A dual-network conductive hydrogel and a preparation method and application thereof

Abstract

The present application discloses a double network conductive hydrogel and its preparation method and application, using polyvinyl alcohol, acrylic acid and ferric sulfate as main raw materials, and utilizing tannic acid and Fe 3+ The redox reaction between the two groups was carried out by free radical polymerization and direct immersion method to prepare polyvinyl alcohol / polyacrylic acid-iron ion double network hydrogel, namely PVA / PAA-Fe 3+ Hydrogel. PVA / PAA-Fe prepared in the present embodiment 3+ The hydrogel has good strength, toughness and electrical conductivity, and there is no obvious difference in its conductive properties under tensile deformation mode, so it has potential applications in the field of stretchable conductors.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer hydrogels, and in particular relates to a double-network conductive hydrogel and a preparation method and application thereof. Background Art

[0002] Hydrogels are a class of functional polymers that form a three-dimensional network structure through physical or chemical cross-linking and can retain a large number of water molecules without damage. Integrating multiple energy dissipation mechanisms into a matrix and utilizing their synergistic effects to resist damage, thereby obtaining strong hydrogels, has become a common strategy for hydrogel synthesis. Existing strategies for synthesizing strong hydrogels usually involve complex processes, chemical modifications, or the addition of reinforcing fillers. Therefore, constructing strong hydrogels through a simple method remains a challenge. Summary of the Invention

[0003] The purpose of the present invention is to provide a double-network conductive hydrogel and its preparation method and application, and to construct a strong hydrogel by a simple method, that is, to obtain a strong polyvinyl alcohol / polyacrylic acid-iron ion double-network conductive hydrogel.

[0004] To achieve the above objectives, this application adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a double-network conductive hydrogel, comprising the following steps:

[0006] S1, dissolving polyvinyl alcohol (PVA) in deionized water, heating to 95°C with mechanical stirring for 2 h, and then cooling to 30°C to obtain a PVA aqueous solution, i.e., a first solution;

[0007] S2. Weigh tannic acid TA and iron sulfate Fe2(SO4)3 and dissolve them in deionized water to obtain a second solution;

[0008] S3, weighing ammonium persulfate (APS) and dissolving it in deionized water to obtain an APS aqueous solution, i.e., the third solution;

[0009] S4. Sequentially measure the first solution, the second solution, and the third solution, stir them evenly, then add acrylic acid monomer AA, stir rapidly for 60 seconds, transfer the mixed solution to a culture dish, and place it at room temperature for 120 minutes;

[0010] S5, soak in Fe2(SO4)3 solution for several hours to obtain strong polyvinyl alcohol / polyacrylic acid-iron ion PVA / PAA-Fe 3+ Double-network conductive hydrogel.

[0011] Optionally, in step S1, the molecular weight of PVA is 5000-6000, and the mass percentage concentration of the solution is 10-15%.

[0012] Optionally, in step S2, the mass ratio of TA to Fe2(SO4)3 is 0.01-0.05, and the mass percentage concentration of the solution is 1%-5%.

[0013] Optionally, in step S3, the mass percentage concentration of the APS aqueous solution is 2%-8%.

[0014] Optionally, in step S4, the mass ratio of AA to PVA is 6:1 to 1:2.

[0015] Optionally, in step S5, the soaking time in the Fe2(SO4)3 solution is 1-6 hours.

[0016] In a second aspect, an embodiment of the present application provides a double-network conductive hydrogel, which is prepared using the preparation method of the double-network conductive hydrogel provided in the first aspect above.

[0017] In a third aspect, the embodiments of the present application disclose the use of the double-network conductive hydrogel as a stretchable conductor.

[0018] Compared with the prior art, the beneficial effects of the embodiments of the present application are:

[0019] The present invention provides a dual-network conductive hydrogel and its preparation method and application, which utilizes the redox reaction of tannic acid and iron ions to catalyze the polymerization of acrylic acid on the basis of the first cross-linked network of PVA, thereby achieving the rapid synthesis of polyacrylic acid hydrogel at room temperature. 3+ The metal ions penetrate the hydrogel system through osmosis and bind to the carboxylate ions on the PAA molecules, forming a secondary metal-coordinated crosslinked network. After immersion in an Fe₂(SO₄)₃ solution, the resulting polyvinyl alcohol / polyacrylic acid-iron ion double-network hydrogel exhibits a uniform and dense pore structure, resulting in excellent mechanical properties that surpass those of most existing polyacrylic acid hydrogels and exhibits electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 TA powder and PVA hydrogel provided in the embodiment of the present application, PVA / PAA-Fe before and after soaking in Fe2(SO4)3 solution 3+ Schematic diagram of the infrared spectrum of the hydrogel.

[0022] Figure 2PVA / PAA-Fe provided in the embodiment of this application 3+ Schematic diagram of the conductive properties of hydrogels under original, tensile, bending, and torsional deformations.

[0023] Figure 3 PVA / PAA-Fe provided in the embodiment of this application 3+ Scanning electron micrograph of the hydrogel.

[0024] Figure 4 PVA / PAA-Fe without TA and with TA provided in the examples of this application 3+ Schematic diagram of hydrogel.

[0025] Figure 5 The effect of immersion time on PVA / PAA-Fe in the examples of this application 3+ Schematic diagram of the effect of hydrogel mechanical properties. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0027] Polyvinyl alcohol (PVA) is a hydrophilic linear polymer containing hydroxyl groups. It exhibits excellent biocompatibility, biodegradability, and crystallization ability, and is widely used in the preparation of hydrogels. Polyacrylic acid (PAA) is a linear polymer formed by the polymerization of acrylic acid monomers in the presence of an initiator. Although PAA possesses hydrophilic groups, it cannot form a network structure on its own. Physical or chemical crosslinking with metal ions is often used to impart mechanical properties and good self-healing capabilities to PAA hydrogels. However, as a form of physical crosslinking, metal ion coordination suffers from low mechanical strength, limiting its application. Targeted improvements are necessary.

[0028] Tannic acid (TA) is a plant polyphenol with a rich structure of catechol groups. The mutual transformation of phenol structure and quinone structure of tannic acid forms a dynamic redox system with metal ions in solution. 3+ The redox system is used to initiate acrylic acid polymerization, and its redox reaction can improve the efficiency of the initiator ammonium persulfate (APS) in generating sulfate radicals, thereby promoting the acrylic acid polymerization reaction.

[0029] In view of this, the present invention provides a method for preparing a double network conductive hydrogel, which uses free radical polymerization and direct immersion method to use PVA as the first layer of cross-linked network basis, and utilizes TA and Fe 3+The redox reaction of Fe2(SO4)3initiates the polymerization of acrylic acid, and PAA is synthesized in situ at room temperature, and PAA is combined with Fe 3+ By metal coordination, PAA-Fe is constructed on the basis of PVA network 3+ The second layer of the cross-linked network is then directly immersed in a Fe2(SO4)3solution to obtain a strong and tough PVA / PAA-Fe 3+ Hydrogel. Because it contains Fe 3+ Ion conduction, after the conductivity test, PVA / PAA-Fe 3+ Hydrogel has certain conductivity.

[0030] In order to illustrate the technical solutions described in the present application, the following will be described by specific examples.

[0031] In some embodiments, a preparation method of a double-network conductive hydrogel is provided, comprising the following steps:

[0032] Step 1: 12 g of PVA (polyvinyl alcohol) and 88 mL of deionized water are added to a three-necked flask, heated to 95℃ and mechanically stirred for 2 h, and then cooled to 30℃ to obtain a PVA aqueous solution with a mass fraction of 12%, which is the first solution; 0.12 g of TA (tannic acid) and 3.2 g of Fe2(SO4)3are sequentially weighed and dissolved in 80 mL of deionized water to obtain the second solution; 5.0 g of APS (ammonium persulfate) is weighed and dissolved in 100 mL of deionized water to obtain an APS aqueous solution, which is the third solution;

[0033] Step 2: 10 mL of the first solution, 4 mL of the second solution and 0.6 mL of the third solution are sequentially measured, stirred uniformly, and then 5.4 mL of AA (acrylic acid) is added, and the solution is transferred to a culture dish and placed at room temperature for 120 min.

[0034] Step 3: The solution is immersed in a 0.5 mol·L -1 Fe2(SO4)3solution for several hours to obtain a strong and tough PVA / PAA-Fe 3+ Double-network hydrogel (strong and tough polyvinyl alcohol / polyacrylic acid-iron ion double-network conductive hydrogel).

[0035] As an example, based on the preparation method provided in the present embodiment, PVA / PAA-Fe 3+ hydrogels with different feeding ratios can also be prepared according to the feeding table shown in Table 1 below.

[0036] Table 1 Feeding table of PVA / PAA-Fe 3+ hydrogel

[0037] sample PVA / g H2O / mL TA / g <![CDATA[Fe2(SO4)3 / g及质量百分含量 / %]]> <![CDATA[H2O / mL]]> APS / g H2O / mL AA / mL 1 1.2 8.8 0.006 0.02 / 0.1% 4 0.03 0.6 5.4 2 1.2 8.8 0.006 0.04 / 0.2% 4 0.03 0.6 5.4 3 1.2 8.8 0.006 0.08 / 0.4% 4 0.03 0.6 5.4 4 1.2 8.8 0.006 0.12 / 0.6% 4 0.03 0.6 5.4 5 1.2 8.8 0.006 0.16 / 0.8% 4 0.03 0.6 5.4 6 1.2 8.8 0.006 0.20 / 1.0% 4 0.03 0.6 5.4 7 1.2 8.8 0.006 0.24 / 1.2% 4 0.03 0.6 5.4 8 1.2 8.8 0.006 0.32 / 1.6% 4 0.03 0.6 5.4

[0038] As shown in Figure 1 , the infrared spectrum of the double network hydrogel prepared in the embodiment is shown in Figure 1 . Figure 1 In the figure, the abscissa represents wavenumber / cm, and the ordinate represents transmittance. The analysis of the content shown in Figure 1 is as follows.

[0039] In some embodiments, the PVA / PAA-Fe 3+ hydrogel prepared above can be used as a stretchable conductor, for example, to light up an LED light emitting diode lamp under the drive of 1.5 V.

[0040] For example, as shown in Figure 2 , when the PVA / PAA-Fe 3+ hydrogel used as a stretchable conductor is in a state of bending, twisting and tensile deformation with a deformation amount less than 50%, the brightness of the LED lamp is almost unchanged, almost consistent with the original state.

[0041] As an example, Figure 3 , the PVA / PAA-Fe 3+ hydrogel prepared in the above embodiment is shown in the scanning electron microscope image with a scale of 100 um. Alternatively, the scanning electron microscope image also shows that the detection condition is "Regulus8100 10.0kV 11.0mmx300SE(UL)".

[0042] As can be seen from Figure 3 , the PVA / PAA-Fe 3+ hydrogel has a uniform and dense pore structure, so it has good mechanical properties, which is higher than most existing polyacrylic acid hydrogels, and has electrical conductivity.

[0043] It should be noted that the tannic acid TA cannot form a hydrogel, and the system added with the tannic acid TA forms a hydrogel after 30 minutes. In the presence of oxygen, the tannic acid and Fe 3+ have a redox reaction to generate free radicals. These free radicals can act as initiators to start the polymerization reaction of the acrylic acid monomer to obtain PAA, and form a semi-interpenetrating network structure with PVA to form a gel. Figure 4 The PVA / PAA-Fe 3+ hydrogel without adding TA and the PVA / PAA-Fe 3+ hydrogel added with TA are shown in the physical schematic diagram. For example, Figure 4 , the left side is a normal placement schematic diagram, and the right side is an inverted placement schematic diagram.

[0044] Furthermore, based on the above embodiments, in order to illustrate the technical solutions described in this application, the following embodiments are also provided for illustration. Example 1

[0045] Step 1: Add 12 g of PVA and 88 mL of deionized water to a three-necked flask, heat to 95°C and mechanically stir for 2 h, then cool to 30°C to obtain a 12% PVA aqueous solution to obtain the first solution; weigh 0.12 g of TA and 3.2 g of Fe2(SO4)3 and dissolve them in 80 mL of deionized water to obtain the second solution; weigh 5.0 g of APS and dissolve it in 100 mL of deionized water to obtain the third solution;

[0046] Step 2: Sequentially measure 10 mL of the first solution, 4 mL of the second solution, and 0.6 mL of the third solution, stir evenly, then add 5.4 mL of AA, stir rapidly for 60 s, transfer the solution to a Petri dish, and place at room temperature for 120 min.

[0047] Step 3: At 0.5 mol·L -1 PVA / PAA-Fe was obtained by immersing the mixture in Fe2(SO4)3 solution for 2 hours. 3+ hydrogel.

[0048] The mechanical properties test showed that the fracture strength, elastic modulus and toughness of the hydrogel were 709.8 kPa, 234.0 kPa and 3325.3 kJ·m -3 . Example 2

[0049] Same as step 1 and step 2 of Example 1. Then, step 3 is: -1 PVA / PAA-Fe was obtained by immersing the mixture in Fe2(SO4)3 solution for 5 hours. 3+ hydrogel.

[0050] The mechanical properties test showed that the fracture strength, elastic modulus and toughness of the hydrogel were 1526.9 kPa, 921.1 kPa and 6181.4 kJ·m -3 . Example 3

[0051] The same as step 1 of Example 1, step 2 is: 10 mL of the first solution, 2 mL of the second solution and 0.6 mL of the third solution are measured in sequence, stirred evenly, and then 5.4 mL of AA is added. The mixture is rapidly stirred for 60 s, and the solution is transferred to a culture dish and placed at room temperature for 120 min. Step 3 is: in 0.5 mol·L -1PVA / PAA-Fe was obtained by immersing the mixture in Fe2(SO4)3 solution for 5 hours. 3+ hydrogel.

[0052] The mechanical properties test showed that the fracture strength, elastic modulus and toughness of the hydrogel were 657.1 kPa, 575.1 kPa and 1491.0 kJ·m -3 . Example 4

[0053] The same as step 1 of Example 1, step 2 is as follows: 10 mL of the first solution, 8 mL of the second solution and 0.6 mL of the third solution are measured in sequence, stirred evenly, and then 5.4 mL of AA is added. The mixture is rapidly stirred for 60 s, and the solution is transferred to a culture dish and placed at room temperature for 120 min. Step 3 is as follows: in 0.5 mol·L -1 PVA / PAA-Fe was obtained by immersing the mixture in Fe2(SO4)3 solution for 5 hours. 3+ hydrogel.

[0054] The mechanical properties test showed that the fracture strength, elastic modulus and toughness of the hydrogel were 1641.6 kPa, 1593.2 kPa and 3529.3 kJ·m -3 .

[0055] The following is the PVA / PAA-Fe prepared in the above example 3+ The performance of the hydrogel was evaluated.

[0056] like Figure 1 As shown, PVA hydrogel and PVA / TA-Fe3 before and after immersion + Hydrogel at 3293 cm -1 The broad absorption peak at 3382 cm belongs to the stretching vibration of the OH group of the alcohol. -1 The absorption peaks are attributed to the stretching vibration of TA phenolic OH. 3+ The hydrogel becomes wider after soaking, indicating that the intermolecular interaction between OH and the double network polymer is enhanced.

[0057] 1245 cm -1 and 1207 cm -1 The absorption peak of PVA hydrogel is attributed to the C-OH stretching vibration of carboxyl group COOH. -1 The absorption peak at 1065 cm and the absorption peak at 1065 cm of PVA / PAA-Fe3+ hydrogel -1 The absorption peaks at 2940 cm are attributed to the stretching vibration of the C-OH bond of the alcohol in the PVA structure. -1The absorption peak at 1190 cm -1 The absorption peak at 1697 cm -1 The absorption peak at 30° is attributed to the ester carbonyl C=O of TA. Comparing the PVA / PAA-Fe3+ hydrogel before and after immersion, no new peaks are generated in the infrared spectrum, indicating that immersion in Fe2(SO4)3 is a process of strengthening the physical interaction of the double network hydrogel.

[0058] As shown in Table 1 and Table 2, PVA / PAA-Fe with Fe2(SO4)3 content ranging from 0.1 to 1.6% was prepared. 3+ For a series of hydrogels, when Fe2(SO4)3 is less than or equal to 0.6%, the amount of Fe2(SO4)3 in the polymerization process has no obvious effect on the mechanical properties of the hydrogel; when Fe2(SO4)3 increases from 0.6% to 0.8%, PVA / PAA-Fe 3+ The fracture stress, elongation at break and toughness of the hydrogel also increased accordingly; when the Fe2(SO4)3 content continued to increase from 0.8%, the fracture stress of the Fe2(SO4)3 hydrogel did not change much, but the elongation at break steadily decreased. By adjusting the amount of Fe2(SO4)3 used in the PAA polymerization process, the obtained PVA / PAA-Fe 3+ Regulation of the mechanical properties of hydrogels.

[0059] Table 2 PVA / PAA-Fe with different Fe2(SO4)3 contents 3+ Breaking strength, elongation at break, elastic modulus and toughness of hydrogels

[0060] sample Fe2(SO4)3 percentage content / % <![CDATA[Fe2(SO4)3加入量 / g]]> Breaking strength / kPa Elongation at break / % Elastic modulus / kPa <![CDATA[韧性 / kJ·m -3 ]]> 1 0.1 0.2 861.3 337 801.6 2004.6 2 0.2 0.4 854.3 376 756.2 2256.0 3 0.4 0.8 657.1 337 575.1 1491.0 4 0.6 1.2 855.2 462 565.4 2552.3 5 0.8 1.6 1526.9 638 921.1 6181.4 6 1.0 2.0 1569.0 561 1153.7 5883.0 7 1.2 2.4 1556.1 430 1242.3 4523.1 8 1.6 3.2 1641.6 285 1593.2 3529.3

[0061] According to Table 1 and Table 2 above, when the mass ratio of PVA to PAA double network is 1.2:5.4, when the TA content is 0.006 g and the Fe2(SO4)3 content is 0.16 g, the PVA-PAA-Fe 3+ The hydrogel exhibited the best mechanical properties, with the elongation at break and toughness reaching the maximum values ​​of the test range, which were 638% and 6181.4 kJ·m, respectively. -3 , the breaking strength is 1526.9 kPa. According to the conductivity test, PVA / PAA-Fe 3+ The electrical conductivity of the hydrogel is 0.731 S·m -1 Moreover, within the range of 1-6 h of immersion in Fe2(SO4)3 solution, a series of PVA / PAA-Fe with a breaking strength of 519.9-1526.9 kPa and an elastic modulus of 172.1-1425.4 kPa were obtained. 3+hydrogel.

[0062] It should be noted that PVA / PAA-Fe 3+ The tensile strength, elongation at break, elastic modulus and toughness of the hydrogel were significantly affected. 3+ The fracture strength of the hydrogel continued to increase from 519.9 kPa to 1505.6 kPa; the elongation at break decreased from 1304% to 613%; the elastic modulus continued to increase from 172.1 kPa to 1425.4 kPa. 3+ The toughness of the hydrogel has been relatively good, maintaining at 3300-6000 kJ·m -3 PVA / PAA-Fe 3+ The fracture strength of the hydrogel reached a maximum value of 1526.1 kPa when the immersion time was 5 h.

[0063] Figure 5 The results of PVA / PAA-Fe immersion at different times are given. 3+ The tensile stress-strain curve of the hydrogel, the horizontal axis represents the strain percentage (unit: %), and the vertical axis represents the stress (unit: kPa). Table 3 shows the tensile stress-strain curve of the hydrogel under different immersion times. 3+ Elastic modulus and toughness of hydrogels.

[0064] Table 3 PVA / PAA-Fe at different immersion times 3+ Breaking strength, elongation at break, elastic modulus and toughness of hydrogels

[0065] sample Soaking time Breaking strength / kPa Elongation at break / % Elastic modulus / kPa <![CDATA[韧性 / kJ·m -3 ]]> <![CDATA[PVA / PAA-Fe 3+ (1 h)]]> 1 h 519.9 1304 172.1 3341.9 <![CDATA[PVA / PAA-Fe 3+ (2 h)]]> 2 h 709.8 965 234.0 3325.3 PVA / PAA-Fe 3+ (3 h)] 3 h 793.7 805 293.7 3344.1 PVA / PAA-Fe 3+ (4 h) 4 h 1257.4 680 752.5 5274.7 <![CDATA[PVA / PAA-Fe 3+ (5 h)]]> 5 h 1526.1 638 921.1 6181.4 <![CDATA[PVA / PAA-Fe 3+ (6 h)]]> 6 h 1505.6 613 1425.4 6075.1

[0066] According to Table 3 above, with the increase of immersion time (1h~6h), the changing trend of breaking strength is first increasing and then decreasing, the changing trend of breaking elongation is gradually decreasing, the changing trend of elastic modulus is gradually increasing, and the changing trend of toughness is first decreasing, then increasing, and then decreasing again.

[0067] In summary, the embodiments of the present application provide a double-network conductive hydrogel and its preparation method and application.

[0068] Using polyvinyl alcohol, acrylic acid and ferric sulfate as the main raw materials, tannic acid and Fe 3+ The redox reaction between the two groups was carried out, and the polyvinyl alcohol / polyacrylic acid-iron ion double network hydrogel PVA / PAA-Fe was prepared by free radical polymerization and direct immersion method. 3+ Hydrogel. PVA / PAA-Fe prepared in the present embodiment 3+The hydrogel has good strength, toughness and electrical conductivity, and there is no obvious difference in its conductive properties under tensile deformation mode, so it has potential applications in the field of stretchable conductors.

Claims

1. A method for preparing a double-network conductive hydrogel, characterized in that: The following steps are involved: S1, dissolving polyvinyl alcohol (PVA) in deionized water, heating to 95°C with mechanical stirring for 2 h, and then cooling to 30°C to obtain a PVA aqueous solution, i.e., a first solution; S2. Weigh tannic acid TA and iron sulfate Fe2(SO4)3 and dissolve them in deionized water to obtain a second solution; S3, weighing ammonium persulfate (APS) and dissolving it in deionized water to obtain an APS aqueous solution, i.e., the third solution; S4. Sequentially measure the first solution, the second solution, and the third solution, stir them evenly, then add acrylic acid monomer AA, stir rapidly for 60 seconds, transfer the mixed solution to a culture dish, and place it at room temperature for 120 minutes; S5, soak in Fe2(SO4)3 solution for several hours to obtain strong polyvinyl alcohol / polyacrylic acid-iron ion PVA / PAA-Fe 3+ Double-network conductive hydrogel.

2. The method for preparing the double-network conductive hydrogel according to claim 1, wherein: In step S1, the molecular weight of PVA is 5000-6000, and the mass percentage concentration of the solution is 10-15%.

3. The method for preparing the double-network conductive hydrogel according to claim 1, wherein: In step S2, the mass ratio of TA to Fe2(SO4)3 is 0.01-0.05, and the mass percentage concentration of the solution is 1%-5%.

4. The method for preparing the double-network conductive hydrogel according to claim 1, wherein: In step S3, the mass percentage concentration of the APS aqueous solution is 2%-8%.

5. The method for preparing the double-network conductive hydrogel according to claim 1, wherein: In step S4, the mass ratio of AA to PVA is 6:1 to 1:

2.

6. The method for preparing the double-network conductive hydrogel according to claim 1, wherein: In step S5, the soaking time in the Fe2(SO4)3 solution is 1-6 hours.

7. A double-network conductive hydrogel, characterized in that: The double-network conductive hydrogel is prepared by the preparation method of any one of claims 1 to 6.

8. Use of the double-network conductive hydrogel as claimed in claim 7 as a stretchable conductor.

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