Preparation method of two-dimensional nano material and PVA composite hydrogel

Abstract

The invention discloses a preparation method of a two-dimensional nano material and PVA (polyvinyl alcohol) composite hydrogel, which comprises the following steps: adding a polyvinyl alcohol aqueous solution into a two-dimensional nano material mixed solution, and stirring; a two-dimensional nano material in the two-dimensional nano material mixed solution is a mixture of MXene and graphene oxide, molybdenum disulfide or hexagonal boron nitride; adding an aqueous solution of a cross-linking agent, adding a ZnCl2 solution, and standing to obtain MXene-PVA hydrogel; or carrying out repeated freezing and thawing, so as to obtain the MXene-PVA hydrogel. The problems that an existing method is long in consumed time, various in working procedure and complex in preparation process are solved. The MXene and the GO are compounded to serve as an additive to be combined with the PVA, the method is easy to operate, the preparation time is short, the prepared composite hydrogel can effectively lubricate under the high load, and the mechanical strength and the tribological performance are greatly improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing a hydrogel, and in particular to a method for preparing a two-dimensional nanomaterial and PVA composite hydrogel. Background Art

[0002] Hydrogels, three-dimensional materials composed of a cross-linked polymer network loaded with water, have recently played a crucial role as water-based lubricants. Compared to lubricating fluids, hydrogel lubricants not only offer the advantage of eliminating lubrication failure but also show potential applications in underwater lubrication and biolubrication. Hydrogels also possess tunable physicochemical properties, such as exceptional softness and flexibility, wettability and lubricity, biocompatibility, and optical transparency.

[0003] Among hydrogels, polyvinyl alcohol (PVA) hydrogel is a dual-phase, three-dimensional network polymer material with both liquid and solid phases. This network is rich in water and possesses many excellent properties, such as chemical stability, a wide range of tunable mechanical, structural, and physical properties, high hydrophilicity, and good biocompatibility. It has been widely explored for use as a biomedical material. However, due to poor mechanical properties and low light transmittance, the application of PVA hydrogels in industrial lubrication is often severely limited. The appropriate introduction of functionalized nanomaterials can not only enhance the mechanical properties and biocompatibility of hydrogels but also provide new functionality, significantly overcoming the limitations of traditional hydrogels. Several methods are currently under investigation for synthesizing PVA hydrogels. One approach involves chemical crosslinking agents (such as glutaraldehyde, boric acid, L-tryptophan, and epichlorohydrin) reacting with hydroxyl groups (-OH) on PVA molecular chains to form a covalent bond network. Another approach involves physical crosslinking, which involves methods such as freeze-thaw cycling, mechanical training, and ice-templated freeze casting. This involves freezing the water molecules in the PVA solution to form ice crystals. Melting of the ice crystals leaves behind a porous structure, and the PVA molecular chains form a three-dimensional network through hydrogen bonds and crystalline regions. However, these methods are time-consuming and complex, and are primarily used for biolubrication.

[0004] MXene is an emerging class of two-dimensional nanomaterials. Due to its unique structure and properties, it has found widespread application in energy storage, catalysis, sensing, and tribology. Its unique structure, low shear resistance, and ease of modification give MXene exceptional lubrication properties. Similar to MXene, graphene oxide (GO) is a high-performance two-dimensional solid lubricant. Thanks to its lamellar morphology, weak interlayer interactions, and excellent surface properties, GO exhibits exceptional lubrication and mechanical properties under specific conditions. PVA hydrogels prepared with MXene / GO as additives exhibit excellent tribological properties. The MXene / GO / PVA aerogel prepared in existing document 1 (Chinese invention patent application with authorization number CN113979430B) begins by mechanically stirring graphene oxide sheets with a polyvinyl alcohol solution for 30–60 minutes. The mixed solution then undergoes hydrothermal self-assembly in a polytetrafluoroethylene autoclave under high temperature and pressure at a temperature of 120–180°C for 12–24 hours, yielding a graphene oxide hydrogel. The graphene oxide hydrogel is then immersed in a MXene solution for vacuum-assisted infiltration at a pressure of 0.06–0.12 MPa, preferably for 0.5–2 hours, to yield a composite hydrogel. The composite hydrogel is then freeze-dried under vacuum for 24–48 hours and subsequently calcined at 200–300°C for 2–4 hours to yield an aerogel. Finally, the resulting hierarchically porous composite aerogel is immersed in a hexachlorocyclotriphosphazene solution and dried. This method requires complex equipment and high temperature and pressure, is time-consuming, and involves multiple steps. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a two-dimensional nanomaterial and PVA composite hydrogel, which solves the problems of the existing method that it is not only time-consuming but also has many steps and a complicated preparation process. The preparation method of using two-dimensional nanomaterials as additives to composite with PVA hydrogel greatly improves the mechanical properties and tribological properties of the hydrogel.

[0006] In order to achieve the above object, the present invention provides a method for preparing a two-dimensional nanomaterial and PVA composite hydrogel, the method comprising: (1) Adding polyvinyl alcohol aqueous solution to the two-dimensional nanomaterial mixed solution and stirring; The two-dimensional nanomaterial in the two-dimensional nanomaterial mixed solution is a mixture of MXene and graphene oxide, molybdenum disulfide or hexagonal boron nitride; (2) Add a crosslinker aqueous solution, add a ZnCl2 solution, and allow to stand to obtain a MXene-PVA hydrogel.

[0007] Preferably, the two-dimensional nanomaterials in the two-dimensional nanomaterial mixed solution are MXene and graphene oxide.

[0008] Preferably, the mass ratio of the MXene to graphene oxide is (3-6):1.

[0009] Preferably, the concentration of the graphene oxide is 5 mg / mL, and the concentration of the MXene is 15 mg / mL.

[0010] Preferably, the polyvinyl alcohol aqueous solution is obtained by dissolving PVA in deionized water and stirring at 90°C.

[0011] Preferably, the concentration of polyvinyl alcohol water in the polyvinyl alcohol aqueous solution is 0.1 mg / mL to 0.15 mg / mL.

[0012] Preferably, the mass fraction of the crosslinking agent in the crosslinking agent aqueous solution is 5%; and the concentration of the ZnCl2 solution is 0.5 mol / L~1.5 mol / L.

[0013] Preferably, the volume ratio of the cross-linking agent aqueous solution, the ZnCl2 solution, the polyvinyl alcohol aqueous solution and the mixed solution is (0.6-0.8):0.2:1.5:2.

[0014] The method for preparing a two-dimensional nanomaterial and PVA composite hydrogel of the present invention solves the problems of the existing method that it is not only time-consuming, but also has many steps and a complicated preparation process, and has the following advantages: 1. The method of the present invention is simple to operate and has a short preparation time. MXene is evenly mixed with GO and PVA solution by ultrasound for 15 minutes, and then a cross-linking agent is added for chemical cross-linking and allowed to stand. No complicated equipment or high temperature and high pressure conditions are required.

[0015] 2. The MXene and GO composite of the present invention is combined with PVA as an additive to produce a composite hydrogel with a more stable structure. Compared with existing lubricating hydrogels, it can effectively lubricate under high loads. Compared with PVA hydrogels, the mechanical strength and tribological properties of the composite hydrogel have been greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart for the preparation of the MXene, GO and PVA composite hydrogel of the present invention.

[0017] Figure 2 These are the strain scan and frequency scan graphs of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1.

[0018] Figure 3 This is a graph of the tribological coefficients of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1.

[0019] Figure 4These are SEM images of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1.

[0020] Figure 5 This is a physical picture of the MSP hydrogel in Example 2 of the present invention.

[0021] Figure 6 These are the strain scanning diagrams of the MSP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0022] Figure 7 This is a frequency scanning diagram of the MSP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0023] Figure 8 This is a physical picture of the MBP hydrogel in Example 2 of the present invention.

[0024] Figure 9 These are the strain scanning diagrams of the MBP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0025] Figure 10 This is a frequency scanning diagram of the MBP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] The MXene and GO graphene involved in the following examples were synthesized in the laboratory, and borax pentahydrate (Na2B4O7·5H2O), zinc chloride, and polyvinyl alcohol were purchased from Shanghai MacLean Biochemical Co., Ltd.

[0028] 1. The MXene used in the present invention was synthesized with reference to the method of the existing literature (Wang, X.; Zhao, Y.; Dai, B.; Sun, Q.; Wang, X.; Lou, W.; Yang, J. Tribological performance of recyclable oil-soluble magnetic MXene as efficient lubricant additives under boundarylubrication conditions. Tribology International 2025, 204. DOI: 10.1016 / j.triboint.2024.110427).

[0029] 2. The GO used in the present invention was synthesized by referring to the method of the existing literature (Dong, F.; Dai, B.; Zhang, H.; Shi, Y.; Zhao, R.; Ding, X.; Wang, H.; Li, T.; Ma, M.; Ma, Y. Fabrication ofhierarchical reduced graphene oxide decorated with core-shell Fe3O4@polypyrrole heterostructures for excellent electromagnetic wave absorption. Journal of Colloid and Interface Science 2023, 649, 943-954. DOI: 10.1016 / j.jcis.2023.06.085).

[0030] Example 1 A method for preparing a composite hydrogel of MXene, GO and PVA comprises physically mixing a MXene dispersion and a GO dispersion with a PVA aqueous solution, and then preparing a MXene-GO / PVA hydrogel by a chemical cross-linking method, such as Figure 1 As shown in the figure, the preparation flow chart of the MXene, GO and PVA composite hydrogel of the present invention specifically comprises: (1) Take 1 mL of GO aqueous solution with a concentration of 5 mg / mL and add it to 1 mL of MXene dispersion. Stir evenly and ultrasonicate for 15 min to obtain a mixed solution. The concentration of MXene in the mixed solution is 15 mg / mL. Dissolve 5 g of PVA in 45 mL of deionized water and stir vigorously at 90 °C for 4 h to obtain a PVA aqueous solution. Take 1.5 mL of PVA aqueous solution and add it to the mixed solution and stir for 2 h.

[0031] (2) Then, 0.75 mL of a 5% mass fraction Na2B4O7 aqueous solution (a dynamic reversible crosslinker prepared by Na2B4O7·5H2O) was added, followed by 0.2 mL of a 1 mol / L ZnCl2 solution (an ionic crosslinker). After standing for 24 h, MXene-GO / PVA hydrogel was obtained, which was recorded as MGP hydrogel.

[0032] Comparative Example 1 The preparation method of a PVA hydrogel is basically the same as that in Example 1, except that: In step (1), no solution was mixed. Instead, 5 g of PVA was dissolved in 45 mL of deionized water and vigorously stirred at 90 °C for 4 h to obtain a PVA aqueous solution, which was then stirred for 2 h. The same operation as in Example 1 was performed to prepare a PVA hydrogel.

[0033] Example 2 The preparation method of a two-dimensional nanomaterial and PVA composite hydrogel is basically the same as that in Example 1, except that: In step (1), 1 mL of 5 mg / mL GO aqueous solution is adjusted to 1 mL of 5 mg / mL molybdenum disulfide aqueous solution or 1 mL of 5 mg / mL hexagonal boron nitride aqueous solution; By the same operation as in Example 1, MXene-molybdenum disulfide / PVA hydrogel or MXene-boron nitride / PVA hydrogel was obtained, which was recorded as MSP hydrogel or MBP hydrogel.

[0034] like Figure 5 As shown in FIG. , the physical image of the MSP hydrogel in Example 2 of the present invention. Figure 5 It can be seen that in Example 2 of the present invention, after MXene and molybdenum disulfide were added to the PVA aqueous solution, a gel was formed.

[0035] like Figure 8 As shown in FIG. , the physical image of the MBP hydrogel in Example 2 of the present invention. Figure 8 It can be seen that in Example 2 of the present invention, after MXene and boron nitride were added to the PVA aqueous solution, a gel was formed.

[0036] Example 3 The preparation method of a MXene, GO and PVA composite hydrogel is basically the same as that in Example 1, except that: In step (2), 0.75 mL of a 5% by mass Na2B4O7 aqueous solution is adjusted to 0.75 mL of a 5% by mass glutaric acid aqueous solution.

[0037] Example 4 The preparation method of a two-dimensional nanomaterial and PVA composite hydrogel is basically the same as that in Example 2, except that: In step (2), 0.75 mL of a 5% by mass Na2B4O7 aqueous solution (dynamic reversible crosslinking) was adjusted to 0.75 mL of a 5% by mass glutaric acid aqueous solution (covalent crosslinking).

[0038] Example 5 The preparation method of a two-dimensional nanomaterial and PVA composite hydrogel is basically the same as that in Example 2, except that: In step (2), ionic crosslinking was performed after freeze-thaw cycles and after standing for 24 h, MXene-GO / PVA hydrogel was obtained, which was recorded as MGP hydrogel.

[0039] Experimental Example 1 Electron Microscope Scanning The MGP hydrogel of Example 1 and the PVA hydrogel of Comparative Example 1 were subjected to electron microscopy scanning.

[0040] like Figure 4 As shown in FIG, the SEM images of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1. Figure 4 It can be seen that both the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1 have a porous network structure, and the pores are arranged in an irregular shape.

[0041] Experimental Example 2 Rheological Test In rheology, the storage modulus (G') and loss modulus (G") are important parameters for studying hydrogel properties. G' characterizes the solid-like behavior of a material. The higher the storage modulus, the better the elastic recovery of the hydrogel. G" characterizes the liquid-like behavior of a material and refers to the energy lost due to viscous deformation when the material deforms. Strain sweeps and frequency sweeps were performed on the MGP hydrogel of Example 1 and the PVA hydrogel of Comparative Example 1.

[0042] like Figure 2As shown, the strain scan and frequency scan diagrams of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1, wherein MGP is the MGP hydrogel of Example 1; PVA is the PVA hydrogel of Comparative Example 1; the left figure is the strain scan, the abscissa is the strain rate, and the ordinate is G' and G". The right figure is the frequency scan, the abscissa is the frequency, and the ordinate is G' and G". Figure 2 It can be seen that in the strain sweep, the G' and G" of the MGP hydrogel are both higher than those of the PVA hydrogel, which indicates that the MGP hydrogel has excellent mechanical strength. In the frequency sweep, the G' of the MGP hydrogel is always higher than the G" and shows an upward trend, indicating that the prepared hydrogel is relatively stable and exhibits enhanced hydrogel elasticity. Whether in the strain sweep or the frequency sweep, the modulus of the MGP hydrogel in Example 1 of the present invention with the addition of MXene nanosheets and GO nanosheets is significantly improved compared with the PVA hydrogel in Comparative Example 1. This is because the hydrogen bonding between MXene and other components and the lamellar structure of GO as physical cross-linking points enhance the rigidity of the hydrogel network and form a stable elastic structure.

[0043] like Figure 6 As shown, the strain scanning diagrams of the MSP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0044] like Figure 7 As shown, the frequency scanning diagrams of the MSP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0045] Depend on Figure 6 and Figure 7 It can be seen that compared with PVA hydrogel, the modulus of the MSP hydrogel in Example 2 of the present invention to which MXene nanosheets and molybdenum disulfide nanosheets were added was significantly improved.

[0046] like Figure 9 As shown, the strain scanning diagrams of the MBP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0047] like Figure 10 As shown, the frequency scanning diagrams of the MBP hydrogel of Example 2 of the present invention and the PVA hydrogel of Comparative Example 1.

[0048] Depend on Figure 9 and Figure 10 It can be seen that compared with PVA hydrogel, the modulus of the MBP hydrogel in Example 2 of the present invention to which MXene nanosheets and boron nitride nanosheets are added is significantly improved.

[0049] Experimental Example 3 Friction Test The tribological properties of the MGP hydrogel of Example 1 and the PVA hydrogel of Comparative Example 1 were characterized by evaluating the coefficient of friction (COF) by friction testing using an oscillating reciprocating friction and wear tester (Optimol SRV®5, Germany) at 100 N and 25 °C for 1800 s.

[0050] like Figure 3 As shown in FIG. 1 , the tribological coefficient of the MGP hydrogel of Example 1 of the present invention and the PVA hydrogel of Comparative Example 1 are plotted. Figure 3 It can be seen that compared with the PVA hydrogel in Comparative Example 1, the tribological properties of the PVA hydrogel in Example 1 of the present invention are greatly improved by the addition of MXene and GO, and the prepared MXene / GO-PVA hydrogel achieves a friction reduction effect of 50.68%.

[0051] Comprehensive analysis shows that Example 1 of the present invention has the best performance. The modulus and structural stability of Example 1 are better than those of Example 2, and Example 1 has excellent tribological properties.

[0052] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a two-dimensional nanomaterial and PVA composite hydrogel, characterized in that: The method includes: (1) Adding polyvinyl alcohol aqueous solution to the two-dimensional nanomaterial mixed solution and stirring; The two-dimensional nanomaterial in the two-dimensional nanomaterial mixed solution is a mixture of MXene and graphene oxide, molybdenum disulfide or hexagonal boron nitride; The two-dimensional nanomaterial aqueous solution is added to the MXene dispersion, stirred evenly, and then ultrasonicated to obtain a two-dimensional nanomaterial mixed solution; (2) Add a crosslinker aqueous solution, add a ZnCl2 solution, and allow to stand to obtain a MXene-PVA hydrogel.

2. The preparation method according to claim 1, characterized in that The two-dimensional nanomaterials in the two-dimensional nanomaterial mixed solution are MXene and graphene oxide.

3. The preparation method according to claim 2, characterized in that The mass ratio of the MXene to graphene oxide is (3-6):

1.

4. The preparation method according to claim 2, characterized in that The concentration of the graphene oxide is 5 mg / mL, and the concentration of the MXene is 15 mg / mL.

5. The preparation method according to claim 1, characterized in that The crosslinking agent in the crosslinking agent aqueous solution is borax pentahydrate or glutaric acid.

6. The preparation method according to claim 1, characterized in that The polyvinyl alcohol aqueous solution is obtained by dissolving PVA in deionized water and stirring at 90°C.

7. The preparation method according to claim 1, characterized in that The concentration of polyvinyl alcohol water in the polyvinyl alcohol aqueous solution is 0.1 mg / mL to 0.15 mg / mL.

8. The preparation method according to claim 7, characterized in that The mass fraction of the crosslinking agent in the crosslinking agent aqueous solution is 5%; the concentration of the ZnCl2 solution is 0.5 mol / L~1.5 mol / L.

9. The preparation method according to claim 8, characterized in that The volume ratio of the cross-linking agent aqueous solution, the ZnCl2 solution, the polyvinyl alcohol aqueous solution and the mixed solution is (0.6-0.8):0.2:1.5:2.

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