A nanocellulose-reinforced hydrogel wet-adhesive hydrogel

Abstract

The application discloses a preparation method of nanocellulose reinforced wet-state adhesion hydrogel and belongs to the technical field of hydrogel. The method comprises the following steps: controlling a solution environment so that polydopamine is guided to grow on nanocellulose; acrylic acid matrix, conductive substances and drugs are added into a nanocellulose solution with adhesion, and then stirring is carried out for a period of time; an initiator and a crosslinking agent are added, and standing, heat environment polymerization are carried out, so that a composite conductive hydrogel material with wet-state adhesion is prepared. The preparation process is simple, the reaction condition is mild, and the problem of poor adhesion of flexible sensing underwater conductive hydrogel is solved.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel technology, specifically relating to a nanocellulose-enhanced wet adhesion hydrogel. Background Technology

[0002] Hydrogels are polymeric materials with a three-dimensional cross-linked network structure formed through chemical bonding or physical entanglement. They have applications in numerous fields, such as tissue engineering, drug delivery, artificial skin, water treatment, medical rehabilitation, and flexible wearable devices. Conductive hydrogels are crucial for flexible devices, formed by combining various matrices and conductive media. They possess high sensitivity, strong self-healing properties, adjustable mechanical strength, and customizable electronic properties. Currently, most conductive hydrogels exhibit adhesive properties, adhering directly to substrate surfaces without external force, reducing the possibility of signal blockage and capturing minute sensor signals during transmission. They have been applied in areas such as human motion monitoring, clinical diagnosis, and human-computer interaction. However, the application of conductive hydrogels underwater is limited. The water absorption of hydrogels causes them to swell, leading to rapid collapse of the internal structure and loss of adhesive properties. This results in the hydrogel detaching from the skin, making it difficult to detect the user's physical condition, potentially leading to tragic consequences.

[0003] Currently, it is generally believed that the main factors affecting the application of hydrogels in humid environments are the formation of the hydration layer and water absorption swelling. Disrupting the formation of the hydration layer is essential, and hydrophobic groups can solve this problem. By removing the hydration layer from the interface through hydrophobic interactions, the hydrogel is kept away from the contact interface during underwater adhesion, thus facilitating adhesion. Mussels are marine organisms that live in humid environments and can achieve long-term adhesion in water. Inspired by this, small molecules containing catechol groups are combined with nanocellulose to impart adhesive properties to the nanocellulose, further enhancing the underwater adhesion performance of the hydrogel. However, there are few reports on imparting adhesive properties to nanocellulose in humid environments through catechol groups. Summary of the Invention

[0004] This invention addresses the problems of internal structural collapse and reduced adhesion of existing conductive hydrogel sensing materials in humid environments by proposing a method for preparing a nanocellulose-enhanced wet-adhesion hydrogel. This method is simple to operate and economically feasible.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] S1. Take a certain amount of nanocellulose in a beaker, adjust the pH, add dopamine hydrochloride, seal and stir in the dark.

[0007] S2. After stirring for a period of time, centrifuge to obtain polydopamine-modified nanocellulose;

[0008] S3. Disperse the modified nanocellulose into solutions with different mass fractions, take appropriate amounts of methacrylic acid sulfobetaine, aluminum trichloride, tannic acid and acrylic acid, add them to the above solutions, and stir evenly at room temperature.

[0009] S4. Weigh a small amount of initiator (ammonium persulfate, N,N-methylenebisacrylamide), add it to the above solution, stir for 3 hours, transfer to a mold, and let stand at 60 °C for 6 hours to obtain nanocellulose-reinforced wet adhesion hydrogel.

[0010] Furthermore, in step S1, the nanocellulose is derived from one or more of nanocellulose crystals, nanocellulose filaments, and bacterial cellulose, and the mass ratio of nanocellulose to dopamine hydrochloride is 10 to 1. The polymerization environment of dopamine hydrochloride requires the pH to be controlled at 6 to 10.

[0011] Furthermore, in step S2, the centrifugation is performed multiple times, with each centrifugation lasting 10 to 100 minutes and the rotation speed controlled at 3000 to 12000 r / min.

[0012] Furthermore, in step S2, the polydopamine-modified nanocellulose is dispersed into solutions with different cellulose contents, the mass fraction of which is 0.005~0.5%.

[0013] Furthermore, in step S3, the mass ratio of methacrylic acid sulfobetaine to acrylic acid in the added drugs to the solution is 0.1~5, the total molar concentration of the two is controlled at 0.5~5 mol / L, the mass fraction of aluminum trichloride is 0.5%~5%, and the amount of tannic acid is controlled at 100~500 mg.

[0014] Furthermore, in step S4, ammonium persulfate accounts for 0.01% to 0.05% of the mass fraction of the mixed solution, and N,N-methylenebisacrylamide accounts for 0.01% to 0.1% of the total mass fraction of the solution.

[0015] The nanocellulose in this invention is green and environmentally friendly and has a wide range of sources. By adjusting the pH of the solution to create an alkaline environment, polydopamine is guided to grow on the nanocellulose, which enables the hydrogel to adhere even in a humid environment, thus improving the adhesion performance of the composite hydrogel.

[0016] This invention prepares nanocellulose hydrogel sensing materials through thermal polymerization, with mild reaction conditions and relatively few chemical substances used. Attached Figure Description

[0017] Figure 1 Images showing the adhesion of polydopamine-modified nanocellulose composite hydrogels in air and underwater.

[0018] Figure 2A comparison of the adhesion strength of composite hydrogel materials to different substrates in the air and underwater.

[0019] Figure 3 A comparison of the mechanical properties of polydopamine-modified nanocellulose composite hydrogel and nanocellulose composite hydrogel.

[0020] Figure 4 Figures showing the mechanical properties of polydopamine-modified nanocellulose composite hydrogels with different contents; Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0022] Example 1

[0023] 1) Place 100g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 hours, centrifuge and wash, add appropriate amount of liquid in the order of original solution, water, alcohol, water, centrifuge at 10000 r / min for 20 min.

[0024] 2) Take 2.25g of polydopamine-modified nanocellulose (1.14% solid content) and add it to 15g of water. Mix it evenly on a magnetic stirrer. Control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:5. Use a pipette to take the mixture, add 0.6g of aluminum trichloride and 1.05g of tannic acid. Stir at room temperature for 20min, then add 0.4%wt N,N-methylenebisacrylamide and 0.2%wt initiator ammonium persulfate. Stir at room temperature for 3h, transfer to molds of different shapes, and let stand at 60℃ for 6h to obtain wet viscous hydrogel material.

[0025] Example 2

[0026] 1) Place 100g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 hours, centrifuge and wash, in the order of original solution, water, alcohol, water, centrifuge at 10000 r / min for 20 minutes.

[0027] 2) Take 1.76g of polydopamine-modified nanocellulose (2.18% solid content) and add it to 15g of water. Mix it evenly on a magnetic stirrer. Control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:5. Take the solution with a pipette and add 0.6g of aluminum trichloride and 1.05g of tannic acid. Stir at room temperature for 20min. Then add 0.4%wt N,N-methylenebisacrylamide and 0.2%wt initiator ammonium persulfate. Stir at room temperature for 3h. Transfer to molds of different shapes and let stand at 60℃ for 4h to obtain wet viscous hydrogel material.

[0028] The adhesion of the prepared composite hydrogel to the actual object was tested (e.g.) Figure 1 As shown in the figure, the prepared composite hydrogel can adhere well to the surface of various objects, proving that the prepared material has excellent adhesion.

[0029] Example 3

[0030] 1) Place 100g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 hours, centrifuge and wash, in the order of original solution, water, alcohol, water, centrifuge at 10000 r / min for 20 min.

[0031] 2) Take 5.29g of polydopamine-modified nanocellulose (0.97% solid content) and add it to 15g of water. Mix it evenly on a magnetic stirrer. Control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:5. Use a pipette to take the solution, add 0.6g of aluminum trichloride and 1.05g of tannic acid. Stir at room temperature for 15min, then add 0.4%wt N,N-methylenebisacrylamide and 0.2%wt initiator ammonium persulfate. Stir at room temperature for 3h, transfer to molds of different shapes, and let stand at 60℃ for 5h to obtain wet viscous hydrogel material.

[0032] The adhesion and tensile properties of the prepared composite hydrogel were tested (e.g.) Figure 2 , 4 (As shown).

[0033] Comparative Example 1

[0034] 1.82g of nanocellulose (1.4% solid content) was added to 15g of water and mixed evenly on a magnetic stirrer. The mass ratio of methacrylic acid sulfobetaine to acrylic acid was controlled at 1:5. 0.6g of aluminum trichloride and 1.05g of tannic acid were added to the solution. After stirring at room temperature for 30min, 0.4%wt N,N-methylenebisacrylamide and 0.2%wt ammonium persulfate initiator were added. The mixture was stirred at room temperature for 4h and then transferred to molds of different shapes. The mixture was allowed to stand at 60℃ for 5h to obtain the hydrogel material.

[0035] Comparative Example 2

[0036] 1.18g of polydopamine-modified nanocellulose (2.18% solid content) was added to 15g of water and mixed evenly on a magnetic stirrer. The mass ratio of methacrylic acid sulfobetaine to acrylic acid was controlled at 1:5. 0.6g of aluminum trichloride and 0.75g of tannic acid were added to the solution. After stirring at room temperature for 15min, 0.4%wt N,N-methylenebisacrylamide and 0.2%wt ammonium persulfate initiator were added. The mixture was stirred at room temperature for 3h and then transferred to molds of different shapes. The mixture was allowed to stand at 60℃ for 4h to obtain the hydrogel material.

[0037] Comparative Example 3

[0038] 1.18g of polydopamine-modified nanocellulose (2.18% solid content) was added to 15g of water and mixed evenly on a magnetic stirrer. The mass ratio of methacrylic acid sulfobetaine to acrylic acid was controlled at 1:5. 0.75g of aluminum trichloride and 1.05g of tannic acid were added to the solution. After stirring at room temperature for 15min, 0.4%wt N,N-methylenebisacrylamide and 0.2%wt ammonium persulfate initiator were added. The mixture was stirred at room temperature for 3h and then transferred to molds of different shapes. The mixture was allowed to stand at 60℃ for 4h to obtain the hydrogel material.

[0039] As shown in Tables 1 and 2, the addition of polydopamine-modified nanocellulose and tannic acid both improve the adhesion of the composite hydrogel compared to nanocellulose hydrogel. Figure 2 It is easy to see that the adhesion on different substrates is generally higher than that in Comparative Example 1, with the most significant improvement observed in Example 2, especially in wet adhesion. Compared to polydopamine-modified nanocellulose with the same content, the increased tannin content leads to improved adhesion; Al 3+ Increased content leads to improved tensile properties. Figure 3 , Figure 4 The stress-strain data plots show that polydopamine-modified nanocellulose can improve the elongation and stress of the hydrogel. With increasing dosage, the changes in the tensile properties of the hydrogel generally show that elongation first increases and then decreases, while stress increases. See the figure for details.

[0040] Performance testing

[0041] Table 1. Adhesion (kPa) of polydopamine-modified nanocellulose hydrogel to different substrates

[0042]

[0043] Table 2. Wet adhesion (kPa) of polydopamine-modified nanocellulose with different contents to different substrates.

[0044]

[0045] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nanocellulose-enhanced wet adhesion hydrogel, characterized in that, The following steps are required: S1. Place 100 g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 h, centrifuge and wash, and centrifuge at 10000 r / min for 20 min in the order of original solution, water, alcohol and water to obtain polydopamine modified nanocellulose; S2. Take 2.25 g of polydopamine-modified nanocellulose with a solid content of 1.14% and add it to 15 g of water. Mix it evenly on a magnetic stirrer, and control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:

5. Use a pipette to take the mixture, add 0.6 g of aluminum trichloride and 1.05 g of tannic acid, stir at room temperature for 20 min, then add 0.4 wt% N,N-methylenebisacrylamide and 0.2 wt% initiator ammonium persulfate, stir at room temperature for 3 h, transfer to molds of different shapes, and let stand at 60 ℃ for 6 h to obtain wet viscous hydrogel material.

2. A method for preparing a nanocellulose-enhanced wet adhesion hydrogel, characterized in that, The following steps are required: S1. Place 100 g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 h, centrifuge and wash, and centrifuge at 10000 r / min for 20 min in the order of original solution, water, alcohol and water to obtain polydopamine modified nanocellulose; S2. Take 1.76 g of polydopamine-modified nanocellulose with a solid content of 2.18% and add it to 15 g of water. Mix it evenly on a magnetic stirrer. Control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:

5. Take the solution with a pipette and add 0.6 g of aluminum trichloride and 1.05 g of tannic acid. Stir at room temperature for 20 min, then add 0.4 wt% N,N-methylenebisacrylamide and 0.2 wt% ammonium persulfate initiator. Stir at room temperature for 3 h, transfer to molds of different shapes, and let stand at 60 ℃ for 4 h to obtain wet viscous hydrogel material.

3. A method for preparing a nanocellulose-enhanced wet adhesion hydrogel, characterized in that, The following steps are required: S1. Place 100 g of nanocellulose in a beaker, adjust the pH of the nanocellulose solution to 8.5 using the hydrochloric acid-Tris system, mix evenly, add an equal amount of dopamine hydrochloride according to the ratio of nanocellulose to dopamine hydrochloride of 1:1, stir in the dark for 6 h, centrifuge and wash, and centrifuge at 10000 r / min for 20 min in the order of original solution, water, alcohol and water to obtain polydopamine modified nanocellulose; S2. Take 5.29 g of polydopamine-modified nanocellulose with a solid content of 0.97% and add it to 15 g of water. Mix it evenly on a magnetic stirrer. Control the mass ratio of methacrylic acid sulfobetaine to acrylic acid to be 1:

5. Use a pipette to take the solution. Add 0.6 g of aluminum trichloride and 1.05 g of tannic acid. Stir at room temperature for 15 min. Then add 0.4 wt% N,N-methylenebisacrylamide and 0.2 wt% ammonium persulfate initiator. Stir at room temperature for 3 h. Transfer to molds of different shapes and let stand at 60 ℃ for 5 h to obtain wet viscous hydrogel material.

4. The preparation method according to any one of claims 1, 2, and 3, characterized in that, The nanocellulose mentioned in step S1 is selected from one or more of nanocellulose crystals, nanocellulose filaments, and bacterial cellulose.

5. A nanocellulose-reinforced wet adhesion hydrogel prepared by the preparation method according to any one of claims 1 to 4.

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