A lignin-based polymer and its preparation method and application

Abstract

The present application embodiment relates to a lignin-based polymer and its preparation method and application, which belongs to the field of polymer controlled polymerization technology. The preparation method of the lignin-based polymer of the present application embodiment comprises the following steps: step 1, dissolving lignin in water, then adding antifreeze and liquid metal in sequence to obtain a mixed solution and ultrasonically treating it to obtain a suspension; step 2, mixing N-hydroxymethyl acrylamide with hydroxyethyl acrylate, adding the suspension, stirring evenly, then adding an initiator dropwise, performing a polymerization reaction, and obtaining a lignin-based polymer after drying. The lignin-based polymer provided by the present application embodiment has good electrical sensing ability and can be used as an electronic sensor to better monitor the electrical signals generated during human activities.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of macromolecular controlled polymerization, and in particular to a lignin-based polymer and its preparation method and application. Background Art

[0002] Conductive polymers are functional materials that form a three-dimensional porous network structure through cross-linking. In recent years, research on various biomacromolecule polymers (such as gelatin, cellulose, chitosan, agarose, and sodium alginate) has attracted widespread attention due to their excellent mechanical properties, strong biocompatibility, high sensitivity, and good wear resistance. Lignin, a typical biomacromolecule, is primarily composed of phenylpropane units linked by ether bonds and is a major component of lignocellulosic plants. Lignin itself possesses excellent natural properties, such as UV shielding, biodegradability, antibacterial properties, and antioxidant capacity, and therefore holds great potential for the development of polymer electronics. However, the lignin content in wood nanofibers is low, and the resulting polymers suffer from poor interfacial compatibility and adhesion.

[0003] Currently, polyacrylamide (PAM)-based polymers, one of the most common conductive polymers, are formed by the polymerization of acrylamide with a crosslinker or initiator. However, this type of polymer suffers from poor stability, primarily due to its structural heterogeneity and its volume easily changing under external stimuli. Research has shown that liquid metals possess excellent stretchability and flexibility, far surpassing rigid fillers such as vermiculite, bentonite, and montmorillonite. Furthermore, the structural defects of PAM-based polymers can be further improved by introducing functional group-rich biomacromolecules to disperse the liquid metal. For example, Ma et al. exploited intermolecular bonding forces to uniformly disperse liquid metal within a polymer network of sodium alginate and polyacrylamide, developing a PAM-based composite polymer with both high conductivity and robustness. Lignin, the only natural polymer with an aromatic structure, contains reactive groups such as phenolic hydroxyl, alcoholic hydroxyl, and carboxyl groups in its molecular structure, which can form hydrogen bonds with polymers such as polyacrylamide. However, there are few reports on how to use lignin to disperse liquid metal and enhance the interactions between the components and the polymer matrix. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a lignin-based polymer and its preparation method and application. The lignin-based polymer has good electrical sensing capabilities and can be used as an electronic sensor to better monitor the electrical signals generated during human activities, which can effectively overcome the defects of the above-mentioned existing technologies.

[0005] A first aspect of the present invention provides a method for preparing a lignin-based polymer, comprising the following steps:

[0006] Step 1: dissolving lignin in water, then adding antifreeze agent and liquid metal in sequence to obtain a mixed solution, and performing ultrasonic treatment to obtain a suspension;

[0007] Step 2: N-hydroxymethyl acrylamide and hydroxyethyl acrylate are mixed, added to the suspension, stirred evenly, and then an initiator is added dropwise to carry out a polymerization reaction, and dried to obtain a lignin-based polymer.

[0008] In the embodiment of the present application, lignin, glycine and liquid metal are ultrasonically treated, using lignin as a supporting skeleton and to disperse the liquid metal particles, and glycine as an antifreeze agent; secondly, the uniformly dispersed suspension is added to a system of N-hydroxymethyl acrylamide and hydroxyethyl acrylate, and polymerization is initiated by adding the initiator AAPH, so that hydrogen bonds are formed between the components, thereby preparing a conductive lignin-based polymer with high adhesion and antifreeze properties.

[0009] In some embodiments including the above embodiments, in step 2, the polymerization reaction temperature is 30-60° C., and the polymerization reaction time is 1-2 hours.

[0010] In some embodiments that may include the above embodiments, in step 1, the antifreeze agent is glycine; or

[0011] The usage ratio of the lignin, water, glycine and liquid metal is 0.02 g:8 mL:0.4 g:0.24 g.

[0012] In some embodiments that may include the above embodiments, in step 1, the lignin is 2,2,6,6-tetramethylpyridin-1-oxide (TEMPO) oxidized lignin, and the concentration of lignin added is 0.3%, 0.4%, 0.5%, 0.6% or 0.7%.

[0013] In some embodiments including the above embodiments, in step 1, the ultrasonic treatment includes the following process: placing the mixed solution in an ice water bath and ultrasonicating it for 40 minutes using an ultrasonic disruptor.

[0014] In some embodiments that may include the above embodiments, in step 2, the initiator is an aqueous solution of 2,2'-azobisisobutylamidine dihydrochloride; or

[0015] The usage ratio of the N-hydroxymethyl acrylamide, hydroxyethyl acrylate, suspension and 2,2'-azobisisobutylamidine dihydrochloride aqueous solution is 0.3 g:635 μL:3 mL:300 μL.

[0016] In some embodiments including the above embodiments, in step 2, the concentration of the 2,2'-azobisisobutylamidine dihydrochloride aqueous solution is 0.5 g / mol.

[0017] In some embodiments that may include the above embodiments, in step 2, the drying temperature is 50° C. and the drying time is 12-24 hours.

[0018] The second aspect of the embodiments of the present application also provides a lignin-based polymer prepared by the above method.

[0019] The third aspect of the embodiments of the present application also provides the application of the above-mentioned lignin-based polymer in the field of electronics.

[0020] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0021] (1) The embodiment of the present application can effectively disperse the liquid metal by adding lignin, enhance the hydrogen bonding and internal shear force of the polymer, thereby improving the conductivity, adhesion, mechanical strength and antibacterial properties of the lignin-based polymer; and when the concentration of lignin is 5%, the conductivity of the polymer is increased to 0.29S / m, the adhesion can be as high as 5KPa, the compressive stress is also increased from 10KPa to 51KPa, and it has excellent fatigue resistance;

[0022] (2) The addition of glycine in the embodiment of the present application imparts good frost resistance to the polymer, allowing the small bulb to emit light normally within a temperature range of -50°C to 20°C; in addition, glycine can synergize with lignin, thereby improving the water retention of the polymer;

[0023] (3) The lignin-based polymers in the embodiments of the present application have good electrical sensing capabilities and can be used as electronic sensors to better monitor the electrical signals generated during human activities. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a schematic diagram of the design principle of the lignin-based polymer according to an embodiment of the present application;

[0026] Figure 2 FT-IR spectra of the raw materials and the prepared lignin-based polymers in Example 1 of the present application;

[0027] Figure 3 (ac) are SEM images of the lignin-based polymer prepared in Example 1 of the present application, Figure 3(df) are EDS spectra of the lignin-based polymer prepared in Example 1 of the present application;

[0028] Figure 4 Conductive performance test of the lignin-based polymers prepared in Examples 1-5, wherein Figure 4 (ae) represents the brightness change of the small bulb under different lignin concentrations of polymers, Figure 4 (f) Electrical conductivity of polymers with different lignin concentrations;

[0029] Figure 5 Mechanical property tests of the lignin-based polymers prepared in Examples 1-5, wherein (a) and (b) represent a single loading-unloading compression test of polymers with different lignin concentrations at 60% strain, (c) represents a 50-cycle loading-unloading compression test of the lignin-based polymer prepared in Example 1 of the present application at 60% strain, and (df) represents an elasticity test of the lignin-based polymer prepared in Example 1 of the present application;

[0030] Figure 6 (ad) are the luminescence of the small bulb of the lignin-based polymer prepared in Example 1 of the present application at different temperatures, (e) is the water retention rate of the polymer with different lignin concentrations, and (f) is the electrical conductivity of the PAM-0.5% Lignin-LM polymer with different moisture contents;

[0031] Figure 7 Adhesion performance test of the lignin-based polymer prepared in Example 1, where (af) show images showing the polymer can tightly adhere to various substrates, (g) and (h) show images showing the polymer can achieve adhesion between different substrates, and (i) shows an image showing the polymer can adhere to human skin without residue;

[0032] Figure 8 The stripping test and corresponding results of polymers with different lignin concentrations are shown in Figure 2.

[0033] Figure 9 (af) are the antibacterial activities of blank sample and polymers with different lignin concentrations against Gram-negative Escherichia coli, Figure 9 (gl) is the antibacterial activity of the blank sample and polymers with different lignin concentrations against Gram-positive Staphylococcus aureus;

[0034] Figure 10This is a sensing application of the lignin-based polymer prepared in Example 1, wherein Figure (a) shows sensor images of fingers bent at different angles of 0°, 30°, 60°, and 90°, Figure (b) shows sensor images of elbows bent at different angles of 0°, 30°, 60°, and 90°, Figure (c) shows sensor images of leg lifting and leg retraction movements, Figure (d) shows sensor images of muscle vibration, Figure (e) shows sensor images of Adam's apple swallowing, and Figure (f) shows sensor images of the lignin-based polymer prepared in Example 1 under different strains (0%, 20%, 40%, and 60%).

[0035] Figure 11 Graphs showing mechanical properties of the polymers of Comparative Example 1 and Example 1;

[0036] Figure 12 Graph showing the electrical conductivity of the polymers of Comparative Example 1 and Example 1. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] Unless otherwise specified, the experimental methods used in the examples of this application are all conventional methods.

[0039] In the following examples, unless otherwise specified, all raw materials can be purchased commercially or prepared by conventional methods.

[0040] Example 1

[0041] The preparation method of the lignin-based polymer of this embodiment comprises the following steps:

[0042] 0.02 g of 0.5% lignin (2,2,6,6-tetramethylpyridinium-1-oxide (TEMPO) oxidized lignin) was dissolved in 8 mL of water, and then 0.4 g of glycine and 0.24 g of liquid metal (galium indium tin alloy with a melting point of 3°C) were added in sequence to obtain a mixed solution. The mixed solution was ultrasonically treated in an ice-water bath for 40 min using an ultrasonic disruptor to obtain a 0.5% lignin-LM suspension.

[0043] 0.3 g of N-methylolacrylamide was mixed with 635 μL of hydroxyethyl acrylate, and 3 mL of the prepared Lignin-LM suspension was added. After stirring evenly, 300 μL of 2,2'-azobisisobutylamidine dihydrochloride aqueous solution (AAPH, 0.5 g / mol) was added dropwise to initiate the polymerization reaction. The polymerization temperature was 30°C and the polymerization time was 2 h. The mixture was then poured into a mold and placed in a 50°C oven for 12 h to polymerize into a lignin-based polymer. The prepared lignin-based polymer was labeled PAM-0.5% Lignin-LM.

[0044] Example 2

[0045] The preparation method of the lignin-based polymer provided in this example can refer to Example 1, except that the concentration of lignin added is 0.3%, and the prepared lignin-based polymer is labeled PAM-0.3% Lignin-LM.

[0046] Example 3

[0047] The preparation method of the lignin-based polymer provided in this example can refer to Example 1, except that the concentration of lignin added is 0.4%, and the prepared lignin-based polymer is labeled PAM-0.4% Lignin-LM.

[0048] Example 4

[0049] The preparation method of the lignin-based polymer provided in this example can refer to Example 1, except that the concentration of lignin added is 0.6%, and the prepared lignin-based polymer is labeled PAM-0.6% Lignin-LM.

[0050] Example 5

[0051] The preparation method of the lignin-based polymer provided in this example can refer to Example 1, except that the concentration of lignin added is 0.7%, and the prepared lignin-based polymer is labeled PAM-0.7% Lignin-LM.

[0052] Comparative Example 1

[0053] The preparation method of the polymer provided in this comparative example can refer to Example 1, except that no lignin is added.

[0054] Test Case

[0055] 1. Design ideas for lignin-based polymers

[0056] In the present embodiment, lignin, glycine and liquid metal are ultrasonically treated, and lignin is used as a supporting skeleton and to disperse the liquid metal particles, while glycine is used as an antifreeze agent. Next, the uniformly dispersed suspension is added to a system of N-hydroxymethyl acrylamide and hydroxyethyl acrylate, and then polymerization is initiated by dropwise addition of an initiator AAPH, so that hydrogen bonds are formed between the components, thereby preparing a conductive lignin-based polymer with high adhesion and antifreeze properties. The design concept is as follows: Figure 1 shown.

[0057] 2. Functional group structure of lignin-based polymers

[0058] The lignin-based polymer prepared in Example 1 and its raw materials were characterized, and the changes in the functional group structure of the lignin-based polymer were studied using Fourier transform infrared spectroscopy. The results are as follows: Figure 2 The lignin-based polymer prepared in Example 1 was -1 、3079cm -1 and 1544cm -1 The stretching vibration peaks of -OH, -NH and -NO2 appear at 2954 cm -1 、2868cm -1 There is also a stretching vibration peak of -CH3 at 1720 cm -1 The -C=O group at the hydroxyethyl acrylate exhibits significant stretching vibrations, originating from the ester bond in the hydroxyethyl acrylate, indicating that both raw materials are well distributed in the polymer system. In particular, the position of the -OH group in the polymer shifts to lower wavenumbers compared to lignin and hydroxyethyl acrylate, confirming the presence of hydrogen bonding between the polymer components.

[0059] 3. Morphology and structure of lignin-based polymers

[0060] Figure 3 (ac) are the morphological structures of the lignin-based polymer prepared in Example 1 after freeze-drying. As can be seen from the figure, the cross-section of the polymer presents a "bumpy" structure. According to research, this morphological structure is mainly attributed to the fact that the addition of lignin effectively disperses the liquid metal particles and improves the cross-linking degree of the polymer. However, it also fills the pore structure inside the polymer to a certain extent, reducing the specific surface area. While enhancing the adhesion of the polymer, it also affects the self-healing ability and stretchability of the polymer. In addition, the element distribution in the polymer was analyzed by EDS energy spectrum scanning, as shown in FIG. Figure 3 As shown in (df), elements such as C, O, and Ga are evenly distributed in the polymer, indicating that lignin and liquid metal are well dispersed in the system and the synthesized polymer structure is uniform.

[0061] 4. Conductive properties of lignin-based polymers

[0062] By testing the electrical conductivity of the lignin-based polymers prepared in Examples 1-5, Figure 4 As can be seen in (f), as the lignin concentration increases from 0.3% to 0.7%, the conductivity of the polymer first increases and then decreases. When the lignin concentration is 0.5%, the conductivity can reach a maximum of 0.29S / m. Figure 4 As shown in Figures (ae), the polymer and the small light bulb are connected to form a pathway. The light bulb glows normally, and its brightness gradually dims as the lignin concentration increases, consistent with the conductivity results. The experimental results show that lignin effectively improves the conductivity of the polymer, which is attributed to its role as a liquid metal disperser in the polymer system. However, when the lignin concentration exceeds a critical value, it aggregates within the polymer, obstructing the electron transport path and reducing the polymer's conductivity.

[0063] 5. Mechanical properties of lignin-based polymers

[0064] In order to investigate the mechanical properties of lignin-based polymers, polymers with different lignin concentrations were subjected to a single loading-unloading compression test at 60% strain as shown in Figure 5 As shown in (a) and (b). When the concentration of lignin increases from 0.3% to 0.5%, the compressive stress of the polymer increases from 10KPa to 51KPa; when the concentration of lignin further increases to 0.7%, its compressive stress drops to 43 and 32KPa, respectively. This is attributed to the fact that lignin plays the role of skeleton support and dispersion of liquid metal in the polymer system, but when the concentration of lignin exceeds the critical value, it will agglomerate inside the polymer, causing the structure of the polymer to collapse and the mechanical strength to be affected. In addition, in order to further verify the fatigue resistance of lignin-based polymers, a polymer with a lignin concentration of 0.5% was selected to undergo 50 loading-unloading cycle compression tests at 60% strain. The results are shown in Figure 2. Figure 5 (c) As shown. The first compression stress of the polymer is 51 kPa. After 50 cycles of compression, the compressive stress of the polymer is 48 kPa, which is still maintained at 94% of the original stress. This shows that the polymer can maintain excellent reversibility through effective energy dissipation. No obvious displacement or fracture is observed during the entire cycle without rest intervals, confirming its excellent fatigue resistance. Intuitively, as Figure 5 As shown in (df), the polymer with a lignin concentration of 0.5% can still rebound to its original height after being vertically pressed by the clamp, and can be repeatedly compressed and rebounded, further confirming that the polymer has excellent viscoelasticity.

[0065] 6. Freeze resistance and water retention of lignin-based polymers

[0066] The lignin-based polymer prepared in Example 1 was placed at different temperatures for several hours, and then connected to a small light bulb to form a passage. The light emission of the small light bulb was used to determine whether the polymer was antifreeze. Figure 6 As can be seen in (ad), the lignin-based polymer can emit light normally in the temperature range of -50 to 20°C. As the temperature decreases, the brightness of the bulb decreases slightly, but the polymer does not freeze, indicating that glycine has successfully played an antifreeze role inside the polymer. In addition, the water retention of the lignin-based polymer was tested by weighing method, and the results are as follows: Figure 6 As shown in (e), after two months, as the lignin concentration increases, the water retention of the polymer first increases and then decreases. When the lignin concentration is 0.5%, the water retention rate of the polymer can be maintained at 95%, indicating that the stability of the polymer affects its water retention. Therefore, lignin as a supporting skeleton works synergistically with glycine to give the lignin-based polymer excellent water retention properties. In particular, Figure 6 As shown in (f), the moisture content of the lignin-based polymer prepared in Example 1 does not affect its conductivity, thereby revealing that the polymer has good conductive stability.

[0067] 7. Adhesion properties of lignin-based polymers

[0068] Intuitively, if Figure 7 As shown in (af), the lignin-based polymer prepared in Example 1 has excellent adhesion and can adhere to a variety of substrates, such as plastics, iron products, rubber, paper, wood, glass, etc., and can ensure that each substrate does not fall off within a period of time. In addition, Figure 7 (g) and (h) show that the polymer can achieve adhesion between different materials, such as iron and glass, wood and plastic, etc., indicating that the polymer is expected to be used in the adhesive industry. Figure 7 As shown in (i), the lignin-based polymer can adhere to human skin without irritation. When the polymer is removed from the skin, no polymer residue is left on the skin surface. This is attributed to the hydrogen bonding and electrostatic interactions at the interface between the polymer and the skin. The addition of lignin enhances the hydrogen bonding and internal shear force, thereby giving the polymer better adhesion.

[0069] In order to further explore the magnitude of the adhesion of lignin-based polymers, e.g. Figure 8 As shown in (b), the lignin-based polymers prepared in Examples 1-5 were placed between two pieces of glass for peeling tests. The results are shown in FIG. Figure 8As shown in (a), the adhesion of the polymer increases from 1.38 kPa to 5 kPa with the increase of lignin concentration, indicating that the addition of lignin increases the cross-linking points within the polymer and strengthens the hydrogen bonding effect, thereby enhancing the network structure and adhesion of the polymer.

[0070] 8. Antibacterial properties of lignin-based polymers

[0071] In order to verify the antibacterial properties of the lignin-based polymers prepared in Examples 1-5, antibacterial tests were carried out by culturing Gram-negative bacteria Escherichia coli (EC) and Gram-positive bacteria Staphylococcus aureus (SA). Figure 9 As shown in (a1), the blank sample plate without polymer was covered with EC and SA, while the lignin-based polymers prepared in Examples 1-5 all showed obvious antibacterial rings. Most importantly, the antibacterial properties of the polymers were improved after the introduction of lignin into the polymers. As the lignin content increased, the antibacterial ring of the polymers also increased. This is mainly attributed to the interaction between the phenolic hydroxyl groups in the lignin and the Ga in the liquid metal. 3+ The synergistic bactericidal effect, by changing the permeability of cells and blocking their protein synthesis, ultimately leads to bacterial cell death, revealing that this polymer has potential application prospects in the biomedical field.

[0072] 9. Application of lignin-based polymers in sensing

[0073] Since lignin-based polymers have good conductivity, adhesion, mechanical strength and adaptability to human skin, this application explores the potential application of this polymer in the field of wearable electronic devices, such as strain sensors. Figure 10 (ac) show the changes in the electrical signals of the lignin-based polymer strain sensor prepared in Example 1 when monitoring human activities. When the finger joints and elbow joints change from 0° to 90°, the electrical signals generated by the polymer strain sensor show a step-by-step change pattern, and can also make fast, stable and reversible electrical signal responses during leg lifting and leg retraction movements. In particular, Figure 10 As shown in (d) and (e), the polymer can convert weak muscle vibration and swallowing of the Adam's apple into electrical signal output, indicating that the polymer has excellent electrical sensing sensitivity. Figure 10 (f) demonstrates the polymer's rapid response to varying compressive strains, further confirming its excellent viscoelastic properties. During the experiment, the polymer protected human skin from frostbite and remained adhered to the skin for extended periods without causing allergic reactions or damage. Therefore, the polymer could be used in wearable strain sensors to better monitor human activity.

[0074] In summary, the embodiment of the present application ultrasonically treats lignin, glycine, and liquid metal, using lignin as a supporting skeleton and to disperse the liquid metal particles, and glycine as an antifreeze agent; secondly, the uniformly dispersed suspension is added to a system of N-hydroxymethyl acrylamide and hydroxyethyl acrylate, and then polymerization is initiated by dropping the initiator AAPH, so that hydrogen bonds are formed between the components, thereby preparing a conductive lignin-based polymer with high adhesion and antifreeze properties.

[0075] 10. By Figure 11 It can be seen that without adding lignin, the compressive stress of the polymer is only 10KPa. When the concentration of lignin increases to 0.5%, the compressive stress of the polymer increases from 10KPa to 51KPa ( Figure 5 ), which is attributed to the role of lignin in the polymer system as a supporting skeleton and dispersing liquid metal.

[0076] 11. By Figure 12 It can be seen that the resistance value of the polymer without lignin addition (diameter: 26mm, thickness 5mm) is 5000Ω, which is calculated according to the following formula:

[0077] σ=d / (AR)

[0078] Where σ is the conductivity; d is the polymer thickness; A is the polymer area; and R is the polymer impedance. Using this formula, we can calculate that the conductivity of the polymer without lignin is only 0.0018 S / m. This is because without lignin as a dispersant, the liquid metal flocculates and aggregates in the system, reducing the electron transfer rate and further diminishing the polymer's conductive properties.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a lignin-based polymer, characterized in that: The following steps are involved: Step 1: dissolving lignin in water, then adding antifreeze agent and liquid metal in sequence to obtain a mixed solution, and performing ultrasonic treatment to obtain a suspension; Step 2: N-hydroxymethyl acrylamide and hydroxyethyl acrylate are mixed, added to the suspension, stirred evenly, and then an initiator is added dropwise to carry out a polymerization reaction, and dried to obtain a lignin-based polymer; The antifreeze agent is glycine; and the lignin is 2,2,6,6-tetramethylpyridinium-1-oxide (TEMPO) oxidized lignin.

2. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 2, the polymerization reaction temperature is 30-60° C., and the polymerization reaction time is 1-2 h.

3. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 1, the usage ratio of the lignin, water, glycine and liquid metal is 0.02 g:8 mL:0.4 g:0.24 g.

4. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 1, the concentration of lignin added is 0.3%, 0.4%, 0.5%, 0.6% or 0.7%.

5. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 1, the ultrasonic treatment includes the following process: placing the mixed solution in an ice water bath and ultrasonically treating it for 40 minutes using an ultrasonic disruptor.

6. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 2, the initiator is an aqueous solution of 2,2'-azobisisobutylamidine dihydrochloride; or The usage ratio of the N-hydroxymethyl acrylamide, hydroxyethyl acrylate, suspension and 2,2'-azobisisobutylamidine dihydrochloride aqueous solution is 0.3 g:635 μL:3 mL:300 μL.

7. The method for preparing a lignin-based polymer according to claim 6, wherein: In step 2, the concentration of the 2,2'-azobisisobutylamidine dihydrochloride aqueous solution is 0.5 g / mol.

8. The method for preparing a lignin-based polymer according to claim 1, wherein: In step 2, the drying temperature is 50° C. and the drying time is 12-24 hours.

9. A lignin-based polymer obtained by the method according to any one of claims 1 to 8.

10. Use of the lignin-based polymer according to claim 9 in the field of electronics.

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