Preparation method of high-toughness and high-conductivity PIPD enhanced graphene fiber

Abstract

The invention relates to a preparation method of a high-toughness and high-conductivity PIPD enhanced graphene fiber, which comprises the following steps: mixing a graphene oxide solution and a PIPD solution to prepare a spinning solution, carrying out wet spinning by adopting two coagulating baths, and sequentially carrying out chemical reduction and vacuum drying treatment after spinning to obtain the high-toughness and high-conductivity PIPD enhanced graphene fiber. The content of the PIPD in the spinning solution is 0.1-50 wt% of the graphene oxide; the first coagulating bath is a metal ion / phosphoric acid aqueous solution, and the second coagulating bath is an ethanol / water mixed solution; according to the high-toughness and high-conductivity PIPD enhanced graphene fiber, the elongation at break is 2-20%, the ultimate tensile strength is 250-1500 MPa, the fracture toughness is 10-70 MJ / m < 3 >, and the conductivity is 102-106 S.m <-1 >. The graphene fiber is toughened through a small amount of PIPD, the mechanical property of the graphene fiber is improved, and meanwhile the graphene fiber has good conductivity.

Description

Technical Field

[0001] The invention belongs to the technical field of graphene oxide fibers and relates to a method for preparing PIPD-reinforced graphene fibers with high toughness and high conductivity. Background Art

[0002] Two-dimensional graphene sheets possess high electrical and thermal conductivity and unique optical properties. Assembling these sheets into macrostructures through molding processes can be applied to fields such as energy storage, electronic devices, composite materials, sensors, biomedicine, and aerospace. In the energy storage field, graphene-based supercapacitors and lithium-ion batteries have attracted widespread attention due to their excellent electrical conductivity and high surface area, which can improve the charge and discharge rates and energy density of energy storage devices. In the sensor field, graphene's high surface area and sensitive electronic properties make it an ideal material for detecting various chemicals and biomarkers. In the biomedical field, graphene's excellent biocompatibility and electrical conductivity have made it an ideal material for drug delivery platforms, biomarkers, and electrode materials. In the aerospace field, graphene's light weight and high strength make it particularly valuable for lightweight components and protective coatings. Graphene films and graphene fibers are the two main macrostructures. Despite their outstanding electronic and mechanical properties, their performance in applications remains limited. In particular, because graphene sheets are stacked together solely through van der Waals forces, this weak interaction can lead to interlamellar fracture when mechanical loads are applied, increasing the risk of material failure. The alignment and high orientation of graphene sheets within the fiber are crucial to the mechanical properties of the final fiber. New methods are needed to improve interlamellar alignment and orientation to maximize the mechanical, electrical, and thermal conductivity of the fiber. Furthermore, the interfacial properties between graphene sheets and with other materials (such as the polymer matrix) will influence the performance of the final product. Enhancing the interactions between graphene sheets and improving the interfacial forces between them and the matrix are key to improving the overall performance of the material. The weak adhesion between graphene sheets and the polymer matrix material can affect mechanical properties and structural integrity, potentially leading to stress concentration or stress release under peak stress, resulting in performance degradation that deviates from the expected performance. Therefore, when designing graphene fibers for composite reinforcement, special attention should be paid to improving the interfacial interactions between graphene sheets and enhancing the compatibility of graphene with the matrix material.

[0003] The strategies used in existing research to improve the mechanical properties of graphene fibers mainly include metal ion cross-linking reinforcement, organic molecules, polymers and two-dimensional material reinforcement. The existing technology mostly uses polymer-modified graphene to prepare graphene fibers. The polymers used mainly include polyvinyl alcohol (such as patents CN202211190776.5 and CN202211161902.4), chitosan-modified boron nitride (such as patent CN202310211329.1) and silk fibroin (such as the document Silk fibroin reinforced graphene fibers with outstanding electrical conductivity and mechanical strength), etc. Other polymers include polyacrylonitrile (PAN), high molecular weight lignin, polyethersulfone (PES), polysulfone (PS), polyethylene (PE), polylactic acid (PLA), polyphenylene ether (PPO), polyimide (PI), polyacrylic acid (PAA), polyepoxy resin, polyurethane (PU), polyvinylidene fluoride (PVDF), polylactic acid-lactide (PLLA) and polymethyl methacrylate (PMMA), etc. The addition amount of the above polymers is all above 2wt%.

[0004] Specifically, patent CN202311526717.5 discloses a polyacrylonitrile / graphene composite fiber with a core-sheath structure. When the mass fraction of polyacrylonitrile reaches 8.5 wt%, the graphene fiber has high strength (500 MPa) and conductivity (770 S·cm -1 Patent CN202211175033.0 discloses a method for preparing high-performance graphene fibers. Modified graphene oxide, polyacrylic acid, and polyamide are mixed in a mass ratio of 2:1:2. Through hydrogen bonding, the fibers have high strength (100 MPa) and conductivity (373 S·cm -1 Reference 1 (Matter, 2022, 5(12): 4437-4449.) Ultra-strong graphene oxide-based fibers reinforced by crystalline-amorphous superstructures have high strength. After adding 37.2 wt% ZrO2 and 8.5 wt% PVA, the toughness reaches up to 10.6 MJ / m 3 Reference 2 (Carbon, 2023, 203: 886-894.) mentioned that after adding 2wt% of silk fibroin, the graphene composite fiber has excellent mechanical strength and toughness of 16.1 MJ / m 3 , the conductivity is 2.7×10 5 S·m -1Reference 3 (Nano Letters, 2024, 24(14): 4256-4264.) adds 50 wt% of polyvinyl alcohol and polyethylene oxide, regulates interlayer entanglement through hydrogen bonds and ionic bonds to improve toughness, with toughness as high as 52 MJ / m 3 .

[0005] In the aforementioned polymer-addition toughening and strengthening method, the high amount of polymer added results in improved mechanical properties of the reduced graphene fibers, but significantly reduced electrical conductivity. In contrast, the technique of adding a small amount of polymer primarily enhances the toughening and strengthening effects of the composite fibers through hydrogen bonding and π-π interactions between the polymer and graphene oxide. However, these interactions are primarily hydrogen bonding forces, which are significantly weakened after the graphene oxide is reduced to graphene due to the reduction of oxygen-containing functional groups. This results in more pores within the fibers after reduction and reduced toughness.

[0006] Therefore, it is of great significance to study a preparation method of PIPD-reinforced graphene fibers with high toughness and high conductivity to solve the problems existing in the prior art. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing PIPD-reinforced graphene fibers with high toughness and high conductivity.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing high-toughness and high-conductivity PIPD (poly-2,5-dihydroxy-1,4-phenylenepyridinodiimidazole)-reinforced graphene fibers comprises mixing a graphene oxide (GO) solution with a PIPD solution to prepare a spinning solution, wet spinning using two coagulation baths, and subsequent chemical reduction and vacuum drying to produce high-toughness and high-conductivity PIPD-reinforced graphene fibers.

[0010] The solvents of both graphene oxide solution and PIPD solution are methanesulfonic acid; the methanesulfonic acid solvent environment can promote the structural orientation and crystallization of PIPD while maintaining the lamellar structure of graphene oxide, and promote the interfacial interaction (hydrogen bonds and other polar interactions) between PIPD and GO, thereby improving the mechanical properties of graphene composite fibers.

[0011] The content of PIPD in the spinning solution is 0.1~50wt% of graphene oxide;

[0012] The first coagulation bath is a metal ion / phosphoric acid aqueous solution. Phosphoric acid slows down the solute-solvent exchange, and ionic crosslinking enhances fiber strength. The second coagulation bath is an ethanol / water mixed solution to wash away residual metal ions.

[0013] In the first coagulation bath, the metal ion concentration is 2-5 wt%, and the phosphoric acid concentration is 2-20 wt%. In the second coagulation bath, the mass percentage of ethanol relative to water is 60-90%.

[0014] The metal ion is Ca 2+ Mg 2+ 、Co 2+ 、Fe 3+ 、Al 3+ or Cr 3+ ;

[0015] The spinning solution solvent is methanesulfonic acid. Due to its large molecular weight, methanesulfonic acid has a slow double diffusion rate in the coagulation bath. If only water is used as the coagulation bath, a clear skin-core structure will be formed, which will reduce the mechanical properties. Therefore, it is necessary to control the precipitation rate of the solvent in the coagulation bath, from slow diffusion in the first channel to rapid diffusion in the second channel, so that the structural uniformity inside and outside the fiber is increased, thereby improving the mechanical properties to a certain extent.

[0016] The high-toughness and high-conductivity PIPD-reinforced graphene fibers have an elongation at break of 2-20%, an ultimate tensile strength of 250-1500 MPa, and a fracture toughness of 10-70 MJ / m 3 , the conductivity is 10 2 ~10 6 S·m -1 .

[0017] As the preferred technical solution:

[0018] The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber as described above, wherein the PIPD content in the spinning solution is 0.1-1wt% of the graphene oxide, the high-toughness and high-conductivity PIPD-enhanced graphene fiber has an elongation at break of 2-10%, and a fracture toughness of 10-30 MJ / m 3 , the conductivity is 5×10 5 ~10 6 S·m -1 .

[0019] The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber as described above, wherein the PIPD content in the spinning solution is 1-15wt% of the graphene oxide, the high-toughness and high-conductivity PIPD-enhanced graphene fiber has an elongation at break of 5-15%, and a fracture toughness of 30-40 MJ / m 3 , the conductivity is 10 4 ~5×10 5 S·m -1 .

[0020] The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber as described above, wherein the PIPD content in the spinning solution is 15-30wt% of the graphene oxide, the high-toughness and high-conductivity PIPD-enhanced graphene fiber has an elongation at break of 15-18%, and a fracture toughness of 40-50 MJ / m 3 , the conductivity is 10 3 ~10 4 S·m -1 .

[0021] The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber as described above, wherein the PIPD content in the spinning solution is 30-50wt% of the graphene oxide, the high-toughness and high-conductivity PIPD-enhanced graphene fiber has an elongation at break of 18-20%, and a fracture toughness of 50-70 MJ / m 3 , the conductivity is 10 2 ~10 3 S·m -1 .

[0022] The preparation method of a high-toughness and high-conductivity PIPD-reinforced graphene fiber as described in any of the above items, the specific preparation steps are as follows:

[0023] (1) Pre-treating the graphene oxide powder: dispersing the graphene oxide powder in deionized water, filtering and freeze-drying to obtain a graphene oxide powder with a few layers (less than 20 layers);

[0024] (2) Add the pretreated graphene oxide powder to methanesulfonic acid and stir for 24 to 72 hours. Ultrasonicate for 1 to 3 hours during the stirring process to prepare a graphene oxide solution with a concentration of 0.1 to 2 wt%;

[0025] (3) PIPD fibers (PIPD fibers prepared by laboratory wet spinning have a diameter of 30-100 μm, a thermal decomposition temperature greater than 520 °C, and a primary fiber tensile strength greater than 1 GPa) were added to methanesulfonic acid and stirred for 24-72 h. Ultrasonication was performed for 1-3 h during the stirring process to prepare a PIPD solution with a concentration of 0.1-1 wt%;

[0026] (4) mixing the graphene oxide solution in step (2) with the PIPD solution in step (3), stirring and ultrasonicating to obtain a spinning solution, and performing wet spinning;

[0027] (5) The fibers obtained by spinning in step (4) are chemically reduced, taken out, and repeatedly washed with ethanol until the iodine ions are completely washed out. The fibers are then vacuum dried to obtain high-toughness and high-conductivity PIPD-enhanced graphene fibers.

[0028] The method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber as described above comprises the following steps: in step (1), dispersing graphene oxide powder in deionized water, specifically stirring the graphene oxide powder in deionized water for 48 to 96 hours, and ultrasonicating for 2 to 3 hours during the stirring process;

[0029] Use 300~600 mesh nylon cloth for filtration.

[0030] In the method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber as described above, the spinning speed in step (4) is 5-20 mm·min -1 , the collection rate is 5~20 mm·min -1 , it is continuously collected during the spinning process, and after the spinning is completed, it is placed in a 40~60 ℃ oven to dry and remove the solvent.

[0031] In the method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber as described above, the reducing agent used for chemical reduction in step (5) is a hydroiodic acid / ethanol mixture, the volume ratio of hydroiodic acid to ethanol is 1:0.1~3, and the hydroiodic acid is a hydrogen iodide aqueous solution with a mass fraction of 45%.

[0032] Principle of the invention:

[0033] This invention uses the addition of the high-molecular-weight polymer PIPD to modify the graphene fiber and produce a highly tough and conductive graphene fiber through wet spinning. The hydroxyl groups in PIPD readily form hydrogen bonds with graphene oxide, enhancing the flexibility of the PIPD / GO fiber. Furthermore, PIPD contains numerous aromatic heterocycles (phenylene pyridine groups and benzene rings), which offer advantages such as high rigidity and stability. These heterocycles form strong hydrogen bonds, multiple π-π interactions, and van der Waals forces with GO sheets, facilitating the formation of a uniform and stable spinning solution. The strong interfacial interaction between the two after forming significantly enhances the performance of the composite fiber. After wet spinning, PIPD / graphene oxide fibers formed a dual-phase crystalline structure. The reasons for the formation of the dual-phase crystalline region are: 1) heterogeneous nucleation: GO sheets act as nucleating agents, inducing PIPD molecular chains to arrange and crystallize in an orderly manner on their surface, thus forming microcrystalline regions; 2) the formation of a synergistic structure: the strong hydrogen bonding between GO will form a liquid crystal structure, while the PIPD molecular chains have a rigid, highly ordered structure. When PIPD and GO are mixed, the PIPD molecular chains tend to align parallel to the surface of the GO sheets to maximize π-π stacking and hydrogen bonding interactions; 3) mechanical stretching orientation-induced crystallization: the stress during the spinning and stretching process induces further orientation and crystallization of the PIPD molecular chains and GO sheets, and PIPD microcrystalline regions are evenly distributed around the GO crystal regions; while PIPD away from the GO crystal regions has longer molecular chains and acts as a bridge between the crystal regions. During the stretching process, the presence of dual-phase crystalline regions and amorphous regions can promote stress dispersion, increase ductility and plastic deformation capacity, and at the same time absorb a large amount of energy and blunt the crack tip. Due to the formation of the dual-phase crystal structure, the fracture toughness and conductivity are improved, and the metal ions contained in the coagulation bath can undergo ion cross-linking with the PIPD / graphene oxide nanosheets, making the system more stable and further improving the mechanical properties of the graphene oxide fibers.

[0034] After GO reduction, although the reduction of GO's oxygen-containing functional groups weakens the hydrogen bonding with PIPD, the partial π-π conjugated structure is restored, the π electron delocalization area increases, and the multiple π-π interactions between PIPD and graphene are further enhanced, allowing the PIPD / graphene fibers to maintain excellent flexibility and conductivity. Furthermore, PIPD's rigid molecular chains and large molecular weight provide a larger contact area, matching the rigid, large-sheet structure of RGO or graphene. Consequently, the non-covalent interactions before and after reduction are stronger than those of other polymers.

[0035] Beneficial effects:

[0036] (1) The present invention provides a method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber, which is modified by using a high molecular polymer PIPD. The hydroxyl groups contained in PIPD are easy to combine with graphene oxide to form hydrogen bonds, and there are interaction forces such as π-π interaction and van der Waals force between layers. Only a small amount of PIPD needs to be added to form PIPD / graphene oxide fiber, which increases the strength, flexibility and conductivity of PIPD / graphene oxide fiber. It is expected to be applied to bulletproof fabrics, bulletproof armor plates, flexible supercapacitor electrodes, wearable electronic textiles and fiber motors.

[0037] (2) The present invention provides a method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber. Due to the formation of a dual-phase crystal structure, the fracture toughness and conductivity are improved, and the metal ions contained in the coagulation bath can be ionically cross-linked with the PIPD / graphene oxide nanosheets, making the system more stable and further improving the mechanical properties of the graphene oxide fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 XRD patterns of PIPD, 7.5%PIPD / GOFs and 50%PIPD / GOFs; 7.5%PIPD / GOFs means that the content of PIPD in the spinning solution during preparation is 75% of the graphene oxide; 50%PIPD / GOFs means that the content of PIPD in the spinning solution during preparation is 50% of the graphene oxide;

[0039] Figure 2 It is due to the multiple strong non-covalent interactions between PIPD and graphene oxide;

[0040] Figure 3 It is the orientation process of the dual-phase crystal region in the spinning nozzle;

[0041] Figure 4 This is an SEM image of the high-toughness and high-conductivity PIPD-reinforced graphene fiber prepared in Example 3;

[0042] Among them, 1-graphene oxide liquid crystal, 2-PIPD microcrystals, 3-methanesulfonic acid, and 4-metal ions. DETAILED DESCRIPTION

[0043] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0044] The test methods involved in the performance indicators in the embodiments and comparative examples of the present invention are as follows:

[0045] Conductivity: The conductivity of the fiber was measured by a four-probe conductivity tester.

[0046] Mechanical Properties: The elongation at break and ultimate tensile force of the fibers were measured using a tensile-compression dynamometer (Model: Mark-10 IntelliMESUR 2.3.1, USA). The fiber diameter was measured using a scanning electron microscope (Model: Hitachi High-Tech Field Emission Scanning Electron Microscope SU8230), and the cross-sectional area was calculated. The tensile strength and fracture toughness were then calculated.

[0047] Example 1

[0048] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fiber, the specific preparation steps are as follows:

[0049] (1) Pretreatment of graphene oxide powder: The graphene oxide powder was stirred in deionized water at 800 rpm for 48 h, ultrasonicated for 2 h during the stirring process, and then filtered through a 300-mesh nylon cloth. After precooling at -18 °C for 24 h, the powder was freeze-dried for 24 h to obtain a few-layer graphene oxide powder.

[0050] The mass volume ratio of graphene oxide powder to deionized water is 1 g:20 mL;

[0051] (2) The pretreated graphene oxide powder was added to methanesulfonic acid and stirred for 48 h. Ultrasonication was performed for 2 h during the stirring process to prepare a graphene oxide solution with a concentration of 1 wt%;

[0052] (3) PIPD fibers (diameter 30-100 μm, thermal decomposition temperature 530 °C, primary fiber tensile strength 1.2 GPa) were added to methanesulfonic acid and stirred for 24 h. Ultrasonication was performed for 2 h during the stirring process to prepare a PIPD solution with a concentration of 1 wt%;

[0053] (4) The graphene oxide solution in step (2) and the PIPD solution in step (3) are mixed, stirred and ultrasonicated to obtain a spinning solution, two coagulation baths are used for wet spinning, and the spinning solution is dried in an oven at 40°C after the spinning is completed;

[0054] The PIPD content in the spinning solution was 15 wt% of the graphene oxide. The first coagulation bath was an FeCl3 / phosphoric acid aqueous solution with a FeCl3 concentration of 3 wt% and a phosphoric acid concentration of 10 wt%. The second coagulation bath was an ethanol / water mixed solution with a volume ratio of ethanol to water of 3:1. The inner diameter of the needle was 0.4 mm, and the spinning speed was 10 mm min. -1 , the collection rate is 10 mm·min -1 ;

[0055] The biaxial crystal orientation process in the spinning nozzle results in Figure 3 As shown, graphene oxide liquid crystal 1 and PIPD microcrystal 2 are uniformly dispersed in methanesulfonic acid 3 solvent. After the extrusion process through the narrow channel of the spinning needle, the arrangement of the liquid crystal and the microcrystal is more orderly. After reaching the end of the spinning needle, the metal ions 4 participate in cross-linking graphene oxide and PIPD, strengthening the connection between the sheet and the polymer chain, achieving the effect of strengthening and toughening. During the extrusion process in the confined space of the spinning hole, the two crystal regions induce each other to align in an orderly manner.

[0056] (5) The fibers spun in step (4) were chemically reduced at 60°C for 24 h using 20 mL of a 1:3 volume ratio hydroiodic acid / ethanol mixture, and then vacuum dried at 80°C for 36 h to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers; hydroiodic acid was a 45% by mass aqueous solution of hydrogen iodide.

[0057] The resulting high-toughness and high-conductivity PIPD-reinforced graphene fiber has an elongation at break of 15%, an ultimate tensile strength of 800 MPa, and a fracture toughness of 39.7 MJ / m 3 , the conductivity is 10 4 S·m -1 .

[0058] like Figure 2 As shown in the figure, the left and right sides are the structural formulas of PIPD and graphene oxide sheets respectively, and the middle is the strong hydrogen bonds, multiple π-π interactions and van der Waals interface forces formed between the two. The rich and stable interface interactions between the two are conducive to the enhancement of fiber performance after spinning and molding.

[0059] Example 2

[0060] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fiber, the specific preparation steps are as follows:

[0061] (1) Pretreatment of graphene oxide powder: The graphene oxide powder was stirred in deionized water at 700 rpm for 48 h, ultrasonicated for 2 h during the stirring process, and then filtered through a 300-mesh nylon cloth. After precooling at -18 °C for 24 h, the powder was freeze-dried for 24 h to obtain a few-layer graphene oxide powder.

[0062] The mass volume ratio of graphene oxide powder to deionized water is 1 g:20 ml;

[0063] (2) The pretreated graphene oxide powder was added to methanesulfonic acid and stirred for 24 h. Ultrasonic treatment was performed for 2 h during the stirring process to prepare a graphene oxide solution with a concentration of 1 wt%;

[0064] (3) PIPD fibers (diameter 30-100 μm, thermal decomposition temperature 530 °C, primary fiber tensile strength 1.2 GPa) were added to methanesulfonic acid and stirred for 24 h. Ultrasonication was performed for 1 h during the stirring process to prepare a PIPD solution with a concentration of 0.1 wt%;

[0065] (4) mixing the graphene oxide solution in step (2) with the PIPD solution in step (3), stirring and ultrasonicating to obtain a spinning solution, performing wet spinning using two coagulation baths, and drying in an oven at 40°C after spinning;

[0066] The PIPD content in the spinning solution was 0.1 wt% of graphene oxide; the first coagulation bath was a MgCl2 / phosphoric acid aqueous solution with a 2 wt% MgCl2 and a 2 wt% phosphoric acid concentration; the second coagulation bath was an ethanol / water mixed solution with a volume ratio of ethanol to water of 3:1; the inner diameter of the needle was 0.5 mm, and the spinning speed was 5 mm min. -1 , the collection rate is 5 mm·min -1 ;

[0067] (5) The fibers spun in step (4) were chemically reduced at 60 °C for 24 h using 20 mL of a 1:0.1 volume ratio of hydroiodic acid / ethanol mixture, and then vacuum dried at 60 °C for 24 h to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers; the hydroiodic acid was a 45% by mass aqueous solution of hydrogen iodide.

[0068] The resulting high-toughness and high-conductivity PIPD-reinforced graphene fiber has an elongation at break of 2%, an ultimate tensile strength of 250 MPa, and a fracture toughness of 10.3 MJ / m 3 , the conductivity is 10 6 S·m -1 .

[0069] Example 3

[0070] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fiber, the specific preparation steps are as follows:

[0071] (1) Pretreatment of graphene oxide powder: The graphene oxide powder was stirred in deionized water at 700 rpm for 72 h, ultrasonicated for 3 h during stirring, and then filtered through 600 mesh nylon cloth. After precooling at -18 °C for 24 h, the powder was freeze-dried for 48 h to obtain a few-layer graphene oxide powder.

[0072] The mass volume ratio of graphene oxide powder to deionized water is 1 g:40 ml;

[0073] (2) The pretreated graphene oxide powder was added to methanesulfonic acid and stirred for 36 h. Ultrasonic treatment was performed for 2 h during the stirring process to prepare a graphene oxide solution with a concentration of 0.1 wt%;

[0074] (3) PIPD fibers (diameter 30-100 μm, thermal decomposition temperature 530 °C, primary fiber tensile strength 1.2 GPa) were added to methanesulfonic acid and stirred for 72 h. Ultrasonication was performed for 1.5 h during stirring to prepare a PIPD solution with a concentration of 0.5 wt%;

[0075] (4) mixing the graphene oxide solution in step (2) with the PIPD solution in step (3), stirring and ultrasonicating to obtain a spinning solution, performing wet spinning using two coagulation baths, and drying in an oven at 50°C after spinning;

[0076] The PIPD content in the spinning solution was 1 wt% of graphene oxide; the first coagulation bath was a CoCl2 / phosphoric acid aqueous solution with a CoCl2 concentration of 2 wt% and a phosphoric acid concentration of 5 wt%; the second coagulation bath was an ethanol / water mixed solution with a volume ratio of ethanol to water of 3:1; the inner diameter of the needle was 0.4 mm, and the spinning speed was 5 mm min -1 , the collection rate is 5 mm·min -1 ;

[0077] (5) The fibers spun in step (4) were chemically reduced at 90 °C for 12 h using 20 mL of a 1:1 hydroiodic acid / ethanol mixture, and then vacuum dried at 70 °C for 30 h to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers; the hydroiodic acid was a 45% by mass aqueous solution of hydrogen iodide.

[0078] like Figure 4 As shown in Figure 2, after wet spinning, the PIPD / graphene oxide fibers formed a dual-phase crystal structure; the resulting high-toughness and high-conductivity PIPD-reinforced graphene fibers had an elongation at break of 10%, an ultimate tensile strength of 300 MPa, and a fracture toughness of 30 MJ / m 3 , the conductivity is 5×10 5 S·m -1 .

[0079] Comparative Example 1

[0080] A method for preparing silk fibroin-reinforced graphene fibers is basically the same as that in Example 3, except that in step (3), the PIPD fibers are replaced with silk fibroin and the methanesulfonic acid is replaced with water.

[0081] The final silk fibroin-reinforced graphene fiber has an elongation at break of 0.6%, an ultimate tensile strength of 150 MPa, and a fracture toughness of 8 MJ / m 3 , the conductivity is 3×10 5 S·m -1 .

[0082] Comparing Example 3 with Comparative Example 1 reveals significantly lower elongation at break, ultimate tensile strength, and toughness. This is due to the strong adhesive interaction and hydrogen bonding between the silk fibroin (SF) molecules and graphene oxide. Compared to the induced orientation of PIPD, SF hinders the orderly orientation of the graphene oxide sheets during the spinning process. Furthermore, chemical reduction weakens the hydrogen bonding between SF and graphene oxide, resulting in reduced mechanical properties.

[0083] Example 4

[0084] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fiber, the specific preparation steps are as follows:

[0085] (1) Pretreatment of graphene oxide powder: The graphene oxide powder was stirred in deionized water at 900 rpm for 72 h, ultrasonicated for 3 h during stirring, and then filtered through 400 mesh nylon cloth. After precooling at -18 °C for 24 h, the powder was freeze-dried for 36 h to obtain a few-layer graphene oxide powder.

[0086] The mass volume ratio of graphene oxide powder to deionized water is 1 g:30 ml;

[0087] (2) The pretreated graphene oxide powder was added to methanesulfonic acid and stirred for 60 h. Ultrasonic treatment was performed for 2.5 h during the stirring process to prepare a graphene oxide solution with a concentration of 1.5 wt%;

[0088] (3) PIPD fibers (diameter 30-100 μm, thermal decomposition temperature 530 °C, primary fiber tensile strength 1.2 GPa) were added to methanesulfonic acid and stirred for 48 h. Ultrasonication was performed for 2.5 h during stirring to prepare a PIPD solution with a concentration of 0.5 wt%;

[0089] (4) The graphene oxide solution in step (2) and the PIPD solution in step (3) are mixed, stirred and ultrasonicated to obtain a spinning solution, two coagulation baths are used for wet spinning, and the spinning solution is dried in an oven at 50°C after the spinning is completed;

[0090] The PIPD content in the spinning solution was 30 wt% of the graphene oxide; the first coagulation bath was an AlCl3 / phosphoric acid aqueous solution with an AlCl3 concentration of 5 wt% and a phosphoric acid concentration of 15 wt%; the second coagulation bath was an ethanol / water mixed solution with a volume ratio of ethanol to water of 3:1; the inner diameter of the needle was 0.1 mm, and the spinning speed was 15 mm min. -1 , the collection rate is 15 mm·min -1 ;

[0091] (5) The fibers spun in step (4) were chemically reduced at 80 °C for 18 h using 20 mL of a 1:2 volume ratio hydroiodic acid / ethanol mixture, and then vacuum dried at 60 °C for 42 h to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers; hydroiodic acid was a 45% by mass aqueous solution of hydrogen iodide.

[0092] The resulting high-toughness and high-conductivity PIPD-reinforced graphene fiber has an elongation at break of 18%, an ultimate tensile strength of 1500 MPa, and a fracture toughness of 50 MJ / m 3 , the conductivity is 10 3 S·m -1 .

[0093] Example 5

[0094] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fiber, the specific preparation steps are as follows:

[0095] (1) Pretreatment of graphene oxide powder: The graphene oxide powder was stirred in deionized water at a speed of 1000 rpm for 96 h, ultrasonicated for 3 h during the stirring process, and then filtered through a 600-mesh nylon cloth. After precooling at -18 °C for 24 h, the powder was freeze-dried for 48 h to obtain a few-layer graphene oxide powder.

[0096] The mass volume ratio of graphene oxide powder to deionized water is 1 g:40 ml;

[0097] (2) The pretreated graphene oxide powder was added to methanesulfonic acid and stirred for 72 h. Ultrasonic treatment was performed for 3 h during the stirring process to prepare a graphene oxide solution with a concentration of 22 wt%;

[0098] (3) PIPD fibers (diameter 30-100 μm, thermal decomposition temperature 530 °C, primary fiber tensile strength 1.2 GPa) were added to methanesulfonic acid and stirred for 72 h. Ultrasonication was applied for 3 h during stirring to prepare a PIPD solution with a concentration of 1 wt%;

[0099] (4) The graphene oxide solution in step (2) and the PIPD solution in step (3) are mixed, stirred and ultrasonicated to obtain a spinning solution, two coagulation baths are used for wet spinning, and the spinning solution is dried in an oven at 60°C after the spinning is completed;

[0100] The PIPD content in the spinning solution was 50 wt% of the graphene oxide; the first coagulation bath was a CrCl3 / phosphoric acid aqueous solution with a CrCl3 concentration of 5 wt% and a phosphoric acid concentration of 20 wt%; the second coagulation bath was an ethanol / water mixed solution with a volume ratio of ethanol to water of 3:1; the inner diameter of the needle was 0.1 mm, and the spinning speed was 20 mm / min. -1 , the collection rate is 20 mm·min -1 ;

[0101] (5) The fibers spun in step (4) were chemically reduced at 90 °C for 12 h using 20 mL of a 1:3 volume ratio of hydroiodic acid / ethanol mixture, and then vacuum dried at 80 °C for 48 h to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers; hydroiodic acid was a 45% by mass aqueous solution of hydrogen iodide.

[0102] The resulting high-toughness and high-conductivity PIPD-reinforced graphene fibers (50% PIPD / GOFs) have an elongation at break of 20%, an ultimate tensile strength of 1200 MPa, and a fracture toughness of 70.2 MJ / m 3 , conductivity is 100 S·m -1 .

[0103] Example 6

[0104] A method for preparing high-toughness and high-conductivity PIPD-reinforced graphene fibers is basically the same as Example 5, except that the PIPD content in the spinning solution in step (4) is 7.5 wt% of the graphene oxide.

[0105] The resulting high-toughness and high-conductivity PIPD-reinforced graphene fibers (7.5% PIPD / GOFs) have an elongation at break of 13%, an ultimate tensile strength of 500 MPa, and a fracture toughness of 35 MJ / m 3 , the conductivity is 5×10 4 S·m -1 .

[0106] like Figure 1 As shown in the XRD data, it can be seen that the The diffraction peaks at 7.0° and 26.67° correspond to the (001) and (200) planes, respectively. The (001) plane with a d ≈ 12.62 Å interplanar spacing represents the layered stacking structure between PIPD molecular chains, while the (001) plane with a d ≈ 3.35 Å interplanar spacing represents the short-range ordered structure within the PIPD molecules. The interlayer spacing of d ≈ 10.21 Å represents the ordered stacking interlayer spacing of GO sheets. XRD data indicate the presence of a dual-phase crystal structure in PIPD / GOFs.

Claims

1. A method for preparing high-toughness and high-conductivity PIPD-enhanced graphene fiber, characterized in that: The graphene oxide solution and the PIPD solution are mixed to prepare a spinning solution, two coagulation baths are used for wet spinning, and after spinning, chemical reduction and vacuum drying are performed in sequence to obtain PIPD-reinforced graphene fibers with high toughness and high conductivity; The solvents of graphene oxide solution and PIPD solution were both methanesulfonic acid; The content of PIPD in the spinning solution is 0.1~50wt% of graphene oxide; The first coagulation bath is a metal ion / phosphoric acid aqueous solution, and the second coagulation bath is an ethanol / water mixed solution; In the first coagulation bath, the metal ion concentration is 2-5 wt%, and the phosphoric acid concentration is 2-20 wt%. In the second coagulation bath, the mass percentage of ethanol relative to water is 60-90%. The metal ion is Ca 2+ Mg 2+ 、Co 2+ , Fe 3+ 、Al 3+ or Cr 3+ ; The high-toughness and high-conductivity PIPD-reinforced graphene fibers have an elongation at break of 2-20%, an ultimate tensile strength of 250-1500 MPa, and a fracture toughness of 10-70 MJ / m 3 , the conductivity is 10 2 ~10 6 S·m -1 .

2. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 1, characterized in that: The content of PIPD in the spinning solution is 0.1~1wt% of graphene oxide. The elongation at break of the high-toughness and high-conductivity PIPD-reinforced graphene fiber is 2~10%, and the fracture toughness is 10~30 MJ / m 3 , the conductivity is 5×10 5 ~10 6 S·m -1 .

3. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 1, characterized in that: The content of PIPD in the spinning solution is 1~15wt% of graphene oxide. The elongation at break of the high-toughness and high-conductivity PIPD-enhanced graphene fiber is 5~15%, and the fracture toughness is 30~40 MJ / m 3 , the conductivity is 10 4 ~5×10 5 S·m -1 .

4. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 1, characterized in that: The content of PIPD in the spinning solution is 15-30wt% of graphene oxide. The elongation at break of the high-toughness and high-conductivity PIPD-reinforced graphene fiber is 15-18%, and the fracture toughness is 40-50 MJ / m 3 , the conductivity is 10 3 ~10 4 S·m -1 .

5. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 1, characterized in that: The content of PIPD in the spinning solution is 30~50wt% of graphene oxide. The elongation at break of the high-toughness and high-conductivity PIPD-enhanced graphene fiber is 18~20%, and the fracture toughness is 50~70 MJ / m 3 , the conductivity is 10 2 ~10 3 S·m -1 .

6. A method for preparing a high-toughness and high-conductivity PIPD-reinforced graphene fiber according to any one of claims 1 to 5, characterized in that: The specific preparation steps are as follows: (1) Pre-treating graphene oxide powder: dispersing the graphene oxide powder in deionized water, filtering and freeze-drying; (2) adding the pretreated graphene oxide powder to methanesulfonic acid, stirring for 24 to 72 h, and ultrasonicating for 1 to 3 h during the stirring process to prepare a graphene oxide solution with a concentration of 0.1 to 2 wt%; (3) Add PIPD fiber to methanesulfonic acid and stir for 24 to 72 h. Ultrasonicate for 1 to 3 h during stirring to prepare a PIPD solution with a concentration of 0.1 to 1 wt%; (4) mixing the graphene oxide solution in step (2) with the PIPD solution in step (3), stirring and ultrasonicating to obtain a spinning solution, and performing wet spinning; (5) The fibers spun in step (4) are chemically reduced and then vacuum dried to obtain high-toughness and high-conductivity PIPD-reinforced graphene fibers.

7. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 6, characterized in that: In step (1), the graphene oxide powder is dispersed in deionized water, specifically, the graphene oxide powder is stirred in the deionized water for 48 to 96 hours, and ultrasonic treatment is performed for 2 to 3 hours during the stirring process; Use 300~600 mesh nylon cloth for filtration.

8. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 6, characterized in that: The spinning speed in step (4) is 5-20 mm·min -1 , the collection rate is 5~20 mm·min -1 After spinning, it is placed in an oven at 40~60 ℃ to dry.

9. The method for preparing a high-toughness and high-conductivity PIPD-enhanced graphene fiber according to claim 6, characterized in that: The reducing agent used for the chemical reduction in step (5) is a hydroiodic acid / ethanol mixture, the volume ratio of hydroiodic acid to ethanol is 1:0.1-3, and the hydroiodic acid is a 45% by mass hydrogen iodide aqueous solution.

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