A topological cyclodextrin / chitosan composite membrane, its preparation method and application

Abstract

This invention discloses a topologically oriented cyclodextrin / chitosan composite membrane, its preparation method, and its applications, belonging to the field of bio-based nanomaterials technology. Using α-cyclodextrin and polyethylene glycol (PEG) as raw materials, this invention prepares topologically oriented cyclodextrin-PEG "ring-slippery" nanoparticles (TNPs). TNPs, as green and biodegradable nanoparticles, fill the chitosan network matrix, enhancing hydrogen bonding interactions with chitosan molecules and improving the mechanical properties of the chitosan membrane. This method not only uses simple raw materials and is easy to implement, but also effectively improves the mechanical strength of the chitosan composite membrane, effectively overcoming the problem of poor mechanical strength in existing chitosan composite membranes, and providing a simple and effective approach for practical production.

Description

Technical Field

[0001] This invention relates to the field of bio-based nanomaterials technology, specifically to a topological cyclodextrin / chitosan composite membrane, its preparation method, and its application. Background Technology

[0002] In recent years, plastic pollution has caused irreversible damage to soil and water sources. Developing new environmentally friendly biodegradable packaging is an important direction for the future development of food packaging.

[0003] Currently, most commonly used food packaging materials are PE materials synthesized from polyethylene, which are plastic products. These packaging materials not only easily cause secondary environmental pollution but also pose a certain threat to human health. Therefore, developing a green, safe, and biodegradable food preservation packaging material to replace plastic packaging is urgently needed.

[0004] Chitosan is a natural bioactive polymer widely distributed in nature, possessing excellent biocompatibility, biodegradability, and antibacterial activity. Its outstanding film-forming properties make it one of the most popular biodegradable materials; however, pure chitosan films have poor water resistance, and their mechanical properties decrease upon contact with water, greatly limiting their practical applications. Furthermore, pure chitosan films also suffer from insufficient mechanical properties and limited antibacterial activity.

[0005] To address the shortcomings of these chitosan films, current research mainly focuses on developing nanoparticles to enhance the mechanical properties of chitosan films. For example, metal nanoparticles and metal oxide nanoparticles are commonly used additives in bioactive packaging systems, but they have poor biocompatibility, are non-degradable, and have potential biotoxicity.

[0006] Cyclodextrins (CDs) are a class of cyclic oligosaccharides prepared by enzymatic hydrolysis of starch. Their unique hydrophobic cavities can act as host molecules to capture hydrophobic guest molecules, and the host-guest interaction has attracted widespread attention in the design of supramolecular cross-linking agents.

[0007] Chinese patent CN107474295A discloses a method for preparing a β-cyclodextrin-chitosan composite material. Specifically, it involves dissolving β-cyclodextrin, citric acid, and PEG-400 in water to form solution A; adding a catalyst to solution A to form a β-cyclodextrin polymer; and then adding the β-cyclodextrin polymer to a chitosan aqueous solution to prepare the β-cyclodextrin-chitosan composite material. Chinese patent CN105384973B discloses a modified β-cyclodextrin / chitosan composite and its preparation and application. Specifically, it involves using β-cyclodextrin, a modifier, a catalyst, and a crosslinking agent to prepare an intermediate product, which is then added to a chitosan solution. Under the action of a catalyst, the modified β-cyclodextrin / chitosan composite is obtained. Although both methods utilize β-cyclodextrin to enhance the tensile and tear resistance of chitosan, the preparation process requires the use of crosslinking agents and catalysts, making the process cumbersome. Furthermore, the improvement in the mechanical properties of the chitosan composite film is limited, and it still cannot meet the requirements. Summary of the Invention

[0008] [Technical Issues]

[0009] Existing chitosan composite membrane preparation processes are complex, and the tensile strength and elongation at break properties of chitosan composite membranes are poor, failing to meet the requirements.

[0010] [Technical Solution]

[0011] To address the shortcomings and deficiencies of existing technologies, this invention provides a topological cyclodextrin / chitosan composite membrane, its preparation method, and its application. The preparation of this topological cyclodextrin / chitosan composite membrane involves developing elastic cyclodextrin nanoparticles with a topological structure using α-cyclodextrin and polyethylene glycol (molecular weight 600-8000) as raw materials. These nanoparticles are then added to chitosan to prepare a high-strength chitosan composite membrane. This method not only uses simple raw materials and is easy to implement, but also effectively improves the mechanical strength of the chitosan composite membrane, effectively overcoming the problem of poor mechanical strength in existing chitosan composite membranes, and providing a simple and effective approach for practical production.

[0012] The first objective of this invention is to provide a method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0013] (1) Dissolve α-cyclodextrin in water by heating, add polyethylene glycol and stir, let stand to form a precipitate, filter and dry to obtain α-cyclodextrin-polyethylene glycol nanoparticles (TNPs);

[0014] (2) Dissolve chitosan, add glycerol and the α-cyclodextrin-polyethylene glycol nanoparticles prepared in step (1), stir to dissolve, and obtain a mixed membrane solution;

[0015] (3) The mixed membrane solution obtained in step (2) is used to prepare a membrane by casting to obtain a topological cyclodextrin / chitosan composite membrane.

[0016] In one embodiment, the heating temperature in step (1) is 40 to 70°C.

[0017] In one embodiment, the heating temperature in step (1) is 60-70°C.

[0018] In one embodiment, the dissolving of α-cyclodextrin in step (1) refers to dissolving α-cyclodextrin in water to form an α-cyclodextrin aqueous solution; wherein the solid-liquid ratio of α-cyclodextrin to water is 1-5:10-20, g / ml; preferably 1:10, g / ml.

[0019] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 600 to 8000.

[0020] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 800 to 6000.

[0021] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 1000 to 2000.

[0022] In one embodiment, the polyethylene glycol PEG in step (1) is PEG1000.

[0023] In one embodiment, the mass ratio of polyethylene glycol to α-cyclodextrin in step (1) is 1-5:2-3.

[0024] In one embodiment, the mass ratio of polyethylene glycol to α-cyclodextrin in step (1) is 1:1.

[0025] In one embodiment, the stirring time in step (1) is 2 to 6 hours.

[0026] In one embodiment, the stirring time in step (1) is 2 to 4 hours.

[0027] In one embodiment, the filtration in step (1) is performed using a vacuum pump to obtain precipitate.

[0028] In one embodiment, the drying conditions in step (1) are: a temperature of 40 to 60°C, and drying to a constant weight.

[0029] In one embodiment, the chitosan dissolution in step (2) refers to dissolving chitosan in an acetic acid solution to form a chitosan solution; wherein the mass concentration of chitosan in the chitosan solution is 1 wt% to 3 wt%.

[0030] In one embodiment, the acetic acid solution is an aqueous solution of acetic acid with a mass concentration of 1-5%.

[0031] In one embodiment, the chitosan is dissolved in the acetic acid solution by stirring at a stirring speed of 400-800 r / min for 4-8 hours at a temperature of 40-60°C.

[0032] In one embodiment, the chitosan is dissolved in the acetic acid solution by stirring at 600 r / min for 4 hours at 40°C.

[0033] In one embodiment, the mass of glycerol in step (2) is 3% to 5% of the mass of the chitosan solution.

[0034] In one embodiment, the mass of glycerol in step (2) is 3% of the mass of the chitosan solution.

[0035] In one embodiment, the mass of the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) in step (2) is 0.2%-0.8% of the mass of the chitosan solution.

[0036] In one embodiment, the mass of the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) in step (2) is 0.6% of the mass of the chitosan solution.

[0037] In one embodiment, the mass ratio of chitosan to α-cyclodextrin-polyethylene glycol nanoparticles in step (2) is 1:0.2 to 0.8.

[0038] In one embodiment, the mass ratio of chitosan to α-cyclodextrin-polyethylene glycol nanoparticles in step (2) is 1:0.2 to 0.6; preferably 1:0.6.

[0039] In one embodiment, the stirring speed in step (2) is 200-600 r / min, and the time is 2-4 hours.

[0040] In one embodiment, the casting method in step (3) specifically involves removing air bubbles from the mixed film liquid obtained in step (2), then pouring it evenly onto a flat plate, drying it, and balancing it.

[0041] In one embodiment, the air bubble removal is specifically performed using a vacuum.

[0042] In one embodiment, the amount of the mixed membrane solution used is 1–3 mL / cm². 2 .

[0043] In one embodiment, the plate is a polystyrene petri dish.

[0044] In one embodiment, the drying temperature is 40°C to 50°C, and the drying time is 2 to 3 hours.

[0045] In one embodiment, the equilibration conditions are a humidity of 50% to 60% for a period of 2 to 3 days.

[0046] A second objective of this invention is to provide a topological cyclodextrin / chitosan composite membrane prepared by the method described above.

[0047] The third objective of this invention is to provide an application of the aforementioned topological cyclodextrin / chitosan composite film in the preparation of packaging materials, fruit and vegetable preservation, and medical materials.

[0048] The fourth objective of this invention is to provide a packaging material prepared using the aforementioned topological cyclodextrin / chitosan composite film.

[0049] The fifth objective of this invention is to provide a medical composite membrane material, which is prepared using the aforementioned topological cyclodextrin / chitosan composite membrane.

[0050] The sixth objective of this invention is to provide a method for enhancing the mechanical properties of chitosan membranes based on topological cyclodextrin nanoparticles, the method comprising the following steps:

[0051] (1) Dissolve α-cyclodextrin in water by heating, add polyethylene glycol and stir, let stand to form a precipitate, filter and dry to obtain α-cyclodextrin-polyethylene glycol nanoparticles (TNPs);

[0052] (2) Dissolve chitosan, add glycerol and the α-cyclodextrin-polyethylene glycol nanoparticles prepared in step (1), stir to dissolve, and obtain a mixed membrane solution;

[0053] (3) The mixed membrane solution obtained in step (2) is used to obtain a topological cyclodextrin / chitosan composite membrane by casting.

[0054] In one embodiment, the heating temperature in step (1) is 40 to 70°C.

[0055] In one embodiment, the heating temperature in step (1) is 60-70°C.

[0056] In one embodiment, the dissolving of α-cyclodextrin in step (1) refers to dissolving α-cyclodextrin in water to form an α-cyclodextrin aqueous solution; wherein the solid-liquid ratio of α-cyclodextrin to water is 1-5:10-20, g / ml; preferably 1:10, g / ml.

[0057] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 600 to 8000.

[0058] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 800 to 6000.

[0059] In one embodiment, the polyethylene glycol (PEG) in step (1) has a molecular weight of 1000 to 2000.

[0060] In one embodiment, the polyethylene glycol PEG in step (1) is PEG1000.

[0061] In one embodiment, the mass ratio of polyethylene glycol to α-cyclodextrin in step (1) is 1-5:2-3.

[0062] In one embodiment, the mass ratio of polyethylene glycol to α-cyclodextrin in step (1) is 1:1.

[0063] In one embodiment, the stirring time in step (1) is 2 to 6 hours.

[0064] In one embodiment, the stirring time in step (1) is 2 to 4 hours.

[0065] In one embodiment, the filtration in step (1) is performed using a vacuum pump to obtain precipitate.

[0066] In one embodiment, the drying conditions in step (1) are: a temperature of 40 to 60°C, and drying to a constant weight.

[0067] In one embodiment, the chitosan dissolution in step (2) refers to dissolving chitosan in an acetic acid solution to form a chitosan solution; wherein the mass concentration of chitosan in the chitosan solution is 1 wt% to 3 wt%.

[0068] In one embodiment, the acetic acid solution is an aqueous solution of acetic acid with a mass concentration of 1-5%.

[0069] In one embodiment, the chitosan is dissolved in the acetic acid solution by stirring at a stirring speed of 400-800 r / min for 4-8 hours at a temperature of 40-60°C.

[0070] In one embodiment, the chitosan is dissolved in the acetic acid solution by stirring at 600 r / min for 4 hours at 40°C.

[0071] In one embodiment, the mass of glycerol in step (2) is 3% to 5% of the mass of the chitosan solution.

[0072] In one embodiment, the mass of glycerol in step (2) is 3% of the mass of the chitosan solution.

[0073] In one embodiment, the mass of the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) in step (2) is 0.2%-0.8% of the mass of the chitosan solution.

[0074] In one embodiment, the mass of the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) in step (2) is 0.6% of the mass of the chitosan solution.

[0075] In one embodiment, the mass ratio of chitosan to α-cyclodextrin-polyethylene glycol nanoparticles in step (2) is 1:0.2 to 0.8.

[0076] In one embodiment, the mass ratio of chitosan to α-cyclodextrin-polyethylene glycol nanoparticles in step (2) is 1:0.2 to 0.6; preferably 1:0.6.

[0077] In one embodiment, the stirring speed in step (2) is 200-600 r / min, and the time is 2-4 hours.

[0078] In one embodiment, the casting method in step (3) specifically involves removing air bubbles from the mixed film liquid obtained in step (2), then pouring it evenly onto a flat plate, drying it, and balancing it.

[0079] In one embodiment, the air bubble removal is specifically performed using a vacuum.

[0080] In one embodiment, the amount of the mixed membrane solution used is 1–3 mL / cm². 2 .

[0081] In one embodiment, the plate is a polystyrene petri dish.

[0082] In one embodiment, the drying temperature is 40°C to 50°C, and the drying time is 2 to 3 hours.

[0083] In one embodiment, the equilibration conditions are a humidity of 50% to 60% for a period of 2 to 3 days.

[0084] The beneficial effects of this invention are:

[0085] (1) This invention uses α-cyclodextrin and polyethylene glycol (PEG) as raw materials to prepare cyclodextrin-PEG "ring-slip" nanoparticles (TNPs) with a topological structure. TNPs, as a green and biodegradable nanoparticle, fill the chitosan network matrix, enhance the hydrogen bond interaction with chitosan molecules, and improve the mechanical properties of the chitosan membrane. Compared with ordinary chitosan membranes, this composite membrane has stronger tensile strength and elongation at break. Compared with chitosan composite membranes formed with β-cyclodextrin as raw material, the mechanical properties are also significantly improved, such as the tensile strength is increased by more than 160% and the elongation at break is increased by 21.6%. This shows that α-cyclodextrin and PEG can assemble to form "ring-slip" nanoparticles with a topological structure, which is more conducive to enhancing the mechanical properties of chitosan composite membranes.

[0086] (2) In this invention, polyethylene glycol (PEG) acts as a plasticizer, which can enhance the flexibility of the chitosan composite film. In addition, PEG can pass through the cavity of α-cyclodextrin and form stable inclusion complexes (TNPs) with α-cyclodextrin molecules. TNPs generate stronger hydrogen bond interactions with chitosan molecules, thereby improving the mechanical properties of the chitosan composite film. In particular, the improvement of the mechanical properties of the chitosan composite film is more prominent when the molecular weight of PEG is in the range of 600 to 8000.

[0087] (3) The preparation method of the topological cyclodextrin / chitosan composite membrane of the present invention is not only simple in terms of raw materials and easy to operate, but also can effectively improve the mechanical strength of the chitosan composite membrane, effectively making up for the problem of poor mechanical strength of chitosan composite membrane in the prior art, and providing a simple and effective way for actual production. Detailed Implementation

[0088] The present invention will now be described in detail with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0089] 1. Determination of the mechanical properties of chitosan composite membranes

[0090] The mechanical strength tests in this experiment included tensile strength and elongation at break. Chitosan composite membrane samples were prepared into strips measuring 20 mm × 60 mm, and their mechanical properties were measured using a texture analyzer. The initial speed was 1.0 mm / s, the measurement speed was 1.0 mm / s, and the post-measurement speed was 1.0 mm / s. The initial distance was 30 mm. The tensile strength and elongation at break of the membrane were calculated as follows:

[0091] Tensile strength:

[0092] Elongation at break:

[0093] Where F is the maximum tensile force of the membrane (N), d represents the membrane thickness (mm), h represents the membrane width (mm), L represents the displacement when the membrane breaks (mm), and L0 represents the initial length of the membrane (mm).

[0094] Example 1

[0095] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0096] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 1000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-1000.

[0097] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0098] (3) Add 0.3g of glycerol and 0.2g of α-TNPs-1000 (mass concentration of 0.2%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0099] Example 2

[0100] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0101] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 1000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-1000.

[0102] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0103] (3) Add 0.3g of glycerol and 0.4g of α-TNPs-1000 (mass concentration of 0.4%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0104] Example 3

[0105] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0106] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 1000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-1000.

[0107] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0108] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-1000 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0109] Example 4

[0110] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0111] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 1000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-1000.

[0112] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0113] (3) Add 0.3g of glycerol and 0.8g of α-TNPs-1000 (mass concentration of 0.8%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0114] Example 5

[0115] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0116] (1) At 65°C, 10g of α-cyclodextrin was dissolved in 100mL of water and 10g of PEG (molecular weight 600) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40°C to constant weight to obtain α-TNPs-600.

[0117] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0118] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-600 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0119] Example 6

[0120] A method for preparing a topological cyclodextrin / chitosan composite membrane, the method comprising the following steps:

[0121] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 800) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-800.

[0122] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0123] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-800 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness in the petri dish, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0124] Example 7

[0125] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 2000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-2000.

[0126] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0127] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-2000 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, chitosan nanocomposite membrane is obtained.

[0128] Example 8

[0129] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 6000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-6000.

[0130] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0131] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-6000 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure that the solution thickness in the petri dish is uniform, and place it in a drying oven at a drying temperature of 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a chitosan nanocomposite membrane is obtained.

[0132] Example 9

[0133] (1) At 65°C, 10g of α-cyclodextrin was dissolved in 100mL of water and 10g of PEG (molecular weight 8000) was added. The mixture was stirred for 2 hours, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40°C to constant weight to obtain α-TNPs-8000.

[0134] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0135] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-8000 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure that the solution thickness in the petri dish is uniform, and place it in a drying oven at a drying temperature of 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a chitosan nanocomposite membrane is obtained.

[0136] Comparative Example 1

[0137] A method for preparing a chitosan membrane includes the following:

[0138] 1 g of chitosan was dispersed in 100 mL of 1% acetic acid solution and stirred at 600 r / min for 4 h at 40 °C until completely dissolved. 0.3 g of glycerol was added and the mixture was stirred at 400 r / min for 2 h to obtain a chitosan membrane solution. The chitosan membrane solution was degassed under vacuum for 30 min. The degassed membrane solution was then poured evenly onto a polystyrene petri dish (10 mm × 10 mm) with a volume of 20 mL. The petri dish was leveled to ensure a uniform solution thickness and placed in a drying oven at 40 °C for 24 h. After drying, the petri dish was placed in an equilibrator at 53% humidity for 2 days to equilibrate. The membrane was then peeled off to obtain a pure chitosan membrane.

[0139] Comparative Example 2

[0140] (1) At 65℃, 10g of β-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 1000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain β-TNPs.

[0141] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0142] (3) Add 0.3g of glycerol and 0.6g of β-TNPs (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure that the solution thickness in the petri dish is uniform, and place it in a drying oven at a drying temperature of 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a chitosan nanocomposite membrane is obtained.

[0143] Comparative Example 3

[0144] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 400) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-400.

[0145] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0146] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-400 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a topological cyclodextrin / chitosan composite membrane is obtained.

[0147] Comparative Example 4

[0148] (1) At 65℃, 10g of α-cyclodextrin was dissolved in 100mL of water, and 10g of PEG (molecular weight 10000) was added. The mixture was stirred for 2h, allowed to stand and precipitate, and the precipitate was vacuum filtered and then vacuum dried at 40℃ to constant weight to obtain α-TNPs-10000.

[0149] (2) Disperse 1g of chitosan in 100mL of 1% acetic acid solution and stir at 600r / min for 4h at 40℃ until completely dissolved to obtain chitosan solution.

[0150] (3) Add 0.3g of glycerol and 0.6g of α-TNPs-10000 (mass concentration of 0.6%) prepared in step (1) to the chitosan solution prepared in step (2), and stir at 400r / min for 2h to obtain a chitosan nanoparticle mixed membrane solution; degas the mixed membrane solution under vacuum for 30min, and pour the degassed mixed membrane solution evenly onto a polystyrene petri dish (10mm×10mm) with a pouring volume of 20mL. Place the petri dish flat to ensure uniform solution thickness, and dry it in a drying oven at 40℃ for 24h. After drying, take it out and place it in a balancer with 53% humidity for 2d to balance. After peeling off the membrane, a chitosan nanocomposite membrane is obtained.

[0151] Results Measurement

[0152] 1. The mechanical properties of the topological cyclodextrin / chitosan composite membranes prepared in Examples 1-4 and the pure chitosan composite membrane prepared in Comparative Example 1 were measured, and the results are shown in Table 1:

[0153] Table 1. Mechanical strength of Examples 1-4 and Comparative Example 1

[0154] Tensile strength (MPa) Elongation at break (%) Example 1 23.36±0.14 49.23±0.105 Example 2 26.46±0.12 61.6±1.13 Example 3 32.54±0.42 68.39±0.1 Example 4 29.36±0.28 75.06±0.75 Comparative Example 1 7.33±0.05 34.5±1.04

[0155] As shown in Table 1, the tensile properties and elongation at break of the topological cyclodextrin / chitosan composite membranes prepared in Examples 1-4 were significantly higher than those in Comparative Example 1. The pure chitosan membrane prepared in Comparative Example 1 had insufficient mechanical properties, with a tensile strength of only 7.33 MPa. Among them, the tensile strength of the topological cyclodextrin / chitosan composite membrane prepared in Example 3 was as high as 32.54 MPa, which was 4.4 times higher than that in Comparative Example 1. This indicates that the embedding of α-cyclodextrin nanoparticles can effectively improve the mechanical properties of chitosan membranes, which is due to the hydrogen bond interaction between chitosan and α-cyclodextrin.

[0156] 2. The mechanical properties of the topological cyclodextrin / chitosan composite membranes prepared in Examples 3 and 5-9, as well as Comparative Examples 3 and 4, were measured. The results are shown in Table 2.

[0157] Table 2. Mechanical strength of Examples 3, 5-9 and Comparative Examples 3 and 4

[0158] Tensile strength (MPa) Elongation at break (%) Example 5 (PEG600) 30.52±0.10 40.38±0.08 Example 6 (PEG800) 31.63±0.16 50.89±0.67 Example 3 (PEG1000) 32.54±0.42 68.39±0.1 Example 7 (PEG 2000) 30.33±0.10 60.46±0.22 Example 8 (PEG6000) 28.56±0.11 50.47±0.18 Example 9 (PEG8000) 25.37±0.41 45.36±0.15 Comparative Example 3 (PEG400) 28.55±0.06 35.40±0.55 Comparative Example 4 (PEG10000) 23.51±0.51 40.42±0.08

[0159] As shown in Table 2, the molecular weight of PEG has a significant impact on the elongation at break and tensile strength of the chitosan membrane. With increasing PEG molecular weight, the PEG chains lengthen, and the degree of chain tortuosity and cross-linking increases. Simultaneously, the chain lengthening leads to an increase in the number of α-cyclodextrin molecules penetrating the membrane, thereby increasing the degree of cross-linking between molecular chains, enhancing membrane flexibility, and improving tensile strength and elongation at break. When the PEG molecular weight reaches 1000–2000, the elongation at break of the formed chitosan composite membrane can reach 68.39%, and the tensile strength can reach 32.54. However, when the PEG molecular weight is too large, the tensile strength and elongation at break of the chitosan membrane also decrease significantly. This may be because an excessively large molecular weight can disrupt the ordered structure of the membrane, leading to a decline in the mechanical properties of the chitosan membrane.

[0160] 3. The mechanical properties of the composite membranes prepared in Example 3 and Comparative Example 2 were measured, and the results are shown in Table 3:

[0161] Table 3. Mechanical strength of Example 3 and Comparative Example 2

[0162] Tensile strength (MPa) Elongation at break (%) Example 3 32.54±0.42 49.23±0.10 Comparative Example 2 12.48±0.16 40.47±0.26

[0163] As shown in Table 3, different types of cyclodextrin and PEG-1000 form nanoparticles with a significant impact on the tensile strength of chitosan membranes. The tensile strength of the composite membrane prepared in Example 3 is significantly higher than that of Comparative Example 2, exceeding it by 160.74%. This indicates that α-cyclodextrin and PEG can assemble into topologically structured "ring-slip" nanoparticles, which is more conducive to enhancing the mechanical properties of chitosan composite membranes.

Claims

1. A method for preparing a topologically typed cyclodextrin / chitosan composite membrane, characterized in that, The method includes the following steps: (1) Dissolve α-cyclodextrin in water by heating, add polyethylene glycol and stir, let stand to form a precipitate, filter and dry to obtain α-cyclodextrin-polyethylene glycol nanoparticles (TNPs); The polyethylene glycol (PEG) has a molecular weight of 1000-2000; the mass ratio of polyethylene glycol to α-cyclodextrin is 1:

1. (2) Dissolve chitosan, add glycerol and the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) prepared in step (1), stir to dissolve, and obtain a mixed membrane solution; The mass of the α-cyclodextrin-polyethylene glycol nanoparticles (TNPs) is 0.6% of the mass of the chitosan solution; the mass ratio of chitosan to α-cyclodextrin-polyethylene glycol nanoparticles is 1:0.2~0.

6. (3) The mixed membrane solution obtained in step (2) is used to prepare a membrane by casting to obtain a topological cyclodextrin / chitosan composite membrane.

2. The method according to claim 1, characterized in that, The heating temperature in step (1) is 40~70℃.

3. The method according to claim 1, characterized in that, The dissolution of α-cyclodextrin in step (1) refers to dissolving α-cyclodextrin in water to form an α-cyclodextrin aqueous solution; wherein the solid-liquid ratio of α-cyclodextrin to water is 1~5:10~20, g / ml.

4. The method according to claim 1, characterized in that, The stirring time in step (1) is 2 to 6 hours.

5. The method according to claim 1, characterized in that, The filtration in step (1) is performed using a vacuum pump to obtain precipitate.

6. The method according to claim 1, characterized in that, The drying conditions described in step (1) are: temperature of 40~60℃, and drying to constant weight.

7. The method according to claim 1, characterized in that, The chitosan dissolution in step (2) refers to dissolving chitosan in an acetic acid solution to form a chitosan solution; wherein the mass concentration of chitosan in the chitosan solution is 1 wt%~3 wt%.

8. The method according to claim 7, characterized in that, The acetic acid solution is an aqueous solution of acetic acid with a mass concentration of 1-5%.

9. The method according to claim 7 or 8, characterized in that, The chitosan was dissolved in the acetic acid solution by stirring at a speed of 400-800 r / min for 4-8 hours at a temperature of 40-60°C.

10. The method according to claim 1, characterized in that, The mass of glycerol in step (2) is 3% to 5% of the mass of the chitosan solution.

11. The method according to claim 1, characterized in that, The casting method described in step (3) specifically involves removing air bubbles from the mixed film liquid obtained in step (2), then pouring it evenly onto a flat plate, drying it, and balancing it.

12. A topological cyclodextrin / chitosan composite membrane prepared by the method according to any one of claims 1 to 11.

13. The application of the topological cyclodextrin / chitosan composite film according to claim 12 in the preparation of packaging materials, fruit and vegetable preservation or medical materials.

14. A food packaging material, characterized in that, The food packaging material is prepared using the topological cyclodextrin / chitosan composite film as described in claim 12.

15. A medical composite membrane material, characterized in that, The medical composite membrane material is prepared using the topological cyclodextrin / chitosan composite membrane as described in claim 12.