A tough magnetic conductive hydrogel material and a preparation method and application thereof

Abstract

The application discloses a kind of tough magnetic conductive hydrogel materials and preparation method and application thereof, the preparation method of the tough magnetic conductive hydrogel material is as follows: chitosan, acrylamide, crosslinking agent, thermal initiator are added to water, and uniformly mixed to obtain transparent solution;Iron oxide is added to the transparent solution, uniformly mixed in vacuum environment and after degassing to obtain reaction liquid;The reaction liquid is heated to make acrylamide occur radical polymerization and generate polyacrylamide composite hydrogel;Finally, polyacrylamide composite hydrogel is immersed in ammonium sulfate solution to obtain target product.The application adds appropriate amount of iron oxide powder which can produce hydrogen bond effect with hydrogel network and appropriate amount of ammonium sulfate solution which can occur Hofmeister effect with chitosan, so as to overcome the shortcomings that the breaking energy of magnetic hydrogel is low, and it is brittle and easy to break, and the prepared hydrogel has good mechanical properties, electrical properties and magnetic properties.

Description

Technical Field

[0001] This invention belongs to the field of smart soft materials, and specifically relates to a tough magnetic conductive hydrogel material, its preparation method, and its application. Background Technology

[0002] Hydrogels are composite materials composed of a large amount of water and a three-dimensional polymer network. Magnetic hydrogels are a special type of hydrogel, typically acquired by adding magnetic materials (such as iron, cobalt, nickel, iron(III) oxide, neodymium iron boron, etc.) to the polymer network. Conductive hydrogels are also a special type of hydrogel, mainly acquired by incorporating conductive materials (such as carbon nanotubes, silver nanowires), free ions, or conductive networks (such as polyaniline) to achieve conductivity.

[0003] In recent years, magnetic hydrogels have become increasingly widely used in fields such as flexible robotics, drug delivery, tissue engineering, and environmental remediation. However, the mechanical properties of magnetic hydrogels have consistently been poor. In short, compared to other hydrogels, magnetic hydrogels have lower fracture energy, are brittle, and easily break, which limits their applications. Meanwhile, although the demand for multifunctional hydrogels is growing, there are currently few examples of hydrogels that simultaneously possess good magnetic and electrical properties. This is because, generally, chemically stable conductive materials used to prepare conductive hydrogels do not possess magnetic properties. Conversely, chemically stable magnetic materials used to prepare magnetic hydrogels typically do not possess good electrical conductivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a strong and tough magnetic conductive hydrogel material, its preparation method, and its applications.

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

[0006] The first objective of this invention is to provide a method for preparing a strong and tough magnetically conductive hydrogel material, comprising the following steps:

[0007] (1) Chitosan, acrylamide, crosslinking agent and thermal initiator are added to water and mixed evenly to obtain a transparent solution; preferably, the mass ratio of chitosan, acrylamide and water is (0.3-0.7):2.2:10; further, the crosslinking agent is N,N'-methylenebis(acrylamide) and the thermal initiator is 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0008] (2) Add iron(III) oxide to a transparent solution, mix evenly in a vacuum environment and degas to obtain a reaction solution; preferably, the mass ratio of iron(III) oxide to water is (2-6):10; the particle size of iron(III) oxide is 200 nm to 2 μm.

[0009] (3) The reaction solution is heated to cause the acrylamide in it to undergo a free radical polymerization reaction to generate a polyacrylamide composite hydrogel; preferably, the heating temperature is 50℃~65℃ and the time is 8~12h.

[0010] (4) The polyacrylamide composite hydrogel is impregnated in an ammonium sulfate solution to obtain a strong, tough, magnetically conductive hydrogel material. Preferably, the mass fraction of ammonium sulfate in the ammonium sulfate solution is 25-43%; the mass ratio of ammonium sulfate solution to chitosan is (200-500):(0.3-0.7). Further, the temperature of the ammonium sulfate solution is 0℃-35℃; the impregnation time is 48h-72h.

[0011] The second objective of this invention is to provide a strong and tough magnetic conductive hydrogel material, which is prepared by the preparation method described in the first objective of this invention.

[0012] A third object of the present invention is to provide a strong, magnetically conductive hydrogel material as described in the second object for use in the fabrication of wearable sensing devices, flexible magnetic actuators, or tissue thermotherapy devices.

[0013] The beneficial effects of this invention are as follows:

[0014] This invention overcomes the shortcomings of traditional magnetic hydrogels, such as low fracture energy, brittleness, and easy fracture, by adding an appropriate amount of iron oxide powder (which can form hydrogen bonds with the hydrogel network) and an appropriate amount of ammonium sulfate solution (which can undergo the Hofmeister effect with chitosan) during the preparation of a strong and tough magnetic conductive hydrogel material. Furthermore, the addition of ammonium sulfate solution provides a large number of free ions to the hydrogel, resulting in a hydrogel with certain electrical conductivity and a significant resistance-strain effect. The hydrogel prepared by this invention exhibits excellent mechanical, magnetic, and electrical properties. Attached Figure Description

[0015] Figure 1 The stress-strain curve test results are for the hydrogels prepared in the comparative examples and embodiments.

[0016] Figure 2 The results of the relative resistance change-strain curve test of the hydrogel prepared in Example 3 are shown.

[0017] Figure 3The results are obtained from thermal imaging tests of the hydrogel prepared in Example 3 under an alternating magnetic field of 0.99 kA / m and 350 kHz.

[0018] Figure 4 The deformation of the hydrogel prepared in Example 3 under different magnetic induction intensities is shown. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0020] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the raw materials used in the following experiments are all commercially available products.

[0021] Comparative Example 1

[0022] (1) Add 0.5g chitosan, 2.2g acrylamide, 16.4mg N,N'-methylenebis(acrylamide), and 8.15mg 2,2'-azobis(2-methylpropanediamine) dihydrochloride to 10mL of deionized water and stir to form a transparent solution.

[0023] (2) The above transparent solution was mixed evenly by vacuum stirring for 5 minutes and degassed. Then it was injected into a mold consisting of two glass plates separated by a 2mm silicone gasket. The mold was placed in a constant temperature oven at 50°C to allow the acrylamide to undergo a free radical polymerization reaction for 12 hours, resulting in a polyacrylamide composite hydrogel.

[0024] (3) At room temperature, the polyacrylamide composite hydrogel was immersed in 300g of 30% ammonium sulfate solution for 72h to obtain chitosan-polyacrylamide ion-covalent double network hydrogel.

[0025] Comparative Example 2

[0026] 1) Add 0.5g chitosan, 2.2g acrylamide, 16.4mg N,N'-methylenebis(acrylamide), and 8.15mg 2,2'-azobis(2-methylpropanediamine) dihydrochloride to 10mL of deionized water and stir to form a transparent solution.

[0027] (2) Add 2g of ferric oxide with a particle size of 200nm to the transparent solution and stir under vacuum to make the ferric oxide and the transparent solution mix evenly and degas;

[0028] (3) The mixture was injected into a mold consisting of two glass plates separated by a 2mm silicone gasket. The mold was placed in a constant temperature oven at 50°C to allow the acrylamide to undergo free radical polymerization for 12 hours, resulting in a polyacrylamide composite hydrogel.

[0029] (4) At room temperature, the polyacrylamide composite hydrogel was immersed in 300g of ammonium sulfate solution with a mass fraction of 15% for 72h to obtain ferric oxide / chitosan-polyacrylamide magnetic conductive hydrogel.

[0030] Example 1

[0031] (1) Add 0.5g chitosan, 2.2g acrylamide, 16.4mg N,N'-methylenebis(acrylamide), and 8.15mg 2,2'-azobis(2-methylpropanediamine) dihydrochloride to 10mL of deionized water and stir to form a transparent solution.

[0032] (2) Add 2g of ferric oxide with a particle size of 200nm to the transparent solution and stir under vacuum to make the ferric oxide and the transparent solution mix evenly and degas;

[0033] (3) The mixture was injected into a mold consisting of two glass plates separated by a 2mm silicone gasket. The mold was placed in a constant temperature oven at 50°C to allow the acrylamide to undergo free radical polymerization for 12 hours, resulting in a polyacrylamide composite hydrogel.

[0034] (4) At room temperature, the polyacrylamide composite hydrogel was immersed in 300g of 30% ammonium sulfate solution for 72h to obtain a strong magnetic conductive hydrogel of iron oxide / chitosan-polyacrylamide.

[0035] Example 2

[0036] The difference between Example 2 and Example 1 is that the amount of iron(III) oxide used in step (2) is 4g, while the other processes are the same as in Example 1.

[0037] Example 3

[0038] The difference between Example 3 and Example 1 is that the amount of iron(III) oxide used in step (2) is 6g, while the other processes are the same as in Example 1.

[0039] Example 4

[0040] The difference between Example 4 and Example 3 is that in step (4), the mass fraction of ammonium sulfate solution is 43%, and the other processes are the same as in Example 3.

[0041] Performance testing:

[0042] Example 3 was cut into test strips with a width of 5mm and a length of 30mm, and tensile and load tests were performed on them. The test results showed that it could be stretched to more than four times its own length and could withstand a load of 500g, exhibiting good mechanical properties.

[0043] When the hydrogel prepared in Example 3 was attracted by a permanent magnet, it was found that it could be easily attracted by the permanent magnet, exhibiting excellent magnetic properties.

[0044] Stress-strain curve testing:

[0045] Stress-strain curve tests were performed on the hydrogels prepared in all the comparative examples and embodiments described above. The test results are as follows: Figure 1 As shown. Figure 1 Figures a, b, c, d, e, and f show the test results of the hydrogels prepared in Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4, respectively. As can be seen from the figures, the hydrogel prepared in the Comparative Example, due to the lack of doping with iron(III) oxide, has significantly lower mechanical properties than the hydrogels prepared in Examples 1 to 4. Figures b to d show that the mechanical properties of the hydrogels obtained in Examples 1 to 3 increase with the increase of iron(III) oxide content. Comparative Example 2, due to the low concentration of ammonium sulfate solution used, exhibits a weak Hofmeister effect, resulting in the worst mechanical properties. Example 4, using an ammonium sulfate solution concentration close to saturation (43%), exhibits a more pronounced Hofmeister effect, resulting in the hydrogel with the best mechanical properties.

[0046] Relative resistance change-strain curve test:

[0047] The hydrogel prepared in Example 3 was made into test strips 30 mm long and 5 mm wide. Relative resistance-strain curve tests were performed, and the change in relative resistance was measured to obtain the results. Figure 2 As shown in Figure a, the sample prepared in Example 3 exhibits a significant resistance-strain effect; its resistance increases with increasing strain, and its sensitivity reaches a maximum of 12.19, indicating that the hydrogel prepared in this invention possesses excellent electrical properties related to resistance-strain sensitivity. (For a more intuitive demonstration...) Figure 2 The resistance-strain phenomenon in example a involves fabricating a 20mm long and 5mm wide strip from the hydrogel in Example 3. A 10mm section of the strip is connected to a circuit and a 3V LED bulb is connected in series. With the power supply resistance set to 6V, stretching the strip reveals that the LED's brightness significantly decreases as the strip is stretched. This demonstrates that the hydrogel prepared in this invention exhibits good resistance-strain sensitivity. It also demonstrates that the hydrogel prepared in this invention possesses good electrical conductivity.

[0048] Thermal imaging test:

[0049] The hydrogel prepared in Example 3 was subjected to thermal imaging testing under an alternating magnetic field of 0.99 kA / m and 350 kHz. The test results are as follows. Figure 3 As shown, the temperature of the hydrogel gradually increases with time, reaching 90℃ after 2 minutes. This indicates that the prepared hydrogel can be rapidly heated by an alternating magnetic field and can be used in wearable sensing devices, flexible magnetic actuators, and tissue hyperthermia.

[0050] Figure 4 The figure shows the deformation of the hydrogel prepared in Example 3 under different magnetic induction intensities. As can be seen from the figure, the deformation of the hydrogel gradually increases with the increase of magnetic induction intensity, indicating that the deformation of the hydrogel prepared in this invention can be controlled by the magnetic field and has good maneuverability in the magnetic field.

[0051] It should be noted that in other embodiments, the objective of this invention can be achieved when the experimental process meets the following conditions:

[0052] The preferred mass ratio of ferric oxide to deionized water is (2-6):10, specifically 2:10, 4:10 or 6:10.

[0053] The preferred particle size for iron oxide (Fe3O4) is 200 nm to 2 μm. Specifically, it can be 200 nm, 800 nm, 1 μm, or 2 μm.

[0054] For the temperature and time of the free radical polymerization reaction, the preferred temperature is 50℃~65℃, and the preferred time is 8~12h.

[0055] The mass fraction of ammonium sulfate in the ammonium sulfate solution is preferably 25% to 43%, specifically 30% or 43%.

[0056] The preferred mass ratio of ammonium sulfate solution to chitosan is (200-500):(0.3-0.7), specifically 200:0.3, 300:0.5, 400:0.5 or 500:0.7.

[0057] The soaking time is preferably 48h to 72h, specifically 48h or 72h.

[0058] Those skilled in the art can make appropriate selections of the above process parameters according to actual needs, and all of them can achieve the purpose of this invention.

[0059] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a strong and tough magnetic conductive hydrogel material, characterized in that: Includes the following steps: (1) Add chitosan, acrylamide, crosslinking agent and thermal initiator to water and mix well to obtain a transparent solution; (2) Add iron(III) oxide to the transparent solution, mix evenly in a vacuum environment and degas to obtain the reaction solution; (3) The reaction solution is heated to cause the acrylamide in it to undergo free radical polymerization to generate polyacrylamide composite hydrogel; (4) The polyacrylamide composite hydrogel is immersed in ammonium sulfate solution to obtain a tough magnetic conductive hydrogel material. In step (1), the mass ratio of chitosan, acrylamide, and water is (0.3~0.7):2.2:10; the crosslinking agent is N,N'-methylenebis(acrylamide), and the thermal initiator is 2,2'-azobis(2-methylpropanediamine) dihydrochloride; In step (2), the mass ratio of iron(III) oxide to water is (4~6):10; The particle size of the iron oxide is 200 nm to 2 μm; The ammonium sulfate solution contains 25-43% ammonium sulfate by mass.

2. The method for preparing the strong and tough magnetic conductive hydrogel material according to claim 1, characterized in that: In step (3), the heating temperature is 50℃~65℃ and the time is 8-12h.

3. The method for preparing the strong and tough magnetic conductive hydrogel material according to claim 1, characterized in that: In step (4), the mass ratio of the ammonium sulfate solution to chitosan is (200~500): (0.3~0.7).

4. The method for preparing the strong and tough magnetic conductive hydrogel material according to claim 1, characterized in that: In step (4), the temperature of the ammonium sulfate solution is 0℃~35℃; the soaking time is 48h~72h.

5. A strong and tough magnetic conductive hydrogel material, characterized in that: It is prepared by the preparation method as described in any one of claims 1 to 4.

6. The strong and tough magnetic conductive hydrogel material as described in claim 5 is used to prepare wearable sensing devices, flexible magnetic actuators, or tissue thermotherapy devices.

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