Multifunctional PVA-based hydrogel and preparation method and application thereof

Abstract

This invention discloses a multifunctional PVA-based hydrogel, its preparation method, and its applications. By using CNC as a template to synthesize PPy, the problem of uneven polymerization and deposition of pyrrole monomers in traditional aqueous solutions is solved, successfully preparing a CNC-PPy composite material. Subsequently, this composite material is combined with PVA and PVA-SbQ to prepare a composite hydrogel. Through ultraviolet light irradiation and immersion in a FeCl3-PA composite solution followed by solvent replacement, a PVA / PVA-SbQ / CNC-PPy / FeCl3 / PA hydrogel with excellent antifreeze, adhesion, self-healing, conductivity, and sensing properties is finally obtained.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel materials technology, specifically relating to a multifunctional PVA-based hydrogel, its preparation method, and its applications. Background Technology

[0002] With the rapid development of wearable devices and smart sensors, flexible electronics has gradually become a research hotspot. Flexible sensors, with their excellent flexibility, stretchability, and conductivity, can efficiently sense environmental changes such as temperature, humidity, and pressure, showing broad application prospects in fields such as biomedicine. Hydrogel materials, due to their high water content and good biocompatibility, show significant application potential in the field of flexible wearable sensing.

[0003] However, the weak interfacial adhesion and self-healing properties of hydrogels limit their practical application in fields such as biomimetic electronic skin. To address this issue, constructing hydrogels with multifunctional properties has become an important research direction for improving the performance of biomimetic electronic devices. Researchers have explored various methods, such as preparing self-healing conductive hydrogels by introducing dynamic hydrogen bond networks. These hydrogels can rapidly recover after damage and exhibit excellent conductivity, showing broad application potential in complex environments. Polyvinyl alcohol (PVA), as a key component of hydrogels, plays a crucial role in providing controllable and reliable wet adhesion. The abundant hydroxyl groups on the PVA molecular chain can form multiple hydrogen bonds and van der Waals forces with functional groups on the skin surface, thereby achieving a stable yet reversible adhesion to biological tissues. This inherent adhesion eliminates the need for a strong adhesive layer, effectively solving the signal noise and wearing discomfort problems caused by interfacial mismatch in traditional sensors, laying the material foundation for long-term, stable, and comfortable health monitoring.

[0004] However, the existing hydrogel network structure design relies on only single or dual interactions, resulting in limited functionality. Furthermore, it is prone to problems such as relaxation of conductive paths and attenuation of adhesion during long-term use, which cannot meet the long-term cyclic use requirements of flexible sensors. Based on the above discussion, the development of an adhesive self-healing and antifreeze conductive hydrogel with multiple cross-linked networks has broad application prospects, especially in the fields of human-computer interaction and health monitoring under extreme environmental conditions. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a multifunctional PVA-based hydrogel.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solutions, including: Nanocrystalline cellulose aqueous solution and FeCl3-NaSSA aqueous solution were uniformly mixed and then frozen to obtain nanocrystalline cellulose-FeCl3-NaSSA ice crystals. After adding pyrrole-cyclohexane solution to ice crystals and carrying out interfacial polymerization at 1-4℃ for 36-4h, the solution was washed, sonicated, and rotary evaporated to obtain a CNC-PPy solution with a solid content of 4-5 wt%. CNC-PPy solution was mixed with ammonium persulfate, heated and stirred, and then cooled to obtain CNC-PPy / APS solution. Polyvinyl alcohol, polyvinyl alcohol-styrenepyridine quaternary ammonium salt, CNC-PPy / APS solution and water are mixed uniformly, and the resulting mixture is allowed to stand at room temperature for 6 to 8 hours to form a PVA / PVA-SbQ / CNC-PPy / APS gel. In the mixture, the mass fraction of polyvinyl alcohol is 9-11%, the mass fraction of polyvinyl alcohol-styrenepyridine quaternary ammonium salt is 4-6%, and the mass fraction of CNC-PPy / APS is 2-4%. The gel solution was irradiated with ultraviolet light at a wavelength of 365 nm for 0.3~1.2 h to obtain PPCP hydrogel, which was then immersed in FeCl3-PA composite solution for 15~40 minutes and rinsed to obtain multifunctional PVA-based hydrogel.

[0009] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the solid content of the nanocrystalline cellulose aqueous solution is 1~3 wt%.

[0010] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the preparation method of the nanocrystalline cellulose aqueous solution includes: Microcrystalline cellulose and a 60-70 wt% sulfuric acid aqueous solution are mixed evenly at a ratio of 1 g: 15-25 mL, heated at 45-50℃ and stirred to carry out acid hydrolysis reaction for 40-55 min to obtain nanocellulose colloid. To terminate the reaction, add 1-2 L of water to the nanocellulose colloid, let it stand, centrifuge to obtain the precipitate, and disperse it in water to form a suspension. After dialysis to neutral pH, the nanocrystalline cellulose was dispersed by ultrasonication and then rotary evaporated to obtain an aqueous solution.

[0011] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the FeCl3-PA composite solution is prepared by mixing ferric chloride, 70 wt% phytic acid aqueous solution and water in a mass ratio of 1~4∶6∶0~4.

[0012] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the FeCl3-NaSSA aqueous solution has a molar concentration of FeCl3·6H2O of 0.3–0.5 M and a molar concentration of sodium 5-sulfosalicylate of 0.3–0.4 M.

[0013] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the mass fraction of pyrrole in the pyrrole-cyclohexane solution is 1.5~3 wt%.

[0014] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the volume ratio of the nanocrystalline cellulose aqueous solution, FeCl3-NaSSA aqueous solution and pyrrole-cyclohexane solution used for the interfacial polymerization reaction is 1:1~3:1~3.

[0015] In a preferred embodiment of the preparation method of the multifunctional PVA-based hydrogel of the present invention, the mass ratio of the CNC-PPy solution to ammonium persulfate is 1.9~2.3:0.1~0.3.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide a multifunctional PVA-based hydrogel.

[0017] The third objective of this invention is to overcome the shortcomings of the prior art and provide an application of a multifunctional PVA-based hydrogel in the fabrication of flexible strain sensors.

[0018] Beneficial effects of this invention: This invention provides a multifunctional PVA-based hydrogel and its preparation method. The method is simple to operate, and the hydrogel prepared can simultaneously achieve the following properties: (1) excellent antifreeze performance: it can resist low temperature of -30 ℃; (2) good adhesion and self-healing properties: it can adhere to various materials and complete self-healing within 10 s; (3) excellent conductivity: the conductivity is not less than 10 mS / cm; (4) strain sensing performance: the transmission signal is stable and the resistance change rate is less than 20%. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The graph shows the antifreeze properties of the hydrogels prepared in Example 1 and Comparative Examples 1-3.

[0020] Figure 2 The graph shows the adhesion properties of the hydrogels prepared in Example 1 and Comparative Examples 1-3.

[0021] Figure 3 The diagram shows the self-healing properties of the hydrogels prepared in Example 1 and Comparative Examples 1-3.

[0022] Figure 4 The graph shows the electrical conductivity of the hydrogels prepared in Example 1 and Comparative Examples 1-3.

[0023] Figure 5 The graph shows the sensing performance of the hydrogels prepared in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0028] Microcrystalline cellulose: analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.; Pyrrole: Purchased from Shanghai Xihang New Materials Co., Ltd.; Ferric chloride hexahydrate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Sodium 5-sulfosalicylate: purchased from Sinopharm Chemical Reagent Co., Ltd.; Cyclohexane: purchased from Sinopharm Chemical Reagent Co., Ltd.; Ammonium persulfate: purchased from Sinopharm Chemical Reagent Co., Ltd.; Polyvinyl alcohol: purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Polyvinyl alcohol-styrene-pyridine quaternary ammonium salt: purchased from Shanghai Guangyi Printing Equipment Technology Co., Ltd.

[0029] The abbreviations of the substances in this invention are as follows: Nanocrystalline cellulose (CNC), ferric chloride (FeCl3·6H2O), sodium 5-sulfosalicylate (NaSSA), ammonium persulfate (APS), phytic acid (PA), polyvinyl alcohol (PVA), styrylpyridine quaternary ammonium salt (SbQ), polypyrrole (PPy), and pyrrole (Py).

[0030] The materials obtained in the embodiments of the present invention were subjected to performance testing according to the following method: Freeze-thaw resistance: DSC analysis is mainly used to study the low-temperature crystallization behavior of hydrogels. Take 3-5 mg of hydrogel, place it in an aluminum crucible, and then put it in a DSC furnace. Under a nitrogen atmosphere of 50 mL / min, control the cooling rate at 5 °C / min to cool from 25 °C to -60 °C to eliminate thermal history. Then, heat up to 25 °C at a rate of 5 °C / min, and finally cool from 25 °C to -60 °C at a rate of 5 °C / min.

[0031] Adhesion Properties: The adhesion properties test mainly studies the interfacial adhesion properties of the hydrogel. Hydrogels were cut into strips of 30 mm × 25 mm × 5 mm and then adhered to the midpoint between two identical substrates (metal plate, glass plate, polyethylene terephthalate (PET) plastic sheet, rubber sheet, and wood chip). A weight was applied to the overlap for 10 min to achieve a tight bond between the hydrogel and the substrate. The samples were then fixed on a universal testing machine and stretched at 50 mm / min until the overlap sheared and the specimen separated or broke. Each sample was tested five times.

[0032] Self-healing properties: The self-healing ability of the hydrogel was studied by cutting the hydrogel into four parts and then connecting them at the fracture points. Observations were made after placing it at 25 °C for different times. Additionally, a dynamic step strain oscillation test was used, alternating between 500% large strain (lasting 30 s) and 1% small strain (lasting 30 s), and the self-healing ability was quantitatively evaluated by the recovery of the storage modulus.

[0033] Conductivity and Sensing Performance Testing: This mainly studies the conductivity and sensing performance of the hydrogel. The hydrogel sample was cut into rectangular blocks of 20 mm × 10 mm × 2 mm; its resistance was measured using a linear scanning voltammetry method on an electrochemical workstation; the conductivity (σ) of the hydrogel sample was calculated using equation (1): σ = L / RS (1) In the formula, σ (S / m) represents the conductivity of the hydrogel sample, R (Ω) represents the resistance of the hydrogel sample, and L and S are the length (mm) and cross-sectional area (mm²) of the hydrogel sample, respectively. 2 ).

[0034] Hydrogel samples were encapsulated with 3M ultra-high adhesion tape (VHB) and used as strain sensors (hydrogel sensors). They were fixed to different parts of the human body (e.g., elbows, knees, fingers, wrists, throats, and feet) to study their sensing capabilities. The relative resistance change ΔR / R0 of the hydrogel sensor at a constant voltage of 0.5 V was detected using the It curve test method on an electrochemical workstation. The relative resistance change ΔR / R0 of the hydrogel was calculated using equation (2): ΔR / R0=(R−R0) / R0×100% Equation (2) In the formula, R0 and R are the resistance without strain and the real-time resistance under a certain strain (the hydrogel is strained due to the movement of different parts of the human body, such as the fingers bending 90°, the elbows bending 90°, and the knees bending 60°).

[0035] Example 1 This embodiment provides a method for preparing a multifunctional PVA-based hydrogel, specifically as follows: 1) Preparation of aqueous solution of nanocrystalline cellulose (CNC): Add 5 g of microcrystalline cellulose to 100 mL of 64 wt% sulfuric acid aqueous solution, mix well, and stir at 50 ℃ for 45 min to carry out acid hydrolysis reaction to obtain nanocellulose colloid. Add 1 L of deionized water to the nanocellulose colloid to terminate the acid hydrolysis reaction, let it stand, take the lower layer of turbid liquid and centrifuge it. The resulting precipitate is dispersed in water to obtain the nanocellulose suspension. The nanocellulose suspension was placed in a dialysis bag with a molecular weight cutoff of 12,000 and dialyzed at room temperature for 6 days to bring the pH of the nanocellulose suspension to neutral. The dialyzed nanocellulose suspension was then ultrasonically dispersed and rotary evaporated to obtain a CNC aqueous solution with a solid content of 1.5 wt%. 2) Preparation of nanocrystalline cellulose-polypyrrole complex solution: 97.65 g of cyclohexane and 2.34 g of pyrrole (Py) were mixed evenly to obtain a pyrrole-cyclohexane solution with a mass fraction of 2.34 wt%. 10.8 g FeCl3·6H2O and 8.6 g sodium 5-sulfosalicylate (NaSSA) were added to water and brought to a final volume of 100 mL. The mixture was stirred until homogeneous to obtain a FeCl3-NaSSA aqueous solution. The molar concentration of FeCl3·6H2O in the FeCl3-NaSSA aqueous solution was 0.4 M and the molar concentration of NaSSA was 0.36 M. 20 mL of CNC aqueous solution and 20 mL of FeCl3-NaSSA aqueous solution were mixed evenly and frozen at -20℃ for 4 h to obtain CNC-FeCl3-NaSSA ice crystals. 20 mL of pyrrole-cyclohexane solution was added to the ice crystals. The volume ratio of CNC aqueous solution, FeCl3-NaSSA aqueous solution and pyrrole-cyclohexane solution was 1:1:1. The polymerization reaction was carried out at 4℃ for 48 h. Subsequently, the mixture was washed multiple times with ethanol and water until the pH of the washing solution was 7 to remove unreacted oxidant (FeCl3) and monomer (Py) from the system. The mixture was then subjected to ultrasonic treatment and rotary evaporation to obtain a CNC-PPy solution with a solid content of 4 wt%.

[0036] 3) Preparation of a mixture of nanocrystalline cellulose, polypyrrole, and ammonium persulfate: 1.925 g of 4 wt% CNC-PPy solution was mixed with 0.154 g of ammonium persulfate (APS), i.e., the mass ratio of CNC-PPy solution to APS was 1.925:0.154. The mixture was stirred at 90 °C for 9 h and then cooled to obtain a CNC-PPy / APS solution.

[0037] 4) Preparation of polyvinyl alcohol / polyvinyl alcohol-styrene pyridine quaternary ammonium salt-nanocellulose / polypyrrole / ammonium persulfate hydrogel: 5.00 g of polyvinyl alcohol (PVA), 3.33 g of polyvinyl alcohol-styrenepyridine quaternary ammonium salt aqueous solution (PVA-SbQ), 0.92 g of the CNC-PPy / APS solution obtained in step 3), and 0.75 mL of water were mixed and allowed to stand at room temperature for 7 h to obtain a PVA / PVA-SbQ / CNC-PPy / APS gel. The mass fraction of CNC-PPy / APS in the mixture was 2.3%, the mass fraction of PVA was 10%, and the mass fraction of PVA-SbQ was 5%. The mixture was irradiated with ultraviolet light at a wavelength of 365 nm for 1 h to obtain a PVA / PVA-SbQ / CNC-PPy / APS hydrogel, denoted as PPCP hydrogel.

[0038] 5) Preparation of ferric chloride-phytic acid composite solution: 16.2 g of ferric chloride (FeCl3) was mixed with 30 g of phytic acid (PA) and 3.8 g of water to obtain a FeCl3-PA composite solution.

[0039] 6) Preparation of polyvinyl alcohol / polyvinyl alcohol-styrene-pyridine quaternary ammonium salt-nanocellulose / polypyrrole / ammonium persulfate-ferric chloride-phytic acid hydrogel: The PVA / PVA-SbQ / CNC-PPy / APS hydrogel was immersed in FeCl3-PA composite solution for 20 min to obtain the PVA / PVA-SbQ / CNC-PPy / APS / FeCl3 / PA hydrogel of this embodiment, denoted as P. 10 P5CPF 1.2 P-20 hydrogel.

[0040] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in step 4) of preparing the polyvinyl alcohol / polyvinyl alcohol-styrene pyridine quaternary ammonium salt-nanocellulose / polypyrrole / ammonium persulfate hydrogel, the mass of PVA is adjusted to 2.00 g and the mass of PVA-SbQ is 7.33 g, so that the mass fraction of PVA in the mixed system is 4% and the mass fraction of PVA-SbQ is 11%. The remaining preparation process is the same as in Example 1, resulting in the P4P of this comparative example. 11 CPF 1.2 P-20 hydrogel.

[0041] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in step 4) of preparing the polyvinyl alcohol / polyvinyl alcohol-styrene pyridine quaternary ammonium salt-nanocellulose / polypyrrole / ammonium persulfate hydrogel, the mass of PVA is adjusted to 3.50 g and the mass of PVA-SbQ is adjusted to 5.33 g, so that the mass fraction of PVA in the mixed system is 7% and the mass fraction of PVA-SbQ is 8%. The remaining preparation process is the same as in Example 1, resulting in the P7P8CPF of this comparative example. 1.2 P-20 hydrogel.

[0042] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in step 4) of preparing the polyvinyl alcohol / polyvinyl alcohol-styrene pyridine quaternary ammonium salt-nanocellulose / polypyrrole / ammonium persulfate hydrogel, the mass of PVA is adjusted to 6.00 g and the mass of PVA-SbQ is 2.00 g, so that the mass fraction of PVA in the mixed system is 12% and the mass fraction of PVA-SbQ is 3%. The remaining preparation process is the same as in Example 1, resulting in the PVA of this comparative example. 12 P3CPF 1.2 P-20 hydrogel.

[0043] The antifreeze properties of the hydrogels prepared in the above examples and comparative examples were characterized, and the results are as follows: Figure 1 As shown.

[0044] Figure 1 (a) is the DSC curve of the hydrogel. From the graph, it can be seen that PPCPF 1.2 The freezing temperature of P-20 hydrogel ranges from -16℃ to -53℃, primarily attributed to the synergistic effect of high concentrations of PA and FeCl3 in the hydrogel. The phosphate groups in PA can form strong hydrogen bonds with water molecules, disrupting the orderly arrangement of water molecules, thereby inhibiting ice crystal formation and lowering the crystallization temperature of the hydrogel. Furthermore, Fe... 3+ It can also form ionic coordination bonds with phosphate groups in PA, enhancing the network structure of the hydrogel and improving its stability at low temperatures. When the ratio of PVA to PVA-SbQ in the hydrogel is adjusted, appropriately increasing the PVA ratio and decreasing the PVA-SbQ ratio, the hydrogel's antifreeze properties weaken. This is because the chemical cross-linking network within the hydrogel decreases, and the cross-linking density drops.

[0045] Figure 1 As shown in (b), for P 10 P5CPF 1.2 P-20 hydrogel underwent simple tensile tests at temperatures of 25℃, -18℃, and -30℃. The test results showed that even at low temperatures of -18℃ and -30℃, P... 10 P5CPF 1.2 The mechanical properties of P-20 hydrogel are similar to those at room temperature, which fully demonstrates that the hydrogel has excellent low-temperature adaptability and mechanical stability.

[0046] Figure 1 As shown in (c), PPCPF hydrogels with different ratios 1.2 The conductivity of P-20 showed significant differences at different temperatures, while that of P4P 11 CPF 1.2 P-20 has a conductivity of 83.2% at -30℃ compared to 25℃. 10 P5CPF 1.2 The P-20 hydrogel has an electrical conductivity of 79.2% at -30℃ compared to 25℃, while P... 12 P3CPF 1.2 P-20 dropped sharply to 32.9%. This is because PA and Fe... 3+ The coordination between the PVA and SbQ effectively inhibits ice crystal formation and increases the crystallization temperature, thus giving the hydrogel a certain degree of freeze resistance. However, as the proportion of PVA increases and the proportion of PVA-SbQ decreases, the number of chemical cross-linking networks inside the hydrogel gradually decreases, and the cross-linking density decreases accordingly, weakening the overall stability of the hydrogel.

[0047] The adhesion properties of the hydrogels prepared in the above embodiments and comparative examples were characterized, and the results are as follows: Figure 2 As shown.

[0048] Figure 2 It is P 10 P5CPF 1.2 Adhesion properties and applications of P-20 hydrogel. For example... Figure 2 As shown in (a), P 10 P5CPF 1.2 P-20 hydrogel exhibits good adhesion to glass, metal, wood, rubber, and PET film surfaces. For example... Figure 2 As shown in (b), PPCPF with different PVA and PVA-SbQ ratios 1.2 The adhesion strength of P-20 hydrogel varied, with the highest adhesion strength to wood (36.6 kPa). P4P 11 CPF 1.2 The adhesion strength of P-20 hydrogel is very low. However, as the PVA content in the hydrogel increases, the adhesion strength of PPCPF1.2P-20 hydrogel gradually increases. This is because the PVA molecular chain contains a large number of -OH groups, which can form hydrogen bonds, van der Waals forces, and other interactions with atoms or groups on other material surfaces. The gradually increasing PVA content indicates that more -OH groups can participate in the interaction between the hydrogel and the material surface groups, thereby enhancing the adhesion between the hydrogel and other material surfaces, resulting in a gradual increase in the adhesion strength. Furthermore, due to the synergistic effect between PVA, PA, and FeCl3, the -OH groups on the PA molecules can more effectively contact and interact with the material surface, forming more hydrogen bonds, van der Waals forces, or electrostatic interactions with the adhered material surface, thus enhancing the adhesion. In addition, as... Figure 2 As shown in (c), P is demonstrated. 10 P5CPF 1.2 P-20 adhesive hydrogel simulates electronic skin for human-computer interaction. Due to the hydrogel's good adhesion, it can be directly adhered to gloves to simulate electronic skin. As shown in the figure, in the human-computer interaction scenario simulating electronic skin, P... 10 P5CPF 1.2 The P-20 adhesive hydrogel can effectively sense external operating commands and provide corresponding feedback, demonstrating its good application potential in the field of human-computer interaction. During the interaction process, the hydrogel maintains a good adhesion to the device surface and does not detach.

[0049] The self-healing properties of the hydrogels prepared in the above embodiments and comparative examples were characterized, and the results are as follows: Figure 3 As shown.

[0050] Figure 3 It is P 10 P5CPF 1.2The self-healing properties of P-20 hydrogel. For example... Figure 3 As shown in (a), P 10 P5CPF 1.2 Following cutting with P-20 hydrogel, the hydrogel self-healed within 10 minutes. 10 P5CPF 1.2 The self-healing ability of P-20 hydrogel stems from the synergistic effect of triple dynamic bonds: First, the reversible hydrogen bond network between the -OH group of PVA and the phosphate group of PA enables rapid reconstruction of fracture surfaces; second, the phosphate group of PA and Fe... 3+ The dynamic coordination bonds formed endow the interface with instant repair properties; in addition, dynamic hydrogen bonds are generated between PVA molecular chains after a single freeze-thaw process. Figure 3 (b) is P 10 P5CPF 1.2 Dynamic alternating strain scanning curves during the self-healing process of P-20 hydrogel. At low strain (1%), P... 10 P5CPF 1.2 The G′ of the P-20 hydrogel is greater than G″, indicating that the hydrogel is in a gel state and its internal network structure is stable. When the strain increases to a high strain (500%), G′ becomes less than G″, meaning that the internal network structure of the hydrogel is destroyed. However, when the strain returns to a low strain (1%), G′ recovers to its initial value, indicating that the network structure of the hydrogel has been effectively restored, suggesting that P-20 hydrogel is stable. 10 P5CPF 1.2 P-20 hydrogel has excellent self-healing ability. Figure 3 (d) shows P 10 P5CPF 1.2 The load-bearing capacity of P-20 hydrogel after self-healing. As shown in the figure, the self-healing hydrogel can withstand loads up to 50 g (equivalent to 15 times its own weight) and maintains structural integrity under different loads. This indicates that the mechanical properties of the hydrogel are effectively restored after self-healing.

[0051] The conductivity properties of the hydrogels prepared in the above embodiments and comparative examples were characterized, and the results are as follows: Figure 4 As shown.

[0052] like Figure 4 As shown in (a), P 10 P5CPF 1.2 P-20 hydrogel is sandwiched between two copper electrodes, and an LED light illuminates. Initial state P 10 P5CPF 1.2 P-20 hydrogel is initially bright, but its brightness decreases after stretching. This is because stretching the hydrogel lengthens the ion migration path and increases its internal resistance. This phenomenon indicates that P... 10 P5CPF 1.2P-20 hydrogel has good electrical conductivity and strain sensitivity, thus affecting the brightness of the small light bulb. For example... Figure 4 As shown in (b), P4P 11 CPF 1.2 The conductivity of P-20 hydrogel is 10.65 ± 2.59 mS / cm. As the proportion of PVA in the hydrogel increases and the proportion of PVA-SbQ decreases, the conductivity of the hydrogel initially increases and then decreases. This is because the addition of PVA enhances hydrogen bonding in the hydrogel, resulting in excessive cross-linking density, which hinders the formation of conductive pathways, making it difficult for charge carriers to move freely, thus leading to a decrease in conductivity. Conversely, as the proportion of PVA-SbQ decreases, the chemical cross-linking in the hydrogel weakens, and the cross-linking density decreases. When the proportion of PVA in the hydrogel is 8% and the proportion of PVA-SbQ is 7%, the conductivity of P7P8CPF... 1.2 The P-20 hydrogel exhibited optimal electrical conductivity at 25 °C, reaching 22.45 ± 5.41 mS / cm. This is attributed to the synergistic effect between PPy, PA, and high-concentration FeCl3, which together effectively enhanced the carrier density and mobility within the hydrogel. The π-π conjugation of PPy provides an electron transport pathway, enabling electron conduction via delocalized electron clouds; Fe... 3+ Its hydrated ions act as mobile charge carriers, enhancing conductivity through ion migration; furthermore, PA can dissociate H+. + It enhances electrical conductivity and can react with Fe. 3+ A dynamic coordination network is formed to optimize ion transport pathways. Under this synergistic effect, even P 10 P5CPF 1.2 Despite the reduction in the chemical cross-linking network in the P-20 hydrogel, its conductivity remains at 12.11 ± 2.06 mS / cm, maintaining good electrical conductivity. However, when the proportion of PVA is further increased, the conductivity of the hydrogel decreases again. This is because insufficient PVA-SbQ content weakens the chemical cross-linking network in the hydrogel, failing to provide sufficiently effective migration channels for charge carriers, thus limiting carrier transport and ultimately leading to a decrease in conductivity.

[0053] The sensing properties of the hydrogels prepared in the above embodiments and comparative examples were characterized, and the results are as follows: Figure 5 As shown.

[0054] like Figure 5 As shown in (a), P 10 P5CPF 1.2 P-20 hydrogel exhibits rapid response and recovery properties during stretching and rebound. When 100% strain is applied to the hydrogel, its response time is 300 ms and its recovery time is 400 ms. This result indicates that P... 10 P5CPF1.2 P-20 hydrogel exhibits excellent strain response. From Figure 5 (b) It can be obtained that P 10 P5CPF 1.2 P-20 hydrogel exhibits excellent sensing properties across different strain ranges: the GF is 1.09 in the low strain region (0% ~ 400%), increases to 3.71 in the medium strain range (400% ~ 630%), and reaches 5.08 in the high strain range (630% ~ 800%), fully demonstrating the superior sensing performance of P-20 hydrogel. 10 P5CPF 1.2 P-20 hydrogel exhibits excellent strain sensitivity. Figure 5 (c ~ e) demonstrates P 10 P5CPF 1.2 The P-20 hydrogel sensor's sensing performance was tested under different temperature conditions. At 25℃, the hydrogel sensor produced significant resistance responses to the movement of different parts of the human body: the relative resistance change rate was 40% when the fingers were bent, 20% when frowning, and 5.3% when speaking. When the temperature dropped to -18℃, the resistance change rate of each part decreased slightly, but still maintained a stable signal output: the relative resistance change rate was 23% when the fingers were bent, 15% when frowning, and 1.65% when speaking. Even under extreme low temperature conditions of -30℃, the sensor still exhibited reliable sensing performance, with measured resistance change rates of 19%, 12%, and 1.26% for the fingers, arm, and throat, respectively. These data fully demonstrate that the hydrogel sensor can maintain stable operating performance within a temperature range of -30℃ to 25℃, and its output signal has good distinguishability and repeatability, without signal abrupt changes or failures, demonstrating excellent low-temperature environmental adaptability.

[0055] In summary, this invention uses CNC as a template to synthesize PPy, solving the problems of uneven polymerization and deposition of pyrrole monomers in traditional aqueous solutions, and successfully preparing CNC-PPy composite materials. Subsequently, this composite material was combined with PVA and PVA-SbQ to prepare a composite hydrogel. By irradiation with ultraviolet light and immersion in a FeCl3-PA composite solution followed by solvent replacement, a PVA / PVA-SbQ / CNC-PPy / FeCl3 / PA hydrogel with excellent antifreeze, adhesion, self-healing, conductivity, and sensing properties was finally obtained.

[0056] This invention has found that adjusting the ratio of PVA to PVA-SbQ affects the properties of the PVA / PVA-SbQ / CNC-PPy / FeCl3 / PA hydrogel. 10 P5CPF 1.2At P-20, the following properties can be achieved simultaneously: (1) Excellent antifreeze performance: able to withstand low temperatures of -30 ℃; (2) able to adhere to various materials and rapidly self-heal within 10 s; (3) Excellent electrical conductivity: electrical conductivity not less than 10 mS / cm; (4) Excellent strain sensing performance: resistance change rate less than 20%. Compared with existing hydrogel strain sensors, the hydrogel prepared by this invention has excellent antifreeze performance, certain adhesion and self-healing properties, and high conductivity, sensing sensitivity and stability, and is widely used.

[0057] Based on the above research, this invention provides a new approach for developing hydrogel materials with multiple biomimetic functions. By adjusting the ratio of PVA to PVA-SbQ to achieve performance optimization, it provides a reliable candidate material for the application of flexible electronic devices in complex environments, promoting the practical application of hydrogels in wearable devices, human-computer interaction, and other fields.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a multifunctional PVA-based hydrogel, characterized in that: include, Nanocrystalline cellulose aqueous solution and FeCl3-NaSSA aqueous solution were uniformly mixed and then frozen to obtain nanocrystalline cellulose-FeCl3-NaSSA ice crystals. After adding pyrrole-cyclohexane solution to ice crystals and carrying out interfacial polymerization at 1-4℃ for 36-4h, the solution was washed, sonicated, and rotary evaporated to obtain a CNC-PPy solution with a solid content of 4-5 wt%. CNC-PPy solution was mixed with ammonium persulfate, heated and stirred, and then cooled to obtain CNC-PPy / APS solution. Polyvinyl alcohol, polyvinyl alcohol-styrenepyridine quaternary ammonium salt, CNC-PPy / APS solution and water are mixed uniformly, and the resulting mixture is allowed to stand at room temperature for 6 to 8 hours to form a PVA / PVA-SbQ / CNC-PPy / APS gel. In the mixture, the mass fraction of polyvinyl alcohol is 9-11%, the mass fraction of polyvinyl alcohol-styrenepyridine quaternary ammonium salt is 4-6%, and the mass fraction of CNC-PPy / APS is 2-4%. The gel solution was irradiated with ultraviolet light at a wavelength of 365 nm for 0.3~1.2 h to obtain PPCP hydrogel, which was then immersed in FeCl3-PA composite solution for 15~40 minutes and rinsed to obtain multifunctional PVA-based hydrogel.

2. The method for preparing the multifunctional PVA-based hydrogel as described in claim 1, characterized in that: The solid content of the nanocrystalline cellulose aqueous solution is 1~3 wt%.

3. The method for preparing the multifunctional PVA-based hydrogel as described in claim 2, characterized in that: The method for preparing the nanocrystalline cellulose aqueous solution includes, Microcrystalline cellulose and a 60-70 wt% sulfuric acid aqueous solution are mixed evenly at a ratio of 1 g: 15-25 mL, heated at 45-50℃ and stirred to carry out acid hydrolysis reaction for 40-55 min to obtain nanocellulose colloid. To terminate the reaction, add 1-2 L of water to the nanocellulose colloid, let it stand, centrifuge to obtain the precipitate, and disperse it in water to form a suspension. After dialysis to neutral pH, the nanocrystalline cellulose was dispersed by ultrasonication and then rotary evaporated to obtain an aqueous solution.

4. The method for preparing the multifunctional PVA-based hydrogel as described in claim 2, characterized in that: The FeCl3-PA composite solution is prepared by mixing ferric chloride, 70 wt% phytic acid aqueous solution, and water in a mass ratio of 1~4∶6∶0~4.

5. The method for preparing the multifunctional PVA-based hydrogel as described in claim 1, characterized in that: In the FeCl3-NaSSA aqueous solution, the molar concentration of FeCl3·6H2O is 0.3–0.5 M, and the molar concentration of sodium 5-sulfosalicylate is 0.3–0.4 M.

6. The method for preparing the multifunctional PVA-based hydrogel as described in claim 1, characterized in that: The pyrrole-cyclohexane solution contains 1.5 to 3 wt% pyrrole.

7. The method for preparing the multifunctional PVA-based hydrogel as described in claim 1, characterized in that: The volume ratio of the nanocrystalline cellulose aqueous solution, FeCl3-NaSSA aqueous solution, and pyrrole-cyclohexane solution used for the interfacial polymerization reaction is 1:1~3:1~3.

8. The method for preparing the multifunctional PVA-based hydrogel as described in claim 1, characterized in that: The mass ratio of the CNC-PPy solution to ammonium persulfate is 1.9~2.3:0.1~0.

3.

9. A multifunctional PVA-based hydrogel prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the multifunctional PVA-based hydrogel as described in claim 9 in the fabrication of a flexible strain sensor.

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