A fast-gelling double network hydrogel, and a preparation method and application thereof

Abstract

The application provides a rapid-gelation double-network hydrogel and a preparation method and application thereof, and the preparation method comprises the following steps: adding an aqueous solution of MXene into an acetic acid solution of chitosan and performing ultrasonic dispersion; then adding an aqueous solution of metal ion salt, acrylamide and N-N-methylene bisacrylamide and dissolving; finally adding an initiator and gelating under normal temperature conditions to form the double-network hydrogel. The hydrogel prepared in the application is gelated within 5-15s at room temperature without any induced energy input; meanwhile, the double-network hydrogel prepared in the application has high tensile property, a wide strain detection range, high sensitivity, low energy dissipation and excellent adhesion, and is convenient for monitoring large-scale and subtle human motion, which provides a promising direction for integrated wearable smart devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogel, in particular to a kind of double-network hydrogel of rapid gelation and its preparation method and application. BACKGROUND

[0002] In recent years, wearable devices are becoming more and more common in our daily life, from smartwatches that can track body temperature, steps, and heart rate, to various forms of wearable devices such as tattoos and textiles. Wearable devices have important commercial value in numerous applications. Hydrogels have gradually gained attention and rapidly developed due to their biocompatibility, stretchability, adhesion, and other characteristics. However, during the study of hydrogels, it has been noticed that the gelation process often requires specific conditions such as light and heat. For example, polyvinyl alcohol (PVA) hydrogels require multiple freeze-thaw cycles in liquid nitrogen to establish hydrogen bonds and form gel structures, while polyacrylamide (PAA) hydrogels require the decomposition of free radicals at high temperatures to form a continuous polymer network. These gelation processes not only take a long time, but also may lead to incomplete reactions and insufficient performance in actual environments. Therefore, there is an increasing need to develop and study hydrogels with rapid gelation capabilities.

[0003] Yuxi Li et al. (Literature-ACS Nano 2022, 16, 1567-1577) prepared MXene-polyacrylic acid (PAA) Fe 3+ multi-bond network physical hydrogel by controlling the permeation of Fe 3+ The MXene-PAA hydrogel can be obtained within ten minutes at room temperature. However, this hydrogel has a significant energy dissipation during stretching, with an energy dissipation coefficient of 0.7 in the first cycle. Therefore, it is a challenging task to combine rapid, low-cost preparation with high adhesion, conductivity, and low energy dissipation to produce multifunctional hydrogels. SUMMARY

[0004] The present application proposes a kind of double-network hydrogel of rapid gelation and its preparation method and application, in normal temperature condition, without any form energy initiation can quickly synthesize hydrogel.

[0005] The technical solution of the present application is as follows: a preparation method of a double-network hydrogel of rapid gelation, comprising the following steps:

[0006] (1) adding a water solution of MXene to an acetic acid solution of chitosan and ultrasonic dispersing;

[0007] (2) then adding a water solution of metal ion salt, acrylamide (AAM) and N-N-methylene bisacrylamide (MBAA) and dissolving;

[0008] (3) Finally, the initiator is added, and the gelation is formed at room temperature to form the double network hydrogel.

[0009] The chitosan is dispersed in the aqueous solution in the form of polymer chains, and the acrylamide is dispersed in the form of short chains. When the initiator is added, the short chains of acrylamide form long chains through the crosslinking agent N-N-methylene bisacrylamide. Thus, the double network hydrogel is synthesized.

[0010] When the MXene is added to the synthesis system of the hydrogel, the characteristic peaks of Ti 2+ and Ti 3+ at 455.9 eV and 457.2 eV in the Ti 2p orbital spectrum of the MXene nanosheet indicate that the MXene nanosheet has strong reduction activity and has undergone a redox reaction with the initiator, thereby reducing the decomposition activation energy of the initiator, generating a large number of free radicals, and causing the rapid gelation phenomenon. At the same time, the addition of the MXene nanosheet also improves the conductivity, self-adhesion, and stretchability of the hydrogel. First, the MXene nanosheet forms a conductive path inside the hydrogel, solving the poor conductivity caused by the polymer itself. Second, various functional groups (-OH, -F, etc.) on the MXene nanosheet can form chain entanglement structures, electrostatic interactions, and supramolecular interactions with the chitosan chains, together forming an extensible hydrogel network, further improving the self-adhesion and stretchability of the hydrogel, so that the functions of each part of the hydrogel can work together to form an integrated wearable monitoring platform.

[0011] Further, the metal ion salt is iron nitrate.

[0012] Further, the initiator includes 2,2-azobis(2-methylpropylimid) dihydrochloride (AIBA) and ammonium persulfate (APS).

[0013] Further, the aqueous solution of the MXene contains 5-25 mg of MXene.

[0014] The amount of the acetic acid solution of chitosan is 15-25 g, and the acetic acid solution of chitosan is prepared as follows: 3-5 g of chitosan (CS) is dissolved in 200 ml of 0.2 M (mol / L) acetic acid solution.

[0015] The amount of the metal ion salt is 500-1000 mg, the amount of AAM is 3-5 g, and the amount of the aqueous solution of MBAA is 350-900 ul, and the concentration of the aqueous solution of MBAA is 1 wt%.

[0016] The initiator includes 200-600 ul of the aqueous solution of AIBA and 3-5 ml of the aqueous solution of APS, and the concentration of the aqueous solution of APS is 0.7 wt%, and the concentration of the aqueous solution of AIBA is 10 wt%.

[0017] Further, in step (3), the gelling time is 5-15s. The gelling time can be 5s, 7s, 10s, 12s, 15s, etc.

[0018] Compared with other reported literatures, the hydrogel with a gelling time of 5-15s is several orders of magnitude faster than the conventional preparation process, and does not need to introduce energy in the form of heat, light, etc. during the preparation process.

[0019] Further, the aqueous solution preparation method of MXene is as follows: 2g of Ti3AlC2 powder and 2g of LiF are added to 40ml of 9M HCl solution, stirred at 35℃ for 22-34h, then the product is washed with deionized water until the pH value of the solution is 7, and the supernatant after washing is collected.

[0020] A double-network hydrogel with rapid gelation is prepared by the preparation method.

[0021] A double-network hydrogel with rapid gelation includes a three-dimensional network structure formed by the entanglement between chitosan chains and polyacrylamide chains, and Mxene nanosheets and metal ions are doped in the three-dimensional network structure.

[0022] The application of a double-network hydrogel with rapid gelation in a wearable sensor.

[0023] The beneficial effects of the present application are:

[0024] The present application utilizes the combined action of MXene and metal ions to synthesize a MXene-based conductive hydrogel with rapid gelation capability. This hydrogel gels in 5-15 seconds at room temperature without any induced energy input. At the same time, the double-network hydrogel prepared by the present application has high stretchability (1350%), wide strain detection range (100-500%), high sensitivity (GF=2.86 when the strain is 300-500%), low energy dissipation (0.40kJ m -3 ) and excellent adhesion of the double-network hydrogel. This hydrogel can be easily attached to the surface of human skin to monitor large-scale and subtle human movements, showing stability and repeatability, which provides a promising direction for integrated wearable smart devices. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and other drawings can be obtained by those of ordinary skill in the art without any creative effort.

[0026] Figure 1 Physical photos of hydrogels for Example 1 and Comparative Examples 1-2;

[0027] Figure 2 Stress-strain curves of hydrogels prepared for Examples 1-5 and Comparative Examples 3 and 4;

[0028] Figure 3 PAA-C-Fe-M prepared for Example 1 10 Mechanical property curves of hydrogels;

[0029] Figure 4 PAA-C-Fe-M prepared for Example 1 10 Adhesion comparison chart for ten times.

[0030] Figure 5 PAA-C-Fe-M prepared for Example 1 10 Real-time resistance change monitoring of hydrogels to monitor the electrical self-healing behavior of hydrogels.

[0031] Figure 6 PAA-C-Fe-M prepared for Example 1 10 Identification chart of hydrogels to different sound. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0033] Example 1

[0034] A preparation method of a fast-gelating double-network hydrogel, comprising the following steps:

[0035] (1) 4 g of CS is dissolved in 200 ml of 0.2 M acetic acid solution, and stirred for 12 h for dissolution to obtain an acetic acid solution of chitosan;

[0036] The preparation method of the aqueous solution of MXene: 2g of Ti3AlC2 powder and 2g of LiF are added to 40ml of 9M HCl solution, stirred at 35℃ for 22-34h, then the product is washed with deionized water until the pH value of the solution is 7, the supernatant after washing is collected, and the obtained supernatant is measured by suction filtration to measure the concentration;

[0037] The aqueous solution containing 10mg of MXene is added to 20.5g of chitosan acetic acid solution, and ultrasonic dispersion is carried out at a power of 500W for 30min; the water content in the aqueous solution of MXene does not affect the preparation of the double network hydrogel, and the content of MXene is 10mg.

[0038] (2) Then 4.6g of AAM, 500mg of ferric nitrate, 390ul of MBAA aqueous solution are added, and stirred for 15min;

[0039] (3) Finally, 600ul of AIBA aqueous solution and 3.6ml of APS aqueous solution are added, and then transferred into a mold and placed for 10s to obtain a fast-gelated double network hydrogel (abbreviation: PAA-C-Fe-M 10 ). The concentration of the MBAA aqueous solution is 1wt%, the concentration of the APS aqueous solution is 0.7wt%, and the concentration of the AIBA aqueous solution is 10wt%.

[0040] Example 2

[0041] This example is basically the same as example 1, except that in step (1), an aqueous solution containing 5mg of MXene is added to 20.5g of chitosan acetic acid solution; PAA-C-Fe-M5 is prepared.

[0042] Example 3

[0043] This example is basically the same as example 1, except that in step (1), an aqueous solution containing 15mg of MXene is added to 20.5g of chitosan acetic acid solution; PAA-C-Fe-M 15 is prepared.

[0044] Example 4

[0045] This example is basically the same as example 1, except that in step (1), an aqueous solution containing 20mg of MXene is added to 20.5g of chitosan acetic acid solution; PAA-C-Fe-M 20 is prepared.

[0046] Example 5

[0047] This example is basically the same as Example 1, except that in step (1), the aqueous solution containing 25 mg MXene is added to the acetic acid solution of 20.5 g chitosan; PAA-C-Fe-M 25 .

[0048] Comparative Example 1

[0049] This comparative example is basically the same as Example 1, except that in step (1), no aqueous solution of MXene is added, and in step (2), 4.6 g of AAM, 500 mg of ferric nitrate, and 390 ul of MBAA aqueous solution are added to the acetic acid solution of 20.5 g chitosan.

[0050] Comparative Example 2

[0051] This comparative example is basically the same as Example 1, except that in step (2), no ferric nitrate is added.

[0052] Figure 1 The physical photos of the hydrogels of Example 1 and Comparative Examples 1-2. The hydrogels of Example 1 and Comparative Examples 1-2 are prepared according to the following methods: Figure 1 It can be seen that the simultaneous introduction between MXene and iron ions is also the basis for the rapid formation of hydrogels. In the hydrogels without the simultaneous addition of Fe 3+ and MXene, the hydrogels do not appear to be rapidly gelled, but after the simultaneous introduction, the hydrogels will change from a flowing state to a gelled state within 10 s.

[0053] Comparative Example 3

[0054] First, 4 g of CS is dissolved in 200 ml of 0.2 M acetic acid solution, stirred for 12 h for dissolution, to obtain an acetic acid solution of chitosan; 4.6 g of AAM and 390 ul of MBAA aqueous solution are added to 20.5 g of the acetic acid solution of chitosan, and stirred for 15 min; then 600 ul of AIBA aqueous solution and 3.6 ml of APS aqueous solution are added, and stirred for 15 min. Finally, it is put into an oven at 80°C for free radical polymerization for 10 min, to obtain a hydrogel (abbreviated as: PAA-C).

[0055] Comparative Example 4

[0056] The comparative example is basically the same as example 1, except that in step (1), no aqueous solution of MXene is added, in step (2), 4.6 g of AAM, 500 mg of ferric nitrate, 390 ul of MBAA aqueous solution, are added to 20.5 g of chitosan acetic acid solution, stirred for 15 min; (3) then 600 ul of AIBA aqueous solution and 3.6 ml of APS aqueous solution are added, stirred for 15 min, and finally placed in an oven at 80°C for 10 min of free radical polymerization to obtain a hydrogel (abbreviation: PAA-C-Fe).

[0057] Figure 2 Stress-strain curves of the hydrogels prepared for examples 1-5 and comparative examples 3 and 4. From Figure 2 It can be seen that, compared with hydrogels PAA-C and PAA-C-Fe, PAA-C-Fe-M 10 The strain of the hydrogel can reach 1350%.

[0058] Figure 3 Mechanical property curves of the hydrogel prepared in example 1, (a) PAA-C-Fe-M 10 Tensile loading-unloading curves of the hydrogel in the strain range of 100%-1000%; (b) PAA-C-Fe-M 10 Total energy, dissipated energy and energy dissipation rate of the hydrogel in the strain range of 100%-1000%; (b) PAA-C-Fe-M 10 100 loading-unloading cycles of the hydrogel at 100% strain; (d) PAA-C-Fe-M 10 Total energy, dissipated energy and energy retention rate of the hydrogel during 100 loading-unloading cycles at 100% strain. From Figure 3 It can be seen from a that PAA-C-Fe-M 10 The stress curve of the hydrogel increases along the previous path when loaded and unloaded at different strains, proving that the hydrogel has good elastic recovery ability. At the same time, it is found that the hydrogel has only a small energy dissipation (Mullins effect) in a large strain range, and no obvious hysteresis regression line is observed.

[0059] From Figure 3 It can be seen from b that as the strain increases, the total energy required rises sharply, but the energy consumed is only 0.40 kJ / m 3 at 100% strain, which increases to 11.34 kJ / m 3 at 1000% strain. The loss rate of energy is somewhat reduced at large strain, from 10.76% at 100% strain to 5.80% at 1000% strain. From Figure 3cIt can be seen that the tensile stress of the hydrogel has a small decrease within 100 cycles, from 6.4 kPa in the first cycle to 6.3 kPa in the 100th cycle, proving the existence of the Mullins effect. It can be seen that the hydrogel only has a weak energy drop in the first cycle, from 3.80 kJ / m Figure 3 3 3 But the energy then stabilizes at about 3.65 kJ / m 3 3 The energy loss within 100 cycles is also about 0.36 kJ / m 10 Therefore, the hydrogel has a stable energy retention rate of 90% within 100 loading-unloading cycle experiments.

[0060] Compared with PAA-C, PAA-C-Fe and PAA-C-Fe-M 10 The PAA-C-Fe-M hydrogel has more excellent adhesion to wood, paperboard and glass. 10 Ten adhesion comparison charts were prepared. More than three PAA-C-Fe-M 10 hydrogel samples were taken, and the adhesion of the ten samples was compared after ten adhesions. It was found that the hydrogel had some adhesion attenuation in the second use, but the adhesion of the hydrogel was very stable in the 2nd-10th adhesion test, proving that the hydrogel meets the requirements of multiple uses. Figure 4 Compared with the conductivities of 0.123 S / m and 0.139 S / m of PAA-C and PAA-C-Fe, the conductivity of the PAA-C-Fe-M 10 hydrogel is about 0.265 S / m, which is doubled. The PAA-C-Fe-M 10 hydrogel prepared in Example 1 (50 mm, 5 mm wide and 3-4 mm thick in the form of a long strip) was fixed at both ends on the fixed clamp and the moving clamp of the tensile machine, and the length of the hydrogel exposed between the clamps was 30 mm. The tensile speed was 1% / s. The sensitivity GF of the hydrogel was calculated by measuring the change in resistance using the formula

[0061] Within a large strain range of 100-500%, the hydrogel has an excellent and very stable change rate. When the strain is 0-100%, the sensitivity GF is 0.88, when the strain is 100-300%, GF increases to 1.655, and when the strain is 300-500%, GF further increases to 2.86.

[0062] The PAA-C-Fe-M 10 ​​​The real-time resistance change of the hydrogel monitors the electrical self-healing behavior of the hydrogel. From Figure 5 It can be known from the above that the PAA-C-Fe-M 10 The hydrogel can complete the recovery of the electrical performance within 0.91 s, proving that the hydrogel has a certain electrical self-healing ability.

[0063] The PAA-C-Fe-M 10 The hydrogel is self-adhesive at the throat, and slight movements of the throat in different phonations are monitored. Figure 6 The PAA-C-Fe-M 10 The recognition graph of the hydrogel to different phonations is found, different electrical signal changes are monitored in the cases of phonations of "A", "AB" and "ZZU", and the stable signal waveform can be maintained after multiple detections, proving that the hydrogel can stably monitor and recognize slight movements.

[0064] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a dual-network hydrogel with fast gelation, characterized in that, The method comprises the following steps: (1) adding an aqueous solution of MXene to an acetic acid solution of chitosan and ultrasonic dispersion; (2) then adding an aqueous solution of metal ion salt, AAM and MBAA and dissolving, wherein MBAA is N,N'-methylene bisacrylamide; (3) finally adding an initiator, and gelling at normal temperature to form a double-network hydrogel; The metal ion salt is ferric nitrate; The initiator comprises AIBA and ammonium persulfate APS.

2. The method of claim 1, wherein the method is characterized by, The aqueous solution of MXene contains 5-25 mg of MXene; The acetic acid solution of chitosan is used in an amount of 15-25 g, and the acetic acid solution of chitosan is prepared as follows: 3-5 g of chitosan is dissolved in 200 ml of 0.2 M acetic acid solution; The metal ion salt is used in an amount of 500-1000 mg, the AAM is used in an amount of 3-5 g, and the aqueous solution of MBAA is used in an amount of 350-900 ul, and the concentration of the aqueous solution of MBAA is 1 wt%; The initiator comprises 200-600 ul of AIBA aqueous solution and 3-5 ml of APS aqueous solution, and the concentration of the APS aqueous solution is 0.7 wt%, and the concentration of the AIBA aqueous solution is 10 wt%.

3. A process for the preparation of a dual-network hydrogel that gels rapidly according to claim 1 or 2, characterized in that, In step (3), the gelling time is 5-15 s.

4. The method of claim 1 or 2, wherein the method is characterized by, The aqueous solution of MXene is prepared as follows: 2 g of Ti3AlC2 powder and 2 g of LiF are added to 40 ml of 9 M HCl solution, stirred at 35℃ for 22-34 h, then the product is washed with deionized water until the pH value of the solution is 7, and the supernatant after water washing is collected.

5. A double-network hydrogel with rapid gelation, prepared by the preparation method of any one of claims 1-4.

6. The dual-network hydrogel of claim 5, wherein: The three-dimensional network structure is formed by the entanglement between the chitosan chains and the polyacrylamide chains, and the Mxene nanosheets and metal ions are doped in the three-dimensional network structure.

7. The double-network hydrogel of claim 5 or 6 is used in a wearable sensor.

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