High-strength and high-conductivity organic hydrogel fiber and preparation method thereof

Abstract

The invention relates to a high-strength and high-conductivity organic hydrogel fiber and a preparation method thereof.The preparation method comprises the steps that sodium alginate and polyvinyl alcohol which have good biocompatibility are dissolved in deionized water to serve as a spinning solution; carrying out coagulating bath on sulfuric acid and glutaraldehyde; the spinning solution is extruded into a coagulating bath through a needle head, and the high-performance organic hydrogel fiber is formed by combining a wet spinning process and a multi-crosslinking strategy (covalent crosslinking, ionic crosslinking and hydrogen bond network synergistic effect). The organic hydrogel fiber prepared by the invention has the characteristics of continuity and controllable diameter, and has high mechanical strength, high conductivity, good moisture retention and stable structural performance.

Description

Technical Field

[0001] This invention belongs to the field of organic hydrogel fiber preparation, and specifically relates to a high-strength, high-conductivity organic hydrogel fiber and its preparation method. Background Technology

[0002] In recent years, flexible electronics have been widely used in wearable health monitoring, human-computer interaction, and flexible energy storage devices, enabling functions such as real-time physiological signal detection and motion posture recognition. However, when traditional flexible electronic materials are applied to in vivo or surface monitoring, they not only suffer from mismatches with the mechanical properties of biological tissues and insufficient electrical signal stability, but also often lack good moisture retention, easily losing their soft and moist properties in dry environments. This leads to decreased mechanical flexibility and reduced biocompatibility, significantly affecting monitoring accuracy and user experience. Therefore, there is an urgent need for a material that combines good biocompatibility, high mechanical flexibility, stable electrical signal conduction performance, and excellent moisture retention to adapt to complex biological environments and achieve accurate signal transmission.

[0003] Hydrogel fibers, as a novel functional material combining the soft and moist properties of hydrogels with the high aspect ratio and weavability of fibers, exhibit unique advantages in the field of flexible sensing. Their excellent biocompatibility can reduce rejection reactions upon contact with organisms, and the fiber morphology facilitates the construction of flexible wearable devices. However, existing preparation methods mostly employ template methods or physical coating, which not only limit the length and diameter of the material due to the template, making it difficult to achieve large-scale continuous preparation, but also result in poor interfacial bonding between electroactive substances and the fiber substrate, leading to insufficient electrochemical stability and mechanical properties. Furthermore, existing hydrogel fibers have poor moisture retention properties, easily becoming hard and brittle due to moisture loss during use, further limiting their application in flexible electronics. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a high-strength, high-conductivity organic hydrogel fiber and its preparation method. By constructing a multi-crosslinked structure with the synergistic effect of covalent crosslinking, ionic crosslinking and hydrogen bonding network, the invention overcomes the problems of traditional hydrogel fibers, such as limited size, difficulty in continuous production, insufficient mechanical and electrochemical stability, and poor moisturizing performance. In this invention, polyvinyl alcohol and sodium alginate with good biocompatibility are dissolved in deionized water as spinning solution, and a mixed solution of sulfuric acid and glutaraldehyde is used as coagulation bath. The spinning solution is extruded through a needle into the coagulation bath for wet spinning, followed by steps such as soaking in calcium chloride, freeze-thaw treatment, and soaking in a mixed solution of glycerol, potassium chloride and calcium chloride. The combination of multiple crosslinking strategies forms high-performance organic hydrogel fibers.

[0005] The present invention discloses a continuous preparation method for high-strength, high-conductivity organic hydrogel fibers, characterized by comprising the following steps:

[0006] (1) Dissolve polyvinyl alcohol and sodium alginate in deionized water, heat and stir until completely dissolved to form a uniform and stable spinning solution;

[0007] (2) Dissolve sulfur and glutaraldehyde in deionized water in a certain proportion, stir and mix evenly to form a coagulation bath; (3) Extrude the above spinning solution into the coagulation bath through a needle and perform wet spinning. First, the aldehyde group in the glutaraldehyde molecule in the coagulation bath reacts with the hydroxyl group on the polyvinyl alcohol molecular chain to form a preliminary covalent cross-linking network; at the same time, the hydrogen ions provided by sulfuric acid keep the system in an acidic environment, promote the reaction of glutaraldehyde and hydroxyl groups to be more complete, and form nascent fibers with a preliminary structure.

[0008] (4) Remove the nascent fibers from the coagulation bath and immerse them in a calcium chloride solution. At this time, the calcium ions released from the calcium chloride dissociate and the carboxyl groups on the alginate molecular chain undergo ionic cross-linking through electrostatic interaction, forming a second ionic cross-linking network inside the fiber, which further enhances the structural stability of the fiber.

[0009] (5) The fibers soaked in calcium chloride were subjected to a freeze-thaw treatment. During the freezing process, water molecules crystallized, forcing the polymer chains of polyethylene and sodium alginate to come closer together. After thawing, the molecular chains stretched out again, and the hydrogen bond interactions between molecules were enhanced, which promoted the formation of a tighter and more stable three-dimensional network structure of the fibers, and the pore structure was further optimized.

[0010] (6) The frozen and thawed fibers are immersed in a mixed solution of glycerol, potassium chloride, and calcium chloride. The hydroxyl groups in the glycerol molecule form hydrogen bonds with the polar groups on the polyvinyl alcohol and sodium alginate molecular chains, which play a role in moisturizing and enhancing the flexibility of the fibers. At the same time, the potassium ions, calcium ions, and chloride ions dissociated from potassium chloride and calcium chloride attract the charged groups on the polymer chains through electrostatic interactions, stabilizing the network structure of the fibers and finally forming stable organic hydrogel fibers. The finished product is obtained by winding and collecting the fibers.

[0011] The preferred embodiment of the above preparation method is as follows:

[0012] In step (1), the spinning solution contains approximately 25% polyvinyl alcohol, approximately 6% sodium alginate, and the remainder is deionized water.

[0013] The coagulation bath in step (2) consists of a sulfuric acid concentration of 1 mol / L and a glutaraldehyde mass fraction of 25%.

[0014] The needle diameter used in the wet spinning process in step (3) is 0.55-1.00 mm.

[0015] In step (3), the extrusion is performed by using a propulsion pump to extrude the spinning solution through the syringe needle; the extrusion rate is 0.5 mL / min.

[0016] The mass fraction of calcium chloride in step (4) is 5%.

[0017] In step (5), the freezing time is 12 hours and the thawing time is 0.5 hours.

[0018] In step (6), the concentration of potassium chloride is 0.5 mol / L, the concentration of calcium chloride is 1 mol / L, and the ratio of glycerol to deionized water is 1:1.

[0019] An organic hydrogel fiber prepared by the method of the present invention.

[0020] This invention also provides an apparatus for the continuous preparation of organic conductive hydrogel fibers, wherein the apparatus sequentially comprises: a raw material mixing zone, a fiber initial formation zone, a fiber treatment zone, and a finished product collection zone. The raw material mixing zone is equipped with a stirring device for mixing and treating the raw materials to form a uniform and stable spinning solution. The fiber initial formation zone includes a conveying component and a coagulation bath for conveying the spinning solution to the coagulation bath for preliminary reaction to form nascent fibers. The fiber treatment zone includes multiple treatment tanks and treatment equipment for sequentially performing crosslinking, structural optimization, and performance enhancement treatments on the nascent fibers. The finished product collection zone is equipped with a collection component for collecting the finally formed, performance-stable organic hydrogel fibers. The reaction conditions of each treatment stage are coordinated to optimize the overall performance of the fiber.

[0021] Beneficial effects

[0022] To address the shortcomings of traditional hydrogel fibers, such as size limitations, difficulty in large-scale continuous preparation, poor interfacial bonding between electroactive substances and the fiber substrate leading to insufficient mechanical and electrochemical stability, and poor moisturizing performance, this invention achieves the continuous preparation of high-strength, high-conductivity organic hydrogel fibers by constructing a multi-crosslinked structure with synergistic effects of covalent crosslinking, ionic crosslinking, and hydrogen bonding networks, combined with wet spinning technology. This process involves wet spinning of polyvinyl alcohol and sodium alginate spinning solution to form initially covalently crosslinked nascent fibers, followed by sequential soaking in calcium chloride to form ionic crosslinking, freeze-thaw cycles to enhance hydrogen bonding, and soaking in a mixed solution to optimize performance. The synergistic reaction conditions at each stage solve the problems of size limitations, poor continuity, and insufficient performance in traditional preparation methods, while simultaneously improving the fiber's mechanical strength, conductivity, and moisturizing properties.

[0023] The present invention relates to a high-strength, high-conductivity organic hydrogel fiber and its preparation method. The method involves preparing a spinning solution by dissolving sodium alginate and vinyl alcohol, which have good biocompatibility, in deionized water. The spinning solution is then extruded through a needle into a coagulation bath containing sulfuric acid and glutaraldehyde. Following this, the fiber is sequentially immersed in calcium chloride, subjected to freeze-thaw treatment, and then immersed in a mixed solution of glycerol, potassium chloride, and calcium chloride. This process combines wet spinning technology with a multiple crosslinking strategy (covalent crosslinking, ionic crosslinking, and the synergistic effect of hydrogen bonding networks) to form a high-performance organic hydrogel fiber. To address the challenge of balancing mechanical properties and structural stability in traditional hydrogel fibers, this invention constructs a dual crosslinked network structure. This structure comprises a covalent crosslinked network formed by the aldol reaction of glutaraldehyde and the hydroxyl groups of polyvinyl alcohol, and an ionic crosslinked network formed by the electrostatic interaction between calcium ions dissociated from calcium chloride and carboxyl groups on the sodium alginate molecular chain. These two networks work synergistically, and combined with the intermolecular hydrogen bonding enhanced by freeze-thaw treatment, further optimize the three-dimensional network structure of the fiber. This effectively improves the fiber's mechanical strength and structural stability, solving the performance deficiencies caused by the single network structure of traditional hydrogel fibers. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a high-strength, high-conductivity organic hydrogel fiber continuous spinning system in Example 1;

[0025] Figure 2 This is a schematic diagram of the internal structure of the organic hydrogel fiber in Example 1;

[0026] Figure 3 This is a scanning electron microscope image of the organic conductive hydrogel fiber in Example 1;

[0027] Figure 4 The stress-strain curves of the organic conductive hydrogel fiber in Example 1 at different sodium alginate mass fractions at the final concentration are shown.

[0028] Figure 5 The stress-strain curves of the organic conductive hydrogel fiber in Example 1 under different needle sizes are shown.

[0029] Figure 6 This is a graph showing the variation of the strain coefficient of the organic conductive hydrogel fiber in Example 1;

[0030] Figure 7 The graph shows the response time of the organic conductive hydrogel fiber in Example 1. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various modifications or alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims. The apparatus used in the embodiments includes: a raw material mixing zone, a fiber initial formation zone, a fiber processing zone, and a finished product collection zone; the raw material mixing zone is equipped with a stirring device for forming a uniform and stable spinning solution; the fiber initial formation zone includes a propulsion pump, a syringe needle of a specific specification, and a container containing a coagulation bath; the fiber processing zone includes multiple processing tanks and a freeze-thaw device for sequentially processing the nascent fibers; the finished product collection zone is equipped with a winding device for fiber stretching and collection. All reagents used in the experiments are analytical grade and can be used directly without further purification.

[0032] Example 1

[0033] At room temperature, weigh 2.5g of polyvinyl alcohol and place it in 7.5g of deionized water. Stir at 60℃ for 30min until swollen, then raise the temperature to 90℃ and continue stirring until completely dissolved. Add 0.6g of sodium alginate and continue stirring until a uniform and stable spinning solution (polyvinyl alcohol 25% by mass, sodium alginate 6% by mass) is formed. Add an appropriate amount of deionized water to a beaker, then add 1mol / L sulfuric acid and 25% glutaraldehyde by mass, stirring until homogeneous to prepare a coagulation bath. During wet spinning, extrude the spinning solution into the coagulation bath through a 0.65mm syringe needle at a flow rate of 0.5mL / min, and allow it to stand to allow the glutaraldehyde to react with the polyvinyl alcohol. Vinyl alcohol undergoes an aldol reaction to form nascent fibers. The nascent fibers are then removed and soaked in a 5% calcium chloride solution for 30 minutes to allow calcium ions to form ionic crosslinks with the carboxyl groups of sodium alginate. Subsequently, the fibers are frozen in a refrigerator for 12 hours and then thawed at room temperature for 0.5 hours to enhance intermolecular hydrogen bonding. Finally, the fibers are soaked in a mixed solution of glycerol:deionized water = 1:1 containing 0.5 mol / L potassium chloride and 1 mol / L calcium chloride. After removal, the fibers are collected by winding to obtain organic hydrogel fibers with uniform diameter. These fibers exhibit excellent mechanical properties (high tensile strength and fracture strain), high electrical conductivity, and good moisture retention and structural stability.

[0034] A schematic diagram of a continuous spinning system for high-strength, high-conductivity organic hydrogel fibers, as shown below. Figure 1As shown in the figure, the system mainly consists of a raw material mixing zone, a fiber initial formation zone, a fiber treatment zone, and a finished product collection zone. In the raw material mixing zone, a stirring device dissolves polyvinyl alcohol and sodium alginate in deionized water through heating and stirring, forming a uniform and stable spinning solution to provide the basic raw material for subsequent spinning. In the fiber initial formation zone, a pump provides stable power, extruding the spinning solution at a constant rate through a syringe needle into a coagulation bath containing sulfuric acid and glutaraldehyde, allowing glutaraldehyde to react with polyvinyl alcohol to form preliminary covalently cross-linked nascent fibers. In the fiber treatment zone, multiple treatment tanks and equipment are used to optimize the nascent fibers. First, the fibers are soaked in calcium chloride solution to form an ionic cross-linked network. Then, a freeze-thaw treatment enhances intermolecular hydrogen bonding. Finally, soaking in a mixed solution of glycerol, potassium chloride, and calcium chloride improves moisture retention and structural stability, gradually enhancing fiber performance. Finally, the fibers are collected by a winding device in the finished product collection zone, achieving continuous preparation of organic hydrogel fibers. A schematic diagram of the internal structure of the organic hydrogel fiber is shown below. Figure 2 As shown in the figure, polyvinyl alcohol (PVA) and glutaraldehyde form a covalent cross-linked network through an aldol reaction, while calcium ions dissociated from calcium chloride form an ionic cross-linked network with the carboxyl groups on the sodium alginate molecular chain through electrostatic interactions. Simultaneously, the freeze-thaw treatment promotes closer proximity between the PVA and sodium alginate molecular chains, enhancing intermolecular hydrogen bonding. The hydroxyl groups of glycerol molecules also form additional hydrogen bonds with the polar groups of PVA and sodium alginate. Furthermore, the potassium, calcium, and chloride ions dissociated from potassium chloride and calcium chloride attract the charged groups of the polymer chains through electrostatic interactions, further stabilizing the network structure. Ultimately, this results in an organic hydrogel fiber with a tightly packed and stable three-dimensional network structure.

[0035] Scanning electron microscopy image of organic hydrogel fibers as follows Figure 3 As shown in the figure, the fibers have a regular morphology, and the diameter of the organic hydrogel fibers prepared by this method is approximately 750 μm.

[0036] Stress-strain curves of organic hydrogel fibers at different sodium alginate mass fractions at final concentrations, as shown in the figure. Figure 4 As shown in the figure, when the mass fraction of sodium alginate is 3%, the stress-strain curve of the fiber is at a higher position, corresponding to the best mechanical properties, exhibiting better tensile strength and elongation at break. This may be because at this mass fraction, sodium alginate and polyvinyl alcohol molecular chains can form more sufficient interaction, with moderate crosslinking density, resulting in a more uniform and stable structure.

[0037] Stress-strain curves of organic conductive hydrogel fibers under different needle sizes, such as Figure 5As shown in the figure, when using a needle with a diameter of 0.65 mm, the curve is generally higher than the curves corresponding to other needle sizes. The stress of the fiber increases more reasonably with strain, exhibiting the highest elongation at break and tensile strength. However, needle sizes that are too large or too small will cause large fluctuations in the curve and a decrease in mechanical properties, indicating that a 0.65 mm needle is the ideal choice for preparing this fiber.

[0038] The strain coefficient variation graph of organic conductive hydrogel fibers, as shown below. Figure 6 As shown in the figure, the fiber exhibits excellent sensing sensitivity in different strain ranges. When the strain is less than 130%, the strain coefficient (GF) reaches 1.68; in the strain range of 130% to 230%, the GF increases to 2.67; and when the strain exceeds 230%, the GF is as high as 3.53, which is far more sensitive than strain sensors currently on the market.

[0039] Response time test graph of organic conductive hydrogel fiber, as shown Figure 7 As shown in the figure, the fiber exhibits rapid and stable resistance changes during rapid stretching and rebound, with a response time of only 0.15s, demonstrating excellent dynamic response performance.

[0040] Example 2

[0041] At room temperature, 2.5g of polyvinyl alcohol was weighed and placed in 7.5g of deionized water. The mixture was stirred at 60℃ for 30min until swollen, then heated to 90℃ and stirred until completely dissolved. 0.6g of sodium alginate was then added, and stirring continued until a uniform and stable spinning solution (polyvinyl alcohol mass fraction 25%, sodium alginate mass fraction 6%) was formed. An appropriate amount of deionized water was added to a beaker, followed by 1M sulfuric acid and 15% (modified glutaraldehyde mass fraction) of glutaraldehyde. The mixture was stirred until homogeneous to prepare a coagulation bath. During wet spinning, the spinning solution was extruded through a 0.65mm syringe needle at a flow rate of 0.5mL / min. The fibers were placed in a coagulation bath and allowed to stand to allow glutaraldehyde and polyvinyl alcohol to undergo an aldol reaction to form nascent fibers. The nascent fibers were then removed and immersed in a 5% calcium chloride solution for 30 minutes to allow calcium ions to form ionic crosslinks with the carboxyl groups of sodium alginate. Subsequently, the fibers were frozen in a refrigerator for 12 hours and then thawed at room temperature for 0.5 hours to enhance intermolecular hydrogen bonding. Finally, the fibers were immersed in a mixed solution of glycerol:deionized water = 1:1 containing 0.5 mol / L potassium chloride and 1 mol / L calcium chloride. After removal, the fibers were collected by winding to obtain organic hydrogel fibers with uniform diameter. The mechanical properties, electrical conductivity, and other properties of these fibers can be further characterized by subsequent testing.

[0042] Example 3

[0043] Weigh 2.5g of polyvinyl alcohol at room temperature and place it in 7.5g of deionized water. Stir at a constant speed at 60℃ for 30min to allow the polyvinyl alcohol to swell. Then, raise the temperature to 90℃ and continue stirring until completely dissolved. Next, add 0.4g of sodium alginate (adjusting the mass fraction from 6% to 4%) and continue stirring until a uniform and stable spinning solution (polyvinyl alcohol mass fraction 25%) is formed. In a separate beaker, add an appropriate amount of deionized water, then add 1mol / L sulfuric acid and 25% glutaraldehyde, stirring until well mixed to prepare a coagulation bath. Extrude the spinning solution at a flow rate of 0.5mL / min through a 0.65mm syringe needle and inject it into the coagulation bath for wet spinning, allowing the glutaraldehyde to react with the hydroxyl groups of the polyvinyl alcohol. The basal group undergoes an aldol reaction to form nascent fibers. After 30 minutes, the nascent fibers are removed and immersed in a 5% calcium chloride solution for 30 minutes, allowing calcium ions to form ionic crosslinks with the carboxyl groups of sodium alginate through electrostatic interaction. Subsequently, the fibers are frozen in a refrigerator for 12 hours and then thawed at room temperature for 0.5 hours to enhance intermolecular hydrogen bonding. Finally, the fibers are immersed in a mixed solution of glycerol:deionized water = 1:1 containing 0.5 mol / L potassium chloride and 1 mol / L calcium chloride, and collected by a winding device to obtain organic hydrogel fibers with uniform diameter. Compared with the fibers prepared with the original concentration (6% sodium alginate), the ionic crosslinking density is reduced due to the reduced amount of sodium alginate, resulting in slight changes in mechanical properties and electrical conductivity.

Claims

1. A continuous preparation method for high-strength, high-conductivity organic hydrogel fibers, characterized in that, Includes the following steps: (1) Dissolve polyvinyl alcohol and sodium alginate in deionized water, heat and stir until completely dissolved to form a uniform and stable spinning solution; (2) Dissolve sulfuric acid and glutaraldehyde in deionized water in a certain proportion, stir and mix evenly to form a coagulation bath; (3) The above spinning solution is extruded into the coagulation bath through a needle for wet spinning. First, the aldehyde group in the glutaraldehyde molecule in the coagulation bath reacts with the hydroxyl group on the polyvinyl alcohol molecular chain to form a preliminary covalent cross-linking network; at the same time, the hydrogen ions provided by sulfuric acid keep the system acidic, promote the reaction between glutaraldehyde and hydroxyl groups to be more complete, and form nascent fibers with a preliminary structure. (4) Remove the nascent fibers from the coagulation bath and immerse them in a calcium chloride solution. At this time, the calcium ions dissociated from the calcium chloride react with the carboxyl groups on the sodium alginate molecular chain through electrostatic interaction to form a second ionic cross-linking network inside the fiber, which further enhances the structural stability of the fiber. (5) The fibers soaked in calcium chloride were subjected to a freeze-thaw treatment. During the freezing process, water molecules crystallized, forcing the polymer chains of polyvinyl alcohol and sodium alginate to come closer together. After thawing, the molecular chains stretched out again, and the hydrogen bond interactions between molecules were enhanced, which promoted the formation of a tighter and more stable three-dimensional network structure of the fibers, and the pore structure was further optimized. (6) The frozen and thawed fibers are immersed in a mixed solution of glycerol, potassium chloride, and calcium chloride. The hydroxyl groups in the glycerol molecule form hydrogen bonds with the polar groups on the polyvinyl alcohol and sodium alginate molecular chains, which play a role in moisturizing and enhancing the flexibility of the fibers. At the same time, the potassium ions, calcium ions, and chloride ions dissociated from potassium chloride and calcium chloride attract the charged groups on the polymer chains through electrostatic interactions, stabilizing the network structure of the fibers and finally forming stable organic hydrogel fibers. The finished product is obtained by winding and collecting the fibers.

2. The preparation method according to claim 1, characterized in that, In step (1), the spinning solution contains approximately 25% polyvinyl alcohol, approximately 6% sodium alginate, and the remainder is deionized water.

3. The preparation method according to claim 1, characterized in that, The coagulation bath in step (2) consists of a sulfuric acid concentration of 1 mol / L and a glutaraldehyde mass fraction of 25%.

4. The preparation method according to claim 1, characterized in that, The needle diameter used in the wet spinning process in step (3) is 0.55-1.00 mm.

5. The preparation method according to claim 1, characterized in that, In step (3), the extrusion is performed by using a propulsion pump to extrude the spinning solution through the needle of a syringe; Its extrusion rate is 0.5 mL / min.

6. The preparation method according to claim 1, characterized in that, The mass fraction of calcium chloride in step (4) is 5%.

7. The preparation method according to claim 1, characterized in that, In step (5), the freezing time is 12 hours and the thawing time is 0.5 hours.

8. The preparation method according to claim 1, characterized in that, In step (6), the concentration of potassium chloride is 0.5 mol / L, the concentration of calcium chloride is 1 mol / L, and the ratio of glycerol to deionized water is 1:

1.

9. An organic hydrogel fiber prepared according to the method of claim 1.

10. An apparatus for the continuous preparation of organic hydrogel fibers according to claim 1, wherein the apparatus comprises, in sequence: The system comprises a raw material mixing zone, a fiber initial formation zone, a fiber treatment zone, and a finished product collection zone. The raw material mixing zone is equipped with a stirring device to mix and treat the raw materials until a uniform and stable spinning solution is formed. The fiber initial formation zone includes a conveying component and a coagulation bath to transport the spinning solution to the coagulation bath for preliminary reaction to form nascent fibers. The fiber treatment zone includes multiple treatment tanks and treatment equipment to sequentially perform crosslinking, structural optimization, and performance enhancement treatments on the nascent fibers. The finished product collection zone is equipped with a collection component to collect the finally formed, stable organic hydrogel fibers. The reaction conditions of each treatment stage are coordinated to optimize the overall performance of the fibers.

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