A method for preparing aldehyde group functionalized chitin nanocrystals based on SI-ARGET ATRP strategy

Abstract

The application belongs to the technical field of chitin nanocrystal surface modification, and discloses a method for preparing aldehyde group functionalized chitin nanocrystals based on a SI-ARGET ATRP strategy. The preparation method is to use chitin nanocrystals as raw materials, first anchor initiators on the chitin nanocrystals, then prepare lignin-based aromatic aldehyde monomers containing double bonds, and finally react the lignin-based aromatic aldehyde monomers containing double bonds with the chitin nanocrystals with the anchored initiators to obtain aldehyde group functionalized chitin nanocrystals. The application creatively uses biomass-derived monomers as raw materials to prepare chitin nanocrystals with surface aldehyde group functionalized modification for the first time, greatly improves the hydrophobicity of the aldehyde group chitin nanocrystals, and on the other hand, based on the high reactivity of the surface aldehyde group, will make it become a nanomaterial platform easy to realize extensive post-functionalization, and can be applied in the fields of nanocomposites, antibacterial and the like.

Description

Technical Field

[0001] This invention belongs to the field of chitin nanocrystal surface modification technology, specifically relating to a method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy. Background Technology

[0002] Chitin is the second largest natural polymer on Earth after cellulose, mainly derived from crustaceans such as crab and shrimp shells. Hydrolysis of the amorphous regions of chitin via acid hydrolysis can further yield highly crystalline chitin nanocrystals (ChNCs), which possess excellent hydrophilicity, biodegradability, large specific surface area, and high strength and modulus. These nanocrystals show great promise for applications in nanocomposites, food packaging, emulsions, and tissue engineering.

[0003] Surface modification can further regulate the surface properties of chitin nanocrystals and endow them with new specific functions, thus expanding their application range. For example, European Polymer Journal, 2016, 81, 266-283, describes how introducing hydrophobic groups onto chitin nanocrystals can improve their compatibility with hydrophobic polymer matrices and enhance the mechanical properties of nanocomposites.

[0004] Aldehyde groups are crucial intermediate functional groups in organic chemistry, exhibiting high reactivity and capable of participating in various chemical reactions, including Schiff base reactions, Knoevenagel condensation, sulfonation, and acetalization / thioacetalization. Therefore, surface aldehyde functionalization of chitin nanocrystals will make them a readily applicable nanomaterial platform for extensive post-functionalization, with potential applications in nanocomposites, antibacterial materials, and more.

[0005] The International Journal of Biological Macromolecules, 2022, 211, 281-288, mentions that cellulose can be oxidized with sodium periodate to obtain aldehyde cellulose. However, due to the large number of acetylamino groups on the chitin molecular chain, the traditional method of oxidizing cellulose with sodium periodate to obtain aldehyde cellulose, as described in the aforementioned article, cannot be used to prepare aldehyde chitin. Patent CN116375905A discloses a method for preparing aldehyde-modified chitin and its derivatives. Although this method involves pretreatment and modification of chitin followed by oxidation with sodium periodate to obtain aldehyde-modified chitin, overall, the preparation method for aldehyde-modified chitin is singular and cannot meet the needs of diversified development. Furthermore, the raw materials used in the reaction are petroleum-based compounds, which is inconsistent with the trend of green and sustainable development.

[0006] Therefore, the researchers of this invention have developed a novel method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, which is of great significance for expanding the preparation methods of aldehyde-functionalized chitin. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing aldehyde-functionalized chitosan nanocrystals based on the SI-ARGET ATRP strategy. This method is a novel preparation approach that is simple, allows for controllable compound structure, and is green and sustainable.

[0008] One of the technical solutions of the present invention:

[0009] A method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy is provided. The method uses chitin nanocrystals as raw materials, firstly anchoring an initiator on the chitin nanocrystals, then preparing a lignin-based aromatic aldehyde monomer containing double bonds, and finally reacting the lignin-based aromatic aldehyde monomer containing double bonds with the chitin nanocrystals anchored with the initiator to obtain aldehyde-functionalized chitin nanocrystals.

[0010] Preferably, the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy includes the following steps:

[0011] (1) Bromine-containing chitin nanocrystals were obtained by anchoring the initiator α-bromoisobutyryl bromide on the surface of chitin nanocrystals through esterification reaction.

[0012] (2) Using lignin-based aromatic aldehydes as raw materials, and methacryloyl chloride or acryloyl chloride through an acylation reaction to construct lignin-based aromatic aldehyde monomers containing double bonds;

[0013] (3) Mix bromine-containing chitin nanocrystals and lignin-based aromatic aldehyde monomers containing double bonds, and grow polymers on bromine-containing chitin nanocrystals by SI-ARGETATRP to obtain aldehyde-functionalized chitin nanocrystals.

[0014] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, step (1) is specifically as follows:

[0015] Chitin nanocrystals were dispersed in an organic solvent under ice bath and ultrasonic conditions to form a dispersed chitin nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added under stirring, followed by an organic solvent mixture of α-bromoisobutyryl bromide. The mixture was then reacted at 25-70℃ for 3-24 hours under stirring. The resulting suspension was centrifuged to obtain a crude product, which was then repeatedly washed with acetone, dichloromethane, anhydrous ethanol, and water. The crude product was then dispersed in water and freeze-dried to obtain bromine-containing chitin nanocrystals.

[0016] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, the mass concentration of chitin nanocrystals in the chitin nanocrystal suspension is 1-50 g / L, the molar ratio of chitin nanocrystals to α-bromoisobutyryl bromide is 1:5-1:20; the molar ratio of 4-dimethylaminopyridine to α-bromoisobutyryl bromide is 1:1-5:1; and the molar ratio of triethylamine to α-bromoisobutyryl bromide is 1:1-5:1.

[0017] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, step (2) is specifically as follows:

[0018] Using lignin-based aromatic aldehydes as raw materials, the solutions are dissolved in an organic solvent, and pyridine is added as an acid-binding agent. A mixture of methacryloyl chloride or acryloyl chloride in an organic solvent is added under ice bath conditions, and the mixture is refluxed for 1-5 hours. After the reaction, insoluble matter is removed by filtration, dichloromethane is removed by rotary evaporation, ethyl acetate is added, and the mixture is then washed 3-5 times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water, respectively. The organic layer is then dried with anhydrous sodium sulfate for 10-15 hours. Finally, sodium sulfate is removed by filtration, and ethyl acetate is removed by rotary evaporation, yielding an oily, pale yellow crude liquid product. This crude product is then recrystallized from an ethanol-water system and dried to obtain a lignin-based aromatic aldehyde monomer containing double bonds.

[0019] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, the lignin-based aromatic aldehyde is vanillin, eugenol, or p-hydroxybenzaldehyde; the molar ratio of pyridine to the lignin-based aromatic aldehyde is 1:1-5:1; and the molar ratio of methacryloyl chloride to the lignin-based aromatic aldehyde is 1:1-5:1.

[0020] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, step (3) is specifically as follows:

[0021] The bromine-containing chitin nanocrystals prepared in step (1) were ultrasonically dispersed in an organic solvent, and then added to the organic solvent mixture of the lignin-based aromatic aldehyde monomers prepared in step (2). Then, copper bromide catalyst, N,N,N',N',N'-pentamethyldiethylenetriamine ligand, ethyl 2-bromoisobutyrate sacrificial initiator, and ascorbic acid reducing agent were added in sequence. The mixture was stirred for 1-10 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was reacted in an oil bath at 30-80℃ for 3-24 h for surface SI-ARGET ATRP polymerization. The reaction was carried out under nitrogen protection. After the reaction, the mixture was repeatedly washed with acetone, ethanol, and deionized water, and then freeze-dried to obtain aldehyde-functionalized chitin nanocrystals.

[0022] Preferably, in the aforementioned method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, the mass concentration of bromine-containing chitin nanocrystals in the reaction system is 0.05-5 g / L, and the mass molar ratio of bromine-containing chitin nanocrystals, lignin-based aromatic aldehyde monomers, catalysts, ligands, sacrificial initiators, and reducing agents is 300 mg: 30-200 mmol: 0.05-0.2 mmol: 0.5-2 mmol: 0.5-2 mmol: 0.5-2 mmol.

[0023] The second technical solution of the present invention:

[0024] An aldehyde-functionalized chitin nanocrystal is provided, which is prepared by the aforementioned method.

[0025] The third technical solution of the present invention:

[0026] This invention provides an application of the aforementioned aldehyde-functionalized chitin nanocrystals in the fields of nanocomposites and antibacterial agents.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention utilizes a surface SI-ARGET ATRP polymerization strategy to achieve graft polymerization of lignin-based aromatic aldehydes on the surface of chitin nanocrystals, thereby constructing aldehyde-functionalized chitin nanocrystals. Compared with existing preparation methods, this invention represents a novel and simple method, which is of great significance for expanding the preparation methods of aldehyde-functionalized chitin.

[0029] 2. The aldehyde-functionalized chitin nanocrystals prepared by the method of the present invention can effectively control the structure of the grafted polymer by adjusting the component ratio in the grafting polymerization.

[0030] 3. The aldehyde monomer used in the method of this invention is derived from lignin, which is in line with the trend of green and sustainable development.

[0031] 4. The aldehyde-functionalized chitin nanocrystals prepared by the method of the present invention can be used in the fields of nanocomposite and antibacterial materials. Attached Figure Description

[0032] Figure 1 This is the infrared spectrum of vanillin methacrylate from Example 1 of the present invention. In the infrared spectrum, vanillin methacrylate is at 1740 cm⁻¹. -1 1702cm -1 and 1638cm -1 The positions correspond to (-(C=O)-O-), (-(C=O)H), and (-C(CH3)=C), respectively, while vanillin's 3176 cm⁻¹ -1 (-OH) disappears, and... Figure 2 and Figure 3 The NMR results, together with the NMR data, confirmed its successful synthesis.

[0033] Figure 2 This is the hydrogen spectrum of vanillin methacrylate from Example 1 of the present invention.

[0034] Figure 3 This is the carbon spectrum of vanillin methacrylate from Example 1 of the present invention.

[0035] Figure 4 The images show the infrared spectra of chitin nanocrystals (ChNCs), bromine-containing chitin nanocrystals (ChNCs-Br), and aldehyde-functionalized chitin nanocrystals (Examples 1-3) in the embodiments of the present invention. The 1740 cm⁻¹ peak observed in the ChNCs-Br spectrum is shown. -1 The newly emerging carbonyl stretching vibration confirms the successful anchoring of the "Br" initiation site on ChNCs. In the infrared spectra of Examples 1-3, at 1756 cm⁻¹... -1 and 1702cm -1 The newly observed peak was attributed to the ester and aldehyde groups on the grafted chain, at 1597 cm⁻¹. -1 and 1502cm -1 The new peak at this location is a characteristic peak of the benzene ring unit on the grafted chain. As the monomer feed ratio increases, the aldehyde group signal in the sample becomes more and more obvious. All of the above fully confirms the successful surface grafting of the polymer chain.

[0036] Figure 5The XRD patterns of chitin nanocrystals (ChNCs), bromine-containing chitin nanocrystals (ChNCs-Br), and aldehyde-functionalized chitin nanocrystals (Examples 1-3) are shown in the embodiments of the present invention. The crystallinity index of ChNCs-Br is 71.4%, lower than that of ChNCs (86.9%). As grafted chains are grafted from the surface of ChNCs, the crystallinity of Examples 1, 2, and 3 decreases significantly to 47.9%, 41.0%, and 32.3%, respectively. This is because the amorphous polymer chains grafted onto the surface reduce the proportion of crystalline regions. However, characteristic diffraction peaks of unmodified ChNCs can still be observed in all the sample examples, indicating that surface grafting does not damage the internal structure of ChNCs. Grafting only occurs on the surface of ChNCs, and the grafted molecular chains do not penetrate into the interior of ChNCs to cause changes in crystal form.

[0037] Figure 6 These are TEM images of chitin nanocrystals (ChNCs), bromine-containing chitin nanocrystals (ChNCs-Br), and aldehyde-functionalized chitin nanocrystals from Example 3 of the present invention. The morphology of ChNCs-Br is very similar to that of ChNCs; these rod-shaped nanoparticles have lengths mostly between 60-250 nm and an average diameter of 14 nm. After grafting modification using the SI-ARGET ATRP surface modification procedure, the modified chitin nanocrystals still retain their original rod-shaped morphology and exhibit a rougher surface with a larger average diameter of approximately 55 nm. This indicates the formation of densely packed polymer chains on the ChNCs surface, indirectly verifying the success of the modification.

[0038] Figure 7 Images show the contact angles of chitosan nanocrystals (ChNCs) and aldehyde-functionalized chitosan nanocrystals (Examples 1-3) according to embodiments of the present invention. Water droplets rapidly penetrate and diffuse on the ChNCs film, followed by swelling and fluffing, which is due to the high hydrophilicity of the ChNCs. On the other hand, the water contact angle of Example 1 is approximately 59.8°, while that of Example 2 is approximately 66.6°, and that of Example 3 is 73.1°, indicating that the polyvanillin methacrylate chains grafted onto the surface of the ChNCs enhance the hydrophobicity of the nanoparticles. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0040] Embodiments of the present invention

[0041] The SI-ARGET ATRP strategy mentioned in this invention refers to the strategy of "surface-initiated electron transfer activation and regeneration catalyst atom transfer radical polymerization".

[0042] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0043] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0044] Embodiment 1 of the present invention:

[0045] Step (1): Add 2.50 g of ChNCs to a glass bottle containing 250 mL of LMF (N,N-dimethylaminocarbamate) and stir for 2 h. Then sonicate for 2 h under ice bath protection. Add DMAP (4-dimethylaminopyridine) (15.35 g, 123.40 mmol) and TEA (triethylamine) (25.90 mL, 185.00 mmol) to the bottle while stirring. Continue to stir magnetically for about 10 minutes. Then add BiBB (α-bromoisobutyryl bromide, 15.55 mL, 123.30 mmol) dissolved in 50 mL of LMF dropwise. The whole process is protected under ice bath protection. After the addition is complete, place the bottle in an oil bath at 70 °C and react for 24 h. After the reaction is complete, centrifuge at 8000 rpm for 15 min and wash repeatedly with acetone, dichloromethane, anhydrous ethanol and water until the supernatant is colorless. Then disperse in water and freeze dry to obtain bromochidine nanocrystals (ChNCs-Br).

[0046] Step (2): Weigh vanillin (30.40 g, 200.00 mmol) into a 1000 mL three-necked flask, add 500 mL of dichloromethane as solvent, and dissolve it until clear by magnetic stirring. Continue to add pyridine (24.23 mL, 300.00 mmol) as an acid-binding agent and stir for 10 min. Then, using a constant pressure dropping funnel, add methacryloyl chloride (29.00 mL, 200.00 mmol) dissolved in 50 mL of dichloromethane dropwise under ice bath conditions. After the addition is complete, reflux at 38 °C for 3 h. After the reaction is complete... The insoluble matter was removed by filtration, followed by rotary evaporation of dichloromethane. 500 mL of ethyl acetate was added, and the mixture was washed four times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water. The organic layer was dried with anhydrous sodium sulfate for 12 h. The sodium sulfate and ethyl acetate solvent were removed by filtration, yielding an oily, pale yellow liquid. The crude product was dissolved in 300 mL of ethanol, and the solids insoluble in ethanol were removed by filtration. The product was recrystallized twice using an ethanol-water system, and dried to finally obtain a lignin-based aromatic aldehyde monomer containing double bonds (vanillin methacrylate).

[0047] Step (3): 300 mg of bromochidine nanocrystals (ChNCs-Br) were ultrasonically dispersed in 30 mL of DMF. Then, vanillin methacrylate (9.8 g, 44.5 mmol) dissolved in 30 mL of DMF was added dropwise. Then, copper bromide (CuBr2) (20.1 mg, 0.089 mmol), ligand N,N,N',N',N'-pentamethyldiethylenetriamine (PMDETA) (188 μL, 0.89 mmol), and sacrificial initiator 2 were added sequentially. Ethyl bromoisobutyrate (EBiB) (133 μL, 0.89 mmol) and ascorbic acid (AsAc) (0.16 g, 0.89 mmol) were stirred for 5 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was transferred to a 60 °C oil bath for 3 h. The reaction was carried out under nitrogen protection. After the reaction, the mixture was repeatedly centrifuged and washed with acetone, ethanol and deionized water for two days to ensure that the free self-polymers and components involved in the ATRP initiation process were completely removed. After washing, the mixture was freeze-dried to obtain aldehyde-functionalized chitin nanocrystals.

[0048] Embodiment 2 of the present invention:

[0049] In step (3) of Example 1, the amount of vanillin methacrylate was adjusted to 19.6g, while other conditions remained unchanged.

[0050] Embodiment 3 of the present invention:

[0051] In step (3) of Example 1, the amount of vanillin methacrylate was adjusted to 29.4g, while other conditions remained unchanged.

[0052] Embodiment 4 of the present invention:

[0053] Replace step (2) of Example 1 with: Weigh syringaldehyde (36.43 g, 200.00 mmol) into a 1000 mL three-necked flask, add 500 mL of dichloromethane as solvent, and dissolve it until clear by magnetic stirring. Continue to add the acid-binding agent pyridine (24.23 mL, 300.00 mmol) and stir for 10 min. Then, using a constant pressure dropping funnel, add methacryloyl chloride (29.00 mL, 200.00 mmol) dissolved in 50 mL of dichloromethane dropwise under ice bath conditions. After the addition is complete, reflux at 38 °C for 1 h. After completion, the insoluble matter was removed by filtration, followed by rotary evaporation of dichloromethane. 500 mL of ethyl acetate was added, and the mixture was washed three times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water. The organic layer was dried with anhydrous sodium sulfate for 10 h. The sodium sulfate and ethyl acetate solvent were removed by filtration, yielding an oily, pale yellow liquid. The crude product was dissolved in 300 mL of ethanol, and the solids insoluble in ethanol were removed by filtration. The product was recrystallized twice using an ethanol-water system, and after drying, a lignin-based aromatic aldehyde monomer containing double bonds (eugenol methacrylate) was finally obtained.

[0054] Step (3) is replaced by: ultrasonically dispersing 300 mg of bromochitin nanocrystals ChNCs-Br in 30 mL of DMF, then adding dropwise syringaldehyde methacrylate (11.17 g, 44.5 mmol) dissolved in 30 mL of DMF, followed by the addition of the catalyst copper bromide (CuBr2) (20.1 mg, 0.089 mmol), the ligand N,N,N',N',N'-pentamethyldiethylenetriamine (PMDETA) (188 μL, 0.89 mmol), and the salicylic acid precipitate. Ethyl 2-bromoisobutyrate (EBiB) (133 μL, 0.89 mmol) as the initiator and ascorbic acid (AsAc) (0.16 g, 0.89 mmol) as the reducing agent were stirred for 1 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was transferred to an oil bath at 30 °C and reacted for 24 h. The reaction was carried out under nitrogen protection. After the reaction, the mixture was repeatedly centrifuged and washed with acetone, ethanol, and deionized water for two days to ensure that the free self-polymers and components involved in the ATRP initiation process were completely removed. After washing, the product was freeze-dried to obtain the grafted modified product.

[0055] All other conditions remain unchanged.

[0056] Embodiment 5 of the present invention:

[0057] Replace step (2) of Example 1 with: Weigh p-hydroxybenzaldehyde (24.42 g, 200.00 mmol) into a 1000 mL three-necked flask, add 500 mL of dichloromethane as solvent, and dissolve it until clear by magnetic stirring. Continue to add pyridine (24.23 mL, 300.00 mmol) as an acid-binding agent and stir for 10 min. Then, add acryloyl chloride (29.00 mL, 200.00 mmol) dissolved in 50 mL of dichloromethane dropwise using a constant pressure dropping funnel under ice bath conditions. After the addition is complete, reflux at 38 °C for 5 h. After the reaction is complete, filter to remove insoluble matter, then remove dichloromethane by rotary evaporation, add 500 mL of ethyl acetate, and then wash with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution and deionized water 5 times each. The organic layer was dried with anhydrous sodium sulfate for 15 hours; the sodium sulfate was removed by filtration, and the solvent ethyl acetate was removed to obtain an oily, pale yellow liquid; the crude product was dissolved in 300 mL of ethanol, and the solids insoluble in ethanol were removed by filtration. The product was then recrystallized twice through an ethanol-water system, and after drying, a lignin-based aromatic aldehyde monomer containing double bonds (p-hydroxybenzaldehyde methacrylate) was finally obtained.

[0058] Step (3): 300 mg of bromochitin nanocrystals (ChNCs-Br) were ultrasonically dispersed in 30 mL of DMF. Then, 8.41 g (44.5 mmol) of p-hydroxybenzaldehyde methacrylate dissolved in 30 mL of DMF was added dropwise. Following this, copper bromide (CuBr2) (20.1 mg, 0.089 mmol), N,N,N',N',N'-pentamethyldiethylenetriamine (PMDETA) (188 μL, 0.89 mmol), and sacrificial... Ethyl 2-bromoisobutyrate (EBiB) (133 μL, 0.89 mmol) as the initiator and ascorbic acid (AsAc) (0.16 g, 0.89 mmol) as the reducing agent were stirred for 10 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was transferred to an 80 °C oil bath for 3 h. The reaction was carried out under nitrogen protection. After the reaction, the mixture was repeatedly centrifuged and washed with acetone, ethanol, and deionized water for two days to ensure that the free self-polymers and components involved in the ATRP initiation process were completely removed. After washing, the product was freeze-dried to obtain the grafted modified product.

[0059] All other conditions remain unchanged.

[0060] Embodiment 6 of the present invention:

[0061] Chitosan nanocrystals were dispersed in DMF under ice bath ultrasonic conditions to form a dispersed chitosan nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added with stirring, followed by a DMF mixture of α-bromoisobutyryl bromide. The reaction was then carried out at 25°C for 24 hours with stirring. The resulting suspension was centrifuged to obtain a crude product, which was then repeatedly washed with acetone, dichloromethane, anhydrous ethanol, and water, and then dispersed in water and freeze-dried to obtain bromine-containing chitosan nanocrystals. The chitosan nanocrystal suspension contained a chitosan nanocrystal concentration of 1 g / L, and the molar ratio of chitosan nanocrystals to α-bromoisobutyryl bromide was 1:5; the molar ratio of 4-dimethylaminopyridine to α-bromoisobutyryl bromide was 1:1; and the molar ratio of triethylamine to α-bromoisobutyryl bromide was 1:1.

[0062] Using lignin-based aromatic aldehydes as raw materials, the solutions were dissolved in dichloromethane, and pyridine was added as an acid-binding agent. A mixed solution of acryloyl chloride and dichloromethane was added under ice bath conditions, and the mixture was refluxed for 1 hour. After the reaction, insoluble matter was removed by filtration, and dichloromethane was removed by rotary evaporation. Ethyl acetate was added, and the mixture was washed three times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water, respectively. The organic layer was then dried with anhydrous sodium sulfate for 10 hours. Finally, sodium sulfate was removed by filtration, and ethyl acetate was removed by rotary evaporation, yielding an oily, pale yellow liquid crude product. This crude product was recrystallized from an ethanol-water system and dried to obtain a lignin-based aromatic aldehyde monomer containing double bonds. The lignin-based aromatic aldehyde was vanillin. The molar ratio of pyridine to the lignin-based aromatic aldehyde was 1:1, and the molar ratio of acryloyl chloride to the lignin-based aromatic aldehyde was 1:1.

[0063] The bromine-containing chitin nanocrystals prepared in step (1) were ultrasonically dispersed in DMF, and then added to the DMF mixed solution of lignin-based aromatic aldehyde monomers prepared in step (2). Next, copper bromide catalyst, N,N,N',N',N'-pentamethyldiethylenetriamine ligand, ethyl 2-bromoisobutyrate sacrificial initiator, and ascorbic acid reducing agent were added sequentially, and the mixture was stirred for 1 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was reacted in a 30°C oil bath for 24 h to perform surface SI-ARGET. ATRP polymerization was carried out under nitrogen protection during the reaction. After the reaction, the mixture was repeatedly washed with acetone, ethanol, and deionized water, and then freeze-dried to obtain aldehyde-functionalized chitin nanocrystals. In the reaction system, the mass concentration of bromochitin nanocrystals was 0.05 g / L, and the molar ratio of bromochitin nanocrystals, lignin-based aromatic aldehyde monomers, catalyst, ligand, sacrificial initiator, and reducing agent was 300 mg: 30 mmol: 0.05 mmol: 0.5 mmol: 0.5 mmol: 0.5 mmol.

[0064] Embodiment 7 of the present invention:

[0065] Chitosan nanocrystals were dispersed in DMF under ice bath ultrasonic conditions to form a dispersed chitosan nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added with stirring, followed by a DMF mixture of α-bromoisobutyryl bromide. The mixture was then reacted at 70°C for 3 hours with stirring. The resulting suspension was centrifuged to obtain a crude product, which was then repeatedly washed with acetone, dichloromethane, anhydrous ethanol, and water. The crude product was then dispersed in water and freeze-dried to obtain bromine-containing chitosan nanocrystals. The chitosan nanocrystal suspension contained a chitosan nanocrystal concentration of 50 g / L, and the molar ratio of chitosan nanocrystals to α-bromoisobutyryl bromide was 1:20. The molar ratio of 4-dimethylaminopyridine to α-bromoisobutyryl bromide was 5:1, and the molar ratio of triethylamine to α-bromoisobutyryl bromide was 5:1.

[0066] Using lignin-based aromatic aldehydes as raw materials, the solutions were dissolved in dichloromethane, and pyridine was added as an acid-binding agent. A mixed solution of methacryloyl chloride and dichloromethane was added under ice bath conditions, and the mixture was refluxed for 5 hours. After the reaction, insoluble matter was removed by filtration, and dichloromethane was removed by rotary evaporation. Ethyl acetate was added, and the mixture was washed five times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water, respectively. The organic layer was then dried with anhydrous sodium sulfate for 15 hours. Finally, sodium sulfate was removed by filtration, and ethyl acetate was removed by rotary evaporation, yielding an oily, pale yellow liquid crude product. This crude product was recrystallized from an ethanol-water system and dried to obtain a lignin-based aromatic aldehyde monomer containing double bonds. The lignin-based aromatic aldehyde was p-hydroxybenzaldehyde. The molar ratio of pyridine to the lignin-based aromatic aldehyde was 5:1, and the molar ratio of methacryloyl chloride to the lignin-based aromatic aldehyde was 5:1.

[0067] The bromine-containing chitin nanocrystals prepared in step (1) were ultrasonically dispersed in DMF, and then added to the DMF mixed solution of lignin-based aromatic aldehyde monomers prepared in step (2). Then, copper bromide catalyst, N,N,N',N',N'-pentamethyldiethylenetriamine ligand, ethyl 2-bromoisobutyrate sacrificial initiator, and ascorbic acid reducing agent were added sequentially. The mixture was stirred for 1-10 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was reacted in an oil bath at 80°C for 3 h for surface SI-ARGET ATRP polymerization. The reaction was carried out under nitrogen protection. After the reaction, the mixture was repeatedly washed with acetone, ethanol, and deionized water, and then freeze-dried to obtain aldehyde-functionalized chitin nanocrystals. In the reaction system, the mass concentration of bromine-containing chitin nanocrystals was 5 g / L, and the molar ratio of bromine-containing chitin nanocrystals, lignin-based aromatic aldehyde monomers, catalyst, ligand, sacrificial initiator, and reducing agent was 300 mg: 200 mmol: 0.2 mmol: 2 mmol: 2 mmol: 2 mmol.

[0068] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy, characterized in that: Includes the following steps: (1) Chitin nanocrystals were dispersed in an organic solvent under ice bath ultrasonic conditions to form a dispersed chitin nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added under stirring, followed by an organic solvent mixture of α-bromoisobutyryl bromide. The mixture was then reacted at 25-70℃ for 3-24 hours under stirring conditions. The resulting suspension was centrifuged to obtain a crude product. The crude product was washed repeatedly with acetone, dichloromethane, anhydrous ethanol, and water, then dispersed in water and freeze-dried to obtain bromine-containing chitin nanocrystals. The mass concentration of chitin nanocrystals in the chitin nanocrystal suspension was 1-50 g / L, and the molar ratio of chitin nanocrystals to α-bromoisobutyryl bromide was 1:5-1:

20. The molar ratio of 4-dimethylaminopyridine to α-bromoisobutyryl bromide was 1:1-5:

1. The molar ratio of triethylamine to α-bromoisobutyryl bromide was 1:1-5:

1. (2) Using lignin-based aromatic aldehydes as raw materials, and methacryloyl chloride or acryloyl chloride through an acylation reaction to construct lignin-based aromatic aldehyde monomers containing double bonds; (3) Mix bromine-containing chitin nanocrystals and lignin-based aromatic aldehyde monomers containing double bonds, and grow polymers on bromine-containing chitin nanocrystals by SI-ARGET ATRP to obtain aldehyde-functionalized chitin nanocrystals. The method for step (3) is as follows: The bromine-containing chitin nanocrystals prepared in step (1) were ultrasonically dispersed in an organic solvent, and then added to the organic solvent mixture of the lignin-based aromatic aldehyde monomer prepared in step (2). Next, copper bromide catalyst, N,N,N',N',N'-pentamethyldiethylenetriamine ligand, ethyl 2-bromoisobutyrate sacrificial initiator, and ascorbic acid reducing agent were added sequentially, and the mixture was stirred for 1-10 min. After three cycles of freezing-vacuuming-nitrogen purging, the mixture was reacted in an oil bath at 30-80℃ for 3-24 h for surface SI-ARGETATRP polymerization under nitrogen protection. After the reaction, the mixture was repeatedly washed with acetone, ethanol, and deionized water, and then freeze-dried to obtain aldehyde-functionalized chitin nanocrystals. In the reaction system, the mass concentration of the bromine-containing chitin nanocrystals was 0.05-5 g / L, and the molar ratio of the bromine-containing chitin nanocrystals, lignin-based aromatic aldehyde monomer, catalyst, ligand, sacrificial initiator, and reducing agent was [missing information]. 300mg: 30-200mmol: 0.05-0.2mmol: 0.5-2mmol: 0.5-2mmol: 0.5-2mmol.

2. The method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy according to claim 1, characterized in that, The method for step (2) is as follows: Using lignin-based aromatic aldehydes as raw materials, the solutions are dissolved in an organic solvent, and pyridine is added as an acid-binding agent. A mixture of methacryloyl chloride or acryloyl chloride in an organic solvent is added under ice bath conditions, and the mixture is refluxed for 1-5 hours. After the reaction, insoluble matter is removed by filtration, dichloromethane is removed by rotary evaporation, ethyl acetate is added, and the mixture is then washed 3-5 times each with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution, and deionized water, respectively. The organic layer is then dried with anhydrous sodium sulfate for 10-15 hours. Finally, sodium sulfate is removed by filtration, and ethyl acetate is removed by rotary evaporation, yielding an oily, pale yellow crude liquid product. This crude product is then recrystallized from an ethanol-water system and dried to obtain a lignin-based aromatic aldehyde monomer containing double bonds.

3. The method for preparing aldehyde-functionalized chitin nanocrystals based on the SI-ARGET ATRP strategy according to claim 2, characterized in that: The lignin-based aromatic aldehyde is vanillin, syringin, or p-hydroxybenzaldehyde; the molar ratio of the reaction between pyridine and the lignin-based aromatic aldehyde is 1:1-5:1; the molar ratio of the reaction between methacryloyl chloride and the lignin-based aromatic aldehyde is 1:1-5:

1.

4. An aldehyde-functionalized chitin nanocrystal, characterized in that: It is prepared by the method described in any one of claims 1-3.

5. The application of the aldehyde-functionalized chitin nanocrystals according to claim 4 in the fields of nanocomposites and antibacterial agents.

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