Preparation and application of modified chitin nanocrystal-nanosilver antibacterial hybrid material

Abstract

The application relates to the technical field of material preparation, and discloses a preparation and application of a modified chitin nanocrystal-nano silver antibacterial hybrid material. The hybrid material is obtained by in-situ reduction of silver ions by taking aldehyde group functionalized chitin nanocrystals as a template agent and a reducing agent. The method provides a brand-new preparation method of aldehyde group functionalized chitin nanocrystals, is simple, compound structure is controllable, and is green and sustainable; meanwhile, the aldehyde group functionalized chitin nanocrystals are used as a template of nano silver, the reducibility of the surface aldehyde group is utilized to realize loading of the nano silver, and the modified chitin nanocrystal-nano silver antibacterial hybrid material is constructed; in addition, when the modified chitin nanocrystal-nano silver antibacterial hybrid material is used as a polylactic acid filler, the mechanical property, the antibacterial property and the ultraviolet resistance of the polylactic acid can be improved.

Description

Preparation and application of modified chitin nanocrystal-silver nanobacterial hybrid materials Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, specifically relating to the preparation and application of a modified chitin nanocrystal-silver nanobacterial hybrid material. Background Technology

[0002] With the rapid development of society and economy and the continuous progress of science and technology, people's demand for natural resources has exploded, causing many thorny development problems. Among these, the wide-ranging and multi-field use of petroleum-based products has led to problems such as the depletion of petroleum resources and environmental pollution. In 1987, the World Commission on Environment and Development (WCED) published "Our Common Future," which formally used the concept of "sustainable development." Since then, the call for greening resources and sustainable development has been heard worldwide, and researchers at home and abroad have begun to turn their attention to biomass green resources that are abundant, widely distributed, and naturally degradable in nature. Among them, polylactic acid (PLA) has good biocompatibility, excellent processing performance, and biodegradability, making it one of the most promising bio-based polymers. All these characteristics make it a promising alternative to petroleum-based plastics. However, PLA has shortcomings such as insufficient mechanical properties, low water vapor barrier properties, low crystallinity, and low antibacterial activity, which limits its application.

[0003] Chitin nanocrystals are widely recognized as biocompatible polymers due to their biodegradability, good mechanical properties, lack of environmental hazards, non-toxicity, and high absorbability. Their application as nanofillers in polymer-based nanocomposites has attracted considerable attention. However, the large number of hydroxyl and acetylamino groups on the surface of chitin nanocrystals results in strong hydrophilicity, severely limiting their application in most hydrophobic polymer matrices.

[0004] Grafting hydrophobic long chains onto the surface of chitin nanocrystals to achieve hydrophobic modification can improve their application in hydrophobic polymer matrices. Aldehyde-modified chitin nanocrystals are an important type of hydrophobically modified chitin nanocrystals. However, due to the large number of acetylamino groups on the chitin molecular chain, the traditional method of obtaining aldehyde-based chitin through sodium periodate oxidation of cellulose, as described in the aforementioned article, cannot be used. Patent CN116375905A discloses a method for preparing aldehyde-based chitin and its derivatives. Although this method involves pretreatment and modification of chitin followed by sodium periodate oxidation to obtain aldehyde-based chitin, overall, the preparation method for aldehyde-based chitin is singular and cannot meet the needs of diversified development. Furthermore, the use of petroleum-based compounds as raw materials is inconsistent with the trend of green and sustainable development.

[0005] On the other hand, while improving the compatibility between chitin nanocrystals and polymer matrices, how to load silver nanoparticles onto the surface of chitin nanocrystals to form modified chitin nanocrystal-silver nanoparticle antibacterial hybrid materials is also one of the hot research directions in this field. This can play a synergistic role in antibacterial and enhancement at the same time, and can be used to prepare polylactic acid nanocomposites. However, research in this direction has not yet been reported. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material. The method of this invention provides a novel approach for preparing aldehyde-based chitosan nanocrystals, which is simple, allows for controllable compound structure, and is green and sustainable. Simultaneously, using the aldehyde-based chitosan nanocrystals as a template for silver nanoparticles, the silver nanoparticles are loaded using the reducing properties of the surface aldehyde groups, thus constructing the modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material. Furthermore, when this modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material is used as a polylactic acid filler, it can improve its mechanical properties, antibacterial properties, and UV resistance.

[0007] One of the technical solutions of the present invention:

[0008] This invention provides a method for preparing a modified chitosan nanocrystal-silver nano-antibacterial hybrid material. The method involves using aldehyde-functionalized chitosan nanocrystals as a template agent and reducing agent to reduce silver ions in situ, thereby obtaining the modified chitosan nanocrystal-silver nano-antibacterial hybrid material.

[0009] Preferably, the preparation of the aforementioned modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material is specifically carried out by: ultrasonically dispersing aldehyde-functionalized chitin nanocrystals in water, then adding freshly prepared silver ion solution under stirring, mixing evenly, transferring the suspension to an oil bath at 25-70℃ for 2-8 hours, and after the reaction, repeatedly centrifuging and washing with water and freeze-drying to obtain the modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material; wherein the silver ion solution is silver nitrate solution, silver sulfate solution, silver acetate solution, silver ammonia solution, silver phosphate solution, silver lactate or silver trifluoroacetate solution.

[0010] Preferably, in the preparation of the aforementioned modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material, the concentration of aldehyde-functionalized chitin nanocrystals in the reaction system is 1-50 g / L, and the concentration of silver nitrate solution is 1-10 g / L; wherein the molar concentration of silver nitrate in the silver nitrate solution is 3-5 mol / L.

[0011] Preferably, in the preparation of the aforementioned modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material, the method for preparing the aldehyde-functionalized chitosan nanocrystals is as follows:

[0012] (1) Bromine-containing chitin nanocrystals were obtained by anchoring the initiator α-bromoisobutyryl bromide on the surface of chitin nanocrystals through esterification reaction.

[0013] (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;

[0014] (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.

[0015] Preferably, the preparation of the aforementioned modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material, specifically step (1) is as follows:

[0016] Chitosan nanocrystals were dispersed in an organic solvent under ice bath ultrasonic conditions to form a dispersed chitosan nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added with stirring, followed by an organic solvent mixture of α-bromoisobutyryl bromide. The mixture was then reacted at 25-70℃ for 3-24 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 mass concentration of chitosan nanocrystals in the suspension was 1-50 g / L; the molar ratio of chitosan 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; and the molar ratio of triethylamine to α-bromoisobutyryl bromide was 1:1-5:1.

[0017] Preferably, the preparation of the aforementioned modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material, specifically step (2) is 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 liquid crude product. This crude product is recrystallized from an ethanol-water system and dried to obtain a lignin-based aromatic aldehyde monomer containing double bonds. 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.

[0019] Preferably, the preparation of the aforementioned modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material, specifically step (3) is as follows:

[0020] 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). Next, 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 surface SI-ARGETATRP polymerization was carried out in an oil bath at 30-80℃ for 3-24 h. 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 0.05-5 g / L, and the molar ratio of bromine-containing chitin nanocrystals, lignin-based aromatic aldehyde monomers, catalysts, ligands, sacrificial initiators and reducing agents was 300 mg: 30-200 mmol: 0.05-0.2 mmol: 0.5-2 mmol: 0.5-2 mmol: 0.5-2 mmol.

[0021] The second technical solution of the present invention:

[0022] A modified chitin nanocrystal-silver nanocrystal antibacterial hybrid material is provided, which is prepared according to the aforementioned method.

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

[0024] This invention provides an application of the aforementioned modified chitin nanocrystal-silver nanobacterial hybrid material in the fields of nanocomposites, antibacterial and packaging.

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

[0026] A polylactic acid nanocomposite material with antibacterial and enhancing synergistic effects is provided, comprising the aforementioned modified chitin nanocrystal-silver nanocomposite material; its preparation method is as follows:

[0027] The modified chitin nanocrystal-silver nano-antibacterial hybrid material was ultrasonically dispersed in an organic solvent to obtain a suspension; the suspension was added to a mixed solution of polylactic acid and organic solvent to obtain a mixed system; the mixed system was then ultrasonically treated under ice bath protection, and then allowed to stand until the solvent evaporated, and then transferred to an oven to continue drying until the organic solvent was completely removed, finally obtaining a polylactic acid nanocomposite material with antibacterial-reinforcing synergistic effect;

[0028] In the mixed system, the mass concentration of polylactic acid solution is 1-5 wt%, and the modified chitin nanocrystal-silver nano-antibacterial hybrid material accounts for 0.1-10% of the mass of polylactic acid.

[0029] The beneficial effects of this invention are:

[0030] This invention first grafts hydrophobic aldehyde polymer chains onto the surface of chitin nanocrystals, then utilizes the aldehyde functionalities to prepare modified chitin nanocrystal-silver nanoparticle antibacterial hybrid materials, and finally combines them with polylactic acid to obtain a series of nanocomposite materials. Compared with existing technologies, this invention:

[0031] 1. The preparation method of the aldehyde-modified chitin nanocrystals of the present invention is simple, the compound structure is controllable, and it is green and sustainable.

[0032] 2. This invention uses modified chitosan nanocrystals as a template agent for nano-silver and as a reducing agent to reduce and load nano-silver in situ, thereby obtaining a functional nanofiller modified chitosan nanocrystal-nano-silver antibacterial hybrid material. The technical strategy is unique, and the hybrid material has superior performance.

[0033] 3. When the modified chitin nanocrystal-silver nano-antibacterial hybrid material of the present invention is used as a polylactic acid nanofiller, it has a synergistic effect of mechanical reinforcement and antibacterial properties. In addition, it also endows the nanocomposite material with good ultraviolet shielding performance. Attached Figure Description

[0034] Figure 1 shows the infrared characterization of the modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material of the present invention. Characteristic peak of chitin nanocrystals: 3446 cm⁻¹ -1 (-OH stretching), 3270cm -1 (-NH stretching), 1659cm -1 (Amide I) and 1556cm -1 (Amide II), while 1756 and 1702 cm-1 The peaks are attributed to ester and aldehyde groups on the grafted chains of poly(vanillin methacrylate) (PVMA), at 1597 and 1502 cm⁻¹. -1 The peak at this point is a characteristic peak of the benzene ring unit on the PVMA chain. After the reduction reaction, the absorption peak intensity of the aldehyde group weakens, proving that the aldehyde group participates in the reaction as a reducing component and immobilizes AgNPs during the reaction.

[0035] Figure 2 shows the XPS characterization of the modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material of the present invention. Characteristic peaks of silver were observed in the full spectrum of ChNCs-PVMA@Ag, and the peaks at 367.5 eV and 374.0 eV in the high-resolution spectrum are 3d... 5 / 2 and 3D 3 / 2 The binding energy peak proves the existence of AgNPs.

[0036] Figure 3 shows the experimental results of the antibacterial effect of the modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material of the present invention. Since AgNPs are loaded onto ChNCs-PVMA@Ag, it is predicted to have good antibacterial ability, which was preliminarily verified through experiments. As shown in Figure 3, ChNCs-PVMA@Ag has good bactericidal effects against both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus), with an inhibition rate of 99%. This binary nano-hybrid particle has good antibacterial properties. Adding it as an additive to a PLA matrix is ​​expected to construct a PLA-based nano-antibacterial composite film, showing broad application prospects.

[0037] Figure 4 is a schematic diagram of the mechanical properties of the polylactic acid nanocomposite film according to the embodiments of the present invention, where A and G correspond to Examples 1-7, respectively. The tensile strength of Example 1 is approximately 35.54 MPa. When 5 wt% ChNCs and 7 wt% ChNCs-PVMA@Ag are added, agglomeration occurs in the matrix, severely weakening the mechanical properties of the composite film material. The tensile strengths of Examples 2 and 7 decrease to 27.93 MPa and 26.66 MPa, respectively. When the ChNCs-PVMA@Ag content is 1 wt%, 3 wt%, and 5 wt%, the tensile strengths of Examples 4, 5, and 6 are 40.39 MPa, 42.73 MPa, and 46.74 MPa, respectively, which are 1.14 times, 1.20 times, and 1.32 times higher than the 35.54 MPa of pure PLA. This indicates that ChNCs-PVMA@Ag has better interfacial compatibility with the polylactic acid matrix than ChNCs, and can improve the mechanical properties of the PLA film.

[0038] Figure 5 shows the light transmittance and UV shielding performance of the polylactic acid nanocomposite films according to embodiments of the present invention, where A and G correspond to Examples 1-7, respectively. To quantitatively measure the light transmittance and potential UV shielding performance of the nanocomposite films, a UV-Vis spectrophotometer was used for testing. In the transmittance curves, with visible light at 650 nm as a reference, the transmittance of Example 1 was 82%. However, after adding 5 wt% ChNCs, the transmittance of Example 2 dropped sharply to 49%, which was due to the aggregation of unmodified nanoparticles. The composite films prepared by adding 5 wt% ChNCs-PVMA, 1 wt% ChNCs-PVMA@Ag, 3 wt% ChNCs-PVMA@Ag, 5 wt% ChNCs-PVMA@Ag, and 7 wt% ChNCs-PVMA@Ag had transmittances at 650 nm of Example 3: 41%, Example 4: 70%, Example 5: 52%, Example 6: 37%, and Example 7: 14%. Example 6 still maintained a certain level of transparency. In addition, the ultraviolet shielding performance of the composite film with added ChNCs-PVMA@Ag nanoparticles was investigated. It can be found that as the doping amount of ChNCs-PVMA@Ag increases, the ultraviolet shielding capability of the corresponding embodiment gradually improves. Embodiments 6 and 7 achieved full-band shielding of UVB and UVC, demonstrating their excellent ultraviolet shielding capability.

[0039] Figure 6 is a schematic diagram of the antibacterial effect of the polylactic acid nanocomposite film according to the embodiments of the present invention, where af corresponds to Embodiment 1, Embodiment 2, Embodiment 4, Embodiment 5, Embodiment 6, and Embodiment 7, respectively. It can be seen that when the doping amount of ChNCs-PVMA@Ag reaches 5wt% and 7wt%, Embodiments 6 and 7 show good antibacterial effects against Escherichia coli and Staphylococcus aureus, which can broaden its application in the antibacterial field. Detailed Implementation

[0040] 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.

[0041] Embodiments of the present invention

[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: Preparation of aldehyde-functionalized chitin nanocrystals

[0046] Step 1-1: Add ChNCs (2.50 g) to a glass bottle containing 250 mL of DMF (N,N-dimethylaminocarbamate) and stir for 2 hours to ensure effective DMF penetration and diffusion. Then, sonicate for 2 hours under ice bath protection. While stirring, add DMAP (4-dimethylaminopyridine) (15.35 g, 123.40 mmol) and TEA (triethylamine) (25.90 mL, 185.00 mmol), and continue magnetic stirring for approximately [time missing]. After 10 minutes, BiBB (α-bromoisobutyryl bromide, 15.55 mL, 123.30 mmol) dissolved in 50 mL of DMF was added dropwise. The entire process was carried out under ice bath protection. After the addition was completed, the mixture was placed in an oil bath at 70 °C and reacted for 24 h. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 15 min and washed repeatedly with acetone, dichloromethane, anhydrous ethanol and water until the supernatant was colorless. The supernatant was then dispersed in water and freeze-dried to obtain bromochidine nanocrystals (ChNCs-Br).

[0047] Steps 1-2: Weigh vanillin (30.40 g, 200.00 mmol) into a 1000 mL three-necked flask, add 500 mL of dichloromethane as solvent, and dissolve 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 under ice bath conditions, add methacryloyl chloride (29.00 mL, 200.00 mmol) dissolved in 50 mL of dichloromethane dropwise. After the addition is complete, reflux at 38 °C for 3 h. 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).

[0048] Steps 1-3: 300 mg of bromochitin 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. Next, copper bromide (CuBr2) (20.1 mg, 0.089 mmol), N,N,N',N',N'-pentamethyldiethylenetriamine (PMDETA) (188 μL, 0.89 mmol), and 2-bromoisobutylene oxide (2-bromoisobutylene oxide) were added sequentially. Ethyl acetate (EBiB) (133 μL, 0.89 mmol) and reducing agent ascorbic acid (AsAc) (0.16 mg, 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 ChNCs-PVMA.

[0049] Step 2: First, 800 mg of aldehyde-functionalized chitin nanocrystals were placed in 400 mL of deionized water and stirred at room temperature for 1 h. Then, 32 mL of 4 mol / L silver nitrate aqueous solution prepared on-site was added dropwise while stirring. Stirring was continued at room temperature for 2 h. After the mixture was homogeneous, the suspension was transferred to a 70 °C oil bath and reacted for 8 h. After the reaction was completed, the mixture was repeatedly centrifuged and washed with deionized water. Finally, it was freeze-dried to obtain the modified chitin nanocrystal-silver nanocrystal antibacterial hybrid material, which was named ChNCs-PVMA@Ag.

[0050] Step 3: Dissolve 3g of polylactic acid in 100g of chloroform at 40℃. Pour 30g of the solution into a flat-bottomed glass petri dish with a diameter of 150mm and place it on a flat experimental table for 12 hours. After the solvent evaporates and the film solidifies, transfer it to a 70℃ oven and continue drying for 12 hours to ensure that the chloroform is completely removed. Finally, a pure PLA film is obtained.

[0051] Embodiment 2 of the present invention:

[0052] Other conditions remain unchanged. Step 3 of Example 1 is replaced as follows: First, 3g of polylactic acid is dissolved in 80g of chloroform at 40°C and set aside. Then, 150mg of ChNCs is sonicated for 30min under ice bath protection to disperse it in 20g of chloroform. Subsequently, the dispersion is added dropwise to the polylactic acid solution under stirring. After the addition is complete, the mixture is sonicated again under ice bath protection for 30min. Then, 30g of the mixture is poured into a flat-bottomed glass petri dish with a diameter of 150mm and placed on a flat experimental table for 12h. After the solvent evaporates and the mixture solidifies, it is transferred to a 70°C oven to continue drying for 12h to ensure that the chloroform is completely removed, thus obtaining a polylactic acid film modified with chitin nanocrystals.

[0053] Embodiment 3 of the present invention:

[0054] Compared to Example 2, all other conditions remained unchanged. The 150 mg ChNCs in Example 2 were replaced with 150 mg aldehyde-functionalized chitosan nanocrystals ChNCs-PVMA.

[0055] Embodiment 4 of the present invention:

[0056] Compared to Example 2, all other conditions remained unchanged. The 150 mg ChNCs in Example 2 were replaced with 30 mg of modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material ChNCs-PVMA@Ag.

[0057] Embodiment 5 of the present invention:

[0058] Compared to Example 2, all other conditions remained unchanged. The 150 mg ChNCs in Example 2 were replaced with 90 mg of modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material ChNCs-PVMA@Ag.

[0059] Embodiment 6 of the present invention:

[0060] Compared to Example 2, all other conditions remained unchanged. The 150 mg ChNCs in Example 2 were replaced with 150 mg of modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material ChNCs-PVMA@Ag.

[0061] Embodiment 7 of the present invention:

[0062] Compared to Example 2, all other conditions remained unchanged. The 150 mg ChNCs in Example 2 were replaced with 210 mg of modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material ChNCs-PVMA@Ag.

[0063] Embodiment 8 of the present invention:

[0064] Aldehyde-functionalized chitin nanocrystals were ultrasonically dispersed in water, and then freshly prepared silver nitrate aqueous solution was added under stirring. After mixing evenly, the suspension was transferred to an oil bath at 25°C and reacted for 8 hours. After the reaction was completed, the mixture was repeatedly washed with water by centrifugation and then freeze-dried to obtain the modified chitin nanocrystal-silver nanobacterial hybrid material.

[0065] In the reaction system, the concentration of aldehyde-functionalized chitin nanocrystals is 1 g / L, and the concentration of silver nitrate solution is 1 g / L; wherein the molar concentration of silver nitrate in the silver nitrate solution is 3 mol / L.

[0066] Embodiment 9 of the present invention:

[0067] Aldehyde-functionalized chitin nanocrystals were ultrasonically dispersed in water, and then freshly prepared silver nitrate aqueous solution was added under stirring. After mixing evenly, the suspension was transferred to an oil bath at 70°C and reacted for 2 hours. After the reaction was completed, the mixture was repeatedly washed with water by centrifugation and then freeze-dried to obtain the modified chitin nanocrystal-silver nanobacterial hybrid material.

[0068] In the reaction system, the concentration of aldehyde-functionalized chitin nanocrystals is 50 g / L, and the concentration of silver nitrate solution is 10 g / L; wherein the molar concentration of silver nitrate in the silver nitrate solution is 5 mol / L.

[0069] Embodiment 10 of the present invention:

[0070] Chitosan nanocrystals were dispersed in an organic solvent under ice bath ultrasonic conditions to form a dispersed chitosan nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added with stirring, followed by an organic solvent 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, a molar ratio of chitosan nanocrystals to α-bromoisobutyryl bromide of 1:5, a molar ratio of 4-dimethylaminopyridine to α-bromoisobutyryl bromide of 1:1, and a molar ratio of triethylamine to α-bromoisobutyryl bromide of 1:1.

[0071] Using lignin-based aromatic aldehydes as raw materials, the solutions were dissolved in an organic solvent, and pyridine, an acid-binding agent, was added. A mixed solution of acryloyl chloride and organic solvent was added under ice bath conditions, and the mixture was refluxed for 1 hour. After the reaction, insoluble matter was removed by filtration, 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.

[0072] 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). 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-ARGETATR. P polymerization was carried out under nitrogen protection during the reaction process. 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 0.05 g / L, and the mass molar ratio of bromine-containing chitin nanocrystals, lignin-based aromatic aldehyde monomers, catalysts, ligands, sacrificial initiators and reducing agents was 300 mg: 30 mmol: 0.05 mmol: 0.5 mmol: 0.5 mmol: 0.5 mmol.

[0073] Embodiment 11 of the present invention:

[0074] Chitosan nanocrystals were dispersed in an organic solvent under ice bath ultrasonic conditions to form a dispersed chitosan nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine were added with stirring, followed by an organic solvent 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.

[0075] Using lignin-based aromatic aldehydes as raw materials, the solutions were dissolved in an organic solvent, and pyridine, an acid-binding agent, was added. A mixture of methacryloyl chloride and organic solvent was added under ice bath conditions, and the mixture was refluxed for 5 hours. After the reaction, insoluble matter was removed by filtration, 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.

[0076] 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). 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-ARGETATRP 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. The mass concentration of the bromine-containing chitin nanocrystals in the reaction system was 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 300 mg: 200 mmol: 0.2 mmol: 2 mmol: 2 mmol: 2 mmol.

[0077] 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. Preparation of a modified chitosan nanocrystal-silver nanoparticle antibacterial hybrid material, characterized in that: The preparation method is as follows: (1) Chitin nanocrystals are dispersed in an organic solvent under ice bath ultrasonic conditions to form a dispersed chitin nanocrystal suspension. Then, 4-dimethylaminopyridine and triethylamine are added under stirring, followed by an organic solvent mixture of α-bromoisobutyryl bromide. The mixture is then reacted at 25-70℃ for 3-24 hours under stirring conditions. The resulting suspension is centrifuged to obtain a crude product. The crude product is 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 is 1-50 g / L, and the molar ratio of chitin nanocrystals to α-bromoisobutyryl bromide is 1:5-1:

20. The reaction molar ratio with α-bromoisobutyryl bromide is 1:1-5:1; the reaction molar ratio of triethylamine with α-bromoisobutyryl bromide is 1:1-5:1; (2) using lignin-based aromatic aldehydes as raw materials, and methacryloyl chloride or acryloyl chloride through acylation reaction to construct lignin-based aromatic aldehyde monomers containing double bonds; (3) mixing bromine-containing chitin nanocrystals and lignin-based aromatic aldehyde monomers containing double bonds, and growing polymers on bromine-containing chitin nanocrystals by SI-ARGETATRP to obtain aldehyde-functionalized chitin nanocrystals; (4) ultrasonically dispersing aldehyde-functionalized chitin nanocrystals in water, and then adding freshly prepared silver ion solution under stirring, mixing evenly, and then transferring the suspension to an oil bath at 25-70℃ for reaction for 2-8 hours. After the reaction, the material was repeatedly washed by centrifugation with water and freeze-dried to obtain modified chitin nanocrystal-silver nano-antibacterial hybrid material. In the reaction system, the concentration of aldehyde-functionalized chitin nanocrystals was 1-50 g / L, and the concentration of silver nitrate solution was 1-10 g / L. In the silver nitrate solution, the molar concentration of silver nitrate was 3-5 mol / L. The method of 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 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 reducing agent were added in sequence. Ascorbic acid was added and 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. 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 bromochitin nanocrystals was 0.05-5 g / L, and the molar ratio of bromochitin nanocrystals, lignin-based aromatic aldehyde monomers, catalyst, ligand, sacrificial initiator, and reducing agent was 300 mg: 30-200 mmol: 0.05-0.2 mmol: 0.5-2 mmol: 0.5-2 mmol: 0.5-2mmol。.

2. The preparation of the modified chitin nanocrystal-silver nanoparticle antibacterial hybrid material according to claim 1, characterized in that, The specific method of step (2) is as follows: using lignin-based aromatic aldehyde as raw material, dissolving it in an organic solvent, adding pyridine as an acid-binding agent, adding a mixed solution of methacryloyl chloride or acryloyl chloride in an ice bath, and refluxing for 1-5 hours; after the reaction, filtering to remove insoluble matter, rotary evaporating to remove dichloromethane, adding ethyl acetate, and then washing with saturated NaCl aqueous solution, saturated NaHCO3 aqueous solution and deionized water 3-5 times each; then drying the organic layer with anhydrous sodium sulfate for 10-15 hours, finally filtering to remove sodium sulfate, rotary evaporating to remove ethyl acetate, and obtaining an oily, pale yellow liquid crude product; finally recrystallizing the crude product through an ethanol-water system and drying to obtain a lignin-based aromatic aldehyde monomer containing double bonds; wherein, the lignin-based aromatic aldehyde is vanillin, eugenol or p-hydroxybenzaldehyde; the reaction molar ratio of pyridine to lignin-based aromatic aldehyde is 1:1-5:1; the reaction molar ratio of methacryloyl chloride to lignin-based aromatic aldehyde is 1:1-5:

1.

3. A modified chitosan nanocrystal-silver nano-antibacterial hybrid material, characterized in that: Prepared by the method according to any one of claims 1-2.

4. The application of the modified chitin nanocrystal-silver nano-antibacterial hybrid material according to claim 3 in the fields of nanocomposite materials, antibacterial and packaging.

5. A polylactic acid nanocomposite material with antibacterial and reinforcing synergistic effects, characterized in that: It contains the modified chitin nanocrystal-silver nano-antibacterial hybrid material as described in claim 3.

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