An anti-adhesion high-strength natural rubber-polyampholyte composite gel material, a preparation method and application in marine antifouling

Abstract

The application discloses a preparation method of an anti-adhesion high-strength natural rubber-polyampholyte composite hydrogel material, which comprises the following steps: dissolving methacrylic acid sulfobetaine in a natural rubber emulsion, adding N,N-methylene bisacrylamide and ammonium persulfate, fully stirring and dissolving to obtain a prepolymer mixed solution, placing the prepolymer mixed solution in a sealed mold for thermal polymerization, taking the prepolymer mixed solution out of the mold, drying, and then soaking in water to obtain the natural rubber-polyampholyte composite hydrogel material; the mass ratio of the methacrylic acid sulfobetaine to the natural rubber in the prepolymer mixed solution is 3 / 5-1. The composite hydrogel prepared by the method has higher mechanical properties and excellent broad-spectrum antibacterial adhesion, seaweed adhesion and protein adhesion resistance. Based on the excellent mechanical properties and efficient marine antifouling performance, the marine antifouling application in a real marine environment for more than three months is realized.

Description

Technical Field

[0001] This invention relates to the field of new marine antifouling materials, and in particular to an anti-adhesion high-strength natural rubber-zwitterionic composite gel material, its preparation method, and its application in marine antifouling. Background Technology

[0002] Marine biofouling, caused by the attachment and invasion of marine organisms such as bacteria, algae, and shellfish, severely damages underwater facilities. It results in over $15 billion in economic losses annually, particularly in shipping, aquaculture, and offshore oil and gas extraction.

[0003] To address this problem, numerous methods for combating biofouling have been developed, primarily including physical removal and chemical-biological control technologies. Physical removal techniques include manual or mechanical removal of biofouling, as well as more recent ultraviolet or ultrasonic-assisted cleaning methods. These methods are low-cost but cumbersome and inefficient. Chemical-biological control technologies maintain long-term resistance to marine organism adhesion through chemical surface coatings that kill marine organisms. Biocidal agents have evolved from highly toxic (such as chlorinated oxidizing agents, tributyltin, and zinc sulfide) to less toxic (such as organic quaternary ammonium salts and inorganic cuprous oxide). For example, Chinese patent CN201822198294.X discloses a chlorinated natural rubber-based anti-corrosion and antifouling coating. Below the chlorinated natural rubber anti-corrosion layer is a chlorosulfonated natural rubber anti-corrosion layer, below which is a zinc-rich inorganic silicate anti-rust underlayer, and above the chlorinated natural rubber anti-corrosion layer is a copper-containing chlorosulfonated natural rubber antifouling layer. Although these methods offer good resistance to corrosion and marine microbial adhesion, they may release toxic substances that could damage the marine environment. Furthermore, the antifouling layer can detach under the constant onslaught of marine life and the powerful scouring of waves and tides in harsh marine conditions.

[0004] In recent years, researchers have proposed that hydrogels with hydrophilic three-dimensional networks can load various non-toxic bio-bacterial agents and resist marine biofouling over a long period through controlled release. However, existing hydrogels, due to their high water content, have relatively low mechanical strength and cannot withstand the continuous invasion of marine organisms and the strong erosion of waves / tides under harsh marine conditions. Therefore, there is a need to develop a high-strength, anti-adhesion natural rubber-zwitterionic composite gel material. Summary of the Invention

[0005] In view of this, the present invention provides an anti-adhesion high-strength natural rubber-zwitterionic composite gel material, which solves the problem that the existing hydrogel materials have relatively low mechanical strength and cannot withstand the continuous invasion of marine organisms and the strong scouring of waves / tides under harsh marine conditions.

[0006] This invention employs a method for preparing a high-strength, anti-adhesion natural rubber-zwitterionic composite hydrogel material, characterized by the following steps: dissolving sulfobetaine methacrylate in a natural rubber emulsion, adding N,N-methylenebisacrylamide and ammonium persulfate, stirring thoroughly to dissolve and obtain a prepolymer mixture, then placing it in a sealed mold for thermal polymerization, and finally removing it from the mold, drying it, and immersing it in water to obtain the natural rubber-zwitterionic composite hydrogel material; the mass ratio of sulfobetaine methacrylate to natural rubber in the prepolymer mixture is 3 / 5-1.

[0007] Preferably, the mass ratio of methacrylic acid sulfobetaine to natural rubber in the prepolymer mixture is 1.

[0008] Preferably, the solid content of the natural rubber latex is 25%.

[0009] Preferably, the thermal polymerization conditions are 40-70℃ for 2-4 hours.

[0010] Preferably, the thermal polymerization conditions are 65°C for 3 hours.

[0011] Preferably, the drying conditions are 40-70℃ for 1-3 hours.

[0012] Preferably, the drying conditions are 65°C for 2 hours.

[0013] Another aspect of the present invention provides an anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material and its application in the preparation of marine antifouling coatings.

[0014] This invention provides a method for preparing a high-strength, anti-adhesion natural rubber-zwitterionic composite gel material. First, zwitterionic monomers are dissolved in a natural rubber latex, and then thermally polymerized under the action of an initiator and a crosslinking agent. The natural rubber nanoparticles in the latex have a hydrophilic protein shell layer, which can be uniformly dispersed in the zwitterionic covalent crosslinking network. Furthermore, the carboxylic acid groups (negative charge) of the protein shell layer of the natural rubber nanoparticles can form supramolecular crosslinks with the quaternary ammonium groups (positive charge) of the zwitterionic molecular chains. Finally, high-temperature drying is used to induce supramolecular interactions between the natural rubber nanoparticles. The method is simple and easily industrialized.

[0015] Furthermore, a high-strength, anti-adhesion natural rubber-zwitterionic composite hydrogel material prepared using this method not only exhibits higher mechanical strength (tensile strength and elongation at break increased from 0.04 MPa and 94% to 0.52 MPa and 738%, respectively), but also demonstrates excellent broad-spectrum antibacterial, antialgae, and antiprotein adhesion properties. Based on the strong mechanical properties and efficient marine antifouling performance of this NR-PZW composite hydrogel, excellent antifouling performance was achieved for more than 3 months in a real marine environment. This NR-PZW composite hydrogel is expected to achieve efficient, low-cost, and large-scale marine antifouling applications in the future. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the NR-PZW composite hydrogel of the present invention;

[0017] Figure 2 The image shows a comparison of the FT-IR spectrum (a), SEM image (b), and EDS mapping image (c) of the NR-PZW composite hydrogel prepared in Example 1, as well as NR nanoparticles, NR sheets, and PZW hydrogel.

[0018] Figure 3 The XPS spectra of the NR-PZW composite hydrogel prepared in Example 1 and the XPS peak fitting curves of NR and PZW (a) and NR-PZW (b).

[0019] Figure 4 Tensile properties of NR-PZW prepared with different NR and PZW ratios (a), tensile properties of PZW, NR and NR-PZW (b) and SEM images (c).

[0020] Figure 5 The swelling images (a) of the NR-PZW hydrogel of Example 1 and the NR-PAM hydrogel of Comparative Example 1 in pure water and seawater, respectively, and the swelling rate (b) of the NR-PZW hydrogel in pure water and seawater, respectively.

[0021] Figure 6 Laser micrographs (ac) showing the resistance of the NR-PZW hydrogel of Example 1 and the NR-PAM hydrogel of Comparative Example 1 to the adhesion of different bacteria; and the inhibition rate (d) of the NR-PZW hydrogel against the three bacteria.

[0022] Figure 7 Microscopic images (a) and coverage (b) of Chlorella adhering to NR-PAM hydrogel (Comparative Example 1) and NR-PZW hydrogel (Example 1), and fluorescence microscopy images (c) of fluorescently labeled proteins adhering to NR-PAM hydrogel and NR-PZW hydrogel.

[0023] Figure 8 Photographs of marine experiments on NR, NR-PAM hydrogel and NR-PZW hydrogel (a) and fouling coverage (b). Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] The natural rubber latex (60% solid content) involved in this patent was purchased from Huang Chunfa Co., Ltd. in Thailand, and methacrylic acid sulfobetaine, N,N-methylenebisacrylamide, and ammonium persulfate were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0026] Example 1: As Figure 1 A method for preparing a high-strength, anti-adhesion natural rubber-zwitterionic composite gel material includes the following steps:

[0027] (1) Take a natural rubber (NR) emulsion stock solution with a solid content of 60% and sonicate it for 30 minutes, then dilute it with pure water to a natural rubber emulsion with a solid content of 25%.

[0028] (2) Weigh 100 mg of sulfomethacrylic acid betaine (SBMA) and dissolve it in 0.4 g of natural rubber latex with a solid content of 25%. Then, add 1 mg of N,N-methylenebisacrylamide and 1 mg of ammonium persulfate sequentially and stir thoroughly to obtain a prepolymer solution. Then, place it in a sealed mold and heat polymerize it at 65°C for 3 h. After removing it from the mold, dry it at 65°C for 2 h and soak it in water for 30 min to obtain a natural rubber-zwitterionic (NR-PZW) composite hydrogel. The mass ratio of SBMA / NR is 20 / 20.

[0029] In another embodiment, the thermal polymerization conditions are 40-70°C for 2-4 hours.

[0030] In another embodiment, the drying conditions are 40-70°C for 1-3 hours.

[0031] Example 2: The difference between Example 2 and Example 1 is that the amount of natural rubber latex used is 0.186g (solid content 7.7%), 0.233g (solid content 14.3%), 0.3g (solid content 20%), 0.566g (solid content 29.4%), and 0.9g (solid content 33.3%), respectively. The effect of different SBMA / NR mass ratios on the mechanical properties of NR-PZW composite hydrogel is shown in Table 1. With the increase of natural rubber content, the tensile strength of NR-PZW composite hydrogel increases to a maximum of 0.52MPa, and the tensile strain increases to 738%.

[0032] Table 1. Effect of different SBMA / NR mass ratios on the mechanical properties of NR-PZW composite hydrogels

[0033]

[0034] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that acrylamide (AM) is used instead of sulfobetaine methacrylate (SBMA) to obtain NR-PAM composite hydrogel.

[0035] Comparative Example 2: Preparation of PZW hydrogel: Weigh 100 mg of methacrylic acid sulfobetaine, 1 mg of N,N-methylenebisacrylamide and 1 mg of ammonium persulfate and stir thoroughly to dissolve to obtain a mixture. Then place it in a sealed mold and heat polymerize at 65°C for 3 h. Then remove it from the mold and dry it at 65°C for 2 h. Soak it in water to obtain PZW hydrogel.

[0036] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not undergo a drying step. Instead, it is directly placed in a sealed mold and thermally polymerized at 65°C for 3 hours, then immersed in water to obtain a composite hydrogel. This indicates that the drying operation induces supramolecular interactions between the NR nanoparticles, further enhancing the mechanical properties of the composite hydrogel.

[0037] Table 2 Effect of drying time and conditions on the mechanical properties of the composite hydrogel

[0038] project Example 1 Comparative Example 3 Tensile strength 0.52MPa 0.24MPa Tensile strain 738％ 363％

[0039] The NR-PZW composite hydrogel prepared in Example 1 was characterized and its performance was tested. The results are as follows:

[0040] (1) The chemical structures of natural rubber NR, PZW hydrogels, and NR-PZW hydrogels were characterized using Fourier transform infrared spectroscopy (FT-IR), and the results are as follows: Figure 2 a. Comparing the spectra of NR and PZW hydrogels, it can be seen that the PZW hydrogel spectrum contains SBMA located at 1033 cm⁻¹. -1 and 1064cm -1 The NR-PZW hydrogel exhibits two characteristic peaks associated with sulfonic acid groups, while NR nanoparticles (mainly composed of polyisoprene and rubber protein) lack these peaks in their spectrum. Therefore, the presence of these two characteristic peaks in the NR-PZW hydrogel spectrum confirms the presence of PZW in its structure. Furthermore, the NR-PZW hydrogel spectrum also shows four characteristic peaks highly consistent with NR (located at 2751-3014 cm⁻¹). -1 1448cm -1 1375cm -1 840cm -1This demonstrates that the NR-PZW hydrogel also contains NR. Furthermore, the NR nanoparticles were observed using SEM and EDS. Figure 2 b): The average particle size of the NR nanoparticles is approximately 500 ± 300 nm, and each nanoparticle has a wrinkled surface with a high surface area. EDS-mapping revealed a clear but weak sulfur signal, confirming that the thin protein layer on the outer layer of the NR nanoparticles contains a small amount of sulfur (since the interior of the NR nanoparticles is composed of polyisoprene, which does not contain sulfur). Furthermore, elemental analysis was performed on the NR sheets, PZW hydrogel, and NR-PZW hydrogel based on SEM-linked EDS mapping. Figure 2 c). The moderate-intensity S-element signal of the NR-PZW hydrogel, compared to the weak S-element signal of the NR sheet and the ultra-high intensity S-element signal of the PZW hydrogel, also confirms that it is synthesized from NR and PZW. The uniform distribution of the S-element signal in the NR-PZW hydrogel further indicates the homogeneous composite of NR and PZW.

[0041] (2) Elemental analysis of NR, PZW hydrogels, and NR-PZW hydrogels was performed using X-ray photoelectron spectroscopy (XPS). Both PZW and NR-PZW hydrogels exhibited strong S2p characteristic peaks in the 165-170 eV range, while the corresponding positions in the NR spectrum showed almost no signal. Figure 3 a). Experimental results demonstrate the presence of sulfur-containing PZW in the NR-PZW hydrogel. Furthermore, a clearer XPS peak fitting curve was obtained from the NR-PZW hydrogel ( Figure 3 (b) It can be seen that the S2p element signal originates from the superposition of two sulfonic acid group signals, S2p1 / 2 at 167.4 eV and S2p3 / 2 at 168.7 eV, verifying that the S element in the NR-PZW hydrogel originates from the zwitterionic sulfonic acid group. This further demonstrates the successful preparation of the NR-PZW composite hydrogel prepared in Example 1.

[0042] (3) Effect of different SBMA / NR mass ratios on the properties of NR-PZW hydrogels, such as Figure 4a. As the NR increases, from m(SBMA) / m(NR) = 35 / 5 to 20 / 20, the tensile properties of NR-PZW hydrogel gradually improve, reaching a peak at m(SBMA) / m(NR) = 20 / 20, where the tensile strength and tensile strain increase from 0.07 MPa and 111% to 0.52 MPa and 738%, respectively. With further increases in NR, from m(SBMA) / m(NR) = 20 / 20 to 10 / 30, the tensile strength of NR-PZW hydrogel gradually decreases, while the tensile strain remains essentially unchanged. Therefore, the formulation with m(SBMA) / m(NR) = 20 / 20 was selected for preparing NR-PZW hydrogels with optimal mechanical properties. Compared to PZW hydrogels, the tensile strength and tensile strain of NR-PZW hydrogels increase from 0.04 MPa and 94% to 0.52 MPa and 738%, respectively. Figure 4 b). SEM images show that the addition of NR causes significant changes in the microstructure of the NR-PZW hydrogel compared to the PZW hydrogel. Figure 4 c). The results show that the NR-PZW composite hydrogel prepared in Example 1 has sufficient mechanical properties to support its long-term use in harsh real marine environments.

[0043] (4) The swelling properties of NR-PZW hydrogel in fresh water and seawater were studied. Figure 5 When switched from freshwater to seawater, the NR-PZW hydrogel expanded by 50%, with its swelling ratio changing from 210% to 605%, confirming that the NR-PZW hydrogel has better hydrophilicity and a denser water film in seawater, exhibiting excellent anti-biofouling properties. This is attributed to the synergistic effect of the positively charged quaternary ammonium salt groups and negatively charged sulfonic acid groups in the PZW network, generating a strong anti-polyelectrolyte effect in high-salinity seawater. In contrast, the NR-PAM hydrogel, serving as a control group, showed significant volume shrinkage when switched from freshwater to seawater, with its swelling ratio decreasing from 338% to 214%. This is likely due to the PZW network incorporating charged NR nanoparticles, producing a polyelectrolyte-like effect.

[0044] (5) The antibacterial adhesion performance of the NR-PZW hydrogel in Example 1 was tested using a staining method. Representative Gram-positive bacteria (Escherichia coli), Gram-negative bacteria (Staphylococcus aureus), and a unique marine bacterium (Vibrio alginolyticus) were selected. Confocal laser imaging showed that the NR-PAM hydrogel, used as the control group, exhibited severe Escherichia coli adhesion on its surface, while the NR-PZW hydrogel surface showed only a small number of bacteria. The calculated Escherichia coli inhibition rate reached 86.3%. Figure 6 a, Figure 6d). Similar effects were observed in laser confocal images of Staphylococcus aureus and Vibrio alginolyticus, with the NR-PZW hydrogel showing higher inhibition rates against both bacteria, at 94.4% and 95.7%, respectively, demonstrating its highly efficient broad-spectrum antibacterial adhesion in marine environments. Figure 6 (bd). Experiments show that the NR-PZW hydrogel of Example 1 has excellent antibacterial adhesion properties.

[0045] (6) The anti-algae adhesion and anti-protein adhesion properties of NR-PZW hydrogel in marine environments were studied. Figure 7 Chlorella was selected to test the anti-algae adhesion performance of NR-PZW hydrogel. Microscopic images showed that NR-PAM hydrogel, as a control group, exhibited severe algae adhesion, with a Chlorella coverage rate of 7.72% calculated using ImageJ software; while NR-PZW hydrogel showed only a small amount of Chlorella on its surface, with a coverage rate of only 0.86%. Figure 7 b). The anti-algae adhesion performance of NR-PZW hydrogel was improved by 88.9% compared with the control group, further demonstrating that the NR-PZW hydrogel of Example 1 has excellent anti-algae adhesion performance.

[0046] The anti-protein adhesion properties of the NR-PZW hydrogel were further assessed using fluorescently labeled bovine serum albumin (BSA). The hydrogel was immersed in a BSA dispersion for 24 hours, and then removed. The fluorescence intensity on the sample surface was observed under a fluorescence microscope to evaluate the anti-adhesion properties of the NR-PZW hydrogel to BSA. Figure 7 As shown in Figure c, the NR-PAM hydrogel, serving as the control group, exhibits bright green strong fluorescence, indicating the presence of a large amount of BSA; conversely, the fluorescence on the surface of the NR-PZW hydrogel is very weak, indicating almost no BSA adhesion. This further demonstrates that the NR-PZW hydrogel of Example 1 possesses excellent BSA adhesion properties. Therefore, combined with the previous results on antibacterial and antialgae adhesion, its excellent marine antifouling performance is proven.

[0047] (7) To test the antifouling performance of NR-PZW hydrogel in practical applications, a three-month real-world marine trial was conducted in the waters near Haikou. Figure 8After three months of marine antifouling testing, the NR hydrogel exhibited a significant amount of dirt and algae on its surface, with a fouling area of ​​50.69% calculated using ImageJ software. This is attributed to the "blooming" effect produced by the NR after prolonged immersion in seawater, where hydrophilic substances such as proteins migrate to the surface, forming a nutrient-rich thin layer. This attracted a large number of microorganisms to the already weak antifouling properties of the NR. As a control sample, the NR-PAM hydrogel also showed severe fouling, with visible algae and large bacterial colonies, and a fouling area of ​​22.24%, indicating that ordinary hydrogels have limited antifouling performance in the ocean. In contrast, the NR-PZW hydrogel only showed a few slightly discolored areas, with a fouling area of ​​only 0.37%, demonstrating that its dense hydration layer effectively resists the adhesion of various marine organisms and limits subsequent biofouling.

[0048] Furthermore, the NR-PZW hydrogel remained intact after three months of wave impact, with its tensile strength decreasing only slightly from 0.52 MPa to 0.46 MPa. Figure 8 c). From the comprehensive performance comparison chart ( Figure 8 d) It can be seen that NR-PZW hydrogel possesses outstanding mechanical properties and excellent anti-biofouling properties. Therefore, NR-PZW hydrogel can provide long-term anti-biofouling performance in real marine environments.

[0049] In summary, the preparation method of the natural rubber-zwitterionic (NR-PZW) composite hydrogel provided by this invention is simple and easy to mass-produce. The natural rubber NR-PZW composite hydrogel prepared by this method not only possesses excellent mechanical properties, with its tensile strength and elongation at break significantly increased from 0.04 MPa and 94% to 0.52 MPa and 738%, respectively; but also exhibits excellent broad-spectrum antibacterial adhesion, antialgae adhesion, and antiprotein adhesion properties. Utilizing its highly efficient marine antifouling properties and strong mechanical properties, the PZW composite hydrogel can maintain excellent anti-bioadhesion performance for more than 3 months in actual marine environments.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an anti-adhesion, high-strength natural rubber-zwitterionic composite hydrogel material, characterized in that, The process includes the following steps: dissolving sulfobetaine methacrylate in natural rubber latex, adding N,N-methylenebisacrylamide and ammonium persulfate, stirring thoroughly to dissolve and obtain a prepolymer mixture, then placing it in a sealed mold for thermal polymerization, removing it from the mold, drying it, and immersing it in water to obtain a natural rubber-zwitterionic composite hydrogel material; the mass ratio of sulfobetaine methacrylate to natural rubber in the prepolymer mixture is 3:5-1; the drying conditions are 40-70℃ for 1-3 h.

2. The preparation method of the anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 1, characterized in that, The mass ratio of methacrylic acid sulfobetaine to natural rubber in the prepolymer mixture is 1.

3. The method for preparing an anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 1, characterized in that, The solid content of the natural rubber latex is 25%.

4. The preparation method of the anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 1, characterized in that, The thermal polymerization conditions are 40-70℃ for 2-4 hours.

5. The preparation method of the anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 4, characterized in that, The thermal polymerization conditions were 65°C for 3 hours.

6. The method for preparing an anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 5, characterized in that, The drying conditions are 65℃ for 2 hours.

7. A high-strength, anti-adhesion natural rubber-zwitterionic composite hydrogel material prepared by the method according to any one of claims 1 to 6.

8. The application of the anti-adhesion high-strength natural rubber-zwitterionic composite hydrogel material according to claim 7 in the preparation of marine antifouling coatings.

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