Multifunctional alkali lignin-fe 3+ Preparation of polyacrylic acid network hydrogels

Abstract

The application belongs to the field of hydrogel materials and provides a multifunctional alkali lignin-Fe 3+ Polyacrylic acid network hydrogel is prepared, which can be rapidly prepared under green mild conditions. In the system, there is an oxidation-reduction reaction between the components, the reducing group of alkali lignin is oxidized to form semiquinone free radicals, and the alkali lignin is reduced to form Fe 3+ After oxidation, the semiquinone free radicals are generated, and the alkali lignin is reduced to form Fe 2+ , Fe 2+ activates H2O2 to generate hydroxyl radicals, thereby initiating the radical polymerization of acrylic acid (AA) to prepare multifunctional alkali lignin-Fe 3+ Polyacrylic acid network hydrogel. The application aims to solve the problem that the added initiator, crosslinking agent and part of raw materials are non-green toxic reagents, thereby affecting the practical application of the existing catechol-transition metal hydrogel system. The hydrogel prepared by the method has excellent mechanical properties, conductivity, adhesion and ultraviolet blocking efficiency, and can be self-healed without external force after being damaged, and has broad application prospects in the field of wearable electronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogel materials, a multifunctional alkali lignin-Fe 3+ Preparation method of polyacrylic acid network hydrogel. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Hydrogels are non-fluid colloidal networks or polymer meshes whose swelling agent is water. They are a new type of material with high water absorption and water retention, a soft texture, and similar to biological tissues. Due to their excellent properties such as good biocompatibility, stimulus response (temperature response, pH response, etc.), water absorption, water retention, and sustained release, they are widely used in biomedicine, agricultural production, sensing detection and other fields. However, the development of hydrogels still faces many challenges. 1) The biggest problem with traditional hydrogel preparation is that the gelation process is complicated and generally requires external stimulation (such as high temperature, light stimulation, etc.); 2) Environmentally unfriendly initiators and cross-linking agents need to be added during the preparation process; 3) The gelation time is too long. Therefore, it is of great significance to explore the preparation method of functional hydrogels that are environmentally friendly, mild, and have rapid gelation.

[0004] Previous research has explored the rapid preparation of multifunctional hydrogels using catechol-transition metals and ammonium persulfate as initiators, methylenebisacrylamide as a crosslinker, and acrylic acid (or acrylamide) as monomers. However, these initiators and crosslinkers are toxic. Using more widely available, cost-effective, and environmentally friendly raw materials to prepare multifunctional hydrogels would promote their sustainable and green application. Summary of the Invention

[0005] In order to solve the problem of low toxicity, low cost and greenness, the present invention proposes a method of using alkali lignin-Fe 3+ , hydrogen peroxide and acrylic acid to prepare a multifunctional hydrogel.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a multifunctional alkali lignin-Fe 3+ The preparation method of polyacrylic acid network hydrogel comprises:

[0008] Add alkali lignin, trivalent iron salt, acrylic acid and H2O2 aqueous solution into sodium hydroxide solution and mix and dissolve;

[0009] After the above substances are fully dissolved, place them at 35℃~40℃ and wait for the solution to gel;

[0010] This method is the first to report H2O2-mediated alkali lignin-Fe 3+ Method for preparing polyacrylic acid hydrogel by dynamic redox system. The reducing alkali lignin and Fe 3+ There is a redox reaction between the two, which can produce semiquinone free radicals, and Fe 3+ Reduced to Fe 2+ . And Fe 2+ Then Fenton reaction occurs with H2O2, Fe 2+ Oxidized to Fe 3+ , and at the same time generate hydroxyl radicals to form alkali lignin-Fe 3+ / Fe 2+ -H2O2 dynamic redox system. This method uses greener, non-toxic alkali lignin and low-concentration H2O2 to prepare polyacrylic acid hydrogel, and the overall performance of the hydrogel is greatly improved.

[0011] Based on the above hydrogel, the present invention also explored the required ingredients and amounts of alkali lignin, ferric iron salt, acrylic acid, and others. It was verified that when the mass ratio of alkali lignin, ferric iron salt, NaOH, acrylic acid, and H2O2 was 0.001-0.01:0.015-0.1:1.4-1.5:2.7-3.0:0.02-0.07, the mechanical properties, electrical conductivity, adhesion, light transmittance, and self-healing properties of the hydrogel provided by the present invention were enhanced.

[0012] The second aspect of the present invention provides the mechanical properties, electrical conductivity, adhesion, light transmittance and self-healing properties of the hydrogel as Fe 3+ Based on the concentration variation pattern, hydrogels with target properties can be prepared according to requirements.

[0013] The third aspect of the present invention provides applications of the above-mentioned hydrogel in pressure sensors and wearable electronic devices.

[0014] Beneficial effects of the present invention

[0015] (1) Compared with the prior art, the present invention reports for the first time a method for preparing multifunctional hydrogel using alkali lignin and H2O2. The entire preparation process is simple and environmentally friendly, and the raw materials are green and low-toxic.

[0016] (2) The present invention is based on Fe 3+ Different concentrations can adjust the mechanical properties, electrical conductivity, adhesion, light transmittance and self-healing properties of the hydrogel.

[0017] (3) The preparation method of the present invention is green, low-toxic, simple, practical and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application, and are incorporated herein by reference. The embodiments of the present application, together with its

[0019] Figure 1 is a technical roadmap of the present application;

[0020] Figure 2 is the performance of the hydrogel obtained in Example 1 of the present application;

[0021] Figure 3 is the performance of the hydrogel obtained in Example 2 of the present application;

[0022] Figure 4 is the performance of the hydrogel obtained in Example 3 of the present application. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0024] In a first aspect of the present application, a method for preparing a green, low-toxicity, multifunctional hydrogel is provided, comprising:

[0025] Preparing a NaOH solution;

[0026] Adding alkaline lignin, FeCl3·6H2O, acrylic acid, and an aqueous H2O2 solution into the NaOH solution and mixing to dissolve;

[0027] After the above substances are fully dissolved, placing them in a 35°C oven and waiting for the solution to gel.

[0028] In some embodiments, the ferric salt is FeCl3·6H2O.

[0029] In some embodiments, the concentration of the NaOH solution is 0.005-0.01 moL / L.

[0030] In some embodiments, the mass concentration of the aqueous H2O2 solution is 30%.

[0031] In some embodiments, the amount of 30% aqueous H2O2 solution used is 20-60 μL.

[0032] In some embodiments, the amount of ferric salt used is 0.15-1% (wt / wt).

[0033] In some embodiments, the amount of acrylic acid used is 2.7-3 mL.

[0034] In some embodiments, the amount of 0.005 mol / L NaOH solution used is 7-10 mL.

[0035] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0036] Example 1

[0037] Using H2O2-mediated alkali lignin-Fe 3+ A novel dynamic redox system was used to prepare a network polyacrylic acid hydrogel. A 0.005 mol / L NaOH solution was prepared. Using an electronic precision balance, 0.001 g of alkali lignin was placed in a sample vial. Then, 0.02 g of FeCl₃·6H₂O was added to the vial. Using a pipette, 7 mL of 0.005 mol / L NaOH solution, 2.7 mL of acrylic acid, and 50 μL of a 30% H₂O₂ aqueous solution were added to the vial and mixed to dissolve. After the vial was fully dissolved, the solution was placed in a 35°C oven and allowed to gel, yielding the polyacrylic acid hydrogel.

[0038] Example 2

[0039] Using H2O2-mediated alkali lignin-Fe 3+ A novel dynamic redox system was used to prepare a network polyacrylic acid hydrogel. A 0.005 mol / L NaOH solution was prepared. Using an electronic precision balance, 0.001 g of alkali lignin was placed in a sample vial. Then, 0.06 g of FeCl₃·6H₂O was added to the vial. Using a pipette, 7 mL of 0.005 mol / L NaOH solution, 2.7 mL of acrylic acid, and 50 μL of a 30% H₂O₂ aqueous solution were added to the vial and mixed to dissolve. After the vial was fully dissolved, the solution was placed in a 35°C oven and allowed to gel, yielding the polyacrylic acid hydrogel.

[0040] Example 3

[0041] Using H2O2-mediated alkali lignin-Fe 3+ A novel dynamic redox system was used to prepare a network polyacrylic acid hydrogel: A 0.005 mol / L NaOH solution was prepared. Using an electronic precision balance, 0.001 g of alkali lignin was placed in a sample vial. Then, 0.10 g of FeCl₃·6H₂O was added to the sample vial. Using a pipette, 7 mL of 0.005 mol / L NaOH solution, 2.7 mL of acrylic acid, and 50 μL of a 30% H₂O₂ aqueous solution were added to the sample vial and mixed to dissolve. After the sample vial was fully dissolved, the solution was placed in a 35°C oven and allowed to gel, yielding the polyacrylic acid hydrogel.

[0042] Performance testing:

[0043] The properties of the polyacrylic acid hydrogels prepared in Examples 1-3 were tested using the following test methods:

[0044] 1) Mechanical properties

[0045] The mechanical properties of the hydrogels were determined using a texture analyzer (TA.XT Plusc, Stable Micro Systems, United Kingdom). For the tensile test, the hydrogel samples were cut into strips (10 mm wide and 2 mm thick) using scissors, with a loading speed of 30 mm / min and an initial spacing of 5 mm.

[0046] 2) Adhesion strength

[0047] The adhesion properties of the hydrogels were characterized by lap shear tests. Prior to testing, the various substrates (pigskin, glass, and wood) were washed with deionized water and allowed to air dry. The lap shear tests were performed by bonding hydrogel samples (10 mm long × 10 mm wide × 2 mm thick) between two identical substrates. Adhesion strength was calculated as the maximum load measured divided by the bonded area.

[0048] 3) Optical properties

[0049] The transparency and UV blocking efficiency of the hydrogels were measured using a UV-Vis spectrophotometer (UV-2600, Shimadzu, Japan). The thickness of the tested samples was 2 mm.

[0050] 4) Conductivity

[0051] A digital source meter (SMU) (Keithley 2450, Keithley, USA) was used to measure the hydrogel resistance (R). The dimensions of the hydrogel sample to be tested were 20 mm long × 5 mm wide × 4 mm high. The conductivity was calculated as follows:

[0052] σ=L / (R×S)

[0053] where L, R, and S are the length, resistance measured by the SMU, and cross-sectional area of ​​the hydrogel, respectively.

[0054] The test results are as follows Figure 2-Figure 4 As shown, the hydrogel prepared by the present invention has excellent mechanical properties, conductive properties, adhesion properties, light transmittance, and self-healing properties.

[0055] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multifunctional alkali lignin-Fe 3+ The preparation method of polyacrylic acid network hydrogel is characterized in that: include: Adding alkali lignin, trivalent iron salt, acrylic acid and H2O2 aqueous solution into sodium hydroxide solution and mixing and dissolving; After the above substances are fully dissolved, place them at 35℃~40℃ and wait for the solution to gel; Among them, the mass ratio of alkali lignin, trivalent iron salt, NaOH, acrylic acid, and H2O2 is 0.001~0.01:0.015~0.1:1.4~1.5:2.7~3.0:0.02~0.07; The trivalent iron salt is FeCl3•6H2O; The concentration of the NaOH solution is 0.005-0.01 mol / L; the mass concentration of the H2O2 aqueous solution is 30%; and the amount of the H2O2 aqueous solution used is 20-60 μL.

2. The multifunctional alkali lignin-Fe as claimed in claim 1 3+ The preparation method of polyacrylic acid network hydrogel is characterized in that: The amount of the ferric salt is 0.15-1% wt / wt.

3. The multifunctional alkali lignin-Fe as claimed in claim 1 3+ The preparation method of polyacrylic acid network hydrogel is characterized in that: The amount of acrylic acid used is 2.7-3 mL.

4. The multifunctional alkali lignin-Fe as claimed in claim 1 3+ The preparation method of polyacrylic acid network hydrogel is characterized in that: The dosage of 0.005mol / L NaOH solution is 7~10 mL.

5. Multifunctional alkali lignin-Fe prepared by the method according to any one of claims 1 to 4 3+ Polyacrylic acid network hydrogel.

6. The multifunctional alkali lignin-Fe according to claim 5 3+ Application of polyacrylic acid network hydrogel in wearable electronic devices.

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