Preparation method of polyvinyl alcohol-polyethylene glycol hydrogel film with low equilibrium swelling degree and high toughness

Abstract

The present invention discloses a method for preparing a polyvinyl alcohol-polyethylene glycol hydrogel film with low equilibrium swelling and high toughness. The present invention adds PEG to a PVA aqueous solution, mixes the mixture evenly under high temperature and stirring, and then undergoes ultrasonic degassing, cast casting, drying, and swelling treatment in an aqueous solution to obtain a finished product in one step. The prepared hydrogel film exhibits an excellent combination of properties, including adjustable thickness, low swelling, high toughness at swelling equilibrium, uniformity, and excellent acid and alkali stability and biosafety. The preparation process of the method of the present invention is simple and fast, takes a short time (24 h), does not contain toxic reagents, does not require a cross-linking agent, and only uses three substances, all of which are harmless to the human body, green and safe, with low raw material, equipment and storage costs. The film thickness is easy to control (0.2~0.7 mm), is uniform and flat, and can be produced in large quantities on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogel film preparation, and particularly relates to a method for preparing a PVA-PEG hydrogel film with low equilibrium swelling and high toughness. Background Art

[0002] The toughness of traditional hydrogel materials is often inversely proportional to the degree of swelling, making it difficult to simultaneously exhibit excellent toughness in the state of swelling equilibrium. However, hydrogels are often used in liquid environments, and their swelling phenomenon is unavoidable, which changes properties such as toughness and volume. Therefore, the study of low-swelling or non-swelling high-toughness hydrogel technology has important scientific value and practical significance. In many published papers and patents, the prepared hydrogels are mostly three-dimensional, and sheet-like hydrogel films are rare. There are three main reasons: (1) The preparation of most hydrogels requires a mold, but very thin parallel plate molds are not conducive to the gelation process and demolding; (2) The mechanical properties of hydrogels limit the formation of hydrogel films; (3) Many application scenarios require bulk hydrogels, and there is less demand for hydrogel films. However, compared with bulk hydrogels, hydrogel films have unique advantages in certain aspects. For example, because they are thinner, they have better interface adhesion, easier soft deformation, and more sensitive sensing capabilities, which makes them show unique application potential in the fields of flexible biosensors, wearable electronic devices, underwater conductive materials, and drug sustained-release carriers.

[0003] Patent CN108395549A discloses a high-strength, high-toughness, antibacterial polyvinyl alcohol hydrogel and its preparation method. The hydrogel is made from polyvinyl alcohol and tea polyphenols, and is gelled by a cross-linking mechanism that forms microcrystalline regions between PVA molecular chains through multiple freeze-thaw cycles. This method has a long preparation cycle and produces a common hydrogel shape, making it difficult to produce a uniform hydrogel film with thickness ranging from micrometers to millimeters.

[0004] Patent CN118126356A discloses a strong and transparent polyvinyl alcohol composite hydrogel and its preparation method, which is prepared by mixing polyvinyl alcohol aqueous solution and cellulose nanofiber aqueous dispersion in a 60 Cross-linking and gelation under Coγ-ray or electron beam irradiation. This preparation method requires the use of high-energy radiation, which is less common and has safety risks.

[0005] Patent 105885064A discloses a toughened polyvinyl alcohol composite hydrogel and its applications. Liquid A is a PVA and PEG aqueous solution, or a PVA and sodium alginate aqueous solution, and Liquid B is a boron compound aqueous solution. Liquids A and B are sprayed simultaneously in equal volumes onto a surface, resulting in a rapid reaction that coats the surface with a hydrogel. The gelation mechanism of this hydrogel is chemical crosslinking. PEG, as a toughening agent, does not participate in the chemical crosslinking of the boron compound. This rapid crosslinking method after spraying does not guarantee uniform crosslinking.

[0006] Patent CN118515902A discloses a strong and tough composite hydrogel film, its preparation, and application. Using polyvinyl alcohol and montmorillonite as building blocks and a glutaraldehyde / hydrochloric acid solution as a crosslinking agent, the film is prepared through evaporative self-assembly. The gelation mechanism of the hydrogel film in this invention is chemical crosslinking, and the preparation method uses toxic glutaraldehyde and hydrochloric acid, making it generally unsuitable for certain biomedical applications.

[0007] Patent CN104151584B discloses a method for preparing an ultra-thin high-strength hydrogel film and its product. The preparation method first obtains a random copolymer solution A by monomer polymerization, and then drops A onto the surface of a poor solvent B of the random copolymer to obtain an ultra-thin high-strength hydrogel film. The gelation mechanism is the exchange of good solvent and poor solvent. The film has a breaking strength of 15 kPa~300 kPa and a corresponding breaking elongation of 220%~120%. The film thickness obtained by this strategy of laying on the solvent surface is ultra-thin, 10~200 μ The preparation method of this patent is slightly complicated, and the thin water film is too soft and difficult to achieve self-expansion out of water. It is easily damaged by external forces and is not convenient for practical application.

[0008] Patent CN116410501A discloses a method for preparing an ultra-thin, high-strength hydrogel film. The method requires the use of four substances: a film-forming agent, a modifier, an anti-gelling agent, and a pore-forming agent. The prepared sol-gel solution is then applied to a purified and hydroxylated base film, and then dried and soaked to produce an ultra-thin, high-strength hydrogel film. This method does not require large instruments or equipment. In this patent, PVA can be a film-forming agent, and PEG can be a pore-forming agent and an anti-gelling agent. However, a modifier must be added and the base film must be cleaned and hydroxylated. The film thickness is between 20 and 150 mm. μ m, 4 to 6 types of raw materials are used, and there are slightly more steps.

[0009] In conclusion, there is currently a lack of a simple, rapid, and gentle large-scale preparation process that uses biosafe raw materials, as few raw material types as possible, and a moderate thickness (greater than 200 μm, less than 1 mm), which greatly limits the expansion of its application fields and the realization of multifunctionality. Summary of the Invention

[0010] To address the shortcomings of the aforementioned prior art, the present invention provides a method for preparing a PVA-PEG hydrogel film with a low equilibrium swelling ratio and high toughness. The hydrogel film, made from PVA and PEG and formed through a multi-hydrogen bond crosslinking mechanism, exhibits a low equilibrium swelling ratio and high toughness at equilibrium. It is biosafe, has a gentle, simple, and efficient preparation method, and is amenable to large-scale production.

[0011] The present invention uses only three biosafe substances, PVA, PEG and water, as raw materials. Through a multiple hydrogen bond cross-linking mechanism, a hydrogel film with low equilibrium swelling, high toughness and easily controllable thickness is prepared at room temperature to 95°C. The preparation method is gentle, simple and efficient, and can be produced on a large scale. Only a water bath, a common oven and stirring equipment are required, making it easy to industrialize.

[0012] The method for preparing a low equilibrium swelling degree and high toughness PVA-PEG hydrogel film of the present invention comprises the following steps:

[0013] At room temperature, liquid low molecular weight PEG or high molecular weight PEG aqueous solution is added to the PVA aqueous solution, and the mixture is heated at high temperature and stirred to obtain a casting mixture. Ultrasonic degassing and cast are performed. After drying, the film is immersed in a solvent to swell, and a low-swelling and high-toughness PVA-PEG hydrogel film can be obtained.

[0014] The PVA aqueous solution is obtained by dissolving a solid PVA raw material in water at 85-95° C. under stirring. The mass concentration of the PVA aqueous solution is 2-12 wt %.

[0015] The relative molecular mass of the PVA is 60,000 to 200,000.

[0016] The low molecular weight PEG in liquid form at room temperature refers to PEG100, PEG200, PEG400, PEG600, etc. with a relatively small molecular weight, which can be directly added to the PVA aqueous solution or prepared into a PEG aqueous solution before being added to the aqueous solution; the high molecular weight PEG refers to PGE800, PEG1000, PEG2000, PEG4000, PEG6000, PEG8000, PEG10000, etc. that are solid at room temperature, which are prepared into corresponding aqueous solutions and then added to the PVA aqueous solution; the concentration of the PEG aqueous solution is related to its own solubility. PEG with a small molecular weight that is liquid at room temperature can be added directly, and high molecular weight PEG can be prepared into a 1-60 wt% aqueous solution before being added.

[0017] The mass ratio of the solutes PVA and PEG in the hydrogel film is 1:0.5-3.0.

[0018] Furthermore, the high-temperature heating and mixing method involves heating the prepared PVA-PEG aqueous solution between room temperature and 80°C while stirring to fully disrupt localized high-density hydrogen bonds and evenly disperse the PVA and PEG molecular chains. The higher the temperature, the better the mixing effect. However, when adding a low-molecular-weight PEG or its aqueous solution to a low-concentration PVA aqueous solution, stirring at room temperature alone can also be used to produce a uniform membrane.

[0019] The tape casting is to spread the mixed casting mixture in a flat bottom container, and control the amount of the casting mixture to be 0.16~0.56 g / cm 2 The final film thickness can be controlled by adjusting the height of the casting mixture and / or the mass fraction of the PVA and PEG solutes. The low-swelling, high-toughness PVA-PEG hydrogel film produced by the present invention has a thickness of 0.2-0.7 mm.

[0020] The drying can be carried out at room temperature or under heated blast. When drying under heated blast, the temperature is between 25°C and 60°C. The higher the temperature, the shorter the time required to complete the drying. The time required to complete the drying is also related to the mass of the casting solution per unit area.

[0021] The solvent used for the swelling is water.

[0022] The cross-linking mechanism of PVA-PEG hydrogel film of the present invention is the multiple hydrogen bond interactions between PVA and PEG.These two macromolecules only contain C, H, O three kinds of elements, and structural units are consistent, all are-(C2H4O)-.In PVA, O is positioned on the side chain hydroxyl group, and in PEG, O is positioned on the main chain. Such O element distribution makes the widespread hydrogen bond between these two macromolecules anchor each other, is difficult for dissociation, thereby shows as the low affinity to free small molecule water.Just because of this, the equilibrium swelling degree of this kind hydrogel film is low, toughness is high, no biological toxicity, and acid and alkali resistance stability is good.

[0023] The unique crosslinking system of the PVA-PEG polymers of the present invention stems from the similarity in their molecular structures. The key to crosslinking lies in the mass ratio of the two polymers in the casting solution: PVA:PEG = 1:0.5-3, resulting in a high PEG content. When the PVA-PEG hydrogel film is dried, the PEG mass fraction can reach 30-75 wt%. This high PEG ratio is crucial for ensuring that the aqueous solution of PVA and PEG can evaporate and dry at room temperature (drying at high temperatures shortens the film-forming cycle) to form a film. A suitable mass ratio of PVA to PEG ensures the formation of multiple crosslinks, with these crosslinking points anchoring each other, thereby reducing the number of hydrogen bonding sites between the polymers and water.

[0024] The preparation method of the low equilibrium swelling degree and high toughness PVA-PEG hydrogel film of the present invention comprises the following specific steps:

[0025] (1) Prepare a PVA aqueous solution with a mass fraction of 2~12 wt%.

[0026] (2) Adding an aqueous solution of a low molecular weight PEG that is liquid at room temperature or a high molecular weight PEG that is solid at room temperature to the above-mentioned PVA aqueous solution, wherein the concentration of the aqueous solution is 1 to 60 wt%, to obtain a casting mixture.

[0027] (3) The above-mentioned casting mixture is thoroughly mixed under heating and stirring, and the heating temperature is room temperature to 80 °C.

[0028] (4) The mixed casting mixture is degassed by ultrasonic treatment.

[0029] (5) The mixed casting mixture is cast into a flat-bottomed container.

[0030] (6) The film casting mixture cast in the flat-bottom container is dried at room temperature or under heating and blowing. When drying under heating and blowing, the temperature is between 25 and 60 °C to obtain a dry film.

[0031] (7) Soak the dried film in water until it reaches equilibrium swelling, thereby obtaining a low-swelling and high-toughness PVA-PEG hydrogel film.

[0032] The mixing operation is performed during and / or after adding other raw materials or raw material solutions to the polymer aqueous solution, and can be one or more of mechanical stirring, stirring, shaking, ultrasound, and heating.

[0033] The low-swelling, high-toughness PVA-PEG hydrogel films produced in the present invention exhibit low swelling, high toughness at swelling equilibrium, and biosafety. Unless otherwise specified, the PVA-PEG hydrogel films and performance data presented herein are for samples at swelling equilibrium in water, not samples that were dried and then subjected to swelling equilibrium. The PEG used was PEG1000, with a molecular weight of 1000.

[0034] Patent CN118240245A discloses a chitosan-polyvinyl alcohol-tannic acid cross-linked network hydrogel, its preparation method, and applications. Tannic acid, which has multiple phenolic hydroxyl groups, serves as a small molecule crosslinker. The invention aims to produce a bulk-shaped hydrogel material, using a freeze-drying step during the preparation process, which prolongs the material preparation cycle.

[0035] Patent CN115570859B discloses a recyclable, high-strength and tough composite hydrogel. This method involves preparing a composite film through inorganic ion polymerization and self-assembly, followed by directional stretching and layer-by-layer bonding. This invention also aims to produce a high-strength and tough bulk material. The gelation mechanism is ionic crosslinking, resulting in a relatively complex preparation process and a relatively long production cycle.

[0036] Patent CN115850745B discloses a method for preparing a natural polymer hydrogel film, its products, and applications. A dilute acetic acid solution of chondroitin sulfate and chitosan is simultaneously added dropwise to a dilute acetic acid solution to produce a milky suspension. This suspension is then vacuum-dried and soaked to swell to produce a hydrogel film, which can be used as an intrauterine anti-adhesion diaphragm. The gelation mechanism is electrostatic interaction between positive and negative charges. The in vivo degradation period of this sample is 7 to 14 days. The raw materials used in this patent and the gelation mechanism differ from those of the present invention.

[0037] Patent CN108066819B discloses a high-strength natural polymer hydrogel film and its preparation method. It is formed by cross-linking carrageenan and chitosan through ionic and hydrogen bonds. Similarly, the film-forming liquid is poured into a flat-bottomed container, dried, and then immersed in water to swell to swelling equilibrium. The resulting hydrogel film has a maximum elongation at break of no less than 120% and a maximum breaking stress of no less than 6.7 MPa. The casting, drying, and swelling steps of the film in the present invention are consistent with these, but the raw material types are completely different from those in the aforementioned patent. Furthermore, the gelation mechanism of the hydrogel film in the present invention also involves only hydrogen bonding. The resulting hydrogel film has a minimum elongation at break of no less than 350%, and its deformability is somewhat different.

[0038] The low-swelling and high-toughness PVA-PEG hydrogel film prepared by the present invention can be added with other functional substances such as drugs, fertilizers, conductive substances, etc. during the preparation process. The corresponding functional film can be used in the fields of filtration membranes, sustained-release materials, underwater conductivity, and underwater sensing.

[0039] The preparation process of the hydrogel film of the present invention is simple and time-consuming (24 hours). It does not contain toxic reagents or cross-linking agents. It only uses three substances, all of which are harmless to the human body, green and safe. The raw material, equipment and storage costs are all low. The film prepared by the existing preparation process is relatively thin, ranging from 20 to 150 μ m (poor solvent surface laying method, it is difficult to prepare a film with a larger thickness). Thickness less than 200 μ The hydrogel film of the present invention spontaneously aggregates into bundles when out of water and cannot spread itself, making it difficult to use. The thickness of the film of the present invention is 0.2-0.7 mm, which is easy to control, uniform and flat, and can be produced in large quantities.

[0040] The low swelling and high toughness PVA-PEG hydrogel film prepared by the present invention is formed by multiple hydrogen bond cross-linking, and has low equilibrium swelling degree (the water content of the original film is 93±0.9%, the equilibrium swelling degree is 14.3±0.9; the equilibrium swelling degree of the film after drying once is 3.2±0.7), high toughness (0.5~1.1 MJ / m 3 ), high fracture energy (0.8~2.8 KJ / m 2 ), elongation at break of 350%-460%, and breaking strength of 300-700 kPa. It exhibits excellent biosafety, mild preparation conditions, a simple method, and can be scalably produced in large sizes (30 cm × 50 cm or larger, depending on the size of the flat-bottom container). Raw material, equipment, and storage costs are low. The film's thickness, crosslink density, swelling properties, and toughness are easily adjustable, and the membrane itself can be embedded with a variety of functional materials. It has applications in water filtration membranes, pharmaceutical and fertilizer slow-release materials, underwater conductivity, and underwater sensing, offering excellent economic benefits and commercial potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The following are photos and flexibility demonstrations of the PVA-PEG hydrogel film prepared in Example 1 of the present invention.

[0042] Figure 2 This is a large-sized 30 cm × 50 cm PVA-PEG hydrogel film prepared in Example 1 of the present invention.

[0043] Figure 3 The PVA-PEG hydrogel films of different thicknesses prepared in Example 1 of the present invention are shown.

[0044] Figure 4 This is the PVA-PEG (PEG4000) hydrogel film prepared in Example 7 of the present invention.

[0045] Figure 5 The PVA-CMCNa hydrogel film prepared in Example 8 of the present invention: (a) macroscopic photographs of PVA-CMCNa hydrogel films with three different component ratios, and (b) photographs of the PVA-CMCNa hydrogel film spontaneously aggregating into bundles after being separated from water.

[0046] Figure 6 The PVA-maltodextrin hydrogel film prepared in Example 9 of the present invention: (a) macroscopic photograph of the PVA-maltodextrin hydrogel film, (b) photograph of the PVA-maltodextrin hydrogel film spontaneously aggregating into bundles after being separated from water.

[0047] Figure 7 Schematic diagram of the extensive mutual anchoring hydrogen bond interactions between PVA and PEG in the PVA-PEG hydrogel film prepared in Example 1 of the present invention.

[0048] Figure 8 This is an SEM image of the surface of the PVA-PEG hydrogel film prepared in Example 1 of the present invention.

[0049] Figure 9 This is a demonstration of the thermal stability of the PVA-PEG hydrogel film prepared in Example 1 of the present invention.

[0050] Figure 10 This figure shows the acid and alkali resistance of the PVA-PEG hydrogel film prepared in Example 1 of the present invention after being immersed in different pH environments for 14 days.

[0051] Figure 11 These are photos of the PVA-PEG hydrogel film prepared in Example 1 of the present invention being able to withstand twisting, knotting, and hand-held stretching.

[0052] Figure 12 These are the tensile stress-strain curves of PVA-PEG hydrogel films of different thicknesses prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] To further understand the present invention, the following describes a low-swelling, high-toughness PVA-PEG hydrogel film provided by the present invention, its preparation method, and basic properties, in conjunction with examples. However, the present invention is not limited to these examples. Non-essential modifications made by those skilled in the art based on the core concept of the present invention remain within the scope of protection of the present invention.

[0054] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art can be used. Example 1:

[0055] Prepare 5 wt% PVA (1799 type) aqueous solution and 50 wt% PEG (PEG1000, M w =1000) aqueous solution, 2.5 g of PEG aqueous solution was added to 10 g of PVA aqueous solution under mechanical stirring to obtain a casting mixture, which was kept constant at 40°C for 1 h and laid in a flat-bottomed container by tape casting. The amount of the casting mixture was controlled to be 0.16 g / cm 2 , open and placed in a 40℃ forced air oven, dry for 12 hours to obtain a dry film, which is translucent. Soak in a large amount of water to obtain a PVA-PEG hydrogel film. The preparation cycle is 24 hours. The photos and flexibility of the PVA-PEG hydrogel film are shown in Figure 1 The same method was used to prepare a large-scale 30 cm × 50 cm PVA-PEG hydrogel film, see Figure 2 . Example 2:

[0056] The difference from Example 1 is that the amount of the casting mixture is controlled to be 0.24 g / cm 2 , the rest of the content is consistent with Example 1. Example 3:

[0057] The difference from Example 1 is that the amount of the casting mixture is controlled to be 0.24 g / cm 2 , the rest of the content is consistent with Example 1. Example 4:

[0058] The difference from Example 1 is that the amount of the casting mixture is controlled to be 0.32 g / cm 2 , the rest of the content is consistent with Example 1. Example 5:

[0059] The difference from Example 1 is that the amount of the casting mixture is controlled to be 0.40 g / cm 2 The rest of the contents are the same as those in Example 1. The photos of the PVA-PEG hydrogel films of different thicknesses prepared in Examples 2, 3, and 4 are shown in the attached Figure 3 . Example 6:

[0060] The difference from Example 1 is that the film is left open at room temperature during drying, and a dry film can be obtained after 3 days, which is then soaked in a large amount of water to obtain a PVA-PEG hydrogel film. The preparation cycle is 3 days. Example 7:

[0061] Prepare 5 wt% PVA (1799 type) aqueous solution and 50 wt% PEG (PEG4000, M w =4000) aqueous solution, 0.9 g of PEG aqueous solution was added to 10 g of PVA aqueous solution under mechanical stirring to obtain a casting mixture, which was kept constant at 70 °C for 1 h and laid in a flat-bottomed container by tape casting. The amount of the casting mixture was controlled to be 0.32 g / cm 2 , open and placed in a 60℃ forced air oven, dried for 12 hours to obtain a dry film, which is translucent. Soaked in a large amount of water, a PVA-PEG supramolecular hydrogel film was obtained. The preparation cycle was 24 hours. The prepared PVA-PEG (PEG4000) hydrogel film is similar to PVA-PEG (PEG1000) and has good uniformity. The thickness and macroscopic photos are shown in Figure 4 . Example 8:

[0062] This example is a disproven experiment to assist in verifying the cross-linking mechanism of PVA-PEG hydrogel films. A 5 wt% aqueous solution of PVA (type 1799) and a 0.1 wt% aqueous solution of sodium carboxymethylcellulose (CMCNa) were prepared. 2.0 g, 3.0 g, and 4.0 g of the CMCNa aqueous solution were added to 10 g of the PVA aqueous solution under mechanical stirring to obtain a homogeneous casting mixture. This mixture was kept constant at 70°C for 1 hour and then cast onto a flat-bottomed vessel. The amount of the casting mixture was controlled to be 0.24 g / cm 2 , placed in a 60℃ forced air oven, dried for 12 hours to obtain a dry film. The dry film is colorless and transparent and easily broken. After soaking in a large amount of water, only a very thin flexible film remains within 5 minutes. After soaking for 48 hours, it is observed that the film does not dissolve, but has almost no mechanical properties. It gathers into bundles when it leaves the water. Figure 5 . Example 9:

[0063] This example also serves as a counter-evidence experiment to assist in verifying the cross-linking mechanism of PVA-PEG hydrogel films. A 5 wt% aqueous solution of PVA (type 1799) and a 10 wt% aqueous solution of maltodextrin were prepared. Under mechanical stirring, 7.0 g of the aqueous solution of maltodextrin was added to 10 g of the aqueous solution of PVA to obtain a homogeneous casting mixture. This mixture was kept constant at 70°C for 1 hour and then cast onto a flat-bottomed vessel. The amount of the casting mixture was controlled to be 0.24 g / cm 2 , placed in a 60℃ forced air oven, dried for 12 hours to obtain a dry film. The dry film is colorless and transparent and easily broken. After soaking in a large amount of water, only a very thin flexible film remains within 5 minutes. After soaking for 48 hours, it is observed that the film does not dissolve, but has almost no mechanical properties. It gathers into bundles when it leaves the water. Figure 6 .

[0064] Comparative Example 1:

[0065] The difference from Example 1 is that no PEG was added, only a PVA aqueous solution was used, and the resulting dried PVA film dissolved in water without forming a hydrogel.

[0066] Performance Test 1:

[0067] The swelling properties of the PVA-PEG hydrogel film prepared in Example 1 were tested. The results showed that the original film had a moisture content of 93±0.9% and an equilibrium swelling degree of 14.3±0.9. After drying once, the equilibrium swelling degree of the film was 3.2±0.7. The low swelling properties of the PVA-PEG hydrogel film are attributed to the fact that both PVA and PEG contain only three elements: C, H, and O, and share the same structural unit, -(C2H4O)-. Furthermore, the mass ratio of PVA to PEG is appropriate (PVA:PEG = 1:0.5-3.0). The O atoms in PVA are present as hydroxyl groups in the side chains, resulting in greater flexibility, while the O atoms in PEG are located on the main chain, limiting their flexibility. This distribution of O atoms and the appropriate ratio between the two polymers allow the extensive hydrogen bonds between them to anchor each other, preventing dissociation. This results in a low affinity for free small water molecules, and therefore low swelling properties. Figure 7 This is a schematic diagram of the extensive multiple hydrogen bond cross-linking between PVA and PEG. It has to be said that this diagram does not combine the actual molecular bond length (in PVA and PEG, the C-C bond length is about 0.15 nm, the C-O bond length is about 0.14 nm, the C-H bond length is about 0.11 nm, and the O-H bond length is about 0.096 nm) and configuration information very well, but it also reflects the interaction hypothesis of extensive cross-linking and mutual anchoring by hydrogen bonds. In order to further support this hypothesis, the inventors also designed a counter-proof experiment. PVA and sodium carboxymethyl cellulose (chemical formula [C6H7O2(OH)2OCH2COONa] n ) mixed solution (Example 8), PVA and maltodextrin (chemical formula (C6H 10 O5) n ) mixture (Example 9). Without exception, the resulting films largely dissolved in water, resulting in very thin films, far less than the expected thickness of the starting material. This suggests that extensive, multiple hydrogen bonds cannot form between the PVA and polysaccharide structures. This is because the polysaccharide and PVA structures have fewer sites for hydrogen bonding, making it difficult to form a mutual anchoring relationship, resulting in a weaker degree of crosslinking.

[0068] Performance Test 2:

[0069] The microstructure of the PVA-PEG hydrogel film prepared in Example 1 was tested, and the results are shown in FIG. Figure 8 , the surface of the film is smooth and dense.

[0070] Performance Test 3:

[0071] The thermal stability of the PVA-PEG hydrogel film prepared in Example 1 was tested. Figure 9The results showed that the PVA-PEG hydrogel film could remain stable for a long time (tested for 24 h) at 50°C, but when the temperature was higher than 60°C, it became soft, thinner and deformed, indicating that at this temperature the hydrogen bond cross-linking effect of the PVA hydrogel film began to be significantly destroyed.

[0072] Performance Test 4:

[0073] The acid and alkali resistance of the PVA-PEG hydrogel film prepared in Example 1 was tested by soaking it in pH = 1 (0.1 mol / L HCl aqueous solution), pH = 7 (ultrapure water) and pH = 13 (0.1 mol / L NaOH aqueous solution). After soaking for 14 days, the swelling before and after soaking was compared. Figure 10 The results showed that there was no difference in the hydrogel films immersed in solutions with pH = 1, 7, and 13 for 14 days, indicating that the hydrogen bond cross-linking mechanism was not greatly affected by pH, and the PVA hydrogel film had excellent acid and alkali resistance.

[0074] Performance Test 5:

[0075] The mechanical properties of the PVA-PEG hydrogel film prepared in Example 1 were tested by hand-held twisting, knotting and stretching. Figure 11 The results show that the PVA-PEG hydrogel film can withstand normal deformation and recover quickly. Furthermore, the above sample (the film sample with a water content of 93±0.9% was a sample in a swelling equilibrium state, not a sample that had been dried and re-swelled) was subjected to a tensile test at a rate of 50 mm / min. Figure 12 The results showed that the modulus of PVA-PEG hydrogel films of different thicknesses was 50~180 kPa, the elongation at break was 350%~460%, the breaking strength was 300~700 kPa, and the toughness was 0.5~1.1 MJ / m 3 , fracture energy is 0.8~2.8 kJ / m 2 , showing high toughness under excellent swelling balance.

[0076] Performance Test 6:

[0077] The biosafety of the PVA-PEG hydrogel film prepared in Example 1 was tested and evaluated by a fertilized zebrafish egg hatching experiment. The experimental group was hatched in pure water containing the PVA-PEG hydrogel film. Five groups were set up in the experiment, each group initially used 30 eggs, and the hatching results after 3 days were 27, 27, 28, 24, and 23 live fry, respectively. The control group was hatched in pure water. Four groups were set up in the experiment, each group initially used 30 eggs, and the hatching results after 3 days were 27, 24, 29, and 30 live fry, respectively. The statistical significance test level between the two groups of data was p=0.32, p≥0.05, indicating that there was no significant difference in the experimental results of the two groups, indicating that the presence of the PVA-PEG hydrogel film did not affect the hatching of zebrafish eggs, and the biosafety was good.

Claims

1. A method for preparing a low equilibrium swelling and high toughness PVA-PEG hydrogel film, characterized in that The steps include: At room temperature, a low-molecular-weight PEG or high-molecular-weight PEG aqueous solution is added to a PVA aqueous solution, heated at high temperature and stirred to obtain a film-casting mixture, subjected to ultrasonic degassing, and cast. After drying, the film is immersed in water to swell, thereby obtaining a low-swelling and high-toughness PVA-PEG hydrogel film. The PVA aqueous solution is obtained by dissolving a solid PVA raw material in water at 85-95° C. under stirring, and the mass concentration of the PVA aqueous solution is 2-12 wt %; The low molecular weight PEG is selected from one or more of PEG100-PEG600; the high molecular weight PEG is selected from one or more of PEG800-PEG10000; The relative molecular mass of the PVA is 60,000 to 200,000; The mass ratio of the solute PVA and PEG in the hydrogel film is 1:0.5-3.

0.

2. The preparation method according to claim 1, wherein: The tape casting is to spread the mixed film mixture in a flat bottom container, and control the amount of the film mixture to be 0.16~0.56 g / cm 2 The final film thickness can be controlled by adjusting the height of the casting mixture and / or the mass fraction of PVA plus PEG solute.

3. The preparation method according to claim 2, wherein: The thickness of the prepared PVA-PEG hydrogel film is 0.2~0.7 mm.

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