A lignin-based elastic material, its preparation method and application

Abstract

This invention discloses a lignin-based elastic material, its preparation method, and its applications. The invention involves a click polymerization reaction of a diacetylene compound, polyethylene glycol, lignin, and an organic base catalyst in an organic solvent to obtain a prepolymer solution. The prepolymer solution is then poured into a mold to allow the organic solvent in the prepolymer solution to evaporate, thus preparing the lignin-based elastic material. The preparation method of this invention is simple, using readily available raw materials. It utilizes lignin, a waste product from bio-papermaking, for high-value utilization. The conditions are mild, and lignin-based functional materials can be prepared without inert gas protection. This polymer possesses a stable cross-linked network, thermal stability, excellent mechanical properties, and good photothermal properties. It can achieve laser-controlled shape memory and laser-controlled remote lifting of heavy objects. Due to the good dynamics of the alkenylene ether bonds formed by the ester-acetylene monomers, it exhibits excellent degradability and is biofriendly.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemistry and materials science, specifically relating to a lignin-based elastic material and its preparation method and application. Background Art

[0002] Biorenewable materials have been widely used in low-cost reinforcement of polymer composites. Most polymer composites designed for various applications are based on natural cellulose fibers. Along with these cellulose fibers, lignin is a promising alternative to traditional petrochemical-based reinforcement materials. Lignin, along with cellulose and hemicellulose, is one of the major components of natural polymers, providing strength and rigidity to plant roots and stems. Lignin is the most abundant byproduct of the paper industry and the second most abundant natural polymer on Earth after cellulose.

[0003] Lignin possesses biodegradability, carbon dioxide neutralization, abundant presence in industrial waste, low cost, environmental friendliness, antioxidant properties, antibacterial properties, and stability, making it a promising low-cost reinforcing material. Due to these advantages, lignin-based polymer composites, as a novel environmentally friendly and low-cost composite material, have broad development prospects. However, research on lignin or lignin-based polymer composites is still in its early stages, with limited literature on lignin-reinforced polymer composites. Based on existing literature, lignin-reinforced polymer composites show promising potential as an alternative to traditional synthetic fiber-reinforced composites.

[0004] The chemical structure and physical properties of starting lignin have a significant impact on the thermal properties of these bio-based materials. Due to its aromatic-rich structure, lignin can often improve the thermal stability of copolymers, blends, and composites. Its abundant hydroxyl groups provide the possibility of forming intermolecular hydrogen bonds with polar polymers containing electronegative groups. This intermolecular interaction not only facilitates the compatibility of lignin with polar synthetic polymers but also influences the glass transition temperature of the material. Furthermore, lignin-modified materials have made significant progress in fields such as battery energy storage, functional elastomers, biomedicine, and photothermal evaporators, achieving not only the functionalization of lignin but also adhering to sustainable, low-cost, and environmentally friendly design principles.

[0005] Recent advances in biopolymer processing are promising for designing sustainable, low-cost materials. Current applications of lignin face challenges such as complex synthesis methods, immature large-scale production processes, and poor reproducibility of some material properties. For example, Sun et al. combined mercapto-olefin click chemistry with silane ether crosslinking agents to prepare recyclable lignin-based thermosetting materials. The mechanical properties of lignin-based thermosetting materials are directly related to the ratio of crosslinking agent to lignin. Experimental results show that when a crosslinking agent is prepared using a difunctional thiol and the lignin content is 11%, the tensile strength can reach 2.7 MPa (Tang, MBC, emailprotected, E. Emailprotected, et al. Mechanically Tunable and Reconstructable Lignin Thermosets via "Click" Chemistry and Surface Functionalization[J]. Macromolecules, 2023, 56(7):2831-2840.). Xu et al. prepared a series of lignin-based polyester thermosetting materials with tunable properties by changing the ratio of lignin units, and used microwave extraction and degradation recovery of lignin monomers. The lignin-based thermosetting resin prepared by solvent extraction combined with microwave extraction of lignin monomers had an elongation at break of more than 200% compared with natural lignin, which increased from 99% to more than 200%, and had better mechanical properties (Xu,Y.,K.Odelius and M.Hakkarainen. Recyclable and flexible polyester thermosets derived from microwave-processed lignin[J].ACS Applied Polymer Materials,2020,2(5):1917-1924.). Therefore, the next step in the development of lignin-based elastic materials needs to focus on synthesis methods, formulate more efficient and environmentally friendly synthesis processes, and simplify operation steps. At the same time, in terms of material design, more comprehensive consideration should be given to maximize the performance advantages of lignin. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a lignin-based elastic material, its preparation method, and its application. The preparation method is simple and efficient, the raw materials are readily available, the reaction conditions are mild, and lignin-based elastic materials with excellent mechanical properties and good photothermal properties can be prepared without purification.

[0007] The specific technical solution adopted is as follows:

[0008] This invention provides a method for preparing a lignin-based elastic material, comprising the following steps:

[0009] (1) A prepolymer solution is obtained by clicking polymerization of a dialkynyl compound as shown in formula (I), polyethylene glycol, lignin as shown in formula (II), and an organic base catalyst in an organic solvent.

[0010] (2) Pour the prepolymer solution into a mold to allow the organic solvent in the prepolymer solution to evaporate, and prepare the lignin-based elastic material as shown in Formula (III);

[0011] The structural formula of the aforementioned diacetyl group compound is shown in formula (I):

[0012]

[0013] The structural formula of the lignin is shown in formula (II):

[0014]

[0015] The structure of the lignin-based elastic material is shown in formula (III):

[0016]

[0017] Wherein, R is a straight-chain alkyl group.

[0018] This invention utilizes a hydroxy-alkyne click polymerization reaction to prepare lignin-based elastic materials with excellent mechanical and photothermal properties in a one-pot process. This preparation method ensures that the prepared lignin-based elastic materials possess both excellent mechanical properties and solid-solid phase transition characteristics, which can be used to explore shape memory properties under laser conditions.

[0019] Preferably, R is a straight-chain alkyl group with 1-30 carbon atoms (1, 2, 5, 10, 20, 30, etc.).

[0020] Preferably, in the click polymerization reaction system, the lignin shown in formula (II) is Shanghai Dongsheng lignin, grade LS-1.

[0021] This invention introduces lignin from pulp and paper waste into a click polymerization reaction system as one of the hydroxyl source components. A one-pot method is used to prepare lignin-based elastic materials from diacetyl compounds, polyethylene glycol, lignin, and an organic base catalyst. The introduction of lignin gives the lignin-based elastic materials a better cross-linked network, resulting in excellent mechanical strength. Furthermore, due to the natural photothermal properties of lignin, the prepared lignin-based elastic materials absorb energy and convert it into heat energy under sunlight and laser light, thereby enabling laser-controlled shape memory and remote lifting of heavy objects.

[0022] Preferably, the method for preparing the binary alkynyl compound as shown in formula (I) includes the following steps:

[0023] Under an inert gas atmosphere, the esterification reaction of the alkynyl compound shown in formula (IV) and the dihydroxy compound shown in formula (V) was carried out to prepare the dialkynyl compound shown in formula (I).

[0024]

[0025] Wherein, R is a straight-chain alkyl group.

[0026] More preferably, R is a straight-chain alkyl group with 1-30 carbon atoms (1, 2, 5, 10, 20, 30, etc.).

[0027] More preferably, the inert gas atmosphere is a nitrogen atmosphere or an argon atmosphere, with a nitrogen atmosphere being more preferred.

[0028] Preferably, the average number-average molecular weight of the polyethylene glycol is 2000-20000. The molecular chain length of polyethylene glycol increases with increasing molecular weight. Materials synthesized from polyethylene glycol with lower molecular weight have less stored heat and better tensile properties, but are prone to breakage during stretching, and have shorter molecular chain segments, resulting in poor shape retention and difficulty in directly achieving shape memory under laser conditions. Materials synthesized from polyethylene glycol with higher molecular weight have more stored heat, relatively better tensile strength and toughness, and better shape retention, making them easier to apply under laser conditions. However, the molecular weight of polyethylene glycol cannot be too high, as this will deteriorate its mechanical properties. Therefore, it is necessary to select polyethylene glycol with relatively good heat storage and mechanical properties. After balancing these two factors, a polyethylene glycol molecular weight of 10000 is selected for optimal preparation conditions.

[0029] Preferably, the organic base catalyst is 1,4-diazabicyclo[2.2.2]octane, N-methylmorpholine, 4-dimethylaminopyridine, triisopropylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene or quinine;

[0030] Preferably, the organic solvent is at least one selected from acetonitrile, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, toluene, 1,4-dioxane, dimethyl sulfoxide, and N,N-dimethylformamide.

[0031] Preferably, the click polymerization reaction is carried out at room temperature, at a temperature of 25-28°C, and for a time of 10-50 minutes.

[0032] More preferably, the click polymerization reaction takes 30 minutes.

[0033] Preferably, in the click polymerization reaction system, the molar ratio of the total amount of alkynyl groups of the dialkynyl compound shown in formula (I) to the total amount of hydroxyl groups of polyethylene glycol and lignin is 0.8:1-1.2; the concentration of all dialkynyl compounds, polyethylene glycol and lignin monomers in the organic solvent is 50-300 mg / mL, preferably 175 mg / mL.

[0034] Preferably, in the click polymerization reaction system, the organic base catalyst accounts for 0.3-1.5 wt% of the total mass of the dialkynyl compound, polyethylene glycol, and lignin.

[0035] More preferably, the organic base catalyst accounts for 0.9 wt% of the total mass of the diacetylene compound, polyethylene glycol, and lignin.

[0036] Preferably, the lignin shown in formula (II) accounts for 1-25 wt% of the total mass of polyethylene glycol and lignin. Insufficient lignin content not only leads to inadequate formation of the original cross-linked network, resulting in poor mechanical strength, but also poor photothermal effects; excessive lignin content results in lignin-based elastic materials with excessive rigidity and high elastic modulus, but decreased mechanical properties and poor mechanical strength. Therefore, a lignin content of 2%-10% was selected to balance mechanical and photothermal properties, and ultimately, a lignin content of 8% was chosen for further application exploration, demonstrating superior relative mechanical and photothermal properties.

[0037] The present invention also provides a method for preparing lignin-based elastic materials, resulting in lignin-based elastic materials. These lignin-based elastic materials possess excellent mechanical properties, good photothermal properties, can remain solid without leakage at phase transition temperatures, exhibit good shape memory effects, and, due to the introduction of lignin, a natural photothermal material, can achieve controllable shape memory characteristics through energy input under laser light.

[0038] This invention also provides applications of the lignin-based elastic material in photothermal applications, such as as a memory material, temperature-responsive material, or light-responsive material. The lignin-based elastic material can be customized to explore its controllable shape memory characteristics under laser light, achieving unidirectional shape memory. Furthermore, the prepared lignin-based elastic material possesses excellent mechanical properties, enabling remote lifting of heavy objects under laser light.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The method of the present invention is simple and efficient, the raw materials are readily available, the reaction conditions are mild and can be carried out at room temperature. It does not require high temperature and high pressure or large instruments and equipment. The polymerization efficiency is high, and lignin-based elastic materials can be obtained without purification. The organic base catalyst used is inexpensive, easy to store and use, and has stable properties.

[0041] (2) This invention utilizes lignin, a waste product generated during the pulping and papermaking process, to make it valuable and prepare the lignin-based elastic material. Due to the natural photothermal properties of lignin, there is no need to introduce photothermal molecules separately, making the reaction raw materials easier to obtain and greener and healthier. Furthermore, the lignin-based elastic material prepared has excellent degradation characteristics and is bio-friendly.

[0042] (3) The preparation process ratio of the lignin-based elastic material prepared by this invention can relatively ensure that the product has optimal properties. When the lignin content is 2%, the tensile strength is only 8.71 MPa; when the lignin content is higher, the tensile strength decreases relatively. For example, when the lignin content is 10%, 15%, and 20%, the tensile strength of the lignin-based elastic material is 21.08 MPa, 22.99 MPa, and 22.72 MPa, respectively, and the elongation at break decreases to below 200% when the lignin content is 20%. The mechanical strength is relatively better at 4%, 6%, and 8%, with tensile strengths all above 26 MPa and elongation at break above 600%. That is, the lignin to PEG mass fraction ratio is 4:96, and the PEG chain segment is 10000, resulting in the best mechanical properties, with tensile strength and elongation at break of 31.93 MPa and 845%, respectively. To balance the photothermal effect and the mechanical strength of the material, an 8% lignin content is selected for subsequent applications.

[0043] (4) The lignin-based elastic material prepared by this invention has excellent mechanical properties, which can surpass most lignin-based elastic materials reported in the current literature. It has good photothermal effect and can realize the application of controllable shape memory under laser and light-controlled remote lifting of heavy objects. Attached Figure Description

[0044] Figure 1 This diagram illustrates the lignin, PEG, and diacetyl compounds of the present invention, the preparation process of lignin-based elastic materials, and the internal bonding diagram of the final lignin-based elastic material.

[0045] Figure 2 The infrared spectra of lignin, PEG-10K, diacetyl compounds, and lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 are shown.

[0046] Figure 3The thermogravimetric curve of 8%-Lignin-PEG-10K lignin-based elastic material in Example 1 is shown.

[0047] Figure 4 The image shows the tensile curve of 8%-Lignin-PEG-10K, the lignin-based elastic material in Example 1.

[0048] Figure 5 The cyclic tensile curve of 8%-Lignin-PEG-10K, the lignin-based elastic material in Example 1, under 300% strain.

[0049] Figure 6 The tensile curves of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 are shown.

[0050] Figure 7 The graph shows the temperature rise of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under simulated sunlight irradiation, as well as a comparison graph of the final temperature of the material under different powers.

[0051] Figure 8 The graph shows the temperature rise of the lignin-based elastic material 8%-Lignin-PEG-10K sample irradiated with an 808nm laser in Example 1, as well as a comparison graph of the final temperature of the material under different powers.

[0052] Figure 9 This describes the shape memory process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under an 808nm laser.

[0053] Figure 10 This is a demonstration of the process of remotely lifting heavy objects using light-controlled laser light under an 808nm laser, based on the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1.

[0054] Figure 11 This describes the degradation process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under acidic conditions. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0056] In the examples, the dialkynyl compound 1 was synthesized from propynic acid and dihydroxyhexane under a nitrogen-protected atmosphere according to the synthetic method described in the published literature (Polym. Chem., 2012, 3(4): 1075-1083). The synthetic route is shown below:

[0057]

[0058] The specific synthesis steps are as follows:

[0059] In a 250 mL two-necked flask equipped with a magnetic stirrer, reflux condenser, and Dean-Stark separator, 1,6-hexanediol (3.54 g, 30 mmol), p-toluenesulfonic acid (1.03 g, 6 mmol), and 100 mL of toluene were added sequentially, and magnetic stirring was initiated. Propylene acid (5.6 mL, 90 mmol) was then added dropwise to the stirred solution. After all the propyne acid had been added, the temperature was raised to 110 °C and refluxed for 18 h. Afterward, the solution was cooled to room temperature, and toluene was removed by rotary evaporation. The remaining oily substance was washed with dichloromethane and water, and the organic phase was collected, dried over anhydrous magnesium sulfate, and filtered. The collected filtrate was evaporated to remove the solvent, and the solution was separated by column chromatography using a mixture of petroleum ether and ethyl acetate (10:1, v / v) as eluent to obtain 5.24 g of white crystals (2-1a), with a yield of 79%.

[0060] Example 1

[0061] In this embodiment, the synthetic route of the lignin-based elastic material Lignin-PEG10K is as follows:

[0062]

[0063] Add PEG-10K (1281.3 mg), lignin (LS-1, 111.4 mg) from Shanghai Dongsheng Company, diacetyl compound (125.8 mg), and 9 mL of ultra-dry tetrahydrofuran to a glass bottle. Place the glass bottle in a 60°C water bath and stir for 3 min until the polyethylene glycol (PEG-10K, number average molecular weight 10000) is completely dissolved. Then allow the glass bottle to cool naturally to room temperature. Dissolve the organic base 1,4-diazabicyclo[2.2.2]octyl DABCO (13.7 mg) in 9 mL of ultra-dry tetrahydrofuran and add it to the reaction system through a microsyringe. The molar ratio of total hydroxyl groups of polyethylene glycol and lignin to triple bonds of diacetyl compound in the system is 1:0.8. The organic base catalyst accounts for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl compound, and polyethylene glycol). After adding DABCO and stirring, the product solution was poured into a square polytetrafluoroethylene mold and sealed with aluminum foil. After evaporation at room temperature for 3 days, a dark brown, opaque, flexible lignin-based elastic material of 8% Lignin-PEG-10K was obtained.

[0064] Example 2

[0065] In this embodiment, lignin, as a natural photothermal material, possesses non-toxic, harmless, and environmentally friendly properties. Furthermore, lignin's unique three-dimensional network structure provides a rigid framework for lignin-based elastic materials. By changing the mass ratio of lignin to PEG (with the total mass remaining constant), the mechanical properties of the resulting lignin-based elastic material can be controlled. Adjusting the mass ratio of lignin to PEG from 1:99 to 1:3 significantly alters the mechanical properties, transforming it from easily fractured to relatively tough (see Table 1; the material with 2wt% lignin content fractures easily, while the material with 4wt% lignin content exhibits good relative strength and toughness). The molar ratio of the total hydroxyl groups and triple bonds of the diacetylene compounds in polyethylene glycol and lignin is 1:0.8. The organic base catalyst accounts for 0.9wt% of the total mass of the reaction system (lignin, diacetylene compounds, and polyethylene glycol). Other parameters and methods are the same as in Example 1, resulting in the lignin-based elastic material.

[0066] Example 3

[0067] In Example 1, polyethylene glycol was replaced with polyethylene glycol with an average number-average molecular weight of 2000. The organic base catalyst was replaced with 4-dimethylaminopyridine, and the organic solvent was replaced with dimethyl sulfoxide. The molar ratio of the total hydroxyl groups of polyethylene glycol and lignin to the triple bonds of the diacetyl group in the system was 1:0.8. The organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl group, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0068] Example 4

[0069] In Example 1, polyethylene glycol was replaced with polyethylene glycol of average number-average molecular weight of 4000, and the organic base catalyst was replaced with triisopropylamine, while the organic solvent was replaced with 1,4-dioxane. The molar ratio of the total hydroxyl groups of polyethylene glycol and lignin to the triple bonds of the diacetyl group in the system was 1:0.8, and the organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl group, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0070] Example 5

[0071] In Example 1, polyethylene glycol was replaced with polyethylene glycol of an average number-average molecular weight of 6000, and the organic base catalyst was replaced with quinine, while the organic solvent was replaced with chloroform. The molar ratio of the total hydroxyl groups and triple bonds of the diacetyl group in polyethylene glycol and lignin was 1:0.8. The organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl group, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0072] Example 6

[0073] In Example 1, polyethylene glycol was replaced with polyethylene glycol of average number-average molecular weight of 8000, and the organic base catalyst was replaced with N-methylmorpholine, while the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl groups of polyethylene glycol and the triple bonds of the diacetyl group compound in the system was 1:0.8, and the organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl group compound, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0074] Example 7

[0075] In Example 1, polyethylene glycol was replaced with polyethylene glycol of average number-average molecular weight of 10,000, and the organic base catalyst was replaced with N-methylmorpholine, while the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl groups of polyethylene glycol and the triple bonds of the diacetyl group compound in the system was 1:0.8, and the organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, diacetyl group compound, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0076] Example 8

[0077] In Example 1, polyethylene glycol was replaced with polyethylene glycol of an average number-average molecular weight of 20,000. The organic base catalyst was replaced with N-methylmorpholine, and the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl groups and triple bonds of the diacetyl group in polyethylene glycol and lignin was 1:0.8. The organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (lignin, diacetyl group, and polyethylene glycol). Other parameters and methods were the same as in Example 1, resulting in a lignin-based elastic material.

[0078] Sample Analysis

[0079] Figure 1 This diagram illustrates the lignin, PEG, and diacetyl compound of the present invention, the preparation process of the lignin-based elastic material, and the internal bonding diagram of the final lignin-based elastic material. Since the total number of hydroxyl groups in lignin and polyethylene glycol is excessive, the prepared lignin-based elastic material contains both hydroxyl groups and alkenyl ether bonds. This results in a lignin-based elastic material with a double cross-linked network containing both covalent dynamic bonds and non-covalent hydrogen bonds, thus enhancing the material's mechanical strength.

[0080] Figure 2The infrared spectra of lignin, PEG-10K, diacetyl compounds, and lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 are shown. The disappearance of the triple bond peak proves the successful synthesis of the lignin-based elastic material in Example 1.

[0081] Figure 3 The thermogravimetric curve of 8%-Lignin-PEG-10K, the lignin-based elastic material in Example 1, shows that the material has a good thermal decomposition temperature of 372°C. The higher decomposition temperature is beneficial for subsequent photothermal testing and applications under photothermal conditions.

[0082] Table 1

[0083]

[0084] Figure 4 The image shows the tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1. 8%-Lignin-PEG-10K has a distinct stress-strain curve of a crystalline polymer. PEG-10K provides flexible segments, while lignin provides rigid segments. The soft and hard segments control the mechanical properties of the material. The tensile strength and elongation at break of 8%-Lignin-PEG-10k are 26.51 MPa and 603.54%, respectively, exhibiting excellent mechanical properties.

[0085] Figure 5 The cyclic tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 at 300% strain demonstrates that it has good cyclic stability during the tensile process, which is beneficial for the subsequent photothermal property memory shaping.

[0086] Figure 6 The tensile curves of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under progressive loading show that the tensile stress increases continuously as the strain increases, demonstrating a certain tensile strengthening effect and proving that the material has excellent mechanical properties.

[0087] Figure 7 This section presents a graph showing the temperature rise of the lignin-based elastic material 8%-Lignin-PEG-10K from Example 1 under simulated sunlight irradiation, as well as a comparison of the final temperature of the material at different power levels. The specific procedure involves cutting the lignin-based elastic material 8%-Lignin-PEG-10K from Example 1 into squares and irradiating them with 100mW / cm² light. 2 200mW / cm 2 300mW / cm 2 400mW / cm 2 500mW / cm2 600mW / cm 2 700mW / cm 2 and 800mW / cm 2 The sample was irradiated under simulated sunlight for 5 minutes, after which the simulated sunlight source was turned off, and the temperature change on the material surface was observed and monitored. The curve results clearly show that the material has a significant power dependence, and there is a clear heat absorption and release plateau during the heating and cooling process, which also proves that the lignin-based elastic material has certain heat storage performance.

[0088] Figure 8 The graph shows the temperature rise of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under irradiation with an 808nm laser, as well as a comparison of the final temperature of the material at different powers. The specific procedure involves cutting the lignin-based elastic material 8%-Lignin-PEG-10K from Example 1 into squares and irradiating them with a 200mW / cm² laser. 2 400mW / cm 2 600mW / cm 2 800mW / cm 2 1000mW / cm 2 and 1200mW / cm 2 The sample was irradiated with a simulated laser power for 5 minutes, after which the laser source was turned off, and the temperature change on the material surface was observed and monitored. This also demonstrates that the material exhibits excellent laser power dependence and good photothermal properties.

[0089] Figure 9 This demonstrates the shape memory process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under an 808nm laser. Figure 9 The material is formed in a petal-shaped mold to obtain a petal-shaped lignin-based elastic material. The material is then shaped at a high temperature to close the petals, and after natural cooling to room temperature, the petals remain closed. At 800 mW / cm², 2 Under the illumination of an 808nm laser, the folded petals will restore their original shape and open up under light-driven conditions.

[0090] Figure 10 This demonstrates the process of remotely lifting a heavy object using a light-controlled laser under 808nm laser light, based on the lignin-based elastic material 8%-Lignin-PEG-10K from Example 1. First, the lignin-based elastic material is cut into strips and pre-stretched at room temperature on a tensile testing machine to achieve a certain length. Then, a weight of a certain weight is hung on the sample. The process is performed at 800mW / cm². 2Under the irradiation of an 808nm laser, the sample shrinks and returns to its original shape, allowing the heavy object to be lifted, thus realizing the process of remotely lifting the heavy object by light control.

[0091] Figure 11 This describes the degradation process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under acidic conditions. Figure 11 In the figure, A represents the complete degradation of tetrahydrofuran solution after 24 hours of adding concentrated hydrochloric acid (2 drops / mL of 37wt% concentrated hydrochloric acid) at room temperature. Figure 11 B in the formula refers to acid degradation at 60℃ (2 drops / mL of 37wt% concentrated hydrochloric acid), which can be completely degraded in just 4 hours.

[0092] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a lignin-based elastic material, characterized in that, Includes the following steps: (1) A prepolymer solution is obtained by clicking polymerization of a dialkynyl compound, polyethylene glycol, lignin and an organic base catalyst in an organic solvent; (2) Pour the prepolymer solution into a mold to allow the organic solvent in the prepolymer solution to evaporate, thereby preparing the lignin-based elastic material; The structural formula of the binary alkynyl compound is shown in formula (I): The structural formula of the lignin is shown in formula (II): The structure of the lignin-based elastic material is shown in formula (III): Wherein, R is a straight-chain alkyl group.

2. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The lignin is Shanghai Dongsheng lignin; R is a straight-chain alkyl group with 1-30 carbon atoms.

3. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The preparation method of the binary alkynyl compound includes the following steps: Under an inert gas atmosphere, the esterification reaction of the alkynyl compound shown in formula (IV) and the dihydroxy compound shown in formula (V) was carried out to prepare the dialkynyl compound shown in formula (I). Wherein, R is a straight-chain alkyl group; The inert gas atmosphere is either a nitrogen atmosphere or an argon atmosphere.

4. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The average number-average molecular weight of the polyethylene glycol is 2000-20000.

5. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The organic base catalyst is 1,4-diazabicyclo[2.2.2]octane, N-methylmorpholine, 4-dimethylaminopyridine, triisopropylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene or quinine; The organic solvent is at least one selected from acetonitrile, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, toluene, 1,4-dioxane, dimethyl sulfoxide, and N,N-dimethylformamide.

6. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The click polymerization reaction is carried out at room temperature, specifically at 25℃-28℃, and the reaction time is 10-50 minutes.

7. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The molar ratio of the total alkynyl group of the binary alkynyl compound to the total hydroxyl groups of polyethylene glycol and lignin is 0.8:1-1.2; the concentration of the total amount of the binary alkynyl compound, polyethylene glycol and lignin in the organic solvent is 50-300 mg / mL; the organic base catalyst accounts for 0.3-1.5 wt% of the total mass of the binary alkynyl compound, polyethylene glycol and lignin.

8. The method for preparing the lignin-based elastic material according to claim 1, characterized in that, The lignin accounts for 1%-25% of the total mass of polyethylene glycol and lignin.

9. The lignin-based elastic material prepared by the preparation method according to any one of claims 1-8.

10. The use of the lignin-based elastic material of claim 9 as a memory material, a temperature-responsive material, or a light-responsive material.

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