Preparation method of ionic gel fiber with multi-stage orientation structure

Abstract

The invention discloses a preparation method of an ionic gel fiber with a multi-stage orientation structure. The preparation method comprises the following steps: firstly, taking bacterial cellulose as a framework, and loading silver nanoparticles to form a cellulose nanofiber and silver nanoparticle compound; the preparation method comprises the following steps: performing in-situ polymerization on polyacrylamide and sodium polyacrylate on the surfaces of silver nanoparticles through Ag-S coordination to form a bottle-brush-shaped nano-composite structural unit, and performing shear forming, drying, pre-stretching and twisting and ionic liquid solvent replacement to obtain the bottle-brush-shaped nano-composite structural unit. The ionic gel fiber with a micron-scale orientation structure and a molecular-scale dynamic metal coordination cross-linked structure is formed. The obtained gel fiber has high strength, high toughness, excellent damping performance and humidity response performance, can realize near-infrared light induced self-repairing and water-soluble recovery, and has wide application prospects in the fields of flexible devices, bionic driving, intelligent spinning and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing high-toughness ion gel fibers with a multi-level orientation structure, and belongs to the technical field of intelligent fiber materials. Background Art

[0002] With the rapid development of technologies such as flexible electronics, smart wearable devices, biomimetic robotics, and soft actuators, flexible functional materials have gradually become a cutting-edge research topic in materials science. Among them, gel fibers, due to their high flexibility, weavability, good biocompatibility, and rapid response to various stimuli (such as water, heat, electricity, and light), have shown broad application potential in flexible sensors, wearable electronics, smart textiles, and tissue engineering.

[0003] Gel fibers are essentially three-dimensional polymer networks with high water content, formed into elongated structures through fiberization. Compared to traditional bulk gels, gel fibers possess larger specific surface area, higher mass transfer efficiency, and stronger directional mechanical properties. However, existing gel fiber materials still face challenges such as poor mechanical properties, a conflict between strength and toughness, limited responsiveness, and difficulty in structural control. Against this backdrop, natural materials (such as spider silk and tendon) offer unique biomimetic design inspiration for the construction of artificial gel fibers due to their multi-level oriented microstructures and excellent ability to synergize mechanical and functional properties. Spider silk, in particular, possesses high strength, high toughness, high energy dissipation capacity, and moisture-driven properties, making it an ideal template for the biomimetic construction of high-performance fiber materials.

[0004] Therefore, there is an urgent need to draw inspiration from natural materials and develop a gel fiber material with high strength, high toughness, responsiveness and recyclability, break through the performance bottleneck of traditional gel fiber materials, and promote its application in high-end fields such as flexible electronics, smart textiles, and bionic drives. Summary of the Invention

[0005] To address these issues, the present invention provides a method for preparing ion gel fibers with a multi-level orientation structure. This method utilizes a high-aspect-ratio nanocomposite crosslinker, cellulose nanofibers, and silver nanoparticles to construct a bottlebrush-like polymer composite structural unit. Through shear molding, pre-stretching and twisting, and solvent displacement, the fibers achieve high fiber orientation and multi-level structure. The resulting ion gel fibers exhibit high strength, high toughness, high damping capacity, and stimulus responsiveness.

[0006] The present invention discloses a method for preparing ion gel fibers with a multi-level oriented structure. The method comprises the following steps: using bacterial cellulose as a skeleton to load silver nanoparticles as a nanocomposite crosslinking agent; in situ growing polyacrylamide / sodium acrylate chains on the surface of the silver nanoparticles through Ag-S coordination to form bottle-brush-shaped nanocomposite structural units; and finally obtaining ion gel fibers with a micron-level oriented structure and a molecular-level dynamic metal coordination crosslinking structure through shearing, drying, pre-stretching and twisting, and ionic liquid solvent replacement.

[0007] The method for preparing the ion gel fiber having a multi-level orientation structure of the present invention comprises the following steps:

[0008] Step 1: Preparation of bacterial cellulose nanofibrils

[0009] The Acetobacter xylinum strain (purchased from the China General Microbiological Culture Collection Center (CGMCC), No. 1.1812) was inoculated into a solid culture medium and cultured at 28°C. During the subsequent continuous fermentation process, liquid nutrients gradually deposited on the surface of the solid culture medium in the form of aerosols. After 24 hours of continuous fermentation, bacterial cellulose was obtained. The obtained bacterial cellulose was then mechanically treated using a blender and fully dispersed in deionized water. The resulting dispersion was further treated in a high-pressure homogenizer at a pressure of 1000 bar for at least three times to obtain a cellulose nanofibril dispersion.

[0010] In step 1, the solid culture medium comprises: 50 g / L glucose, 5 g / L yeast extract, 10 g / L calcium carbonate, and 20 g / L agar. Each component is dissolved in deionized water and sterilized by high pressure at 121° C. for 30 min.

[0011] Step 2: Preparation of cellulose nanofiber@silver nanoparticle composite

[0012] Using the hydrothermal deposition method, 0.4 mL of 1% silver nitrate solution and 15 mL of 0.3% mass fraction cellulose nanofiber solution were mixed in 14.6 mL of deionized water. The above solution was then transferred to a 50 mL polytetrafluoroethylene substrate, placed in a reactor and heated at 110°C for 12 h. The silver ions were reduced to silver nanoparticles by utilizing the reducing property of the hydroxyl groups on the surface of the cellulose nanofibers and anchored on the surface of the cellulose nanofibers. The resulting light yellow suspension was centrifuged at 10,000 rpm for 10 min and then washed three times with deionized water to remove unreacted reactants to obtain a cellulose nanofiber@silver nanoparticle nanocomposite material.

[0013] In step 2, the length of a single cellulose nanofiber is between 4-10 μm and the diameter is between 7-20 nm; the particle size of the silver nanoparticles is 10-30 nm, they are evenly distributed and are surface-modified by a sulfur-containing initiator in a subsequent step.

[0014] Step 3: Preparation of bottlebrush nanocomposite gel

[0015] 2.5 mL of cellulose nanofiber@silver nanoparticle solution was placed in a glass bottle, and 1 mg of the photoinitiator 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone was added. The solution was then ultrasonically treated for 10 minutes to ensure adsorption on the surface of the silver nanoparticles to form a nanocomposite crosslinker. Acrylamide and sodium acrylate monomers were then added, ultrasonically mixed, and polymerized under xenon lamp irradiation (wavelength 320 nm-2500 nm) to obtain a uniform, light yellow bottle-brush-type nanocomposite gel.

[0016] In step 3, the mass concentration of the cellulose nanofiber@silver nanoparticle solution is 0.1%-0.5%; the mass of the monomer acrylamide is 0.3-0.7 g, the molar ratio of acrylamide to sodium acrylate is 2:1-5:1, and the polymerization time is controlled at 25-35 min.

[0017] Step 4: Preparation of multi-level oriented ion gel fibers

[0018] The bottlebrush-shaped nanocomposite gel prepared in step 3 was placed in an injection syringe and extruded through a needle with an inner diameter of 0.4 mm using an air compressor, precisely controlling the injection pressure. This produced hydrogel fibers. Subsequently, the resulting hydrogel fibers were briefly dried under ambient conditions and pre-stretched and twisted. The stretched and twisted hydrogel fibers were fixed at both ends and further stabilized by water evaporation. They were then placed in an ionic liquid for solvent exchange for a specified period of time, yielding ion gel fibers with a hierarchically oriented structure.

[0019] In step 4, the drying time is 30-60 min; the pre-stretching ratio is 1-5 times, the twisting number is 20 turns / cm, the ionic liquid used is 1-ethyl-3-methylimidazolyl ethyl sulfate, and the solvent replacement time is 5-30 min.

[0020] The resistivity of the deionized water used in the present invention is 18.2 MΩ·cm at 25°C.

[0021] The beneficial effects of the present invention are embodied in:

[0022] When preparing high-performance ion gel fibers, the present invention uses inorganic nanomaterials with a high aspect ratio as the skeleton, and constructs a one-dimensional bottle brush-type structural unit based on the Ag-S coordination effect. Through shearing, pre-stretching and water evaporation auxiliary induction, the polymer chains in the network are directional arranged to form a multi-level ordered structure, and the dynamic reversible Ag-S coordination bond, hydrogen bond and entanglement effect are synergistically exerted, thereby significantly improving the mechanical properties and stimulus response performance of the gel fiber.

[0023] In summary, the present invention provides a method for preparing high-performance ion gel fibers. By combining nanocomposite network design with multi-level structural control technology, the material's mechanical properties, recyclability, and responsiveness are significantly improved. This results in synergistic optimization of strength and toughness, and mechanical and stimuli-responsive performance. This invention provides a new method and theoretical basis for the structural design and performance improvement of gel fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The transmission electron microscope photos of the cellulose nanofibers and cellulose nanofibers@silver nanoparticles prepared in the present invention are shown in FIG. Figure 1 It can be seen from the figure that cellulose nanofibers have a high aspect ratio; silver nanoparticles are evenly distributed on the surface of cellulose nanofibers, and their diameters are mainly distributed between 14-30 nm.

[0025] Figure 2 The viscosity-shear rate curve of the nanocomposite hydrogel prepared by the present invention is shown in FIG. Figure 2 It can be seen that with the increase of monomer mass fraction (the mass proportion of monomer in the entire gel system), the initial viscosity of the hydrogel increases, and with the increase of shear rate, the viscosity of all hydrogels decreases significantly, meeting the initial screening conditions for shearability, laying the foundation for the preparation of high-performance ion gel fibers.

[0026] Figure 3 This is a scanning electron microscope photo of the ion gel fiber with a multi-level orientation structure prepared by the present invention. Figure 3 It can be seen that as the twisting is applied, the fiber forms a spiral structure and the interface is well welded through hydrogen bonding.

[0027] Figure 4 This is the stress-strain curve of the ion gel fiber with a multi-level orientation structure prepared by the present invention. Figure 4 It can be seen that with the increase of pre-stretching ratio, the breaking strength of the fiber increases and the breaking strain decreases.

[0028] Figure 5 The loading-unloading curves of the ion gel fiber with multi-level orientation structure prepared by the present invention under different strains. Figure 5It can be seen that the tensile strain ranges from 100% to 500% and exhibits obvious hysteresis behavior, reflecting its excellent energy dissipation capacity and damping performance.

[0029] Figure 6 The shrinkage stress-time curve of the ion gel fiber with multi-level orientation structure prepared by the present invention is shown in FIG. Figure 6 It can be seen that the fiber pre-stretched 5 times has a shrinkage stress of 16.09 MPa, reflecting its good stimulus response performance.

[0030] Figure 7 The stress-strain curves of the ion gel fiber prepared by the present invention before and after water recovery. Figure 7 It can be seen that the fibers prepared after recycling still maintain good mechanical properties, indicating that the recycling process has no significant effect on the mechanical properties of the fibers. DETAILED DESCRIPTION

[0031] The reagents, raw materials and equipment used in the present invention are all commercially available products and can be purchased on the market.

[0032] Example 1: Preparation of bacterial cellulose nanofibril dispersion

[0033] Acetobacter xylinum (purchased from the China General Microorganism Culture Collection Center (CGMCC), No. 1.1812) was inoculated into a solid culture medium and cultured at 28°C. After 24 hours of continuous fermentation, bacterial cellulose was obtained. The resulting bacterial cellulose was then mechanically treated using a blender and thoroughly dispersed in deionized water. This dispersion was further treated at least three times in a high-pressure homogenizer at 1000 bar to obtain the final CNF dispersion.

[0034] The solid culture medium consists of glucose (50 g / L), yeast extract (5 g / L), calcium carbonate (10 g / L) and agar (20 g / L), which are dissolved in deionized water. The culture medium is heated and stirred to ensure that all components are fully dissolved, and then heated at 121 o Sterilize by high pressure at C for 30 min.

[0035] Example 2: Preparation of cellulose nanofiber@silver nanoparticle composite

[0036] 0.4 mL of a 1% silver nitrate solution and 15 mL of a 0.3% cellulose nanofiber solution were mixed in 14.6 mL of deionized water. The solution was then transferred to a 50 mL polytetrafluoroethylene substrate, placed in a reactor, and heated at 110°C for 12 hours. The silver ions were reduced to silver nanoparticles by utilizing the reducing properties of the hydroxyl groups on the cellulose nanofiber surface and immobilized on the cellulose nanofiber surface. The resulting pale yellow suspension was centrifuged at 10,000 rpm for 10 minutes and then washed three times with deionized water to remove unreacted reactants, resulting in a cellulose nanofiber-silver nanoparticle composite.

[0037] Example 3: Preparation of bottlebrush nanocomposite gel

[0038] To a 2.5 mL glass vial containing a 0.5% cellulose nanofiber / silver nanoparticle solution, 1 mg of the photoinitiator 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone was added. The solution was ultrasonically treated for 10 minutes to ensure adsorption onto the silver nanoparticle surface, forming a nanocomposite crosslinker. A predetermined amount of acrylamide and sodium acrylate monomers (at a molar ratio of 4:1) were then added, and the solution was ultrasonicated for 10 minutes in an ultrasonic bath. After thorough mixing, the solution was polymerized in a xenon lamp for 25 minutes, yielding a uniform, pale yellow, bottle-brush-like nanocomposite gel.

[0039] Example 4: Preparation of multi-level oriented ion gel fibers

[0040] The hydrogel prepared in the previous step was placed in an injection syringe and extruded through a 0.4 mm inner diameter needle using an air compressor to precisely control the injection pressure, thereby producing hydrogel fibers. Subsequently, the resulting hydrogel fibers were briefly dried under ambient conditions and subjected to a pre-stretching and twisting treatment. The pre-stretched, stretched, and twisted hydrogel fibers were fixed at both ends to further stabilize their structure through hydrogen bonding and water evaporation. Subsequently, they were placed in an ionic liquid for a period of solvent exchange, resulting in ion gel fibers with a hierarchical orientation.

[0041] Example 5: Study on the Stimulus Response and Water Recovery Performance of Multi-Level Oriented Ion Gel Fibers

[0042] The ion gel fibers (100 mm in length) prepared in the previous step, pre-stretched 2-5 times, were clamped at both ends on an electronic universal material testing machine. Hydration stimulation was applied, and the shrinkage stress-time curve of the gel fibers was obtained to evaluate the shrinkage stress of the material under different pre-stretching conditions. The prepared fibers were dissolved in deionized water at room temperature for 24 hours, and then the excess water was evaporated to obtain the recovered nanocomposite hydrogel, which was then reassembled to prepare the ion gel fibers. The recovered fibers were then subjected to uniaxial stretching again to obtain the stress-strain curve of the recycled gel fibers.

[0043] The present invention introduces bacterial cellulose as a one-dimensional skeleton and utilizes Ag-S coordination to construct a nanocomposite network. The present invention provides a high-strength, high-toughness, self-repairable and recyclable ion gel fiber and its preparation method. By introducing bacterial cellulose nanofibrils as a one-dimensional skeleton, Ag-S coordination is utilized to in situ grow polymer chains on the surface of silver nanoparticles to construct a nanocomposite network, and a multi-level entanglement structure and high-density hydrogen bonding are introduced between the polymer chains, thereby significantly improving the overall mechanical properties and structural stability of the gel network. On this basis, combined with the structural characteristics of bionic spider silk, a sequential assembly strategy of shear molding, pre-stretching twisting assembly and solvent replacement is adopted to successfully construct a high-performance ion gel fiber with a multi-level oriented structure. The obtained fiber exhibits excellent mechanical properties, including a breaking strength of 278.54 MPa and a high-density hydrogen bond of 1652.15 MJ / m 3 At the same time, the material has good stimulus response ability, and can achieve an actuation strain of 60.3% and an energy density of 236.38 J / kg under hydration conditions. In addition, thanks to its dynamically reversible Ag-S coordination bond and hydrogen bond network structure, the gel fiber can be recycled and reprocessed multiple times through the dissolution-recombination process, showing good sustainability. This invention provides a new strategy for the design and engineering application of flexible smart materials and has broad industrial prospects.

Claims

1. A method for preparing an ion gel fiber having a multi-level oriented structure, characterized in that: First, bacterial cellulose is used as the skeleton to load silver nanoparticles to form a cellulose nanofiber@silver nanoparticle complex; through the Ag-S coordination effect, polyacrylamide and sodium polyacrylate are in situ polymerized on the surface of silver nanoparticles to form a bottle-brush-like nanocomposite structural unit. After shearing, drying, pre-stretching and twisting, and ionic liquid solvent replacement steps, an ion gel fiber with a micron-scale orientation structure and a molecular-level dynamic metal coordination cross-linking structure is formed.

2. The preparation method according to claim 1, wherein The steps include: Step 1: Preparation of bacterial cellulose nanofibrils The Acetobacter xylinum strain is inoculated into a solid culture medium and cultured at 28°C. During the subsequent continuous fermentation process, liquid nutrients are gradually deposited on the surface of the solid culture medium in the form of aerosols. After a certain period of continuous fermentation, bacterial cellulose is obtained. The obtained bacterial cellulose is stirred and fully dispersed in deionized water, and a cellulose nanofibril dispersion is obtained after high-pressure homogenization. Step 2: Preparation of cellulose nanofiber@silver nanoparticle composite Using a hydrothermal deposition method, a silver nitrate solution and a cellulose nanofiber solution were mixed in deionized water, then transferred to a polytetrafluoroethylene substrate, placed in a reactor, and heated at 110°C. The silver ions were reduced to silver nanoparticles by utilizing the reducing property of the hydroxyl groups on the surface of the cellulose nanofibers and anchored on the surface of the cellulose nanofibers, resulting in a light yellow suspension. The suspension was then centrifuged and washed with deionized water to obtain a cellulose nanofiber@silver nanoparticle nanocomposite. Step 3: Preparation of bottlebrush nanocomposite gel The photoinitiator 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone was added to the cellulose nanofiber@silver nanoparticle solution and ultrasonically treated to ensure adsorption on the surface of the silver nanoparticles to form a nanocomposite crosslinker. Then, monomers acrylamide and sodium acrylate were added, ultrasonically mixed, and then polymerized under xenon lamp irradiation to obtain a uniform, light yellow, bottle-brush-shaped nanocomposite gel. Step 4: Preparation of multi-level oriented ion gel fibers The bottle brush-type nanocomposite gel prepared in step 3 is placed in an injection syringe, and the injection pressure is precisely controlled by an air compressor so that it is extruded through a needle with an inner diameter of 0.4 mm to obtain hydrogel fibers; the hydrogel fibers obtained by briefly drying under ambient conditions are then pre-stretched and twisted, and the two ends of the stretched and twisted hydrogel fibers are fixed, and their structure is further stabilized by water evaporation. They are then placed in an ionic liquid for solvent replacement for a certain period of time to obtain ion gel fibers with a multi-level oriented structure.

3. The preparation method according to claim 2, wherein: In step 1, the solid culture medium comprises: 50 g / L glucose, 5 g / L yeast extract, 10 g / L calcium carbonate, and 20 g / L agar. Each component is dissolved in deionized water and sterilized by high pressure at 121° C. for 30 min.

4. The preparation method according to claim 2, wherein: In step 2, the length of a single cellulose nanofiber is between 4-10 μm and the diameter is between 7-20 nm; the particle size of the silver nanoparticles is between 10-30 nm.

5. The preparation method according to claim 2, wherein: In step 3, the mass concentration of the cellulose nanofiber@silver nanoparticle solution is 0.1%-0.5%.

6. The preparation method according to claim 2, wherein: In step 3, the molar ratio of acrylamide to sodium acrylate is 2:1-5:1, and the polymerization time is controlled at 25-35 min.

7. The preparation method according to claim 2, characterized in that: In step 4, the pre-stretching ratio is 1-5 times, and the twisting number is 20 turns / cm.

8. The preparation method according to claim 2, wherein: In step 4, the ionic liquid is 1-ethyl-3-methylimidazolyl ethyl sulfate, and the solvent replacement time is 5-30 min.

9. The preparation method according to claim 2, wherein: The resistivity of the deionized water at 25° C. is 18.2 MΩ·cm.

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