A long-lasting anti-marine biofouling polyvinyl alcohol film, its preparation method and application

Abstract

This invention relates to the field of functional coating technology, and discloses a long-lasting antifouling polyvinyl alcohol film, its preparation method, and its application. The preparation includes the following steps: Step 1, dissolving an antibacterial agent and a polysaccharide in a solvent and reacting at room temperature for 10-48 hours, followed by dialysis to obtain an antibacterial powder; then mixing the antibacterial powder and dopamine in a solvent for polymerization, and dialysis the reaction solution to obtain a modified antibacterial agent; Step 2, dissolving the modified antibacterial agent and polyvinyl alcohol in a solvent, mixing, and coating the mixture onto a substrate to obtain the polyvinyl alcohol film; the antibacterial agent is polyhexamethylene guanidine and / or polyethyleneimine; the polysaccharide is oxidized dextran or oxidized hyaluronic acid. This invention utilizes the excellent film-forming properties and abundant hydroxyl functional groups of polyvinyl alcohol, using dopamine as a linker to form hydrogen bonds with various antibacterial agents and polysaccharides, thus subjecting the antibacterial agents to more chemical bond constraints and limiting their release rate, thereby achieving long-lasting antifouling effect of the film.

Description

Technical Field

[0001] This invention relates to the field of functional coating technology, specifically to a long-lasting polyvinyl alcohol film that prevents marine biofouling, its preparation method, and its application. Background Technology

[0002] In recent years, biofouling and corrosion problems caused by marine equipment such as ships and coastal facilities in the marine environment have become increasingly serious. Marine biofouling can disrupt the streamlined structure of ships, increase their drag, thereby increasing fuel consumption and greenhouse gas emissions. In addition, marine biofouling can also cause invasive species and reduce aquaculture production. At the same time, large fouling organisms such as barnacles and mussels attached to materials can secrete acidic substances, accelerating the corrosion of marine equipment and causing serious safety hazards.

[0003] Marine fouling is widely recognized as a global challenge due to the extreme complexity of the marine environment and the diversity of fouling organisms (>4000 species). To address this challenge, several antifouling technologies have been applied to marine monitoring instruments, including substrate rinsing, ultrasonic control, and antifouling coatings. To date, antifouling coatings remain the most economical and effective measure to prevent marine fouling organisms from adhering to equipment surfaces.

[0004] However, the long-term antifouling effect of current antifouling coatings is still unsatisfactory, necessitating the shutdown of marine equipment for coating replacement and resulting in economic losses. The antifouling effect of marine antifouling coatings stems from the continuous release of antifouling agents into the environment. By binding the antifouling agent to the coating through physicochemical processes, the release rate can be reduced. Slower release not only prolongs the release process but also mitigates the damage to the marine ecosystem, making the antifouling coating more environmentally friendly. Furthermore, over 4,000 species of marine fouling organisms have been identified, and commonly used antifouling agents are unlikely to be effective against all of them. Additionally, some antimicrobial agents can lead to antibiotic resistance in fouling organisms, significantly reducing the antifouling performance of the coating.

[0005] CN 111410809 A discloses a sustained-release antibacterial polyvinyl alcohol (PVA) film based on an organometallic framework (MOF) and its preparation method. First, silver is loaded onto a MOF to obtain Ag-MOF nanoparticles. Then, the Ag-MOF nanoparticles are mixed into a PVA-based mixed solution and cast into a film to obtain a PVA / Ag-MOF film. This film exhibits excellent antibacterial properties. However, the interaction between the MOF and the silver nanoparticles is physical, limiting the sustained-release effect. Furthermore, Ag, as a heavy metal ion, can disrupt the marine ecological balance if released into the marine environment.

[0006] CN 106634275 A discloses a superhydrophilic / underwater superoleophobic coating material and its preparation method. The coating material consists of a primer layer and a topcoat layer. The primer layer mainly consists of hydroxyl-containing acrylic resin and its curing agent, while the topcoat layer consists of polyvinyl alcohol and nanoparticles. The curing agent in the primer can undergo a chemical crosslinking reaction with the polyvinyl alcohol. The specific preparation steps are as follows: coating the substrate surface with the primer layer; coating the topcoat layer and drying it at room temperature or low temperature for pre-crosslinking, so that chemical bonding occurs between the primer layer and the topcoat layer; immersing the coating in a crosslinking agent aqueous solution for a certain time; removing the coating from the crosslinking agent aqueous solution and drying it at room temperature, or subjecting it to high-temperature heat treatment to fully cure the primer layer. The coating material obtained by the above steps has a gradient micro / nano structure surface, exhibiting outstanding superhydrophilic and underwater superoleophobic properties, strong adhesion to the substrate, and good transparency. This coating material can be used as an anti-fog coating and also as a self-cleaning and antifouling coating for underwater facilities. However, the preparation method is very complex, and the nanoparticles are inorganic materials with limited compatibility with polyvinyl alcohol.

[0007] Therefore, it is crucial to develop a green, broad-spectrum, long-lasting, corrosion-resistant, antifouling, and erosion-resistant antifouling coating. Summary of the Invention

[0008] This invention addresses the shortcomings of existing antifouling coatings, such as short-lasting antifouling effects and decreased antifouling performance, by providing a polyvinyl alcohol film with broad applicability and long-lasting antifouling effect. In this film structure, amino compounds such as polyhexamethylene guanidine are used as antibacterial agents, which react with polysaccharides and dopamine, thereby subjecting the antibacterial agents to more chemical bond constraints and limiting their release rate, thus achieving long-lasting antifouling effect.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a long-lasting polyvinyl alcohol film that resists marine biofouling includes the following steps:

[0011] Step 1: Dissolve the antibacterial agent and polysaccharide in a solvent and react at room temperature for 10-48 hours, then dialyze to obtain antibacterial powder; then mix the antibacterial powder and dopamine in a solvent for polymerization reaction, and dialyze the reaction solution to obtain modified antibacterial agent;

[0012] Step 2: The modified antibacterial agent is dissolved and mixed with polyvinyl alcohol in a solvent and then coated onto the substrate to obtain the polyvinyl alcohol film;

[0013] The antibacterial agent is polyhexamethylene guanidine and / or polyethyleneimine; the polysaccharide is oxidized dextran or oxidized hyaluronic acid.

[0014] This invention utilizes the excellent film-forming properties and abundant hydroxyl functional groups of polyvinyl alcohol, which can form hydrogen bonds with various antibacterial agents. In addition, by adding a certain amount of dopamine to the solution, dopamine will simultaneously undergo Schiff base reaction and Michael addition reaction with polyvinyl alcohol, antibacterial agents and polysaccharides, which will subject the antibacterial agents to more chemical bond constraints and limit their release rate, thereby achieving long-term antifouling of the film. At the same time, the addition of polysaccharides also makes the film biocompatible, reducing the harm to other marine microorganisms while achieving long-term antifouling, thus achieving green and environmentally friendly functions.

[0015] The modified antibacterial powder selected in this invention carries a strong positive charge in a liquid environment, while the cell membranes of most fouling microorganisms are negatively charged. The modified antibacterial agent will destroy the cell membranes of fouling organisms through electrostatic action, causing them to die, thereby achieving a broad-spectrum antifouling effect. At the same time, this mechanism of electrostatic destruction of the cell membranes of fouling organisms will not produce drug resistance.

[0016] The mass ratio of the antibacterial agent to the polysaccharide is 1-5:1. The polysaccharide plays a role in improving the biocompatibility of the film, and the abundant hydroxyl groups in the polysaccharide also facilitate the formation of hydrogen bonds with the hydroxyl groups in polyvinyl alcohol. The ratio of the two affects the antibacterial properties and biocompatibility. Preferably, the mass ratio of the antibacterial agent to the polysaccharide is 2-3:1.

[0017] The mass ratio of dopamine to polysaccharide is 1:0.5-2.

[0018] The mass ratio of the modified antibacterial agent to polyvinyl alcohol is 1-2:1. As a film-forming agent, too little polyvinyl alcohol results in poor film-forming properties, and the antibacterial agent is released too quickly and lacks persistence. Conversely, too little antibacterial agent leads to a low release concentration that is insufficient for sterilization. Preferably, the mass ratio of the modified antibacterial agent to polyvinyl alcohol is 1:1.

[0019] The solvents used in steps 1 and 2 include at least one of deionized water, phosphate buffer, and artificial seawater. Deionized water is a common organic-inorganic solvent for antibacterial agent powders, while phosphate buffer and artificial seawater have higher ion concentrations, which can chelate with some functional groups of the antibacterial agent, thereby enhancing the mechanical properties of the film.

[0020] The polymerization reaction in step 1 is carried out at room temperature for 4-48 hours.

[0021] The antibacterial agent is polyhexamethylene guanidine, and the polysaccharide is oxidized dextran.

[0022] In step 1, the dialysis bag used for dialysis has a molecular weight cutoff of 6000-8000, and the dialysis time is 1-12 hours.

[0023] Preferably, in step 2, polyvinyl alcohol is dissolved in a solvent in advance, such as by heating to promote dissolution, or by stirring and dissolving at 60-100°C for 3-6 hours.

[0024] The substrate includes at least one of stainless steel sheet, titanium sheet, glass sheet, and silicon wafer.

[0025] Preferably, the pretreatment method for the substrate surface before coating includes at least one of sandblasting, sanding, and mechanical polishing.

[0026] Preferably, the coating includes any one of brush coating, spin coating, spray coating, etc.

[0027] This invention also provides a method for preparing a long-lasting antifouling polyvinyl alcohol (PVA) film according to the aforementioned method. The method produces a simple, rapid, uniform, and dense film with controllable thickness and good adhesion to the substrate. Due to the use of a brushing method and the excellent film-forming properties of PVA, coupled with its abundant hydroxyl groups, the film forms in the solvent while simultaneously bonding well with the metal substrate. Furthermore, the added modified antibacterial agent is uniformly distributed within the film. The antifouling agent's molecular chains form hydrogen bonds with the hydroxyl groups in PVA, reducing the antifouling agent's release rate and thus achieving a long-lasting, broad-spectrum antifouling effect on the film surface.

[0028] This invention also provides a long-lasting antifouling polyvinyl alcohol film prepared according to the described method. Due to its long-lasting antifouling effect, the polyvinyl alcohol film can be used in antifouling applications, including various marine equipment and numerous coastal facilities requiring fouling and corrosion resistance. The slow-release antifouling agent in the film, along with the strong positive charge of the antifouling agent, can destroy the cell membranes of marine fouling organisms such as bacteria and algae without inducing drug resistance, preventing effective attachment and growth, thereby achieving the purpose of preventing marine biofouling and providing a truly effective protective measure for marine equipment and coastal facilities.

[0029] The present invention also provides the application of the polyvinyl alcohol film as a coating in marine equipment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In this invention, substances with low toxicity such as amino-containing polyhexamethylene guanidine are used as antibacterial agents. They are combined with polysaccharides and dopamine. Through the bridging effect of dopamine, they interact with polyvinyl alcohol to achieve a long-lasting antifouling effect. The thickness of the film is controllable and it is well bonded to the substrate. The preparation process is simple, efficient, not limited by the shape and size of the substrate, and low in cost.

[0032] (2) The film in this invention does not contain heavy metal ions. The polyhexamethylene guanidine in the film has low toxicity and broad-spectrum antibacterial function. The film has a dense structure and can have good application prospects and economic benefits in the field of preventing marine biofouling. Attached Figure Description

[0033] Figure 1 This is a surface morphology diagram of a polyvinyl alcohol film containing a modified antibacterial agent.

[0034] Figure 2 Infrared spectra of polyvinyl alcohol film (a) and polyvinyl alcohol film containing modified antibacterial agent (b).

[0035] Figure 3 The bacterial attachment morphology on the surface of the polyvinyl alcohol film containing the modified antibacterial agent in Example 1 is as follows: (a) Pseudomonas aeruginosa, (b) Staphylococcus aureus.

[0036] Figure 4 The image shows the release curve of the polyvinyl alcohol film containing the modified antibacterial agent in Example 1.

[0037] Figure 5 The bacterial attachment morphology on the surface of the polyvinyl alcohol film containing the modified antibacterial agent in Comparative Example 1 is shown in the figures: (a) Pseudomonas aeruginosa, (b) Staphylococcus aureus.

[0038] Figure 6 The surface morphology of the polyvinyl alcohol film containing the modified antibacterial agent is shown in Comparative Example 2.

[0039] Figure 7 The release curve of the polyvinyl alcohol film containing the modified antibacterial agent in Comparative Example 3 is shown.

[0040] Figure 8 The bacterial morphology on the surface of the polyvinyl alcohol film in Comparative Example 4 is shown in (a) Pseudomonas aeruginosa and (b) Staphylococcus aureus.

[0041] Figure 9 The release curve of the polyvinyl alcohol film containing the antibacterial agent in Comparative Example 5 is shown. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0043] To characterize the performance of the long-lasting anti-marine biofouling polyvinyl alcohol film of this invention, the prepared film samples were characterized using field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectrophotometry. The specific performance testing methods are as follows:

[0044] (1) Observation of the microstructure of the thin film surface: The dust on the surface of the prepared sample was blown off with a rubber bulb, and then gold was sprayed for 120s to make it conductive and prevent charge accumulation. Finally, the microstructure of the thin film surface was observed using SEM, and the thickness of the thin film was measured by a micrometer.

[0045] (2) Infrared spectroscopy test: The sample surface was inverted on the infrared spectrometer probe. Using ATR mode and with air as the background, the sample was measured sequentially at 400-4000 cm⁻¹. -1 Absorbance.

[0046] (3) Antifouling test: The prepared sample was immersed in a marine bacterial environment for 1 to 30 days. After that, the sample was fixed with glutaraldehyde, dehydrated with ethanol gradient, dried at critical point and sputtered with gold for 120 seconds. The adhesion, proliferation and growth of the sample on the material surface were observed by scanning electron microscopy.

[0047] (4) Antimicrobial agent release curve: Antimicrobial agent and modified antimicrobial agent solutions with gradient concentrations were prepared, and the characteristic absorption peaks of the solutions were tested at 200nm-2500nm to establish the relationship between the absorption peaks and the antimicrobial agent concentration. Then, the membrane was immersed in seawater for 1-15 days, and the concentration of antimicrobial agent released was calculated by testing the intensity of the antimicrobial agent absorption peak in the environment.

[0048] Example 1

[0049] Step 1: Weigh 1g of oxidized dextran and dissolve it in 50ml of deionized water. After it is fully dissolved, add 2g of polyhexamethylene guanidine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted polyhexamethylene guanidine. Then freeze-dry to obtain antibacterial powder.

[0050] Step 2: Weigh 1g of antibacterial agent powder and dissolve it in 10ml of deionized water. Add 1g of dopamine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted dopamine. Then freeze-dry to obtain modified antibacterial agent powder.

[0051] Step 3: Add 6g of polyvinyl alcohol powder to 100ml of deionized water, set the water bath heating temperature to 80℃, and stir for 5h to obtain a polyvinyl alcohol solution.

[0052] Step 4: Mix the polyvinyl alcohol solution and the modified antibacterial agent solution at a mass ratio of 1:1 (polyvinyl alcohol to modified antibacterial agent), and prepare a thin film sample on the metal surface by brush coating.

[0053] The thin films prepared above were subjected to the following performance tests:

[0054] (1) Observation of film surface morphology: The surface morphology of the film was detected using SEM, such as... Figure 1As shown, the surface is smooth and flat, the structure is dense, and the thickness is 12 micrometers.

[0055] (2) Thin film infrared spectroscopy test: The infrared absorption peaks of the thin film were detected using ATR mode, such as... Figure 2 As shown, (a) is a polyvinyl alcohol film, and (b) is a polyvinyl alcohol film containing a modified antibacterial agent, wherein 845.80 cm -1 1084.98cm -1 1327.52cm -1 1413.29cm -1 3248.88cm -1 The infrared characteristic peak of the polyvinyl alcohol film is shown. After adding the modified antibacterial agent, the infrared peak of the film shifts slightly, and a new peak at 1631.3 cm⁻¹ appears. -1 The infrared characteristic peak of the guanidine group in the modified antibacterial agent is shown. Furthermore, the hydrogen bonds formed between the modified antibacterial agent and the polyvinyl alcohol film cause the hydroxyl peak to rise from 3248.88 cm⁻¹. -1 Offset to 3266.42cm -1 .

[0056] (3) Antifouling test: Typical marine fouling bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, were selected and subjected to standard culture (culture medium, shaking), bacterial attachment (immersing the sample in artificial seawater containing bacteria and culturing normally for 7 days), glutaraldehyde fixation, and alcohol gradient dehydration. The bacterial colonization on the film surface was detected using a scanning electron microscope (SEM). The results are as follows: Figure 3 As shown, (a) *Pseudomonas aeruginosa* and (b) *Staphylococcus aureus*. It is evident that the amount of bacteria adhering to the film surface is small, indicating good antifouling effect.

[0057] (4) Antibacterial agent release curve: After soaking in seawater for a period of time, such as Figure 4 As shown, the total release of modified antibacterial agent is about 50% after 70 hours.

[0058] Comparative Example 1

[0059] Step 1: Weigh 1g of oxidized dextran and dissolve it in 50ml of deionized water. After it is fully dissolved, add 0.5g of polyhexamethylene guanidine and react at room temperature for 24h. Dialyze the reaction solution with a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted polyhexamethylene guanidine. Freeze-dry to obtain antibacterial agent powder.

[0060] Step 2: Weigh 1g of antibacterial agent powder and dissolve it in 10ml of deionized water. Add 1g of dopamine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted dopamine. Then freeze-dry to obtain modified antibacterial agent powder.

[0061] Step 3: Add 6g of polyvinyl alcohol powder to 100ml of deionized water, set the water bath heating temperature to 80℃, and stir for 5h to obtain a polyvinyl alcohol solution.

[0062] Step 4: Mix the polyvinyl alcohol solution and the modified antibacterial agent solution at a mass ratio of 1:1 (polyvinyl alcohol to modified antibacterial agent), and prepare a thin film sample on the metal surface by brush coating.

[0063] The thin films prepared above were subjected to the following performance tests:

[0064] (1) Observation of film surface morphology: The surface morphology of the film was detected by SEM. The surface was smooth and flat with a dense structure.

[0065] (2) Antifouling Test: Typical marine fouling bacteria, *Pseudomonas aeruginosa* and *Staphylococcus aureus*, were selected and subjected to a series of processes including standard culture (culture medium, shaking), bacterial attachment (immersing the sample in artificial seawater containing bacteria and incubating for 7 days), glutaraldehyde fixation, and gradient dehydration with alcohol. The bacterial colonization on the film surface was then detected using a scanning electron microscope (SEM). For example... Figure 5 As shown, (a) Pseudomonas aeruginosa and (b) Staphylococcus aureus have a large number of bacteria adhering to the surface containing modified antibacterial agent, indicating that the content of modified antibacterial agent in polyvinyl alcohol film is too low to achieve long-term antifouling effect.

[0066] Comparative Example 2

[0067] Step 1: Weigh 1g of oxidized dextran and dissolve it in 50ml of deionized water. After it is fully dissolved, add 2g of polyhexamethylene guanidine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted polyhexamethylene guanidine. Then freeze-dry to obtain antibacterial powder.

[0068] Step 2: Weigh 1g of antibacterial agent powder and dissolve it in 10ml of deionized water. Add 1g of dopamine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted dopamine. Then freeze-dry to obtain modified antibacterial agent powder.

[0069] Step 3: Add 6g of polyvinyl alcohol powder to 100ml of deionized water, set the water bath heating temperature to 80℃, and stir for 5h to obtain a polyvinyl alcohol solution.

[0070] Step 4: Mix the polyvinyl alcohol solution and the modified antibacterial agent solution at a mass ratio of 1:2 (polyvinyl alcohol to modified antibacterial agent), and prepare a thin film sample on the metal surface by brush coating.

[0071] The thin films prepared above were subjected to the following performance tests:

[0072] (1) Observation of film surface morphology: The surface morphology of the film was detected using SEM, such as... Figure 6 As shown, the surface is rough and the film is discontinuous with obvious cracks.

[0073] (2) Antifouling test: Typical marine fouling bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, were selected and subjected to standard culture (culture medium, shaking), bacterial adhesion (immersing the sample in artificial seawater containing bacteria and culturing normally for 7 days), glutaraldehyde fixation, and alcohol gradient dehydration. The bacterial colonization on the film surface was detected using a scanning microscope (SEM). A large amount of bacteria attached to the film surface indicated poor antifouling effect.

[0074] Comparative Example 3

[0075] Step 1: Weigh 1g of oxidized dextran and dissolve it in 50ml of deionized water. After complete dissolution, add 2g of polyhexamethylene guanidine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted polyhexamethylene guanidine. Then freeze-dry to obtain antibacterial agent powder.

[0076] Step 2: Weigh 1g of antibacterial agent powder and dissolve it in 10ml of deionized water. Add 1g of dopamine and react at room temperature for 24h. Dialyze the reaction solution through a dialysis bag with a molecular weight of 7000 for 72h to remove unreacted dopamine. Then freeze-dry to obtain modified antibacterial agent powder.

[0077] Step 3: Add 6g of polyvinyl alcohol powder to 100ml of deionized water, set the water bath heating temperature to 80℃, and stir for 5h to obtain a polyvinyl alcohol solution.

[0078] Step 4: Mix the polyvinyl alcohol solution and the modified antibacterial agent solution at a mass ratio of 2:1, and prepare a thin film sample on the metal surface by brush coating.

[0079] The thin films prepared above were subjected to the following performance tests:

[0080] (1) Observation of film surface morphology: The surface morphology of the film was detected by SEM and it was observed that the surface was smooth and the structure was dense.

[0081] (2) Antibacterial agent release curve: After soaking in seawater for a period of time, such as Figure 7 As shown, the total release of modified antibacterial agent was about 17.8% after 6 hours. The release rate of antibacterial agent was too slow, resulting in a low concentration of antibacterial agent in the surrounding environment, which could not achieve the antifouling function.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 is that no antibacterial agent is added, and pure polyvinyl alcohol film is prepared directly, while the other steps are the same.

[0084] The thin films prepared above were subjected to the following performance tests:

[0085] (1) Observation of film surface morphology: The surface morphology of the film was detected by SEM. The surface was smooth and flat with a dense structure. The film thickness was about 8 micrometers.

[0086] (2) Antifouling Test: Typical marine fouling bacteria, *Pseudomonas aeruginosa* and *Staphylococcus aureus*, were selected and subjected to a series of processes including standard culture (culture medium, shaking), bacterial attachment (immersing the sample in artificial seawater containing bacteria and incubating for 7 days), glutaraldehyde fixation, and gradient dehydration with alcohol. The bacterial colonization on the film surface was then detected using a scanning electron microscope (SEM). For example... Figure 8 As shown, (a) Pseudomonas aeruginosa and (b) Staphylococcus aureus, a large number of bacteria adhere to the surface of the film, resulting in poor antifouling effect.

[0087] Comparative Example 5

[0088] The difference between this comparative example and Example 1 is that the dopamine reaction in step 2 is omitted, and the antibacterial agent obtained in step 1 is directly mixed with polyvinyl alcohol to prepare a film. All other steps are the same.

[0089] The thin films prepared above were subjected to the following performance tests:

[0090] (1) Observation of film surface morphology: The surface morphology of the film was detected by SEM. The surface was smooth and flat with a dense structure. The film thickness was about 10 micrometers.

[0091] (2) Antifouling test: Pseudomonas aeruginosa, a typical marine fouling bacterium, was selected and subjected to a series of processes including standard culture (culture medium, shaking), bacterial adhesion (immersing the sample in artificial seawater containing bacteria and culturing normally for 7 days), glutaraldehyde fixation, and alcohol gradient dehydration. The bacterial colonization on the film surface was detected using a scanning electron microscope (SEM). Only a small number of bacteria adhered to the film surface.

[0092] (3) Antibacterial agent release curve: After soaking in seawater for a period of time, such as Figure 9 As shown, the total antibacterial agent release rate is approximately 70%, but the release rate is very fast, especially in the first few hours. For example, Example 1 releases about 37% after 3 hours, while this comparative example releases 53% after 3 hours.

[0093] This invention utilizes the abundant functional groups of dopamine to undergo physicochemical reactions with antibacterial agents and polyvinyl alcohol films, thereby reducing the release rate of antibacterial agents in the seawater environment, providing a new solution for long-term antifouling of marine equipment surfaces.

Claims

1. A method for preparing a long-lasting polyvinyl alcohol film that prevents marine biofouling, characterized in that, Including the following steps: Step 1: Dissolve the antibacterial agent and polysaccharide in a solvent and react at room temperature for 10-48 hours. Then, dialyze the mixture to obtain the antibacterial powder. Next, mix the antibacterial powder and dopamine in a solvent to polymerize and undergo a Schiff base reaction. The reaction solution is then dialyzed to obtain the modified antibacterial agent. Step 2: The modified antibacterial agent is dissolved and mixed with polyvinyl alcohol in a solvent and then coated onto the substrate to obtain the polyvinyl alcohol film; The antibacterial agent is polyhexamethylene guanidine and / or polyethyleneimine; the polysaccharide is oxidized dextran or oxidized hyaluronic acid. The mass ratio of the antibacterial agent to the polysaccharide is 1-5:1; the mass ratio of the modified antibacterial agent to polyvinyl alcohol is 1:

1.

2. The method for preparing a long-lasting anti-marine biofouling polyvinyl alcohol film according to claim 1, characterized in that, The mass ratio of dopamine to polysaccharide is 1:0.5-2.

3. The method for preparing a long-lasting anti-marine biofouling polyvinyl alcohol film according to claim 1, characterized in that, The solvent in step 1 or step 2 includes at least one of deionized water, phosphate buffer, and artificial seawater.

4. The method for preparing a long-lasting anti-marine biofouling polyvinyl alcohol film according to claim 1, characterized in that, The polymerization reaction in step 1 is carried out at room temperature for 4-48 hours.

5. The method for preparing a long-lasting anti-marine biofouling polyvinyl alcohol film according to claim 1, characterized in that, The antibacterial agent is polyhexamethylene guanidine, and the polysaccharide is oxidized dextran.

6. The method for preparing a long-lasting anti-marine biofouling polyvinyl alcohol film according to claim 1, characterized in that, In step 1, the dialysis bag used for dialysis has a molecular weight cutoff of 6000-8000, and the dialysis time is 1-12 hours.

7. A long-lasting anti-marine biofouling polyvinyl alcohol film prepared by the preparation method according to any one of claims 1-6.

8. The application of the polyvinyl alcohol film as a coating in marine equipment according to claim 7.

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