Preparation method of nano-copper-based conductive composite material

Abstract

This invention discloses a method for preparing a nano-copper-based conductive composite material, comprising the following preparation steps: Step 1, preparation of a poly(catechol-polyamine)-copper precursor suspension: S11, preparing a mixed monomer solution, wherein the mixed monomer solution contains a catechol-polyamine system, 3,4-dihydroxyphenylalanine, gallic acid, and Tween-80; S12, adjusting the pH of the mixed monomer solution to 8.5-9.0 using Tris-HCl buffer, and then sequentially adding copper sulfate, a composite oxidation system, dithiothreitol, and phytic acid. In this invention, through the synergistic polymerization of the catechol-polyamine system and 3,4-dihydroxyphenylalanine gallic acid, a poly(catechol-polyamine) coating layer with steric hindrance effect is formed on the surface of copper ions. Simultaneously, Tween-80 optimizes the hydrophilicity / hydrophobicity of the particle surface, and dithiothreitol regulates the charge distribution on the particle surface. These multiple effects fundamentally inhibit particle aggregation.

Description

Technical Field

[0001] This invention relates to the field of conductive composite materials technology, specifically to a method for preparing a nano-copper-based conductive composite material. Background Technology

[0002] In modern high-tech fields such as electronic information and new energy, the performance of conductive composite materials directly affects the reliability and service life of end products. Nano-copper, with its excellent electrical and thermal conductivity, low cost, and good processing compatibility, is gradually replacing traditional conductive fillers such as nano-nickel and silver, becoming the core component for preparing high-performance conductive composite materials. It is widely used in key areas such as electronic packaging materials, flexible conductive films, electromagnetic shielding materials, and antistatic coatings.

[0003] However, due to their large specific surface area and extremely high surface energy, copper nanoparticles are prone to irreversible agglomeration during preparation, storage, and composite processing due to van der Waals forces and electrostatic forces. This results in poor dispersion uniformity within the polymer matrix, preventing the formation of a continuous and stable conductive network. This not only significantly reduces the conductivity and conductivity stability of the composite material but also induces internal stress concentration, affecting its mechanical strength, flexibility, and environmental stability.

[0004] Existing solutions to the agglomeration problem of copper nanoparticles have significant limitations: First, single dispersants (such as traditional surfactants) can only improve the hydrophilicity and hydrophobicity of the particle surface through physical adsorption, but cannot fundamentally inhibit the interaction between particles, resulting in poor dispersion durability. Second, simple surface coating or passivation treatments (such as single modification with silane coupling agents) are difficult to balance dispersibility and oxidation resistance, and the interfacial bonding between the coating layer and the matrix material is insufficient, making it prone to peeling during long-term use. Third, the uncontrollable growth direction of copper nanoparticles in the reduction process leads to uneven particle morphology, further exacerbating the risk of agglomeration. These problems severely limit the application of copper nanoparticle-based conductive composite materials in high-end electronics, precision manufacturing, and other fields. Therefore, this invention proposes a method for preparing copper nanoparticle-based conductive composite materials to solve the aforementioned problems. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a nano-copper-based conductive composite material, which solves the problems mentioned in the background section.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides a method for preparing a nano-copper-based conductive composite material, comprising the following preparation steps:

[0009] Step 1: Preparation of poly(catechol-polyamine)-copper precursor suspension:

[0010] S11. Prepare a mixed monomer solution, wherein the mixed monomer solution contains a catechol-polyamine system, 3,4-dihydroxyphenylalanine, gallic acid and Tween-80;

[0011] S12. The pH of the mixed monomer solution was adjusted to 8.5-9.0 using Tris-HCl buffer, and then copper sulfate, the complex oxidation system, dithiothreitol and phytic acid were added to it in sequence.

[0012] S13. Stir the above solution for 30-45 minutes to form a poly(catechol-polyamine)-copper precursor suspension;

[0013] Step 2, directional reduction and antioxidant coating of nano-copper: Add 100 mL of a mixed reducing solution with a concentration of 25 g / L to the poly(catechol-polyamine)-copper precursor suspension, wherein the mixed reducing solution contains glucose, disodium ethylenediaminetetraacetate and polydopamine-polyethylene glycol block copolymer, and stir for 1.5-2 h;

[0014] Step 3: Interface passivation and post-processing:

[0015] S31. The product after step two reaction is washed multiple times using a 1:1 volume ratio of deionized water and isopropanol mixture.

[0016] S32. Add 3-aminopropyltriethoxysilane and stearic acid to the washed product and stir for 10-15 min.

[0017] S33. The above product is dried under vacuum at 65-75℃ to obtain a nano-copper-based conductive composite material.

[0018] Preferably, in S11, the polyamine is selected from any one of ethylenediamine, hexamethylenediamine, or putrescine.

[0019] Preferably, in S11, the molar ratio of catechol to polyamine in the catechol-polyamine system is 1:1, and the total concentration is 13-15 mM; the amount of 3,4-dihydroxyphenylalanine added is 5-7% of the total molar amount of the catechol-polyamine system, the amount of gallic acid added is 1.6-2% of the total molar amount of the catechol-polyamine system, and the concentration of Tween-80 is 1.8-2 mM.

[0020] Preferably, in S12, the concentration of copper sulfate is 5 mM, the composite oxidation system is composed of 15-20 mM ascorbic acid and 3-5 mM hydrogen peroxide, and the concentration of phytic acid is 0.8-1 mM.

[0021] Preferably, in S12, the amount of dithiothreitol added is 0.1-0.5 mM, and the molar ratio of dithiothreitol to catechol is 1:15-30.

[0022] Preferably, in step two, the molar ratio of glucose to disodium ethylenediaminetetraacetate is 5-8:1, and the molar ratio of disodium ethylenediaminetetraacetate to copper sulfate is 1:2-5.

[0023] Preferably, in step two, the concentration of the polydopamine-polyethylene glycol block copolymer is 0.35-0.5 g / L, wherein the mass ratio of polydopamine segments to polyethylene glycol segments is 1:2-5, the number average molecular weight of the polyethylene glycol segments is 2000-5000, and the mass ratio of the polydopamine-polyethylene glycol block copolymer to copper sulfate is 1:5-10.

[0024] Preferably, in S32, the molar ratio of 3-aminopropyltriethoxysilane to stearic acid is 1-2:1, the concentration of stearic acid is 1-1.5 mM, and the amount of 3-aminopropyltriethoxysilane added is 0.5-1% of the total mass of the product.

[0025] (III) Beneficial Effects

[0026] This invention provides a method for preparing a nano-copper-based conductive composite material. Compared with the prior art, it has the following advantages:

[0027] (1) In this invention, a poly(catechol-polyamine) coating layer with steric hindrance effect is formed on the surface of copper ions by synergistic polymerization of the catechol-polyamine system and 3,4-dihydroxyphenylalanine gallic acid. At the same time, Tween-80 optimizes the hydrophilicity and hydrophobicity of the particle surface, and dithiothreitol regulates the charge distribution on the particle surface. Multiple effects inhibit particle aggregation from the root. During the reduction process, EDTA-2Na complexes with copper ions to achieve directional growth. The polydopamine-polyethylene glycol block copolymer further plays a synergistic role in dispersion and coating, and finally makes the nano copper particles present a uniform dispersion state in the matrix, forming a continuous and stable conductive network.

[0028] (2) In this invention, during the preparation process, phytic acid and copper ions form an integrated structure, which initially enhances the antioxidant capacity of the particles; during the reduction stage, the in-situ coating of polydopamine-polyethylene glycol block copolymer forms a dense antioxidant layer, blocking the contact between nano-copper and oxygen; in the post-treatment, the synergistic passivation of 3-aminopropyltriethoxysilane and stearic acid further constructs a dual protection system, which significantly reduces the oxidation rate of nano-copper.

[0029] (3) In this invention, 3-aminopropyltriethoxysilane is used as a coupling agent. Its amino and hydroxyl groups react chemically with the polymer matrix and the surface coating layer of the nano-copper to form chemical bonds, which significantly enhances the interfacial bonding force between the nano-copper and the matrix and avoids interfacial peeling during use. At the same time, the synergistic effect of each component makes the composite material have excellent conductivity, good mechanical strength and flexibility, which can meet the application requirements of high-end fields such as electronic packaging and flexible conductive materials. Attached Figure Description

[0030] Figure 1 SEM image of the nano-copper-based conductive composite material provided by this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] Step 1: Preparation of poly(catechol-polyamine)-copper precursor suspension:

[0034] S11. Prepare a mixed monomer solution with the catechol-ethylenediamine system as the core, wherein the molar ratio of catechol to ethylenediamine is 1:1 and the total concentration is 14 mM. Add 3,4-dihydroxyphenylalanine (6% of the total molar amount of the catechol-ethylenediamine system) and gallic acid (1.8% of the total molar amount of the catechol-ethylenediamine system) to the system, and add Tween-80 to make the concentration reach 1.9 mM. Stir until completely dissolved.

[0035] S12. Adjust the pH of the above mixed monomer solution to 8.7 using Tris-HCl buffer. Then, add copper sulfate (final concentration 5mM), the complex oxidation system (composed of 18mM ascorbic acid and 4mM hydrogen peroxide), dithiothreitol (final concentration 0.3mM, molar ratio with catechol 1:20), and phytic acid (final concentration 0.9mM) in sequence. Stir for 5 minutes after each addition to ensure uniform mixing.

[0036] S13. Place the above mixed solution on a magnetic stirrer and stir at 300 r / min at 25°C for 40 min to form a uniform and stable poly(catechol-polyamine)-copper precursor suspension.

[0037] Step 2: Directed reduction and antioxidant coating of nano-copper: Slowly add 100 mL of a mixed reducing solution with a concentration of 25 g / L to the above precursor suspension (where the molar ratio of glucose to EDTA-2Na is 6:1, the molar ratio of EDTA-2Na to copper sulfate is 1:3; the concentration of polydopamine-polyethylene glycol block copolymer is 0.4 g / L, and its mass ratio with copper sulfate is 1:7). After the addition is complete, raise the temperature to 40 °C and stir at 250 r / min for 1.8 h to achieve the directional growth and in-situ coating of nano-copper.

[0038] Step 3: Interface passivation and post-processing:

[0039] S31. The product after reduction reaction was centrifuged and washed with a 1:1 volume ratio of deionized water and isopropanol (8000 r / min, 10 min each time), and the washing was repeated 4 times to remove unreacted monomers, impurities and excess reagents.

[0040] S32. Add 3-aminopropyltriethoxysilane and stearic acid (molar ratio 1.5:1, final stearic acid concentration 1.2mM, 3-aminopropyltriethoxysilane addition amount is 0.8% of the total mass of the product) to the washed precipitate, stir at 30℃ for 12 min to achieve interface passivation modification.

[0041] S33. The modified product was transferred to a vacuum drying oven and dried at 70°C and a vacuum of -0.09 MPa for 8 hours. After cooling to room temperature, it was ground through a 200-mesh sieve to obtain a nano-copper-based conductive composite material.

[0042] Example 2

[0043] Step 1: Preparation of poly(catechol-polyamine)-copper precursor suspension

[0044] S11. Prepare a mixed monomer solution with a molar ratio of catechol to hexamethylenediamine (polyamine reagent) of 1:1 and a total concentration of 13 mM; add 5% of the total molar amount of 3,4-dihydroxyphenylalanine in the catechol-hexamethylenediamine system, add 1.6% of gallic acid, and add 1.8 mM of Tween-80. Stir to dissolve.

[0045] S12. Adjust the pH to 8.5 with Tris-HCl buffer, then add copper sulfate (5mM), the complex oxidation system (15mM ascorbic acid + 3mM hydrogen peroxide), dithiothreitol (0.1mM, molar ratio of 1:15 with catechol), and phytic acid (0.8mM) in sequence, and mix well.

[0046] S13, stir at 300 r / min for 30 min at 25℃ to form a precursor suspension;

[0047] Step 2, directional reduction and antioxidant coating of nano-copper: Add 100 mL of mixed reducing solution (molar ratio of glucose to EDTA-2Na 5:1, molar ratio of EDTA-2Na to copper sulfate 1:2; concentration of polydopamine-polyethylene glycol block copolymer 0.35 g / L, mass ratio of polydopamine-polyethylene glycol block copolymer to copper sulfate 1:5), and stir at 35 °C for 1.5 h;

[0048] Step 3: Interface passivation and post-processing:

[0049] S31. Wash three times by centrifugation with deionized water and isopropanol (1:1).

[0050] S32. Add 3-aminopropyltriethoxysilane and stearic acid (molar ratio 1:1, stearic acid concentration 1mM, 3-aminopropyltriethoxysilane addition amount 0.5%), and stir for 10 min;

[0051] S33, vacuum dried at 65℃ for 10 hours, then ground and sieved to obtain the finished product.

[0052] Example 3

[0053] Step 1: Preparation of poly(catechol-polyamine)-copper precursor suspension

[0054] S11, catechol and putrescine (polyamine reagent) molar ratio 1:1, total concentration 15mM; 3,4-dihydroxyphenylalanine added 7%, gallic acid added 2%, Tween-80 concentration 2mM;

[0055] S12, pH adjusted to 9.0, add copper sulfate (5mM), compound oxidation system (20mM ascorbic acid + 5mM hydrogen peroxide), dithiothreitol (0.5mM, molar ratio with catechol 1:30), phytic acid (1mM).

[0056] Stirring at 25℃ for 45 minutes under S13 conditions to form a precursor suspension;

[0057] Step 2, directional reduction and antioxidant coating of nano-copper: Add 100 mL of mixed reducing solution (molar ratio of glucose to EDTA-2Na 8:1, molar ratio of EDTA-2Na to copper sulfate 1:5; concentration of polydopamine-polyZ glycol block copolymer 0.5 g / mL, mass ratio of polydopamine-polyZ glycol block copolymer to copper sulfate 1:10), and stir at 45 °C for 2 h;

[0058] Step 3: Interface passivation and post-processing:

[0059] S31. Wash 5 times by centrifugation with deionized water and isopropanol (1:1);

[0060] S32, 3-aminopropyltriethoxysilane and stearic acid in a molar ratio of 2:1, stearic acid concentration of 1.5 mM, 3-aminopropyltriethoxysilane added at 1% and stirred for 15 min;

[0061] S33, vacuum dried at 75℃ for 6 hours, then ground and sieved to obtain the finished product.

[0062] Comparative Example 1

[0063] Compared with Example 1, the difference is that the poly(catechol-polyamine) system is not added; everything else remains the same.

[0064] Comparative Example 2

[0065] Compared with Example 1, the difference is that no composite oxidation system is added; everything else remains the same.

[0066] Comparative Example 3

[0067] Compared with Example 1, the difference is that polydopamine-polyethylene glycol block copolymer is not added; everything else remains the same.

[0068] Comparative Example 4

[0069] Compared to Example 1, the difference is that only 3-aminopropyltriethoxysilane is used in the post-treatment; everything else remains the same.

[0070] Comparative Example 5

[0071] Compared with Example 1, the difference lies in the non-directional reduction and multiple coating, that is, copper sulfate and glucose are directly mixed and reduced, and the product is washed with deionized water and then directly dried.

[0072] Dispersion uniformity: The cross-sectional morphology of the composite material was observed using scanning electron microscopy (SEM), the particle size distribution of the copper nanoparticle agglomerates was statistically analyzed, and the average agglomerate particle size was calculated; the results are shown in Table 1.

[0073] Interfacial adhesion: The surface adhesion of the composite material was tested by cross-cut test (cross-cut spacing 1 mm, cross-cut depth to the matrix), and the rating standard was based on GB / T9286-1998 (level 1 is the best, level 5 is the worst); the results are shown in Table 1.

[0074] Conductivity test: The volume resistivity of the composite material was tested using a four-probe tester (test pressure 10N, room temperature 25℃); the results are shown in Table 1.

[0075] Antioxidant stability test: The composite material was placed in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for accelerated aging test. The volume resistivity was measured after aging for 0h, 500h and 1000h respectively, and the conductivity decay rate was calculated. The results are shown in Table 2.

[0076] Mechanical property testing: The tensile strength of the composite material was tested using a universal tensile testing machine (tensile rate 5 mm / min, specimen size 100 mm × 10 mm × 2 mm); the results are shown in Table 2.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081] As shown in Tables 1 and 2, the dispersion uniformity of the nano-copper particles in Examples 1-3 is less than 0.5 μm, which is much smaller than that of the comparative examples (1.25 μm-4.37 μm). This indicates that the multiple dispersion system of the present invention (catechol-polyamine polymerization coating, Tween-80, and dithiothreitol synergy) can effectively inhibit agglomeration.

[0082] Conductivity: The initial volume resistivity of the embodiment is as low as 1.2 x 10⁻⁶. -4 The conductivity of Ω·cm is only 1 / 125 of that of the traditional method (Comparative Example 5), and the conductivity decay rate after aging is extremely low, which reflects the synergistic effect of continuous conductive network and excellent oxidation resistance.

[0083] Mechanical and interfacial properties: The tensile strength of the embodiment was improved by more than 104% compared with the conventional method, and the interfacial adhesion reached level 1, indicating that the synergistic passivation of 3-aminopropyltriethoxysilane and stearic acid can significantly enhance the interfacial bonding force.

[0084] Comparing Comparative Examples 1-4 with Example 1, it can be seen that the poly(catechol-polyamine) system, the composite oxidation system, the polydopamine-polyethylene glycol block copolymer, and the stearic acid synergistic passivation are all core elements for improving the overall performance of the material, and none of them can be omitted.

[0085] like Figure 1 As shown, (a) is the SEM image of the composite material of Example 1, (b) is the SEM image of the composite material of Comparative Example 1, and (c) is the SEM image of the composite material of Comparative Example 5. It can be seen that in Example 1, the nano-copper particles are uniformly monodisperse without obvious agglomerates, and the particle size distribution is concentrated (the average agglomerate particle size is only 0.35 μm), and the gaps between particles are uniform. In Comparative Example 1, the particles show obvious agglomeration, with the size of a single agglomerate reaching 2.86 μm. The particles adhere to each other, and the dispersion uniformity is greatly reduced. In Comparative Example 5, the particles show a severe agglomeration state, forming large-sized "particle clusters" (the average agglomerate particle size is 4.36 μm), and the particles completely lose their independent dispersion.

[0086] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0088] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a nano-copper-based conductive composite material, characterized in that, The preparation steps include the following: Step 1: Preparation of poly(catechol-polyamine)-copper precursor suspension: S11. Prepare a mixed monomer solution, wherein the mixed monomer solution contains a catechol-polyamine system, 3,4-dihydroxyphenylalanine, gallic acid and Tween-80; S12. The pH of the mixed monomer solution was adjusted to 8.5-9.0 using Tris-HCl buffer, and then copper sulfate, the complex oxidation system, dithiothreitol and phytic acid were added to it in sequence. S13. Stir the above solution for 30-45 minutes to form a poly(catechol-polyamine)-copper precursor suspension; Step 2, directional reduction and antioxidant coating of nano-copper: Add 100 mL of a mixed reducing solution with a concentration of 25 g / L to the poly(catechol-polyamine)-copper precursor suspension, wherein the mixed reducing solution contains glucose, disodium ethylenediaminetetraacetate and polydopamine-polyethylene glycol block copolymer, and stir for 1.5-2 h; Step 3: Interface passivation and post-processing: S31. The product after step two reaction is washed multiple times using a 1:1 volume ratio of deionized water and isopropanol mixture. S32. Add 3-aminopropyltriethoxysilane and stearic acid to the washed product and stir for 10-15 min. S33. The above product is dried under vacuum at 65-75℃ to obtain a nano-copper-based conductive composite material.

2. The method according to claim 1, wherein the method is characterized by, In S11, the polyamine is selected from any one of ethylenediamine, hexamethylenediamine, or putrescine.

3. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In S11, the molar ratio of catechol to polyamine in the catechol-polyamine system is 1:1, and the total concentration is 13-15 mM; the amount of 3,4-dihydroxyphenylalanine added is 5-7% of the total molar amount of the catechol-polyamine system, the amount of gallic acid added is 1.6-2% of the total molar amount of the catechol-polyamine system, and the concentration of Tween-80 is 1.8-2 mM.

4. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In S12, the concentration of copper sulfate is 5 mM, the composite oxidation system is composed of 15-20 mM ascorbic acid and 3-5 mM hydrogen peroxide, and the concentration of phytic acid is 0.8-1 mM.

5. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In S12, the amount of dithiothreitol added is 0.1-0.5 mM, and the molar ratio of dithiothreitol to catechol is 1:15-30.

6. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In step two, the molar ratio of glucose to disodium ethylenediaminetetraacetate is 5-8:1, and the molar ratio of disodium ethylenediaminetetraacetate to copper sulfate is 1:2-5.

7. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In step two, the concentration of the polydopamine-polyethylene glycol block copolymer is 0.35-0.5 g / L, wherein the mass ratio of polydopamine segments to polyethylene glycol segments is 1:2-5, the number average molecular weight of the polyethylene glycol segments is 2000-5000, and the mass ratio of the polydopamine-polyethylene glycol block copolymer to copper sulfate is 1:5-10.

8. The method for preparing a nano-copper-based conductive composite material according to claim 1, characterized in that, In step S32, the molar ratio of 3-aminopropyltriethoxysilane to stearic acid is 1-2:1, the concentration of stearic acid is 1-1.5 mM, and the amount of 3-aminopropyltriethoxysilane added is 0.5-1% of the total mass of the product.

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