed onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5. The mixture was dispersed for 20 min using a high-speed disperser at 3000 rpm until the system was homogeneous. This mixture was then applied to the surface of the bottom anti-corrosion coating using a scraping method, with a wet film thickness of 50 μm. Curing was carried out at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer. The prepared intelligent composite coating was sprayed onto the surface of the middle corrosion-inhibiting coating at a spraying pressure of 850 psi, with a wet film thickness of 160 μm. After spraying, curing was carried out at room temperature (25 ± 2 ℃) for 26 h, resulting in a complete three-layer protective system.

[0018] The beneficial effects of this invention are: (1) The present invention prepares a GPTMS-PPMS-PU / GPM-Imine / CUR-CS composite system through the synergistic design of polyurea crosslinking network, N→B coordination pH response and disulfide bond self-repair, which has high mechanical strength, precise pH response antifouling and damage self-repair function: the synergistic effect of polyurea crosslinking network and polymethylphenylsiloxane enhances the mechanical properties and resistance to extreme environments of the coating; the imine bond-phenylboronic acid ester bifunctional structure of GPM-Imine forms N→B internal coordination, realizing the targeted release of CUR-CS under weak acid environment; the disulfide bond introduced by DSP gives the coating damage self-repair ability, and at the same time relies on the low surface energy characteristics of HPPMS to realize fouling desorption under high-speed water flow.

[0019] (2) This invention synthesizes GPTMS-PPMS-PU polyurea backbone, GPM-Imine multi-response intermediate and CUR-CS natural antifouling agent, and constructs a three-layer protection system of polyaniline bottom layer - flexible epoxy resin / MnO2 middle layer - intelligent composite outer layer. The polyurea cross-linking network is used to improve the tensile strength of the coating and the 0-level adhesion of the cross-linking method. With the help of N→B coordination, the cumulative release of curcumin in a weak acid environment (pH=5.8) for 7 days is increased by 72.3% compared with the neutral environment, and the antibacterial rate against Escherichia coli reaches 98.1%. The scratch self-repair rate of 90% is achieved in 24 hours through disulfide bond self-repair. At the same time, through the synergistic effect of the three layers, the defects of traditional organosilicon coatings such as weak static antifouling, easy damage and poor adaptability to extreme environments are solved.

[0020] (3) Significantly improved mechanical properties and adaptability to extreme environments: Through the synergistic effect of polyurea crosslinking network and polymethylphenylsiloxane, the coating tensile strength reaches 32 MPa, the adhesion of the cross-cut test reaches level 0 (no peeling after 1 mm cross-cut test), and the salt spray resistance reaches 850 h, making it suitable for polar to tropical sea areas and deep-sea high-pressure environments. (4) Precise and controllable pH response and broad antifouling spectrum: Utilizing the N→B internal coordination structure of GPM-Imine, in the weakly acidic environment (pH=5.8) formed by microbial metabolism, the cumulative release of curcumin in 7 days is 72.3% higher than that in the neutral environment, and the antibacterial rate against Escherichia coli reaches 98.1%, filling the gap in the static antifouling ability of traditional organosilicon coatings; (5) Self-healing function extends service life: The disulfide bonds introduced by DSP enable the coating scratches (width ≤ 50 μm) to achieve a self-healing rate of 90% in 24 hours, and extend the service life after seawater immersion to 36 months, solving the pain point of antifouling failure after coating damage; (6) Strong environmental protection and industrialization adaptability: The natural curcumin-chitosan graft material replaces the heavy metal antifouling agent, which meets the IMO environmental protection standards and releases no toxic substances; the coating preparation process is mild and the coating process is compatible with the existing Graco X7 high-pressure airless spraying equipment. The maintenance cycle is more than twice that of traditional PDMS coatings, which can reduce the overall cost of marine engineering facilities by 40% and has significant energy-saving and emission-reduction effects. Attached Figure Description

[0021] Figure 1 This is a morphological feature diagram of GPTMS-PPMS-PU. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0023] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available or commonly used in the field. The methods described in the following embodiments are conventional methods in the field, unless otherwise specified.

[0024] Bis(hydroxypropyl)-terminated polymethylphenylsiloxane (HPPMS) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a number-average molecular weight of Mn≈3200.

[0025] The test methods and standards used in this invention are as follows: (1) Tensile strength The test was conducted in accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0026] (2) Adhesion test using the cross-cut adhesion test The rating is based on GB / T 9286-2021 "Cross-cut test for paints and varnishes", with grade 0 being the best.

[0027] (3) Antibacterial properties (Escherichia coli) The tests were conducted in accordance with GB / T 21866-2008 "Test Methods for Antibacterial Performance and Antibacterial Effect of Antibacterial Coatings".

[0028] (4) Salt spray resistance The test was conducted in accordance with GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes".

[0029] (5) pH response release The cumulative release of antifouling agent over 7 days was determined using a UV-Vis spectrophotometer at pH=7.0 (neutral seawater) and pH=5.8 (simulated acidic microbial environment).

[0030] (6) Self-repair rate The 24-hour self-healing rate was calculated by microscopic observation of the scratch width change. Self-healing rate = (initial scratch width) / (initial scratch width) (Repaired scratch width) / Initial scratch width × 100%.

[0031] (7) Seawater immersion life Accelerated seawater aging tests were conducted in accordance with GB / T 23982-2009, with the failure criteria being no coating peeling, no chalking, and an antibacterial retention rate of ≥90%.

[0032] Example 1 A composite marine antifouling coating with a multi-layered dynamic system that synergistically regulates antifouling, self-healing, and structural stability includes the following steps: 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 °C and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain a yellow powder product, CUR-CS.

[0033] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU. Figure 1 As shown, the phase separation process of the synthesized product was well controlled, and no large-scale aggregation occurred.

[0034] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1, w / w) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0035] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0036] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was packaged in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, where a 10 wt% polyaniline ethanol solution was uniformly sprayed onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5. The mixture was dispersed for 20 min using a high-speed disperser at 3000 rpm until homogeneous. This mixture was then applied to the surface of the bottom anti-corrosion coating using a scraping method, with a wet film thickness controlled at 50 μm. Curing was performed at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, where the prepared intelligent composite coating was sprayed onto the surface of the middle corrosion-inhibiting coating. The spraying pressure was set to 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, curing was performed at room temperature (25 ± 2 ℃) for 26 h, resulting in a complete three-layer protective system.

[0037] Example 2 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 °C and stirred for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain a yellow powder product, CUR-CS.

[0038] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is completed, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0039] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0040] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.4 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0041] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was packaged in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, where a 10 wt% polyaniline ethanol solution was uniformly sprayed onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5. The mixture was dispersed for 20 min using a high-speed disperser at 3000 rpm until homogeneous. This mixture was then applied to the surface of the bottom anti-corrosion coating using a scraping method, with a wet film thickness controlled at 50 μm. Curing was performed at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, where the prepared intelligent composite coating was sprayed onto the surface of the middle corrosion-inhibiting coating. The spraying pressure was set to 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, curing was performed at room temperature (25 ± 2 ℃) for 26 h, resulting in a complete three-layer protective system.

[0042] Example 3 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 °C and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain a yellow powder product, CUR-CS.

[0043] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is completed, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0044] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0045] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.8 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0046] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5, dispersing the mixture for 20 min using a high-speed disperser at 3000 rpm until homogeneous, and then coating it onto the bottom anti-corrosion coating surface using a scraping method. The wet film thickness was controlled at 50 μm, and the coating was cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, spraying the prepared intelligent composite coating onto the middle corrosion-inhibiting coating surface. The spraying pressure was set at 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system.

[0047] Example 4 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 ℃ and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 ℃ for 12 h to obtain a yellow powder product, CUR-CS.

[0048] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0049] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0050] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 5.2 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0051] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5, dispersing the mixture for 20 min using a high-speed disperser at 3000 rpm until homogeneous, and then coating it onto the bottom anti-corrosion coating surface using a scraping method. The wet film thickness was controlled at 50 μm, and the coating was cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, spraying the prepared intelligent composite coating onto the middle corrosion-inhibiting coating surface. The spraying pressure was set at 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system.

[0052] Example 5 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 ℃ and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 ℃ for 12 h to obtain a yellow powder product, CUR-CS.

[0053] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0054] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0055] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 5.6 g CUR-CS, and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, and stir at room temperature for 45 min until the system is homogeneous. Seal and store for later use. Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 min using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven for 30 min and cool to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer. A 10 wt% polyaniline ethanol solution was uniformly sprayed onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 hours. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5. The mixture was dispersed for 20 minutes using a high-speed disperser at 3000 rpm until homogeneous. This mixture was then applied to the surface of the bottom anti-corrosion coating using a scraping method, controlling the wet film thickness to 50 μm. Curing was carried out at room temperature (25 ± 2 ℃) for 12 hours. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer. The prepared intelligent composite coating was sprayed onto the surface of the middle corrosion-inhibiting coating, with a spraying pressure of 850 psi and a wet film thickness of 160 μm. After spraying, curing was carried out at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system. Example 6 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 °C and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain a yellow powder product, CUR-CS.

[0056] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0057] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0058] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.8 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0059] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5, dispersing the mixture for 20 min using a high-speed disperser at 3000 rpm until homogeneous, and then coating it onto the bottom anti-corrosion coating surface using a scraping method. The wet film thickness was controlled at 50 μm, and the coating was cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, spraying the prepared intelligent composite coating onto the middle corrosion-inhibiting coating surface. The spraying pressure was set at 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system.

[0060] Example 7 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 ℃ and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 ℃ for 12 h to obtain a yellow powder product, CUR-CS.

[0061] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0062] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.1. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0063] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.8 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0064] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5, dispersing the mixture for 20 min using a high-speed disperser at 3000 rpm until homogeneous, and then coating it onto the bottom anti-corrosion coating surface using a scraping method. The wet film thickness was controlled at 50 μm, and the coating was cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, spraying the prepared intelligent composite coating onto the middle corrosion-inhibiting coating surface. The spraying pressure was set at 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system.

[0065] Example 8 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 ℃ and stirred at a constant temperature for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 ℃ for 12 h to obtain a yellow powder product, CUR-CS.

[0066] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0067] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.3. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0068] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.8 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0069] Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 minutes using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse it 2-3 times with anhydrous ethanol to remove residual acetone. Finally, place it in an 80 ℃ forced-air drying oven to dry for 30 minutes and cool it to room temperature for later use. The substrate was prepared in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5, dispersing the mixture for 20 min using a high-speed disperser at 3000 rpm until homogeneous, and then coating it onto the bottom anti-corrosion coating surface using a scraping method. The wet film thickness was controlled at 50 μm, and the coating was cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, spraying the prepared intelligent composite coating onto the middle corrosion-inhibiting coating surface. The spraying pressure was set at 850 psi, and the wet film thickness was controlled at 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 hours. h, ultimately resulting in a complete three-layer protection system.

[0070] Example 9 1. Synthesis and preparation of CUR-CS (curcumin-chitosan graft compound): 10 g of chitosan (CS) and 100 mL of 1% acetic acid aqueous solution were added sequentially to a dry three-necked flask and stirred magnetically for 30 min until completely dissolved. 8 g of curcumin (CUR) and 5 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were added, and the mixture was heated to 50 °C and stirred for 6 h. After the reaction was completed, the pH of the system was adjusted to 7.0 with 10% NaOH solution. After standing to precipitate, the solid was collected by filtration, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain a yellow powder product, CUR-CS.

[0071] 2. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of dihydroxypropyl-terminated polymethylphenylsiloxane (HPPMS) to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of hexamethylene diisocyanate trimer (HDI trimer) in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C and add 5.2 g of γ-glycidoxypropyltrimethoxysilane (GPTMS) in one go, and continue the reaction for 3 h to complete the end-capping; after the reaction is completed, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0072] 3. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g of 3-aminopropylmethyldimethoxysilane (APMDS) and 4.1 g of 3-formyl-4-hydroxyphenylboronic acid (3-FPBA) were dissolved in 60 mL of anhydrous ethanol at a molar ratio of 1:1.4. 0.08 g of p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0073] 4. Preparation of intelligent composite coatings: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine, 4.8 g CUR-CS and 3.5 g dithiodisuccinimide propionate (DSP), add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use. Place the substrate to be coated (steel plate / marine engineering component metal substrate) in acetone and ultrasonically clean it for 15 min using a 300 W ultrasonic cleaner to remove surface oil. After removal, rinse 2-3 times with anhydrous ethanol to remove residual acetone. Finally, dry in an 80 ℃ forced-air drying oven for 30 min and cool to room temperature for later use. The substrate was packaged in three layers: First, the bottom anti-corrosion coating was applied using a Graco X7 high-pressure airless sprayer, where a 10 wt% polyaniline ethanol solution was uniformly sprayed onto the pretreated substrate surface. After spraying, the substrate was transferred to a 60 ℃ constant temperature oven for curing for 2 h. Second, the middle corrosion-inhibiting coating was applied by mixing MnO2 nanoparticles with flexible epoxy resin at a mass ratio of 1:4.5. The mixture was dispersed for 20 min using a high-speed disperser at 3000 rpm until homogeneous. This mixture was then applied to the surface of the bottom anti-corrosion coating using a scraping method, with a wet film thickness of 50 μm, and cured at room temperature (25 ± 2 ℃) for 12 h. Third, the outer anti-fouling coating was applied using a Graco X7 high-pressure airless sprayer, where the prepared intelligent composite coating was sprayed onto the surface of the middle corrosion-inhibiting coating. The spraying pressure was set to 850 psi, and the wet film thickness was controlled to 160 μm. After spraying, the coating was cured at room temperature (25 ± 2 ℃) for 26 h, resulting in a complete three-layer protective system.

[0074] Comparative Example 1 1. Synthesis of GPTMS-PPMS-PU (polymethylphenylsiloxane-polyurea copolymer): Add 50 g of HPPMS to a dry three-necked flask, heat to 40 °C and stir for 30 min; dissolve 9.5 g of HDI trimer in 30 mL of anhydrous propylene glycol methyl ether acetate, and slowly add it dropwise to the three-necked flask through a constant pressure dropping funnel, purging with high-purity nitrogen for protection, and stir at 40 °C for 4 h to complete the chain extension reaction; then heat to 75 °C, add 5.2 g of GPTMS at once, and continue the reaction for 3 h to complete the end-capping; after the reaction is complete, remove the solvent by vacuum distillation (60 °C / 0.08 MPa), cool to room temperature, and obtain the pale yellow transparent viscous liquid product GPTMS-PPMS-PU.

[0075] 2. Synthesis of GPM-Imine (a bifunctional intermediate containing an imine bond-phenylboronic ester): 5.2 g APMDS and 4.1 g 3-FPBA were dissolved in 60 mL anhydrous ethanol at a molar ratio of 1:1.2. 0.08 g p-toluenesulfonic acid was added as a catalyst, and the mixture was stirred at 40 °C for 7 h under high-purity nitrogen protection. After the reaction was completed, the anhydrous ethanol was removed by vacuum distillation (50 °C / 0.08 MPa). The residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1) and dried under reduced pressure to obtain a pale yellow oily product, GPM-Imine.

[0076] 3. Coating preparation: Mix 40 g GPTMS-PPMS-PU, 6.2 g GPM-Imine and 3.5 g DSP, add 0.06 g catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0077] The substrate to be coated was placed in acetone and ultrasonically cleaned for 15 min using a 300 W ultrasonic cleaner. After removal, it was rinsed three times with anhydrous ethanol. Finally, it was dried in an 80 ℃ forced-air drying oven for 30 min and cooled to room temperature for later use. The substrate was then packaged into three layers: the bottom anti-corrosion coating was sprayed with a 10 wt% polyaniline ethanol solution using a Graco X7 high-pressure airless sprayer and cured at 60 ℃ for 2 h; the middle corrosion inhibitor coating was a mixture of MnO2 nanoparticles and flexible epoxy resin at a mass ratio of 1:4.5, dispersed at 3000 rpm for 20 min, and applied with a wet film thickness of 50 μm, then cured at room temperature for 12 h; the outer anti-fouling coating was sprayed with the above mixture using a Graco X7 high-pressure airless sprayer at a spray pressure of 850 psi, a wet film thickness of 160 μm, and cured at room temperature for 26 h, resulting in a complete three-layer protective system.

[0078] Comparative Example 2 1. Preparation of PDMS coating: Mix 50 g of polydimethylsiloxane (PDMS) with 3.5 g of DSP, add 0.06 g of catalytic amount of acetic acid, stir at room temperature for 45 min until the system is homogeneous, and seal for later use.

[0079] The substrate to be coated was placed in acetone and ultrasonically cleaned for 15 min using a 300 W ultrasonic cleaner. After removal, it was rinsed three times with anhydrous ethanol. Finally, it was dried in an 80 ℃ forced-air drying oven for 30 min and cooled to room temperature for later use. The substrate was then packaged into three layers: the bottom anti-corrosion coating was sprayed with a 10 wt% polyaniline ethanol solution using a Graco X7 high-pressure airless sprayer and cured at 60 ℃ for 2 h; the middle corrosion inhibitor coating was a mixture of MnO2 nanoparticles and flexible epoxy resin at a mass ratio of 1:4.5, dispersed at 3000 rpm for 20 min, and applied with a wet film thickness of 50 μm, then cured at room temperature for 12 h; the outer anti-fouling coating was sprayed with the above PDMS mixed solution using a Graco X7 high-pressure airless sprayer at a spray pressure of 850 psi, a wet film thickness of 160 μm, and cured at room temperature for 26 h, resulting in a complete three-layer protective system.

[0080] The properties of the coatings prepared according to the embodiments and comparative examples of the present invention are shown in the table below: Table 1. Properties of coatings prepared in Examples 1-9 and Comparative Examples 1-2

[0081] Examples 1-5, and Comparative Examples 1 and 2, show that the addition of CUR-CS has a significant impact on the antibacterial properties, salt spray resistance, and seawater immersion life of the prepared smart composite coating. When the amount of CUR-CS added is 12% of the mass of GPTMS-PPMS-PU, the antibacterial properties, salt spray resistance, and seawater immersion life of the coating are optimal. When the amount added exceeds 12 wt%, the compatibility of the coating decreases, and some properties show slight degradation.

[0082] As can be seen from Example 3, Comparative Example 1, and Comparative Example 2, the molar ratio of APMDS to 3-FPBA has a key impact on the tensile strength, adhesion, and pH response sensitivity of the smart coating. When the molar ratio of APMDS to 3-FPBA is 1:1.2, the overall performance of the coating is the best. Comparative Example 2 uses only PDMS as the substrate, and its mechanical properties, adhesion, and antifouling performance are significantly inferior to the solution of this invention.

[0083] Test results show that the composite marine antifouling coating of the multilayer dynamic system with synergistic regulation of antifouling, self-healing, and structural stability prepared in this invention is significantly superior to traditional PDMS coatings and comparative samples without CUR-CS in terms of mechanical properties, antibacterial properties, long-lasting effect, self-healing function, and adaptability to extreme environments. Through the synergistic design of enhanced N→B coordination by polyurea crosslinking network, pH response, and disulfide bond self-healing, the unity of antifouling performance, mechanical stability, and self-healing function is achieved.

[0084] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a composite marine antifouling coating, characterized in that, Includes the following steps: (1) Synthesis and preparation of curcumin-chitosan grafts: Curcumin-chitosan grafts were prepared by reacting chitosan, aqueous acetic acid, curcumin, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. (2) Synthesis of polymethylphenylsiloxane-polyurea copolymer: Using dihydroxypropyl-terminated polymethylphenylsiloxane and hexamethylene diisocyanate trimer as raw materials, the chain extension reaction was completed under nitrogen protection. Then, γ-glycidoxypropyltrimethoxysilane was added, and the reaction was continued to complete the end-capping. After the reaction was completed, the polymethylphenylsiloxane-polyurea copolymer was obtained by vacuum distillation. (3) Synthesis of bifunctional intermediates containing imine bonds-phenylboronic esters: Using 3-aminopropylmethyldimethoxysilane and 3-formyl-4-hydroxyphenylboronic acid as raw materials, p-toluenesulfonic acid was added as a catalyst and the reaction was carried out under nitrogen protection. After the reaction was completed, the bifunctional intermediate containing imine bond-phenylboronic ester was obtained by vacuum distillation, silica gel column chromatography purification, and vacuum drying. (4) Preparation of antifouling coatings A mixture of polymethylphenylsiloxane-polyurea copolymer, imine-phenylboronic acid ester bifunctional intermediate, curcumin-chitosan graft compound and dithiodisuccinimide propionate was prepared, and acetic acid was added. The mixture was stirred until the system was homogeneous to obtain an antifouling coating.

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of chitosan to curcumin is 5:4; the amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 62.5% of the mass of curcumin; the mass concentration of acetic acid aqueous solution is 1%; the reaction temperature is 50 ℃ and the reaction time is 6 h.

3. The method according to claim 1, characterized in that, In step (2), the chain extension reaction temperature is 40 ℃ and the stirring time is 4 h; the end-capping reaction temperature is 75 ℃ and the stirring time is 3 h, all under nitrogen protection.

4. The method according to claim 1, characterized in that, In step (2), the mass ratio of hexamethylene diisocyanate trimer to dihydroxypropyl-terminated polymethylphenylsiloxane is 0.15~0.20:1; the amount of γ-glycidoxypropyltrimethoxysilane used is 8.5~11% of the mass of dihydroxypropyl-terminated polymethylphenylsiloxane.

5. The method according to claim 1, characterized in that, In step (3), the molar ratio of 3-aminopropylmethyldimethoxysilane to 3-formyl-4-hydroxyphenylboronic acid is 1:1.0~1.4; the reaction temperature is 40 ℃, the stirring time is 7 h, and the reaction is protected by nitrogen.

6. The method according to claim 1, characterized in that, In step (4), the amount of curcumin-chitosan graft added is 10-14% of the mass of polymethylphenylsiloxane-polyurea copolymer; the amount of imine bond-phenylboronic acid ester bifunctional intermediate is 12.0-16.0% of the mass of polymethylphenylsiloxane-polyurea copolymer; the amount of dithiodisuccinimide propionate is 6.5-9.0% of the mass of polymethylphenylsiloxane-polyurea copolymer; and acetic acid is 0.10-0.15% of the mass of polymethylphenylsiloxane-polyurea copolymer.

7. The composite marine antifouling coating prepared by any one of claims 1 to 6.

8. The application of the composite marine antifouling coating of claim 7 in the protection of facilities against fouling and corrosion in marine environments.

9. A smart composite coating, wherein the composite marine antifouling coating of claim 7 is sprayed onto the surface of a substrate.

10. A method for preparing an intelligent composite coating, characterized in that, Includes the following steps: The substrate to be coated is cleaned and dried, and then coated in three layers: First, the bottom anti-corrosion coating is applied by uniformly spraying a 10 wt% polyaniline ethanol solution onto the pretreated substrate surface using a Graco X7 high-pressure airless sprayer, followed by curing. Second, the middle corrosion-inhibiting coating is applied by mixing MnO2 nanoparticles and flexible epoxy resin at a mass ratio of 1:4.5 until the system is homogeneous, then applying it to the surface of the bottom anti-corrosion coating using a scraping method, followed by curing. Third, the outer anti-fouling coating is applied by spraying the coating described in claim 7 onto the surface of the middle corrosion-inhibiting coating using a Graco X7 high-pressure airless sprayer, followed by curing, ultimately resulting in a composite coating.

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