Carbon nitride-initiated interfacial hydrogel coating and preparation method and application thereof

Abstract

The application provides a carbon nitride-initiated interfacial hydrogel coating as well as a preparation method and application thereof, and belongs to the technical field of composite materials. The preparation method of the carbon nitride-initiated interfacial hydrogel coating provided by the application comprises the following steps: after mixing carbon nitride and dopamine adhesion polymer, the mixture is coated on the surface of a substrate to form a dopamine adhesion bonding layer containing an initiator on the surface of the substrate, thereby obtaining an initiator-modified substrate; the initiator-modified substrate is immersed in a polymer monomer solution, and a second free radical polymerization reaction is carried out under visible light irradiation to form a carbon nitride-initiated interfacial hydrogel coating on the surface of the substrate. The carbon nitride is used as the only initiator to prepare the interfacial hydrogel coating, the coating of the hydrogel can be realized, different substrates can be interfacially modified, the functionalization of the substrate can be realized, and the application range is wide; and the interfacial hydrogel coating prepared in this way has good lubricating capacity and biocompatibility, and also has good antifouling performance.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a carbon nitride-induced interfacial hydrogel coating, its preparation method, and its application. Background Technology

[0002] Hydrogel materials are a class of hydrophilic polymer chains forming a water-containing three-dimensional network through physical or chemical interactions. They are characterized by being "soft" and "wet," but their inherent softness often prevents them from meeting the requirements of some extremely harsh application environments. While traditional materials such as metals, glass, ceramics, plastics, and silicone rubber can withstand some harsh environments, their surface properties often cannot meet the specific functional requirements of applications, such as antifouling, corrosion resistance, drag reduction, low friction, and high wear resistance, thus limiting their respective application ranges. Hydrogel coating technology combines the properties of the substrate material with functionalized surface properties. Without altering the intrinsic properties of the traditional material, it combines functional hydrogels with traditional materials through surface bonding, endowing the surface with unique properties and compensating for the shortcomings of traditional material surface properties.

[0003] Graphitic carbon nitride (g-C3N4), as one of the most promising metal-free photocatalysts, possesses a suitable band gap (2.7 eV) and excellent physicochemical stability. Current techniques typically employ g-C3N4 and co-initiators to initiate monomer polymerization for bulk hydrogel preparation. However, once the bulk hydrogel is prepared, it cannot be modified at the interface, thus limiting the functionalization of the substrate surface and restricting its application. Furthermore, current in-situ hydrogel growth mainly utilizes metal ions (Fe... 3 + This is achieved through redox reactions of Fe2+, but in the medical field, metal ions (Fe2+) are used. 3+ The introduction of ) is harmful to the human body. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon nitride-initiated interfacial hydrogel coating, its preparation method, and its applications. This invention uses carbon nitride as the sole initiator to prepare an interfacial hydrogel coating, enabling the coating of hydrogels, allowing for interfacial modification of different substrates, achieving substrate functionalization, and broad application range. Furthermore, the resulting interfacial hydrogel coating exhibits good lubrication capabilities and biocompatibility.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a carbon nitride-initiated interfacial hydrogel coating, comprising the following steps:

[0007] Carbon nitride and dopamine adhesive polymer are mixed and coated onto the substrate surface to form a dopamine adhesive bonding layer containing an initiator, thus obtaining an initiator-modified substrate; the dopamine adhesive polymer is prepared by a first free radical polymerization reaction of dopamine methacrylamide and methoxyethyl acrylate.

[0008] The initiator-modified substrate is immersed in a solution containing polymer monomers and subjected to a second free radical polymerization reaction under visible light irradiation to form a carbon nitride-initiated interfacial hydrogel coating on the substrate surface.

[0009] Preferably, the mass of the carbon nitride is 0.025 to 0.5% of the total mass of the carbon nitride and the dopamine adhesive polymer.

[0010] Preferably, the substrate includes a metal substrate, a glass substrate, a ceramic substrate, a plastic substrate, or a silicone rubber substrate.

[0011] Preferably, the temperature of the first free radical polymerization reaction is 60-65°C and the time is 12-15 hours.

[0012] Preferably, the polymer monomer in the polymer monomer solution includes at least one of acrylic acid, acrylamide, hydroxyethyl methacrylate, N-isopropylacrylamide, and sulfonate betaine methacrylate.

[0013] Preferably, the concentration of the polymer monomer in the polymer monomer-containing solution is 20–500 mg / mL.

[0014] Preferably, the wavelength of the visible light is 460–465 nm.

[0015] Preferably, the second free radical polymerization reaction is carried out under a nitrogen atmosphere, and the temperature of the second free radical polymerization reaction is 20-35°C, and the time does not exceed 90 minutes.

[0016] The present invention provides a carbon nitride-induced interfacial hydrogel coating obtained by the preparation method described in the above technical solution.

[0017] This invention provides the application of the carbon nitride-induced interfacial hydrogel coating described above in marine antifouling or biomedical devices.

[0018] This invention provides a method for preparing a carbon nitride-initiated interfacial hydrogel coating, comprising the following steps: mixing carbon nitride with a dopamine adhesion polymer and coating it onto a substrate surface to form a dopamine adhesion bonding layer containing an initiator on the substrate surface, thereby obtaining an initiator-modified substrate; the dopamine adhesion polymer is prepared by a first free radical polymerization reaction of dopamine methacrylamide and methoxyethyl acrylate; immersing the initiator-modified substrate in a solution containing polymer monomers and carrying out a second free radical polymerization reaction under visible light irradiation to form a hydrogel coating on the substrate surface. This invention uses carbon nitride as the sole initiator, inducing free radical polymerization of polymer monomers under visible light irradiation to form an interfacial hydrogel coating; simultaneously, the dopamine adhesion polymer promotes the absorption of visible light by carbon nitride and rapid charge separation and transfer; the network topological entanglement between the hydrogel and the dopamine adhesion bonding layer ensures stable and good interfacial bonding, improving the versatility of the substrate. This invention avoids using ultraviolet light for initiation, instead employing visible light. Visible light initiation requires less energy, offers higher irradiation safety, and is more conducive to engineering applications, reducing equipment costs. Furthermore, the polymerization reaction and hydrogel growth occur only at the solid-liquid interface; the bulk reaction solution does not undergo polymerization. Moreover, the preparation method described in this invention is simple to operate and has a wide range of applications. The resulting interfacial hydrogel coating exhibits excellent lubrication capabilities. Examples show that the average coefficient of friction of the acrylamide / acrylic hydrogel coating prepared by this invention is below 0.05.

[0019] Furthermore, this invention introduces carbon nitride, a metal-free photocatalyst, as an initiator into the dopamine adhesion bonding layer to grow a hydrogel coating in situ. This allows the hydrogel to combine with traditional materials, endowing the surfaces of traditional materials with unique properties. Specifically, this invention uses carbon nitride as the sole initiator, utilizing the adhesion of the dopamine adhesion polymer and its ability to enhance the separation and transfer of photogenerated electrons and holes to initiate a hydrogel polymerization reaction at the interface, enabling its in-situ growth. This invention uses carbon nitride as an initiator to achieve the coating of hydrogels, allowing for interface modification of different substrates and functionalization of the substrates, thus broadening its application range. The interfacial hydrogel coating obtained according to the preparation method provided by this invention exhibits good lubrication and biocompatibility, is environmentally friendly, and has excellent antifouling properties. Therefore, the interfacial hydrogel coating has broad application prospects in marine antifouling, biomedicine, and other fields. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a graph showing the growth process of the interfacial hydrogel coating obtained in Example 1 over time.

[0022] Figure 2 The growth kinetics diagrams are shown for the interfacial hydrogel coatings obtained in Examples 1-5.

[0023] Figure 3 The graph shows the test results of the average surface friction coefficient of the interfacial hydrogel coating obtained in Example 1 at different growth times;

[0024] Figure 4 The image shows the results of the antifouling effect of the interface hydrogel coating obtained in Example 1 of this invention on the blank glass slide and the Algae bisporus. Detailed Implementation

[0025] This invention provides a method for preparing a carbon nitride-initiated interfacial hydrogel coating, comprising the following steps:

[0026] Carbon nitride and dopamine adhesive polymer are mixed and coated onto the substrate surface to form a dopamine adhesive bonding layer containing an initiator, thus obtaining an initiator-modified substrate; the dopamine adhesive polymer is prepared by a first free radical polymerization reaction of dopamine methacrylamide and methoxyethyl acrylate.

[0027] The initiator-modified substrate is immersed in a solution containing polymer monomers and subjected to a second free radical polymerization reaction under visible light irradiation to form a carbon nitride-initiated interfacial hydrogel coating on the substrate surface.

[0028] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0029] In this invention, the substrate preferably includes a metal substrate, a glass substrate, a ceramic substrate, a plastic substrate, or a silicone rubber substrate; the metal substrate is preferably an iron substrate, a copper substrate, or an aluminum substrate; the plastic substrate is preferably a polypropylene substrate, a polyethylene substrate, or a polytetrafluoroethylene substrate; and the silicone rubber substrate is preferably a polydimethylsiloxane substrate.

[0030] In this invention, the carbon nitride is used as an initiator. The preferred method for preparing the carbon nitride of this invention includes the following steps: calcining urea to obtain the carbon nitride. In this invention, the calcination temperature is preferably 500–550°C, more preferably 525–550°C; the holding time is preferably 2–4 hours, more preferably 4 hours; and the rate of heating to the calcination temperature is preferably 5–10°C / min, more preferably 10°C / min. After the calcination is completed, the obtained material is preferably cooled to room temperature and then ground to obtain the carbon nitride. The particle size of the carbon nitride of this invention is preferably 100–200 nm, more preferably 100–150 nm.

[0031] In this invention, the dopamine adhesive polymer is prepared by a first free radical polymerization reaction of dopamine methacrylamide and methoxyethyl acrylate. The preferred method for preparing the dopamine adhesive polymer of this invention includes the following steps: mixing dopamine hydrochloride, triethylamine, and methacryloyl chloride, and performing an amidation reaction to obtain dopamine methacrylamide; mixing the dopamine methacrylamide with methoxyethyl acrylate and azobisisobutyronitrile, and performing a first free radical polymerization reaction to obtain the dopamine adhesive polymer. The preparation method of the dopamine adhesive polymer of this invention is referenced in the following literature: Zhang Y, Xu R, Zhao W, et al. Successive redox-reaction-triggered interface radical polymerization for growing hydrogel coatings on diverse substrates. Angewandte Chemie, 2022, 134(39):e202209741.

[0032] This invention involves mixing dopamine hydrochloride, triethylamine, and methacryloyl chloride, and performing an amidation reaction to obtain dopamine methacrylamide. In this invention, the preferred material-to-liquid ratio of dopamine hydrochloride, triethylamine, and methacryloyl chloride is 8–10 g: 7–7.5 g: 5–6 mL, more preferably 10 g: 7.2 g: 6 mL. Preferably, dopamine hydrochloride and triethylamine are dissolved in methanol and placed in an ice bath under a nitrogen atmosphere to obtain a mixture; then, a methacryloyl chloride solution is added dropwise to the mixture, and the amidation reaction is carried out starting from the completion of the addition of the methacryloyl chloride solution. In this invention, the ice bath time is preferably 10–20 min, more preferably 20 min; the dropwise addition time is preferably 0.5–1 h, more preferably 1 h; the methacryloyl chloride solution preferably comprises methacryloyl chloride and dichloromethane, and the volume ratio of methacryloyl chloride to dichloromethane is preferably 4–6: 3–4, more preferably 6: 4. In this invention, the temperature of the amidation reaction is preferably 0–5°C, more preferably 0°C; the time is preferably 1–2 h, more preferably 2 h. In an embodiment of this invention, the amidation reaction is carried out under ice bath conditions. After the amidation reaction is completed, the solvent of the resulting liquid is preferably removed, the resulting material is dissolved in ethyl acetate and then extracted with hydrochloric acid and saturated brine, respectively. The organic phase is collected and dried and recrystallized sequentially to obtain dopamine methacrylamide. In this invention, the solvent of the resulting liquid is preferably removed by rotary evaporation; the number of extractions with hydrochloric acid is preferably 3 times; the number of extractions with saturated brine is preferably 3 times. The drying process in this invention preferably includes sequential drying with anhydrous MgSO4 and rotary evaporation; the anhydrous MgSO4 is preferably removed by filtration after drying. In this invention, the purpose of drying with anhydrous MgSO4 is to remove water from the system; the purpose of rotary evaporation is to remove ethyl acetate from the system. The reagent used for recrystallization in this invention is preferably a mixed solvent of ethyl acetate and n-hexane; in the mixed solvent, the volume ratio of ethyl acetate to n-hexane is preferably 1–2:1–2, more preferably 1:2.

[0033] After obtaining dopamine methacrylamide, the present invention mixes the dopamine methacrylamide with methoxyethyl acrylate and azobisisobutyronitrile (AIBN) and carries out a first free radical polymerization reaction to obtain the dopamine adhesive polymer. In the present invention, the mass ratio of dopamine methacrylamide, methoxyethyl acrylate, and AIBN is preferably 0.01–8.3:4.8–9.6:0.1–0.11, more preferably 1.7:7.5:0.106. The present invention preferably mixes dopamine methacrylamide, methoxyethyl acrylate, and AIBN with N,N-dimethylformamide to carry out the first free radical polymerization reaction. In the present invention, the first free radical polymerization reaction is preferably carried out under a nitrogen atmosphere; the temperature is preferably 60–65°C, more preferably 65°C; and the time is preferably 12–15 h, more preferably 12 h. After the first free radical polymerization reaction, the present invention preferably subjectes the resulting liquid to petroleum ether precipitation, ethyl acetate dissolution, and drying sequentially to obtain the dopamine adhesive polymer. In this invention, the precipitation and dissolution are preferably performed three times independently; the drying is preferably vacuum drying.

[0034] This invention involves mixing carbon nitride with a dopamine adhesive polymer and coating it onto a substrate surface to form a dopamine adhesive bonding layer containing an initiator, thus obtaining an initiator-modified substrate. Preferably, the dopamine adhesive polymer is dissolved in dichloromethane to obtain a solution; carbon nitride is added to the solution and ultrasonically dispersed; the resulting mixture is then coated onto the substrate surface and dried to obtain a dopamine adhesive bonding layer containing carbon nitride on the substrate surface. In this invention, the mass of carbon nitride is preferably 0.025–0.5% of the total mass of carbon nitride and the dopamine adhesive polymer, more preferably 0.05–0.3%. In this invention, the ultrasonic dispersion time is preferably 10–30 min, more preferably 30 min; the coating thickness of the mixture is preferably 5–35 μm, more preferably 5–20 μm; the drying is preferably vacuum drying, and the drying time is preferably 24 h.

[0035] After obtaining the initiator-modified substrate, the present invention immerses the initiator-modified substrate in a solution containing polymer monomers and carries out a second free radical polymerization reaction under visible light irradiation to form a hydrogel coating on the substrate surface.

[0036] In this invention, the polymer monomer in the polymer monomer-containing solution preferably includes at least one selected from acrylic acid, acrylamide, hydroxyethyl methacrylate, N-isopropylacrylamide, and sulfobetaine methacrylate. The concentration of the polymer monomer in the polymer monomer-containing solution is preferably 20–500 mg / mL, more preferably 30–300 mg / mL. In one embodiment of this invention, the polymer monomer in the polymer monomer-containing solution is acrylic acid and acrylamide; the polymer monomer-containing solution includes acrylic acid, acrylamide, N,N'-methylenebisacrylamide, and water, wherein the concentration of acrylic acid is 30 mg / mL and the concentration of acrylamide is 300 mg / mL. In another embodiment of this invention, the polymer monomer in the polymer monomer-containing solution is acrylic acid and hydroxyethyl methacrylate; the polymer monomer-containing solution includes acrylic acid, hydroxyethyl methacrylate, N,N'-methylenebisacrylamide, and water, wherein the concentration of acrylic acid is 30 mg / mL and the concentration of hydroxyethyl methacrylate is 300 mg / mL. In another embodiment of the present invention, the polymer monomers in the polymer monomer-containing solution are acrylic acid and N-isopropylacrylamide; the polymer monomer-containing solution includes acrylic acid, N-isopropylacrylamide, N,N'-methylenebisacrylamide, and water, wherein the concentration of acrylic acid is 30 mg / mL and the concentration of N-isopropylacrylamide is 300 mg / mL. In another embodiment of the present invention, the polymer monomers in the polymer monomer-containing solution are acrylic acid and sulfonated betaine methacrylate; the polymer monomer-containing solution includes acrylic acid, sulfonated betaine methacrylate, N,N'-methylenebisacrylamide, and water, wherein the concentration of acrylic acid is 30 mg / mL and the concentration of sulfonated betaine methacrylate is 300 mg / mL.

[0037] In this invention, the wavelength of the visible light is preferably 460–465 nm, more preferably 460–462 nm. The second free radical polymerization reaction of this invention is preferably carried out under a nitrogen atmosphere; the temperature is preferably 20–35°C, more preferably 25°C; and the time is preferably no more than 90 min, further preferably 20–90 min, and more preferably 60 min.

[0038] The present invention also provides a carbon nitride-induced interfacial hydrogel coating obtained by the preparation method described above.

[0039] This invention also provides the application of the carbon nitride-induced interfacial hydrogel coating described above in marine antifouling or biomedical devices. The interfacial hydrogel coating can be polymerized on marine equipment and exerts its antifouling effect without the need for compounding with other reagents. Furthermore, the interfacial hydrogel coating described in this invention can be applied to the surface of medical devices such as catheters, artificial joints, and scalpels without introducing metal ions (Fe).3+ It has good biocompatibility.

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] Example 1

[0042] (1) Preparation of carbon nitride powder: Weigh 50g of urea and put it into a crucible. After covering the crucible, place it in a muffle furnace and heat it from room temperature to 550℃ at a rate of 10℃ / min. Then keep it at 550℃ for 4h. After that, let the material cool naturally to room temperature and grind it to obtain carbon nitride powder (particle size of 100-200nm).

[0043] (2) Preparation of dopamine-adhesive polymer (Reference: Zhang Y, Xu R, Zhao W, et al. Successive redox-reaction-triggered interface radical polymerization for growing hydrogel coatings on diverse substrates. Angewandte Chemie, 2022, 134(39):e202209741.): 10 g of dopamine hydrochloride and 7.2 g of triethylamine were dissolved in 100 mL of methanol and placed in an ice bath under N2 atmosphere for 20 min. Then, a methacryloyl chloride solution (containing 6 mL of methacryloyl chloride and 4 mL of dichloromethane) was added dropwise at a uniform rate, and the dropping rate was controlled so that the dropping time of the methacryloyl chloride solution was 1 h. Timing was started from the time the methacryloyl chloride solution was completely added, and the resulting mixture was amidated under ice bath conditions for 2 h to obtain a reaction solution (brownish-yellow). The reaction mixture was rotary evaporated, and the resulting material was dissolved in 200 mL of ethyl acetate. The mixture was extracted three times each with 1 mol / L hydrochloric acid and saturated brine, retaining the organic phase. The organic phase was dried with anhydrous MgSO4, filtered, and the filtrate was rotary evaporated to remove ethyl acetate. The residue was recrystallized from the residue using a mixed solvent of ethyl acetate and n-hexane (volume ratio of ethyl acetate to n-hexane: 1:2) to obtain dopamine methacrylamide (DMA). Then, 1.7 g of DMA, 7.5 g of methoxyethyl acrylate, and 106 mg of azobisisobutyronitrile were added to a reaction tube containing 18 mL of N,N-dimethylformamide. The polymerization reaction was carried out at 65 °C under a N2 atmosphere for 12 h. The resulting mixture was successively precipitated with petroleum ether and dissolved in ethyl acetate, with the precipitation and dissolution cycles repeated three times. The solution obtained from the final dissolution was precipitated with petroleum ether, and the precipitate was dried under vacuum to obtain the dopamine adhesive polymer.

[0044] (3) Preparation of a carbon nitride-containing dopamine adhesive bonding layer: The dopamine adhesive polymer was dissolved in dichloromethane to obtain a solution. Carbon nitride powder was then added to the solution and ultrasonically dispersed for 30 min (the concentration of carbon nitride powder was 0.2 wt%). The resulting mixture was coated onto the surface of a glass substrate with a coating thickness of 5 μm. The coated glass substrate was dried in a vacuum drying oven for 24 h to obtain a carbon nitride-containing dopamine adhesive bonding layer on the surface of the glass substrate, thus obtaining a carbon nitride-modified substrate.

[0045] (4) Construction of the interfacial hydrogel coating: Acrylamide, acrylic acid, N,N'-methylenebisacrylamide and 10 mL of water were mixed to obtain a polymer monomer solution (the concentration of acrylamide in the polymer monomer solution was 300 mg / mL, the concentration of acrylic acid was 30 mg / mL, and the concentration of N,N'-methylenebisacrylamide was 0.3 mg / mL). The polymer monomer solution was poured into a reaction tank, and the carbon nitride modified substrate was immersed in the polymer monomer solution. The polymerization reaction was carried out under N2 atmosphere, irradiation with a 460 nm LED lamp and 25 °C for 20 min, 30 min, 60 min and 90 min respectively, so that an interfacial hydrogel coating could be formed in situ on the surface of the dopamine adhesion bonding layer.

[0046] Example 2

[0047] The substrate was adjusted to a ceramic substrate, and the remaining conditions were the same as in Example 1, to prepare an interfacial hydrogel coating.

[0048] Example 3

[0049] The substrate was adjusted to a polypropylene (PP) substrate, and the remaining conditions were the same as in Example 1, to prepare an interfacial hydrogel coating.

[0050] Example 4

[0051] The substrate was adjusted to an iron sheet (Fe) substrate, and the remaining conditions were the same as in Example 1, to prepare an interfacial hydrogel coating.

[0052] Example 5

[0053] The substrate was adjusted to a polydimethylsiloxane (PDMS) substrate, and the remaining conditions were the same as in Example 1, to prepare an interfacial hydrogel coating.

[0054] Example 6

[0055] The substrate was adjusted to a polypropylene (PP) substrate, and the polymer monomers were adjusted to hydroxyethyl methacrylate and acrylic acid. The remaining conditions were the same as in Example 1 (the concentration of hydroxyethyl methacrylate in the polymer monomer solution was 300 mg / mL, the concentration of acrylic acid was 30 mg / mL, and the concentration of N,N'-methylenebisacrylamide was 0.3 mg / mL), and an interfacial hydrogel coating was prepared.

[0056] Example 7

[0057] The substrate was adjusted to a polypropylene (PP) substrate, and the polymer monomers were adjusted to N-isopropylacrylamide and acrylic acid. The remaining conditions were the same as in Example 1 (the concentration of N-isopropylacrylamide in the polymer monomer solution was 300 mg / mL, the concentration of acrylic acid was 30 mg / mL, and the concentration of N,N'-methylenebisacrylamide was 0.3 mg / mL), and an interfacial hydrogel coating was prepared.

[0058] Example 8

[0059] The substrate was adjusted to a polypropylene (PP) substrate, and the polymer monomers were adjusted to sulfobetaine methacrylate and acrylic acid. The remaining conditions were the same as in Example 1 (the concentration of sulfobetaine methacrylate in the polymer monomer solution was 300 mg / mL, the concentration of acrylic acid was 30 mg / mL, and the concentration of N,N'-methylenebisacrylamide was 1.5 mg / mL), and an interfacial hydrogel coating was prepared.

[0060] Test Example 1

[0061] The growth process of the interfacial hydrogel coating over time in Example 1 is as follows: Figure 1 As shown. From Figure 1 As can be seen, with the extension of reaction time, the thickness of the interfacial hydrogel coating gradually increases, and the surface growth of the interfacial hydrogel coating becomes more and more uniform and smooth.

[0062] Data on the change of interfacial hydrogel coating thickness over time in Examples 1-5 are as follows: Figure 2 As shown. By Figure 2 It is known that by controlling the time of free radical polymerization (surface grafting growth) of polymer monomers, the thickness of the resulting interfacial hydrogel coating can be controlled between tens and hundreds of micrometers. At the beginning of the reaction, the number of free radicals generated by carbon nitride on the interface under illumination is limited, resulting in a very slow polymerization reaction and a thin or almost non-existent interfacial hydrogel coating. As the reaction time increases, the number of free radicals generated by carbon nitride increases, and the interfacial polymerization reaction occurs rapidly. However, the rapidly growing interfacial hydrogel coating inhibits the transfer and diffusion of free radicals, leading to a slower overall growth rate. With further increases in the thickness of the interfacial hydrogel coating, the diffusion barrier increases, and the growth rate gradually slows down.

[0063] Furthermore, Examples 1-8 show that the interfacial hydrogel coating can be successfully constructed on different substrates (glass, ceramic, metallic iron, polypropylene, polydimethylsiloxane) using the method of the present invention, demonstrating the universality of the method of the present invention.

[0064] Test Example 2: Tribological Performance Test

[0065] The frictional properties of the samples obtained in Examples 1-8 of this invention were characterized on a conventional ball-disc reciprocating friction machine (CSM). The test method is as follows: The sample was fixed on the sample stage, and the coefficient of friction (COF) was collected. The friction pair used a steel ball with a diameter of 6 mm, a sliding distance of 4 mm, a frequency of 1 Hz, a load of 0.25 N, and deionized water as a lubricant. Water was added at the interface using a microsyringe, just enough to wet the sample surface, to maintain the hydrogel hydration during the test and prevent interface dehydration and drying. The test results of the interface hydrogel coating obtained in Example 1 are as follows. Figure 3 As shown ( Figure 3 Blank in this context refers to a dopamine adhesive bonding layer containing carbon nitride.

[0066] Depend on Figure 3 It can be seen that the dopamine adhesive layer containing carbon nitride has a high coefficient of friction, while the coefficient of friction decreases significantly after the growth of the hydrogel coating, with an average coefficient of friction between 0.04 and 0.06. This indicates that the hydration lubrication of the surface hydrogel coating reduces interfacial friction. Therefore, the substrate modified with the interfacial hydrogel coating has good lubrication capabilities.

[0067] Table 1 shows the average surface friction coefficient of the interfacial hydrogel coatings in Examples 1-8 after 60 min of growth.

[0068] Table 1. Average surface friction coefficient of the interfacial hydrogel coatings in Examples 1-8 after 60 min of growth.

[0069]

[0070] As shown in Table 1, without altering the bulk properties of the substrate, the growth of the interfacial hydrogel imparts lubricating properties to the substrate surface, with average friction coefficients all below 0.05. Furthermore, compared to the adhesive bonding layer, the average friction coefficients of different substrates decreased after growing interfacial hydrogels with different polymer monomers.

[0071] Test Example 3: Antifouling Performance Test

[0072] The antifouling performance of the interfacial hydrogel coating obtained in Example 1 was investigated using *Dendrobium nobile* (test method referenced in the following document: Zhang J, Wang X, Zhang C, et al. Self-lubricating interpenetrating polymer networks with functionalized nanoparticles enhancement for quasi-static and dynamic antifouling[J]. Chemical Engineering Journal, 2022, 429:132300). Some test results are shown below. Figure 4 .

[0073] Depend on Figure 4 It was observed that a large amount of algae adhered to the glass substrate, but after the growth of the acrylic / acrylamide hydrogel coating, almost no algae adhered to the surface. The results indicate that the interfacial hydrogel coating prepared in this invention has excellent anti-algae adhesion properties and can be used for marine antifouling.

[0074] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a carbon nitride-initiated interfacial hydrogel coating, characterized in that, Includes the following steps: Dopamine adhesive polymer was dissolved in dichloromethane to obtain a solution; carbon nitride was added to the solution and then ultrasonically dispersed. The resulting mixture was coated onto a substrate surface with a coating thickness of 5-35 μm and dried to form a dopamine adhesive bonding layer containing an initiator on the substrate surface, thus obtaining an initiator-modified substrate; the dopamine adhesive polymer was prepared by a first free radical polymerization reaction of dopamine methacrylamide and methoxyethyl acrylate; the mass of carbon nitride was 0.025-0.5% of the total mass of carbon nitride and dopamine adhesive polymer. The initiator-modified substrate is immersed in a solution containing polymer monomers and subjected to a second free radical polymerization reaction under visible light irradiation to form a carbon nitride-initiated interfacial hydrogel coating on the substrate surface. The polymer monomer in the polymer monomer solution includes at least one of acrylic acid, acrylamide, hydroxyethyl methacrylate, N-isopropylacrylamide, and sulfonate betaine methacrylate; the wavelength of the visible light is 460~465nm.

2. The preparation method according to claim 1, characterized in that, The substrate includes a metal substrate, a glass substrate, a ceramic substrate, a plastic substrate, or a silicone rubber substrate.

3. The preparation method according to claim 1, characterized in that, The temperature of the first free radical polymerization reaction is 60~65℃, and the time is 12~15h.

4. The preparation method according to claim 1, characterized in that, The concentration of polymer monomers in the polymer monomer-containing solution is 20~500 mg / mL.

5. The preparation method according to claim 1, characterized in that, The second free radical polymerization reaction is carried out under a nitrogen atmosphere, and the temperature of the second free radical polymerization reaction is 20~35℃, and the time does not exceed 90min.

6. The carbon nitride-initiated interfacial hydrogel coating obtained by the preparation method according to any one of claims 1 to 5.

7. The application of the carbon nitride-induced interfacial hydrogel coating of claim 6 in marine antifouling or biomedical devices.

Images