A conductive polymer composite and a method for producing the same

Abstract

The application relates to the technical field of functional materials, and discloses a conductive polymer composite material and a preparation method thereof, which comprises the following steps: providing an oil phase solution comprising an organic solvent and a polymer, and a water phase solution comprising water, graphene oxide and carbon nanotubes; mixing the oil phase solution with the water phase solution, performing homogenization treatment, and then performing supercritical CO2 drying on the obtained graphene oxide stable Pickering emulsion to remove the organic solvent; then adding a reducing agent to perform a reduction reaction; and finally performing heating drying to remove water, so that the conductive polymer composite material is obtained. In the application, the carbon nanotubes are used as conductive fillers, the graphene oxide stable Pickering emulsion is used as a template, and the supercritical anti-solvent method is used to remove the organic solvent; then the graphene oxide is reduced into reduced graphene oxide with conductivity, and the reduced graphene oxide and the carbon nanotubes form double conductive fillers, so that the conductivity of the prepared conductive polymer composite material can reach 211 S.m ‑1 under the condition of low conductive filler content.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional materials, in particular to a conductive polymer composite material and a preparation method thereof. BACKGROUND

[0002] The conductive polymer composite material with polymer as matrix and conductive substance as filler has been widely used in sensors, electromagnetic interference screen and other fields. Due to the excellent conductivity of carbon-based nanomaterials, they are often filled into the polymer matrix as conductive fillers. The carbon-based conductive polymer composite material prepared has the advantages of stable performance, wide range of conductive performance, light weight and low cost, and has received extensive attention and research in recent years. The preparation of carbon-based conductive polymer composite material usually requires filling a large amount of conductive carbon filler to reach the percolation threshold of the composite material, so as to realize the transition from insulator to conductor. However, high filler content will cause problems such as large rigidity of the composite material, high processing difficulty and high production cost. The introduction of mixed fillers, directional arrangement of fillers and construction of isolation structure can solve the above problems. So far, the construction of isolated conductive network in the conductive polymer composite material is an effective strategy to realize low filler and high conductivity.

[0003] In the isolated conductive polymer composite material, the conductive filler is mainly located at the interface between the polymer particles, rather than randomly arranged in the whole conductive polymer composite system. The existing methods for constructing isolated conductive network mainly include in-situ polymerization, dry mixing, solution blending, melt blending and emulsion template method. Among them, in the emulsion template method, the conductive filler can be uniformly coated on the surface of the polymer particles, and the dispersion is good, and the conductive network structure is easy to control. However, this method usually needs a large amount of surfactant to stabilize the emulsion, and the surfactant is usually insulating and difficult to remove, which affects the conductivity of the conductive polymer composite material.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] Based on the deficiencies of the prior art, the purpose of the present application is to provide a conductive polymer composite material and a preparation method thereof, which aims to solve the problem that the existing emulsion template method usually needs a large amount of surfactant to stabilize the emulsion, but the surfactant is usually insulating and difficult to remove, resulting in low conductivity of the prepared conductive polymer composite material.

[0006] The technical scheme of the present application is as follows:

[0007] In a first aspect of the present application, a preparation method of a conductive polymer composite material is provided, which comprises the following steps:

[0008] An oil phase solution and a water phase solution are provided, the oil phase solution comprising an organic solvent and a polymer, and the water phase solution comprising water, graphene oxide and carbon nanotubes;

[0009] The oil phase solution and the water phase solution are mixed, and after homogenization treatment, a graphene oxide stable Pickering emulsion is obtained;

[0010] The graphene oxide stable Pickering emulsion is subjected to supercritical CO2 drying to remove the organic solvent, and then a reducing agent is added to perform a reduction reaction to reduce the graphene oxide into reduced graphene oxide, followed by heating drying to remove water, so as to obtain the conductive polymer composite material.

[0011] Optionally, the reducing agent comprises at least one of ascorbic acid, sodium bisulfite, sodium disulfide and sodium borohydride.

[0012] Optionally, the reaction conditions of the reduction reaction are as follows:

[0013] The temperature is 25-80 ℃, and the time is 1-24 h.

[0014] Optionally, the mass ratio of the reducing agent to the graphene oxide is (1-30):(1-30).

[0015] Optionally, in the water phase solution, the concentration of the graphene oxide is 0.1-20 mg·mL -1 .

[0016] The water phase solution further comprises an electrolyte, and the electrolyte comprises at least one of sodium chloride, potassium chloride, magnesium chloride and lithium chloride; in the water phase solution, the concentration of the electrolyte is 0-20 mg·mL -1 .

[0017] Optionally, in the oil phase solution, the concentration of the polymer is 10-300 mg·mL -1 .

[0018] The polymer comprises at least one of polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyamide, polystyrene, polymethyl methacrylate, nitrocellulose, cellulose acetate, synthetic rubber, polyethylene, polylactic acid, polyvinyl chloride, polyphenylene ether, polyurethane, polyimide, polysulfone, polyether sulfone, polyacrylonitrile and polyvinyl alcohol.

[0019] The organic solvent comprises at least one of benzene, ethyl acetate, chloroform, cyclohexane, n-hexane, cyclohexanone, toluene and xylene.

[0020] Optionally, the mass ratio of the carbon nanotubes in the aqueous solution to the polymer in the oil solution is (0.5-20):100, and the volume ratio of the oil solution to the aqueous solution is (1-10):(1-10).

[0021] Optionally, the preparation method of the aqueous solution comprises the following steps:

[0022] The graphene oxide is added into water, and ultrasonic treatment is performed at a power of 320-800 W for 5-60 min to obtain a graphene oxide dispersion liquid.

[0023] The carbon nanotubes are added into the graphene oxide dispersion liquid, and after stirring, the aqueous solution is obtained; or the carbon nanotubes and the electrolyte are added into the graphene oxide dispersion liquid, and after stirring, the aqueous solution is obtained.

[0024] Optionally, the process conditions for the homogenization treatment are as follows:

[0025] The rotation speed is 300-10,000 rpm, and the time is 0.5-30 min.

[0026] The process conditions for the supercritical CO2 drying are as follows:

[0027] The temperature is 35-60 ℃, the pressure is 7.5-15 MPa, and the time is 1-8 h.

[0028] The process conditions for the heating drying are as follows:

[0029] The temperature is 40-100 ℃, and the time is 0.5-48 h.

[0030] In the second aspect, the application provides a conductive polymer composite, which is prepared by the preparation method of the conductive polymer composite.

[0031] Beneficial effects: the application uses carbon nanotubes as conductive fillers and graphene oxide as a stabilizer, adopts a Pickering emulsion template method combined with a supercritical anti-solvent method and reduction of graphene oxide, and prepares a conductive polymer composite with an electrical conductivity of 211 S·m -1conductive polymer composites. The Pickering emulsion with particle size of 30-240 μm can be stably stored for more than 30 days by using a small amount of stabilizer (graphene oxide) through a Pickering emulsion template method, and the network structure of the conductive filler constructed by the Pickering emulsion template is stable. Then, the supercritical CO2 is used for drying, and the strong solvent capacity of the supercritical CO2 is used to remove the organic solvent, which is conducive to maintaining the network structure of the conductive filler of graphene oxide and carbon nanotubes in the Pickering emulsion template, avoiding the problems of aggregation and uneven network structure in the process of organic solvent evaporation, and finally making the carbon nanotube conductive filler and graphene oxide form a stable network structure and uniformly wrap the surface of the polymer particles. At the same time, the selection range of the organic solvent is expanded, and the selection range of the polymer is expanded, and the applicability is wide. Then, the graphene oxide is reduced to reduced graphene oxide by adding a reducing agent for reduction reaction, and the reduced graphene oxide can be mixed with the carbon nanotube to form a mixed conductive filler. The reduced graphene oxide and the carbon nanotube form a conductive network, which improves the filling density of the conductive filler, provides higher line and surface contact degree and lower interface resistance, constructs an effective conductive network, further improves the conductivity, and then obtains a conductive polymer composite with isolated conductive network structure and high conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure is the test result of the Pickering emulsion prepared in Example 1, wherein (a) is an optical microscope image, and (b) is a particle size distribution graph.

[0033] Figure 2 The figure is the test result of the Pickering emulsion prepared in Example 2, wherein (a) is an optical microscope image, and (b) is a particle size distribution graph.

[0034] Figure 3 The figure is the test result of the single-layer graphene oxide stable Pickering emulsion prepared in Example 3, wherein (a) is an optical microscope image, and (b) is a particle size distribution graph.

[0035] Figure 4 The figure is a scanning electron microscope image of the conductive polymer composite prepared in Example 3.

[0036] In (b) of the above formula (I), Figure 1 In (b) of the above formula (I), Figure 2 In (b) of the above formula (I), and Figure 3 In (b) of the above formula (I), D represents the average particle size. DETAILED DESCRIPTION

[0037] The application provides a conductive polymer composite and a preparation method thereof. To make the purpose, technical scheme and effects of the application more clear and explicit, the application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0039] In the inventor's previous research, a conductive polymer composite was prepared by using a Pickering emulsion stabilized by graphene oxide as a template, but the stabilizer graphene oxide in the conductive polymer composite has poor conductivity and is retained in the conductive polymer composite, which affects the conductivity of the conductive polymer composite to some extent. Based on this, the application provides a preparation method of a conductive polymer composite, which comprises the following steps:

[0040] S1, providing an oil phase solution and a water phase solution, wherein the oil phase solution comprises an organic solvent and a polymer, and the water phase solution comprises water, graphene oxide and carbon nanotubes;

[0041] S2, mixing the oil phase solution and the water phase solution, and performing homogenization treatment to obtain a graphene oxide stabilized Pickering emulsion;

[0042] S3, performing supercritical CO2 drying on the graphene oxide stabilized Pickering emulsion to remove the organic solvent, then adding a reducing agent to perform a reduction reaction, reducing the graphene oxide to reduced graphene oxide, and then performing heating drying to remove water, to obtain the conductive polymer composite.

[0043] In the present application, during the process of mixing the oil phase solution and the water phase solution and homogenizing treatment, graphene oxide and carbon nanotubes are self-assembled at the oil-water interface and wrapped on the surface of oil droplets (the oil droplets have polymer dissolved inside), and the irreversible adsorption of graphene oxide on the oil-water interface can form a layer of solid mechanical barrier to prevent the coalescence of oil droplets, the oil droplets wrapped with graphene oxide and carbon nanotubes are dispersed in water to form a graphene oxide stable Pickering emulsion (oil-in-water type), which is used as a template for preparing a conductive polymer composite, then the organic solvent is removed by supercritical CO2 drying, then a reducing agent is added, and a reduction reaction is carried out to reduce the graphene oxide with poor conductivity into reduced graphene oxide with good conductivity, and then water is removed by heating and drying to obtain a conductive polymer composite with an isolated conductive network structure and high conductivity (wherein the carbon nanotubes and the reduced graphene oxide are used as conductive fillers and uniformly distributed on the surface of the polymer particles to form an isolated conductive network).

[0044] The present application adopts the Pickering emulsion template method combined with the supercritical anti-solvent method and the reduction of graphene oxide to prepare a conductive polymer composite with good conductivity (the conductivity can reach 211 S·m -1) and the preparation method provided by the present application is green, environmentally friendly, has a small amount of fillers, highly dispersed fillers, and good controllability of the filler network structure. Specifically, a small amount of stabilizer (i.e., graphene oxide) can be used to prepare a Pickering emulsion with a particle size of 30-240 μm by the Pickering emulsion template method, which can be stably stored for more than 30 days, and the conductive filler network structure constructed by the Pickering emulsion template is stable. Then, supercritical CO2 is used for drying, and the organic solvent is removed by taking advantage of the fast mass transfer and strong solvent capacity of supercritical CO2, and since supercritical CO2 has no surface tension, the damage to the Pickering emulsion template structure during the removal of the organic solvent is small, which can maximize the maintenance of the network structure constructed by the conductive fillers of graphene oxide and carbon nanotubes in the Pickering emulsion template, obtain high conductivity, avoid the problems of aggregation and uneven network structure during the evaporation of the organic solvent, and finally make the carbon nanotube conductive filler and the graphene oxide form a stable network structure and uniformly wrap the surface of the polymer particles. Then, the graphene oxide is reduced to reduced graphene oxide by adding a reducing agent for reduction reaction, which can form a mixed conductive filler with the carbon nanotubes, and the reduced graphene oxide and the carbon nanotubes form a conductive network, which improves the filling density of the conductive filler, provides higher line and surface contact degree and lower interface resistance, constructs an effective conductive network, further improves the conductivity, and further obtains a conductive polymer composite material with an isolated conductive network structure and high conductivity (when the conductive filler carbon nanotube accounts for 10wt% of the mass of the polymer, the conductivity is as high as 211 S·m -1 ).

[0045] When the existing emulsion template method is used to prepare a conductive polymer composite material, the oil phase solution usually uses a low-boiling-point organic solvent (boiling point <100 ℃), which is difficult to dissolve high-modulus and high-molecular-weight polymers, so the selection of the polymer is limited. In addition, the organic solvent that can dissolve high-modulus and high-molecular-weight polymers has a very high boiling point, which is difficult to remove by solvent evaporation (because the water in the water phase will boil), so the selection of the organic solvent is also limited. The supercritical emulsion extraction method of the present application combines the supercritical CO2 anti-solvent method with the emulsion template method, which has the advantages of completely removing the organic solvent, maintaining the three-dimensional filler network structure, and easily controlling the particle size, which can expand the selection range of the organic solvent (the boiling point of the organic solvent used can be not only lower than 100 ℃, but also higher than 100 ℃), thereby expanding the selection range of the polymer. On the basis of green chemistry, the use of the supercritical emulsion extraction method to develop composite materials has the advantages of simple process, fine control, low cost, green environmental protection, stability and reliability, and large-scale application.

[0046] Graphene oxide (GO) is an oxide of graphene (Gr), and its sheets contain a large number of oxygen-containing functional groups (such as hydroxyl, epoxy, and carboxyl groups). These structural features determine its stability mechanism.

[0047] First, graphene oxide possesses an amphiphilic structure. The numerous oxygen-containing functional groups on the surface and edges of its sheets give it strong hydrophilicity and enable it to form hydrogen bonds with water molecules. Meanwhile, unoxidized sp... 2 The hybrid structure (large π bonds) retains the hydrophobic properties of graphene. This unique amphiphilicity allows graphene oxide to be well adsorbed at the oil-water interface, with its hydrophilic portion in contact with the aqueous phase and its hydrophobic portion in contact with the oil phase, making it very suitable for stabilizing emulsions.

[0048] Secondly, graphene oxide possesses a flexible, sheet-like structure and a large specific surface area. When graphene oxide is adsorbed onto the surface of oil droplets, it can encapsulate the droplets, forming a dense protective layer. This physical coating effectively prevents direct contact and aggregation between oil droplets, providing steric stability.

[0049] Finally, the graphene oxide sheets exhibit electrostatic repulsion between their layers. The functional groups, such as the carboxyl groups, on the surface of graphene oxide ionize in aqueous solution, acquiring a negative charge. When graphene oxide sheets are adsorbed onto the surface of oil droplets, the surface of the oil droplets also acquires a negative charge, generating a strong electrostatic repulsion between the oil droplets and preventing them from coalescing due to collisions.

[0050] In this invention, graphene oxide and carbon nanotubes (acting as both stabilizers and conductive fillers) are used in combination as stabilizers in Pickering emulsions, creating a stronger interfacial barrier through a synergistic effect. Specifically, carbon nanotubes bridge graphene oxide sheets, preventing them from overlapping or agglomerating. Carbon nanotubes can embed themselves into any gaps between graphene oxide sheets, further improving the density of the conductive network. The combined one-dimensional (carbon nanotubes) and two-dimensional (graphene oxide) structure enhances the mechanical strength of the interfacial film, more effectively resisting instability caused by oil droplet collisions and compression. Carbon nanotubes form physical cross-linking points through van der Waals forces and entanglement, imparting elasticity to the network. Strong π-π conjugated interactions and physical entanglement between graphene oxide and carbon nanotubes make it difficult for them to desorb from the interface, thus enabling the emulsion droplets to exhibit stronger stability when facing external disturbances such as temperature changes, pH changes, and mechanical shearing.

[0051] In steps S1 and S2, in some embodiments, the concentration of graphene oxide in the aqueous solution is 0.1~20 mg·mL. -1 For example, it can be 0.1 mg·mL -1 0.5 mg·mL-1 1 mg·mL -1 1.5 mg·mL -1 2 mg·mL -1 5 mg·mL -1 8 mg·mL -1 10 mg·mL -1 12 mg·mL -1 15 mg·mL -1 18 mg·mL -1 20 mg·mL -1 and the like.

[0052] The present application is not limited to a specific type of graphene oxide. For example, in some embodiments, the graphene oxide can be at least one of single-layer graphene oxide, few-layer graphene oxide and multi-layer graphene oxide. In this regard, the particle size of the single-layer graphene oxide can be 0.2-5 μm, the particle size of the few-layer graphene oxide can be 10-20 μm, and the particle size of the multi-layer graphene oxide can be 10-50 μm.

[0053] The present application is not limited to a specific type of carbon nanotube. For example, in some embodiments, the carbon nanotube can be at least one of single-walled carbon nanotube and multi-walled carbon nanotube.

[0054] In this regard, the single-walled carbon nanotube can be at least one of functionalized single-walled carbon nanotube and non-functionalized single-walled carbon nanotube; the functionalized single-walled carbon nanotube can be at least one of carboxylated single-walled carbon nanotube, hydroxylated single-walled carbon nanotube and aminated single-walled carbon nanotube, but is not limited thereto.

[0055] The multi-walled carbon nanotube can be at least one of functionalized multi-walled carbon nanotube and non-functionalized multi-walled carbon nanotube; the functionalized multi-walled carbon nanotube can be at least one of carboxylated multi-walled carbon nanotube, hydroxylated multi-walled carbon nanotube and aminated multi-walled carbon nanotube, but is not limited thereto.

[0056] In some embodiments, the aqueous solution further comprises an electrolyte, and the electrolyte comprises at least one of sodium chloride, potassium chloride, magnesium chloride and lithium chloride. In this embodiment, the addition of the electrolyte in the aqueous solution can shield the electrostatic force.

[0057] In some embodiments, the concentration of the electrolyte in the aqueous solution is 0-20 mg·mL -1 , for example, can be 0 mg·mL -1 0.1 mg·mL -1 1 mg·mL -1 2 mg·mL -15 mg·mL -1 10 mg·mL -1 15 mg·mL -1 or 20 mg·mL -1 etc.

[0058] In some embodiments, the method for preparing the aqueous solution comprises the following steps:

[0059] adding graphene oxide into water, and ultrasonically treating the mixture at a power of 320-800 W (for example, 320 W, 400 W, 500 W, 600 W, 700 W or 800 W, etc.) for 5-60 min (for example, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, etc.) to obtain a graphene oxide dispersion;

[0060] adding carbon nanotubes into the graphene oxide dispersion, and stirring to obtain the aqueous solution; or adding carbon nanotubes and electrolyte into the graphene oxide dispersion, and stirring to obtain the aqueous solution.

[0061] In some embodiments, the concentration of the polymer in the oil phase solution is 10-300 mg·mL -1 for example, 10 mg·mL -1 20 mg·mL -1 50 mg·mL -1 60 mg·mL -1 100 mg·mL -1 120 mg·mL -1 150 mg·mL -1 200 mg·mL -1 250 mg·mL -1 or 300 mg·mL -1 etc.

[0062] In some embodiments, the polymer comprises at least one of polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyamide, polystyrene, polymethyl methacrylate, nitrocellulose, cellulose acetate, synthetic rubber, polyethylene, polylactic acid, polyvinyl chloride, polyphenylene ether, polyurethane, polyimide, polysulfone, polyethersulfone, polyacrylonitrile and polyvinyl alcohol, but is not limited thereto.

[0063] In the present application, low-boiling organic solvents can be selected, and high-boiling organic solvents can also be selected. As an example, in some embodiments, the organic solvent comprises at least one of benzene, ethyl acetate, chloroform, cyclohexane, n-hexane, cyclohexanone, toluene and xylene, but is not limited thereto.

[0064] In some embodiments, the mass ratio of the carbon nanotubes in the aqueous phase solution to the polymers in the oil phase solution is (0.5-20):100, for example, it can be 0.5:100, 1:100, 2:100, 5:100, 8:100, 10:100, 12:100, 15:100, or 20:100, etc.

[0065] In some embodiments, the volume ratio of the oil phase solution to the aqueous phase solution is (1-10):(1-10), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, etc.

[0066] In step S2, in some embodiments, the homogenization treatment adopts the following process conditions:

[0067] The rotation speed is 300-10000 rpm, and the time is 0.5-30 min.

[0068] For example, the rotation speed can be 300 rpm, 400 rpm, 500 rpm, 800 rpm, 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, or 10000 rpm, etc., and the time can be 0.5 min, 1 min, 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, or 30 min, etc.

[0069] In step S3, in some embodiments, the reducing agent includes at least one of ascorbic acid, sodium bisulfite, sodium disulfide, and sodium borohydride, but is not limited thereto.

[0070] In some embodiments, the reaction conditions of the reduction reaction are as follows:

[0071] The temperature is 25-80 ℃ (for example, it can be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, or 80 ℃, etc.), and the time is 1-24 h (for example, it can be 1 h, 2 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 21 h, 22 h, 23 h, or 24 h, etc.).

[0072] In some embodiments, the mass ratio of the reducing agent to the graphene oxide is (1-30):(1-30). The ratio can enable the graphene oxide to be sufficiently reduced, and thus the conductive polymer composite to obtain higher conductivity. For example, the mass ratio of the reducing agent to the graphene oxide can be 1:1, 1:10, 1:20, 1:30, 10:1, 20:1, or 30:1, etc.

[0073] In some embodiments, the process condition for the supercritical CO2 drying is as follows:

[0074] The temperature is 35-60 ℃, the pressure is 7.5-15 MPa, and the time is 1-8 h.

[0075] In this embodiment, the process condition can be used to better and more thoroughly remove the organic solvent. For example, the temperature can be 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, or 60 ℃, etc., the pressure can be 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, or 15 MPa, etc., and the time can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h, etc.

[0076] In some embodiments, the process condition for the heating drying is as follows:

[0077] The temperature is 40-100 ℃, and the time is 0.5-48 h.

[0078] In this embodiment, the process condition can be used to better and more thoroughly remove water. For example, the temperature can be 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, or 100 ℃, etc., and the time can be 0.5 h, 1 h, 2 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, or 48 h, etc.

[0079] The present application also provides a conductive polymer composite, which is prepared by the method for preparing a conductive polymer composite as described above.

[0080] The conductive polymer composite provided by the present application has an isolated conductive network structure and high conductivity. When the content of the conductive filler carbon nanotube is 10 wt% of the polymer, the conductivity of the conductive polymer composite can reach 211 S·m -1 .

[0081] The present application will be further described by specific examples.

[0082] Unless otherwise specified, the materials and equipment used in the following embodiments are all commercially available products.

[0083] The ultrasonic cleaner was purchased from Kunshan Ultrasonic Instrument Co., Ltd., model KQ-800KDE.

[0084] The disperser was purchased from IKA GmbH in Germany, model T25.

[0085] The monolayer graphene oxide was purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with item number 100602 and serial number XF002-2.

[0086] Multi-walled carbon nanotubes (i.e., unfunctionalized multi-walled carbon nanotubes) were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with item number 100234 and serial number XFM04.

[0087] To demonstrate that graphene oxide can stabilize Pickering emulsions, Pickering emulsions were prepared in Examples 1 and 2 using monolayer graphene oxide as a stabilizer.

[0088] Example 1

[0089] This embodiment provides a method for preparing a Pickering emulsion, comprising the following steps:

[0090] (1) Add monolayer graphene oxide to water and use an ultrasonic cleaner at a power of 400 W for 60 min to fully disperse the monolayer graphene oxide, resulting in a monolayer graphene oxide concentration of 4 mg·mL. -1 The aqueous dispersion, namely a single-layer graphene oxide dispersion.

[0091] (2) Add NaCl to the monolayer graphene oxide dispersion to make its concentration 0.5 mg·mL -1 Stir well to obtain an aqueous solution.

[0092] (3) Add polyphenylene ether to xylene, stir to dissolve, and obtain an oil phase solution. The concentration of polyphenylene ether in the oil phase solution is 70 mg·mL. -1 .

[0093] (4) The oil phase solution obtained in step (3) is mixed with the aqueous phase solution obtained in step (2), with a volume ratio of 1:2 between the oil phase solution and the aqueous phase solution. After homogenization using a disperser (10,000 rpm for 10 min), a Pickering emulsion (specifically a single-layer graphene oxide stabilized Pickering emulsion) is obtained.

[0094] The optical microscope image of the obtained Pickering emulsion is shown in (a) of FIG. 1, and the particle size distribution diagram is shown in (b) of FIG. 1. Figure 1 Figure 1

[0095] Example 2

[0096] The difference between this embodiment and Example 1 is that the concentration of single-layer graphene oxide in the aqueous phase solution is 5 mg·mL -1 ; the organic solvent used is xylene, and the volume ratio of the oil phase solution to the aqueous phase solution is 1:1.

[0097] The optical microscope image of the obtained Pickering emulsion is shown in (a) of FIG. 2, and the particle size distribution diagram is shown in (b) of FIG. 2. Figure 2 Figure 2

[0098] The results of Example 1 and Example 2 show that the Pickering emulsion can be successfully prepared by using single-layer graphene oxide as a stabilizer.

[0099] Example 3

[0100] This embodiment provides a preparation method of a conductive polymer composite, which comprises the following steps:

[0101] (1) Single-layer graphene oxide is added to water, and an ultrasonic cleaning machine is used to ultrasonically treat the single-layer graphene oxide at a power of 400 W for 60 min to fully disperse the single-layer graphene oxide, thereby obtaining an aqueous dispersion solution of single-layer graphene oxide with a concentration of 5 mg·mL -1 , i.e., a single-layer graphene oxide dispersion solution.

[0102] (2) NaCl is added to 36 mL of the single-layer graphene oxide dispersion solution to make the concentration of NaCl 10 mg·mL -1 , and then 162.5 mg of multi-walled carbon nanotubes are added and stirred uniformly to obtain an aqueous phase solution.

[0103] (3) Polystyrene is added to toluene, and after being stirred and dissolved, an oil phase solution is obtained, and the concentration of polystyrene in the oil phase solution is 90 mg·mL -1 .

[0104] (4) 18 mL of the oil phase solution is added to the aqueous phase solution obtained in step (2), and a dispersing machine is used for homogenization treatment (at a speed of 10,000 rpm for 5 min), thereby obtaining a single-layer graphene oxide stabilized Pickering emulsion.

[0105] ​​​​(5) The single-layer graphene oxide stable Pickering emulsion obtained in step (4) is subjected to supercritical CO2 drying at 50 ℃ and 7.5 MPa for 4 h to remove the toluene, and then 3 g of ascorbic acid is added, and the reduction is carried out at 80 ℃ for 1 h to reduce the graphene oxide to reduced graphene oxide; the obtained product solution is filtered, and the obtained filter residue is washed with water multiple times to remove NaCl and ascorbic acid, and is dried at 60 ℃ for 5 h to remove water, to obtain a conductive polymer composite (10 wt% of multi-walled carbon nanotubes in polyphenyl ether).

[0106] Test results:

[0107] (1) The optical microscope image of the single-layer graphene oxide stable Pickering emulsion prepared in Example 3 is shown as (a) in Figure 3 , and the particle size distribution graph is shown as (b) in Figure 3 .

[0108] (2) The single-layer graphene oxide stable Pickering emulsion prepared in Example 3 is placed at room temperature for 30 days, and there is basically no change.

[0109] (3) The scanning electron microscope image of the conductive polymer composite prepared in Example 3 is shown as Figure 4 .

[0110] (4) The conductive polymer composite (powder) prepared in Example 3 is hot-pressed using a hot press to obtain a test sample with a size of 4 cm x 4 cm x 1 mm (i.e., a length of 4 cm, a width of 4 cm, and a thickness of 1 mm), and the conductivity of the test sample is measured by a four-probe tester to be 211 S·m -1 .

[0111] Example 4

[0112] The present embodiment provides a method for preparing a conductive polymer composite, comprising the following steps:

[0113] (1) Single-layer graphene oxide is added to water, and an ultrasonic cleaner is used to ultrasonically treat the single-layer graphene oxide at a power of 400 W for 60 min to fully disperse the single-layer graphene oxide, to obtain a water dispersion solution of single-layer graphene oxide with a concentration of 3 mg·mL -1 , i.e., a single-layer graphene oxide dispersion solution.

[0114] (2) KCl is added to 53 mL of the single-layer graphene oxide dispersion solution to make the concentration of KCl 0.1 mg·mL -1 , and then 130 mg of multi-walled carbon nanotubes is added and stirred uniformly to obtain an aqueous phase solution.

[0115] (3) Polystyrene was added into xylene, and after stirring and dissolving, an oil phase solution was obtained, and the concentration of polystyrene in the oil phase solution was 60 mg·mL -1 .

[0116] (4) 26.5 mL of the oil phase solution was taken and added into the water phase solution obtained in step (2), and then homogenization treatment was performed by using a dispersion machine (at a speed of 8000 rpm for 10 min), to obtain a single-layer graphene oxide stable Pickering emulsion.

[0117] (5) The single-layer graphene oxide stable Pickering emulsion obtained in step (4) was subjected to supercritical CO2 drying at 35 ℃ and 8 MPa for 6 h to remove xylene, and then 4 g of sodium borohydride was added, and reduction was performed at 50 ℃ for 6 h to reduce the graphene oxide into reduced graphene oxide; the obtained product solution was filtered, the filter residue was washed with water for multiple times to remove KCl and sodium borohydride, and then the residue was dried at 60 ℃ for 4 h to remove water, to obtain a conductive polymer composite (the content of multi-walled carbon nanotubes in polystyrene was 8.2 wt%).

[0118] Test results:

[0119] (1) The single-layer graphene oxide stable Pickering emulsion prepared in Example 4 was placed at room temperature for 30 days, and no change was observed.

[0120] (2) The conductive polymer composite (powder) prepared in Example 4 was subjected to hot pressing by using a hot press, to obtain a test sample with a size of 4 cm×4 cm×1 mm (i.e., the length was 4 cm, the width was 4 cm, and the thickness was 1 mm), and the conductivity of the test sample was 180 S·m -1 .

[0121] In summary, the present application provides a conductive polymer composite and a preparation method thereof; the present application adopts a Pickering emulsion template method combined with a supercritical anti-solvent method and reduction of graphene oxide, to prepare a conductive polymer composite with a conductivity of 211 S·m -1The conductive polymer composite with isolated conductive structure and high conductivity is prepared by the following steps. Firstly, the Pickering emulsion is prepared by the Pickering emulsion template method. The Pickering emulsion has a particle size of 30-240 μm and can be stored for more than 30 days. The conductive filler network structure constructed by the Pickering emulsion template is stable. Then, the Pickering emulsion is dried by supercritical CO2. The network structure of the conductive filler is maintained by the fast mass transfer and strong solvent capacity of supercritical CO2, which avoids the problems of aggregation and uneven network structure in the process of organic solvent evaporation. Finally, the carbon nanotube conductive filler and graphene oxide form a stable network structure and are uniformly wrapped on the surface of the polymer particles. At the same time, the selection range of the organic solvent is expanded, and the selection range of the polymer is also expanded. The reduction reaction is carried out by adding a reducing agent to reduce graphene oxide to reduced graphene oxide. The reduced graphene oxide and the carbon nanotube form a mixed conductive filler. The reduced graphene oxide and the carbon nanotube form a conductive network, which improves the filling density of the conductive filler, provides higher line and surface contact degree and lower interface resistance, constructs an effective conductive network, further improves the conductivity, and finally obtains the conductive polymer composite with isolated conductive structure and high conductivity.

[0122] It should be understood that the application of the present application is not limited to the above examples. Those skilled in the art can make improvements or changes according to the above description. All these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for preparing a conductive polymer composite material, characterized in that, Includes the following steps: An oil phase solution and an aqueous phase solution are provided, wherein the oil phase solution comprises an organic solvent and a polymer, and the aqueous phase solution comprises water, graphene oxide, and carbon nanotubes; The oil phase solution and the aqueous phase solution are mixed and homogenized to obtain a graphene oxide-stabilized Pickering emulsion; the particle size of the graphene oxide-stabilized Pickering emulsion is 30~240 μm. The graphene oxide-stabilized Pickering emulsion was subjected to supercritical CO2 drying to remove organic solvents, and then a reducing agent was added to carry out a reduction reaction to reduce the graphene oxide to reduced graphene oxide. Then, it was heated and dried to remove water to obtain the conductive polymer composite material. The reducing agent includes at least one of ascorbic acid, sodium bisulfite, sodium disulfide, and sodium borohydride; The reaction conditions for the reduction reaction are as follows: Temperature range: 25~80 ℃; Duration: 1~24 h; The homogenization process conditions are as follows: The rotation speed is 300~10000 rpm, and the time is 0.5~30 min; The process conditions used for supercritical CO2 drying are as follows: The temperature is 35~60 ℃, the pressure is 7.5~15 MPa, and the time is 1~8 h.

2. The method for preparing the conductive polymer composite material according to claim 1, characterized in that, The mass ratio of the reducing agent to the graphene oxide is (1~30):(1~30).

3. The method for preparing the conductive polymer composite material according to claim 1, characterized in that, In the aqueous solution, the concentration of graphene oxide is 0.1~20 mg·mL. -1 ; The aqueous solution further includes an electrolyte, which includes at least one of sodium chloride, potassium chloride, magnesium chloride, and lithium chloride; the concentration of the electrolyte in the aqueous solution is 0-20 mg / mL. -1 .

4. The method for preparing the conductive polymer composite material according to claim 3, characterized in that, In the oil phase solution, the concentration of the polymer is 10~300 mg·mL. -1 ; The polymer includes at least one of polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyamide, polystyrene, polymethyl methacrylate, nitrocellulose, cellulose acetate, synthetic rubber, polyethylene, polylactic acid, polyvinyl chloride, polyphenylene ether, polyurethane, polyimide, polysulfone, polyethersulfone, polyacrylonitrile, and polyvinyl alcohol. The organic solvent includes at least one selected from benzene, ethyl acetate, chloroform, cyclohexane, n-hexane, cyclohexanone, toluene, and xylene.

5. The method for preparing the conductive polymer composite material according to claim 4, characterized in that, The mass ratio of carbon nanotubes in the aqueous solution to polymers in the oil solution is (0.5~20):100, and the volume ratio of the oil solution to the aqueous solution is (1~10):(1~10).

6. The method for preparing the conductive polymer composite material according to claim 1, characterized in that, The method for preparing the aqueous solution includes the following steps: Graphene oxide is added to water and sonicated at 320-800 W for 5-60 min to obtain a graphene oxide dispersion. Carbon nanotubes were added to the graphene oxide dispersion, and after stirring, the aqueous solution was obtained. Alternatively, carbon nanotubes and electrolytes can be added to the graphene oxide dispersion, and after stirring, the aqueous solution can be obtained.

7. The method for preparing the conductive polymer composite material according to claim 1, characterized in that, The process conditions used for the heating and drying are as follows: The temperature is 40~100 ℃, and the time is 0.5~48 h.

8. A conductive polymer composite material, characterized in that, The conductive polymer composite material is prepared by the method for preparing conductive polymer composite materials according to any one of claims 1-7.

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