Anti-adhesion high-strength natural rubber-poly-zwitter-ion composite gel material, preparation method and application in marine antifouling

Abstract

The invention discloses a preparation method of an anti-adhesion high-strength natural rubber-poly-zwitter-ion composite hydrogel material, which comprises the following steps: dissolving methacrylic acid sulfobetaine in natural rubber latex, adding N, N-methylene bisacrylamide and ammonium persulfate, fully stirring and dissolving to obtain a pre-polymerized mixed solution, then putting the pre-polymerized mixed solution in a sealed mold for thermal polymerization, and finally obtaining the anti-adhesion high-strength natural rubber-poly-zwitter-ion composite hydrogel material. Taking out from the mold, drying, and soaking in water to obtain the natural rubber-poly-zwitter-ion composite hydrogel material. The mass ratio of the sulfobetaine methacrylate to the natural rubber in the pre-polymerized mixed solution is 3 / 5-1. The composite hydrogel prepared by the method not only has higher mechanical properties, but also shows excellent broad-spectrum bacterial adhesion resistance, seaweed adhesion resistance and protein adhesion resistance. Based on the excellent mechanical property and the efficient marine antifouling property, the marine antifouling application in a real marine environment for more than 3 months is realized.

Description

Technical Field

[0001] The invention relates to the field of new marine antifouling materials, and in particular to an anti-adhesion high-strength natural rubber-polyzwitterion composite gel material, a preparation method thereof, and application in marine antifouling. Background Art

[0002] Marine biofouling is caused by the attachment and invasion of marine organisms such as bacteria, algae and shellfish, which causes serious damage to underwater facilities. Marine biofouling causes economic losses of more than US$15 billion each year, especially in shipping, aquaculture and offshore oil / gas extraction.

[0003] In order to solve this problem, people have developed many methods to resist biofouling, mainly including physical elimination and chemical biocidal technology. Physical elimination technology includes manual or mechanical removal of biofouling, and more recently, ultraviolet or ultrasonic assisted cleaning methods, which are low-cost, but cumbersome and inefficient. Chemical biocidal technology can maintain resistance to marine bioadhesion for a long time through chemical surface coatings that kill marine organisms. Biocidal agents have evolved from high toxicity (such as chlorine-based oxidizing fungicides, tributyltin and zinc sulfide) to low toxicity (such as organic quaternary ammonium salts and inorganic cuprous oxide). For example, Chinese patent CN201822198294.X discloses an anti-corrosion and anti-fouling coating based on chlorinated natural rubber, wherein a chlorosulfonated natural rubber anti-corrosion layer is below the chlorinated natural rubber anti-corrosion layer, a zinc-rich inorganic silicate anti-rust base layer is below the chlorosulfonated natural rubber anti-corrosion layer, and a copper-containing chlorosulfonated natural rubber anti-fouling layer is above the chlorinated natural rubber anti-corrosion layer. Although these methods have good anti-corrosion and anti-marine microbial adhesion properties, they may release toxic substances, thereby damaging the marine environment. In addition, the anti-fouling layer may also fall off due to the continuous invasion of marine organisms and the strong scouring of waves / tides under harsh marine conditions.

[0004] In recent years, researchers have proposed that hydrogels with hydrophilic three-dimensional networks can load a variety of non-toxic biocidal agents and resist marine biofouling for a long time through controlled release. However, due to the high water content and relatively low mechanical strength of existing hydrogels, they cannot withstand the continuous invasion of marine organisms and the strong scouring of waves / tides under harsh marine conditions. Therefore, it is necessary to develop an anti-adhesion high-strength natural rubber-polyzwitterion composite gel material. Summary of the invention

[0005] In view of this, the present invention provides an anti-adhesion high-strength natural rubber-polyzwitterion composite gel material to solve 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] On one hand, the present invention adopts a preparation method of an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material, which is characterized by comprising the following steps: dissolving methacrylic acid sulfobetaine in natural rubber latex, adding N,N-methylenebisacrylamide and ammonium persulfate and fully stirring and dissolving to obtain a prepolymerization mixture, then placing it in a sealed mold for thermal polymerization, then taking it out from the mold for drying and soaking it in water to obtain the natural rubber-polyzwitterion composite hydrogel material; the mass ratio of methacrylic acid sulfobetaine to natural rubber in the prepolymerization mixture is 3 / 5-1.

[0007] Preferably, the mass ratio of methacrylate 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 condition is 40-70° C. for 2-4 h.

[0010] Preferably, the thermal polymerization condition is 65° C. for 3 h.

[0011] Preferably, the drying condition is 40-70° C. for 1-3 h.

[0012] Preferably, the drying condition is 65° C. for 2 h.

[0013] On the other hand, the present invention also provides an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material and its application in preparing marine antifouling coating.

[0014] The invention provides a preparation method of an anti-adhesion high-strength natural rubber-polyzwitterion composite gel material. The method comprises the following steps: firstly, using natural rubber latex to dissolve zwitterion monomers, and then performing thermal polymerization under the action of an initiator and a crosslinking agent. Natural rubber nanoparticles in the latex have a hydrophilic protein shell layer, which can be uniformly dispersed in a covalently crosslinked network of the polyzwitterion, and carboxylic acid groups (negative charges) of the protein shell layers of the natural rubber nanoparticles can form supramolecular crosslinks with quaternary ammonium groups (positive charges) of polyzwitterion molecular chains. High-temperature drying is then used to generate supramolecular effects between the natural rubber nanoparticles. The method is simple and easy to promote industrialization.

[0015] Furthermore, an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material prepared by this method not only has higher mechanical strength, but also has tensile strength and elongation at break increased from 0.04MPa and 94% to 0.52MPa and 738% respectively; and exhibits excellent broad-spectrum anti-bacterial adhesion, anti-seaweed adhesion and anti-protein adhesion properties. Based on the strong mechanical properties and efficient marine antifouling performance of the NR-PZW composite hydrogel, it has achieved excellent anti-biological fouling performance for more than 3 months in a real marine environment. The NR-PZW composite hydrogel is expected to achieve efficient, low-cost and large-scale marine antifouling applications in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the preparation process of the NR-PZW composite hydrogel of the present invention;

[0017] Figure 2 Comparison of the FT-IR spectra (a), SEM images (b), and EDS mapping images (c) of the NR-PZW composite hydrogel prepared in Example 1, as well as NR nanoparticles, NR flakes, and PZW hydrogel.

[0018] Figure 3 The NR-PZW composite hydrogel prepared in Example 1, as well as the XPS spectra of NR and PZW (a) and the XPS peak fitting curve of 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 rates (b) of the NR-PZW hydrogel in pure water and seawater.

[0021] Figure 6 Laser microscope photos of the NR-PZW hydrogel of Example 1 and the NR-PAM hydrogel of Comparative Example 1 in resisting adhesion of different bacteria (ac); and the inhibition rate of the NR-PZW hydrogel on three types of bacteria (d).

[0022] Figure 7 Microscope photos (a) and coverage (b) of the NR-PAM hydrogel of Comparative Example 1 and the NR-PZW hydrogel of Example 1 on Chlorella, and fluorescence microscope photos (c) of the adhesion of fluorescently labeled proteins on the NR-PAM hydrogel and the NR-PZW hydrogel.

[0023] Figure 8 Marine experimental photos (a) and fouling coverage (b) of NR, NR-PAM hydrogel and NR-PZW hydrogel. DETAILED DESCRIPTION

[0024] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

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

[0026] Embodiment 1: Figure 1 , a method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite gel material, comprising the following steps:

[0027] (1) A natural rubber (NR) latex stock solution with a solid content of 60% was ultrasonically treated for 30 minutes and then diluted with pure water to a natural rubber latex with a solid content of 25%.

[0028] (2) Weigh 100 mg of sulfobetaine methacrylate (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 in sequence and stir and dissolve to obtain a prepolymer solution, then place it in a sealed mold and heat polymerize it at 65°C for 3 hours, then take it out of the mold and dry it at 65°C for 2 hours, and soak it in water for 30 minutes to obtain a natural rubber-polyzwitterion (NR-PZW) composite hydrogel. The mass ratio of SBMA / NR is 20 / 20.

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

[0030] In another embodiment, the drying condition is 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 effects of different SBMA / NR mass ratios on the mechanical properties of NR-PZW composite hydrogel are shown in Table 1. With the increase of natural rubber content, the tensile strength of NR-PZW composite hydrogel is increased to 0.52MPa at the highest, and the tensile strain is increased 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 the NR-PAM composite hydrogel.

[0035] Comparative Example 2: Preparation of PZW hydrogel: Weigh 100 mg of methacrylate sulfobetaine, 1 mg of N,N-methylenebisacrylamide, and 1 mg of ammonium persulfate, stir and dissolve them thoroughly to obtain a mixed solution, then place it in a sealed mold and thermally polymerize it at 65°C for 3 hours, then take it out of the mold and dry it at 65°C for 2 hours, and soak it in water to obtain PZW hydrogel.

[0036] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the composite hydrogel is obtained by directly placing the composite hydrogel in a sealed mold at 65°C for 3 hours and then soaking it in water without the drying step. This indicates that the drying operation causes supramolecular interaction between NR nanoparticles, further improving the mechanical properties of the composite hydrogel.

[0037] Table 2 Effects of drying on the mechanical properties of composite hydrogels

[0038] project Embodiment 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 hydrogel and NR-PZW hydrogel were characterized using Fourier transform infrared spectroscopy (FT-IR). Figure 2 a, Comparing the spectra of NR and PZW hydrogel, it can be seen that the PZW hydrogel spectrum contains a SBMA-derived band at 1033 cm -1 and 1064cm -1 The two characteristic peaks of sulfonic acid groups are present in the spectrum of NR, while the NR formed by NR nanoparticles without sulfonic acid groups (mainly composed of polyisoprene and rubber protein) does not have these two characteristic peaks in the spectrum. Therefore, the appearance of these two characteristic peaks in the spectrum of NR-PZW hydrogel confirms the existence of PZW in its structure. In addition, the spectrum of NR-PZW hydrogel also has four characteristic peaks that are highly consistent with NR (located at 2751-3014cm -1 、1448cm -1 、1375cm -1 、840cm -1), proving that NR-PZW hydrogel also contains NR components. Further, NR nanoparticles were observed by SEM and EDS ( Figure 2 b): The average particle size of NR nanoparticles is about 500±300nm, and each nanoparticle has a wrinkled surface with a high surface area; EDS-mapping shows a clear but weak S element signal, confirming that the thin protein layer on the outer layer of NR nanoparticles contains a small amount of S element (because the inside of NR nanoparticles is composed of polyisoprene and does not contain S element). In addition, based on SEM-connected EDS mapping, elemental analysis of NR flakes, PZW hydrogels, and NR-PZW hydrogels was performed ( Figure 2 c). Compared with the weak S element signal of NR flakes and the ultra-high intensity S element signal of PZW hydrogel, the moderate intensity S element signal of NR-PZW hydrogel also confirms that it is synthesized from NR and PZW. The uniform distribution of S signal of NR-PZW hydrogel further indicates the uniform composite of NR and PZW.

[0041] (2) X-ray photoelectron spectroscopy (XPS) was used to analyze the elements of NR, PZW hydrogel and NR-PZW hydrogel. PZW hydrogel and NR-PZW hydrogel have strong S2p characteristic peaks at 165-170 eV, while there is almost no signal at the corresponding position of the NR spectrum ( Figure 3 a). The experimental results show the existence of PZW containing S element in NR-PZW hydrogel. In addition, the clearer XPS peak fitting curve of NR-PZW hydrogel ( Figure 3 b) It can be seen that the S2p element signal comes from the superposition of the two sulfonic acid group signals S2p1 / 2 at 167.4 eV and S2p3 / 2 at 168.7 eV, which verifies that the S element of the NR-PZW hydrogel comes from the sulfonic acid group of the zwitterion. This further indicates that the NR-PZW composite hydrogel prepared in Example 1 was successfully prepared.

[0042] (3) Effects of different SBMA / NR mass ratios on the properties of NR-PZW hydrogels, such as Figure 4a. With the increase of NR, from m(SBMA) / m(NR)=35 / 5 to 20 / 20, the tensile properties of NR-PZW hydrogel gradually improved and reached a peak at m(SBMA) / m(NR)=20 / 20, with the tensile strength and tensile strain increasing from 0.07MPa and 111% to 0.52MPa and 738%, respectively. With the further increase of NR, from m(SBMA) / m(NR)=20 / 20 to 10 / 30, the tensile strength of NR-PZW hydrogel gradually decreased, while the tensile strain remained basically unchanged. Therefore, the formula of m(SBMA) / m(NR)=20 / 20 was selected to prepare NR-PZW hydrogel with the best mechanical properties. Compared with PZW hydrogel, the tensile strength and tensile strain of NR-PZW hydrogel increased from 0.04MPa and 94% to 0.52MPa and 738%, respectively. Figure 4 b). From the SEM images, it can be observed that the addition of NR causes a significant change in the microstructure of NR-PZW hydrogel compared to 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 hydrogels in fresh water and seawater were studied. Figure 5 ). Switching from fresh water to sea water, the size of the NR-PZW hydrogel expanded by 50%, and the swelling rate changed from 210% to 605%, confirming that the NR-PZW hydrogel has better hydrophilicity and a denser water film for sea water, and has 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 of the PZW network, which produce a strong anti-polyelectrolyte effect in high-salinity seawater. In contrast, the NR-PAM hydrogel as the control group showed a significant volume shrinkage when switched from fresh water to sea water, and the swelling rate decreased from 338% to 214%, which may be due to the PZW network compounding the charged NR nanoparticles, producing a polyelectrolyte-like effect.

[0044] (5) The antibacterial adhesion performance of the NR-PZW hydrogel of Example 1 was tested by staining. Representative Gram-positive bacteria (Escherichia coli), Gram-negative bacteria (Staphylococcus aureus) and unique marine bacteria (Vibrio alginolyticus) were selected. From the confocal laser photos, it can be seen that the surface of the NR-PAM hydrogel as the control group had serious E. coli adhesion, while only a small amount of bacteria appeared on the surface of the NR-PZW hydrogel. The calculated E. coli inhibition rate reached 86.3% ( Figure 6 a, Figure 6d). Similar effects were seen in the laser confocal images of Staphylococcus aureus and Vibrio alginolyticus, where the NR-PZW hydrogel showed higher inhibition rates against these two bacteria, 94.4% and 95.7%, respectively, indicating its high efficiency and broad-spectrum antibacterial adhesion in marine environments ( Figure 6 bd). The experiment shows that the NR-PZW hydrogel of Example 1 has excellent anti-bacterial adhesion performance.

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

[0046] In addition, the anti-protein adhesion performance of NR-PZW hydrogel was tested with fluorescently labeled bovine serum albumin (BSA). The hydrogel was immersed in the BSA dispersion for 24 hours and then taken out. The anti-adhesion performance of NR-PZW hydrogel to BSA was evaluated by observing the fluorescence intensity of the sample surface under a fluorescence microscope. Figure 7 As shown in Figure c, the NR-PAM hydrogel as the control group showed bright green strong fluorescence, indicating the presence of a large amount of BSA; on the contrary, the fluorescence on the surface of the NR-PZW hydrogel was very weak, indicating that there was almost no BSA adhesion. This further illustrates that the NR-PZW hydrogel of Example 1 has excellent protein adhesion performance. Therefore, combined with the previous anti-bacterial adhesion and anti-seaweed adhesion results, its excellent marine antifouling performance is demonstrated.

[0047] (7) In order to test the anti-biofouling performance of NR-PZW hydrogel in practical applications, a three-month real ocean test was conducted in the waters near Haikou. Figure 8). After 3 months of marine antifouling testing, a large amount of dirt and algae were attached to the surface of NR, and the fouling area calculated by ImageJ software was as high as 50.69%. This is because NR produces a "frost" effect after being immersed in seawater for a long time, and hydrophilic substances such as proteins migrate to the surface to form a nutrient-rich thin layer, which makes NR, which originally lacks anti-biological fouling properties, attract a large number of microorganisms to gather and grow. As a control sample, the fouling of NR-PAM hydrogel is also serious, with algae and large colonies visible to the naked eye, and the fouling area is 22.24%, indicating that ordinary hydrogels have limited anti-biological fouling properties in the ocean. In contrast, there are only a few slightly discolored areas on the surface of NR-PZW hydrogel, and the fouling area is only 0.37%, which proves that its dense surface hydration layer can effectively resist the adhesion of various marine organisms and limit the occurrence of subsequent biological fouling.

[0048] In addition, the NR-PZW hydrogel remained intact after 3 months of wave impact, and its tensile strength only slightly decreased from 0.52MPa to 0.46MPa ( Figure 8 c). From the comprehensive performance comparison chart ( Figure 8 d) It can be seen that NR-PZW hydrogel has outstanding mechanical properties and excellent anti-biological adhesion properties. Therefore, NR-PZW hydrogel can provide long-term anti-biological fouling performance in real marine environments.

[0049] In summary, the preparation method of the natural rubber-polyzwitterion (NR-PZW) composite hydrogel provided by the present invention is simple in process and easy to mass produce. The natural rubber NR-PZW composite hydrogel prepared by the method of the present invention not only has excellent mechanical properties, but also its tensile strength and elongation at break are greatly improved from 0.04MPa and 94% to 0.52MPa and 738% respectively; and it exhibits excellent broad-spectrum anti-bacterial adhesion, anti-seaweed adhesion and anti-protein adhesion properties. Utilizing its efficient marine antifouling performance and strong mechanical properties, the PZW composite hydrogel can maintain excellent anti-biological adhesion properties for more than 3 months in an actual marine environment.

[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 in the scope of protection of the present invention.

Claims

1. A method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material, characterized in that: The method comprises the following steps: dissolving methacrylate sulfobetaine in natural rubber latex, adding N,N-methylenebisacrylamide and ammonium persulfate, stirring and dissolving to obtain a prepolymerization mixture, placing the mixture in a sealed mold for thermal polymerization, taking the mixture out of the mold for drying and soaking in water to obtain a natural rubber-polyzwitterion composite hydrogel material; the mass ratio of methacrylate sulfobetaine to natural rubber in the prepolymerization mixture is 3 / 5-1.

2. According to a method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material, it is characterized in that: The mass ratio of methacrylate sulfobetaine to natural rubber in the prepolymer mixture is 1.

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

4. The method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material according to claim 1, characterized in that: The thermal polymerization conditions are 40-70° C. for 2-4 hours.

5. The method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material according to claim 4, characterized in that: The thermal polymerization condition is 65° C. for 3 hours.

6. The method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material according to claim 1, characterized in that: The drying condition is 40-70°C for 1-3h.

7. The method for preparing an anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material according to claim 6, characterized in that: The drying condition is 65° C. for 2 h.

8. An anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material prepared according to the method according to any one of claims 1 to 7.

9. Use of the anti-adhesion high-strength natural rubber-polyzwitterion composite hydrogel material according to claim 8 in the preparation of marine antifouling coatings.

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