A composite nanowire interlaced electromagnetic shielding film and its preparation process

Abstract

The present invention relates to the technical field of nanowire electromagnetic shielding film preparation, and discloses a composite nanowire staggered interconnected electromagnetic shielding film and a preparation process. The S coordinating atoms in a cationic coordination monomer form Cu-S coordination bonds with nano-copper wires, which are adsorbed on the surface of the nano-copper wires to obtain positively charged copper nanowires. The S coordinating atoms in an anionic coordination monomer form Ag-S coordination bonds with nano-silver wires, which are adsorbed on the surface of the nano-silver wires to obtain negatively charged silver nanowires. The amount of positively charged substances on the copper nanowires is greater than the amount of negatively charged substances on the silver nanowires. The silver nanowires and nano-copper wires are electrostatically self-assembled by electrostatic adsorption force to obtain positively charged silver-copper composite nanowires with a staggered interconnected distribution. The silver nanowires are spontaneously deposited on a negatively charged flexible substrate under the action of electrostatic adsorption to obtain a composite nanowire staggered interconnected electromagnetic shielding film. The electromagnetic shielding film exhibits excellent photoelectric properties.

Description

Technical Field

[0001] The present invention relates to the technical field of nanowire electromagnetic shielding film preparation, in particular to a composite nanowire staggered interconnected electromagnetic shielding film and a preparation process thereof. Background Art

[0002] Transparent conductive films such as metal nanowires, such as silver nanowires and silver-plated copper nanowires, have been widely studied and used in applications with transparent electromagnetic shielding as the background. Studies have found that highly ductile silver nanowire films are used in wearable devices. By changing the growth density of silver nanowires, films with different transmittance and electromagnetic shielding efficiency can be achieved. It is worth noting that due to the good mechanical properties of silver nanowires, the film can still maintain a strong electromagnetic shielding ability after repeated stretching within a certain range. Experimental results show that when the tensile force acting on the silver nanowire film increases to 50%, for a density of 333mg / m 2 The shielding efficiency of the above silver nanowire films is also above 20dB.

[0003] Currently, the main methods for preparing nanowire conductive films include Meyer bar coating, spray coating, and transfer methods. However, these traditional preparation processes have certain limitations. For example, deposition can only be achieved on regular flat substrates, which severely restricts the application of transparent conductive films. In addition, when the film is prepared without a binder or after hot pressing, the bond strength between the film and the substrate is very poor, making the film easy to fall off. However, the addition of a binder can reduce the film's conductivity to a certain extent, and the hot pressing process may damage the flexible substrate. Summary of the Invention

[0004] The present invention provides a composite nanowire interlaced interconnected electromagnetic shielding film and a preparation process. The process uses electrostatic adsorption to achieve a very strong bonding ability between the interlaced composite nanowire film and the flexible substrate. Since it relies on the substrate for spontaneous deposition in the composite nanowire solution, there are no requirements for the shape and size of the composite nanowire film, and the film can be formed on any irregular substrate.

[0005] In one aspect, the present invention provides a process for preparing a composite nanowire interlaced electromagnetic shielding film, the process comprising the following steps:

[0006] Step 1: adding copper nanowires and cationic coordination monomers to deionized water and ultrasonically dispersing them uniformly, wherein the S coordination atoms in the cationic coordination monomers form Cu-S coordination bonds with the nano-copper wires and are adsorbed on the surface of the nano-copper wires to obtain a positively charged copper nanowire dispersion; wherein the copper nanowires have a length of 30-80 μm and a diameter of 20-60 nm;

[0007] Silver nanowires and anionic coordination monomers are added to deionized water and ultrasonically dispersed uniformly, so that the S coordination atoms in the anionic coordination monomers form Ag-S coordination bonds with the silver nanowires and are adsorbed on the surface of the silver nanowires to obtain a negatively charged silver nanowire dispersion; wherein the silver nanowires have a length of 30-60 μm and a diameter of 40-60 nm;

[0008] The amount of positively charged species on the copper nanowires is greater than the amount of negatively charged species on the silver nanowires;

[0009] The positively charged copper nanowire dispersion and the negatively charged silver nanowire dispersion are mixed to undergo an electrostatic self-assembly reaction to obtain a positively charged silver-copper composite nanowire dispersion exhibiting an interlaced and interconnected distribution;

[0010] Step 2, preparing a negatively charged flexible substrate;

[0011] Step 3: Immerse the negatively charged flexible substrate prepared in step 2 into the silver-copper composite nanowire dispersion prepared in step 1, and allow the silver-copper composite nanowires to spontaneously deposit on the flexible substrate through electrostatic adsorption force to obtain an electromagnetic shielding film with interlaced composite nanowires.

[0012] Preferably, the preparation method of the cationic coordination monomer is: first, the carboxylic acid functional group of thioglycolic acid is reacted with the hydroxyl functional group of 3-dimethylamino-1-propanol to synthesize the nanowire coordination monomer, and then the nanowire coordination monomer is reacted with 2-chloropropane to undergo a quaternization reaction to synthesize the cationic coordination monomer.

[0013] Preferably, the anionic coordination monomer is prepared by a nucleophilic substitution reaction of sodium 2-chloroethylsulfonate with thioglycolic acid under the catalysis of triethylamine as a phase transfer catalyst.

[0014] Preferably, the negatively charged flexible substrate is prepared by a method of performing a polymerization grafting reaction between sodium allyl sulfonate and a flexible substrate under ultraviolet irradiation.

[0015] Preferably, the concentration of the copper nanowires in the electropositive copper nanowire dispersion is in the range of 0.5-3 mg / mL.

[0016] Preferably, the mass ratio of copper nanowires to cationic coordination monomers in the positively charged copper nanowire dispersion is (10-20):1.

[0017] Preferably, the concentration of the silver nanowires in the negatively charged silver nanowire dispersion is in the range of 0.5-3 mg / mL.

[0018] Preferably, the mass ratio of silver nanowires to anionic coordination monomers in the negatively charged silver nanowire dispersion is (10-20):1.

[0019] Preferably, the amount of the positively charged substance on the copper nanowire and the amount of the negatively charged substance on the silver nanowire is (1.2-2):1.

[0020] On the other hand, the present invention provides a composite nanowire interlaced interconnected electromagnetic shielding film, which uses electrostatic adsorption to spontaneously deposit a positively charged and interlaced composite nanowire film on a negatively charged flexible substrate.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The present invention: firstly, a cationic coordination monomer and an anionic coordination monomer are synthesized, and the S coordination atoms in the cationic coordination monomer are used to form Cu-S coordination bonds with nano-copper wires and adsorbed on the surface of the nano-copper wires to obtain positively charged copper nano-wires; the S coordination atoms in the anionic coordination monomer are used to form Ag-S coordination bonds with nano-silver wires and adsorbed on the surface of the nano-silver wires to obtain negatively charged silver nano-wires, and the amount of positively charged substances on the copper nano-wires is greater than the amount of negatively charged substances on the silver nano-wires; the nano-silver wires and the nano-copper wires are electrostatically self-assembled by electrostatic adsorption force to obtain positively charged silver-copper composite nano-wires with an interlaced interconnected distribution; the composite nano-wires are spontaneously deposited on a negatively charged PET film under the action of electrostatic adsorption to obtain an interlaced interconnected electromagnetic shielding film of the composite nano-wires, and the electromagnetic shielding film exhibits excellent photoelectric properties.

[0023] The preparation process of the present invention has significant advantages over traditional preparation processes: the silver-copper composite nanowires with an interlaced interconnected distribution have a very strong bonding ability with the flexible substrate by virtue of electrostatic adsorption. Since the electrostatic adsorption method relies on the spontaneous deposition of a negatively charged substrate in a positively charged silver-copper composite nanowire solution with an interlaced interconnected distribution, the shape and size of the silver-copper composite nanowire film can be designed according to needs, and the film can be formed on a cylindrical substrate or any irregular substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the synthetic reaction formula of the nanowire coordination monomer;

[0025] Figure 2 is the synthetic reaction formula of cationic coordination monomer;

[0026] Figure 3 This is the synthetic reaction formula for anionic coordination monomers. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The reagents used in the following embodiments can be purchased from conventional manufacturers in the field; the experimental methods used are all conventional experimental methods known to those skilled in the art.

[0028] Example 1:

[0029] Synthesis of nanowire coordination monomer: The nanowire coordination monomer is synthesized by esterification reaction of the carboxylic acid functional group of thioglycolic acid with the hydroxyl functional group of 3-dimethylamino-1-propanol. The specific synthesis steps are as follows: 276 mg of thioglycolic acid, 206 mg of 3-dimethylamino-1-propanol and 1 mL of concentrated sulfuric acid are added to a 100 mL three-necked flask equipped with a stirring device, a reflux condenser device, a liquid separator and a thermometer. The temperature is raised to reflux and maintained at reflux for 8 hours. The reaction is cooled to room temperature and neutralized with a 3% dilute alkali solution. The reaction solution is washed with distilled water until it is weakly acidic. The reaction solution is distilled under reduced pressure and further purified and distilled to obtain the nanowire coordination monomer. The reaction formula is as follows: Figure 1 As shown, the nuclear magnetic resonance spectrum characterization results of the nanowire coordination monomer are: 1 H NMR (300MHz, DMSO), δ: 4.13 (t, 2H), 3.52 (s, 2H), 2.34 (t, 2H), 2.15 (s, 6H), 1.68 (m, 2H), 1.5 (s, 1H); 13 C NMR (75MHz, DMSO), δ: 170.7 (s, C), 60.7 (t, CH2), 57.8 (t, CH2), 47 (q, 2 CH3), 26.4 (t, CH2), 26.5 (t, CH2);

[0030] Synthesis of cationic coordination monomer: A cationic coordination monomer is synthesized by quaternization reaction of nanowire coordination monomer and 2-chloropropane. The specific synthesis steps are as follows: 283 mg of nanowire coordination monomer is dissolved in 20 mL of dichloromethane and placed in a three-necked flask equipped with a magnetic stirrer. Then, 10 mL of dichloromethane solution containing 125 mg of 2-chloropropane is placed in a constant pressure dropping funnel. After heating to 40°C, 2-chloropropane / dichloromethane solution is added dropwise. After stirring for 24 hours, the product is concentrated and added to anhydrous ether. The precipitated product is vacuum dried, washed with dichloromethane, filtered, and vacuum dried at 50°C to obtain a cationic coordination monomer. The reaction formula is as follows: Figure 2 As shown, the NMR spectrum characterization results of the cationic coordination monomer are: 1H NMR (300MHz, DMSO), δ: 4.13 (t, 2H), 3.78 (m, 1H), 3.52 (s, 2H), 3.3 (s, 6H), 3.22 (t, 2H), 2.01 (m, 2H), 1.5 (s, 1H), 1.3 (d, 6H); 13 C NMR (75 MHz, DMSO), δ: 170.7 (s, C), 64.9 (d, CH), 63.0 (t, CH2), 58.1 (t, CH2), 53 (q, 2 CH3), 26.5 (t, CH2), 23.3 (t, CH2), 15.5 (q, 2 CH3).

[0031] Synthesis of anionic coordination monomer: The anionic coordination monomer is synthesized by a nucleophilic substitution reaction of sodium 2-chloroethylsulfonate with thioglycolic acid under the catalysis of a phase transfer catalyst triethylamine. The specific synthesis steps are as follows: 185 mg of sodium 2-chloroethylsulfonate, 20 mg of triethylamine, 10 mg of a polymerization inhibitor phenothiazine, and 10 mL of xylene are added to a 250 mL four-necked flask equipped with a mechanical stirrer, a thermometer, and a reflux condenser. The mixture is stirred and slowly heated to 80° C. for reaction for 2 h. Then, 138 mg of thioglycolic acid is added and the reaction is continued with stirring for 6 h. After the reaction is completed, the mixture is cooled in an ice-water bath, the oil layer is separated, washed with water, the water layer is extracted with petroleum ether, the organic layers are combined, dried, and the solvent is removed by rotary evaporation to obtain the obtained product. The reaction formula is as follows: Figure 3 As shown, the NMR spectrum characterization results of the anionic coordination monomer are: 1 H NMR (300MHz, DMSO), δ: 4.64 (t, 2H), 3.69 (t, 2H), 3.52 (s, 2H), 1.5 (s, 1H); 13 C NMR (75MHz, DMSO), δ: 170.7 (s, C), 64.7 (t, CH2), 51 (t, CH2), 26.5 (t, CH2).

[0032] Example 2:

[0033] Preparation of a positively charged copper nanowire dispersion: 100 mg of copper nanowires with a length of 50 μm and a diameter of 40 nm and 26 mg of the cationic coordination monomer prepared in Example 1 were added to 100 mL of deionized water and ultrasonically dispersed uniformly. The S coordination atoms in the cationic coordination monomer formed Cu-S coordination bonds with the copper nanowires and were adsorbed on the surface of the copper nanowires, thereby obtaining a positively charged copper nanowire dispersion.

[0034] Preparation of a negatively charged silver nanowire dispersion: 100 mg of silver nanowires with a length of 30 μm and a diameter of 40 nm and 11 mg of the anionic coordination monomer prepared in Example 1 were added to 100 mL of deionized water and ultrasonically dispersed uniformly. The S coordination atoms in the anionic coordination monomer formed Ag-S coordination bonds with the silver nanowires and were adsorbed on the surface of the silver nanowires to obtain a negatively charged silver nanowire dispersion;

[0035] Preparation of a silver-copper composite nanowire dispersion with positive charge and an interlaced interconnected distribution: The positive-charged copper nanowire dispersion and the negative-charged silver nanowire dispersion are mixed to undergo an electrostatic self-assembly reaction to obtain silver-copper composite nanowires with an interlaced interconnected distribution. The reaction time is 5 minutes. During the electrostatic self-assembly process, the positive-charged copper nanowires and the negative-charged silver nanowires are electrostatically self-assembled by electrostatic adsorption force. After the assembly is completed, the copper nanowires have excess positive charge, which makes the silver-copper composite nanowires as a whole positively charged.

[0036] Example 3:

[0037] The preparation of negatively charged PET film is carried out in the following steps:

[0038] Step 1: clean the PET film with acetone and alcohol for 10 minutes respectively;

[0039] Step 2, add 10 mg of sodium allyl sulfonate and 50 mL of deionized water into a reaction vessel and mix well;

[0040] Step 3, placing the PET film prepared in Step 1 into the reaction vessel of Step 2, and irradiating the PET film with ultraviolet light generated by a 1000W high-pressure mercury lamp for 3 hours;

[0041] In step 4, the PET film is taken out and rinsed with deionized water to obtain a negatively charged PET film.

[0042] Example 4:

[0043] The negatively charged PET film prepared in Example 3 was immersed in the silver-copper composite nanowire dispersion prepared in Example 2, and the silver-copper composite nanowires were spontaneously deposited on the PET substrate by electrostatic adsorption force. After immersion for 10 minutes, it was taken out to obtain an electromagnetic shielding film with interlaced composite nanowires.

[0044] Example 5:

[0045] The optical transmittance of the composite nanowire interlaced electromagnetic shielding film prepared in Example 4 was measured by UV / visible spectrophotometer at a wavelength of 550 nm and was 88.3%;

[0046] Using a vector network analyzer connected to two X-band waveguides, the electromagnetic shielding performance of the composite nanowire interlaced electromagnetic shielding film prepared in Example 4 was measured at room temperature, a frequency band of X-band (8.2-12.4 GHz), and a bandwidth of 1 kHz. The total shielding performance was 32 dB.

[0047] Example 6:

[0048] Preparation of silver nanowire dispersion: 100 mg of silver nanowires with a length of 30 μm and a diameter of 40 nm were added to 100 mL of deionized water and ultrasonically dispersed to obtain a silver nanowire dispersion.

[0049] Preparation of copper nanowire dispersion: 100 mg of copper nanowires with a length of 50 μm and a diameter of 40 nm was added to 100 mL of deionized water and ultrasonically dispersed to obtain a copper nanowire dispersion.

[0050] Fix the PET film vertically on the working arm of the pulling machine. The specific dipping process is as follows:

[0051] Step 1: moving the PET film at an immersion speed of 60 mm / min to immerse it in the copper nanowire dispersion. When the PET film is completely immersed in the suspension, it is allowed to stand for 30 seconds. The PET film begins to leave the copper nanowire dispersion at a lifting speed of 100 mm / min. After being completely out of the solution, it is naturally dried for 30 seconds.

[0052] Step 2: moving the PET film at an immersion speed of 60 mm / min to immerse it in the silver nanowire suspension. When the PET film is completely immersed in the suspension, it is allowed to stand for 30 seconds. The PET film then begins to leave the silver nanowire suspension at a lifting speed of 100 mm / min. After it is completely out of the solution, it is naturally dried for 30 seconds.

[0053] In step 3, the dipping process of step 1 and step 2 is repeated three times, and then vacuum dried at 80° C. for 5 minutes to obtain a composite nanowire interlaced electromagnetic shielding film.

[0054] Example 7:

[0055] The optical transmittance of the composite nanowire interlaced electromagnetic shielding film prepared in Example 6 was measured by UV / visible spectrophotometer at a wavelength of 550 nm and was 72.4%;

[0056] Using a vector network analyzer connected to two X-band waveguides, the electromagnetic shielding performance of the composite nanowire interlaced electromagnetic shielding film prepared in Example 6 was measured at room temperature, an X-band frequency band (8.2-12.4 GHz), and a bandwidth of 1 kHz. The total shielding performance was 21 dB.

Claims

1. A process for preparing a composite nanowire interlaced electromagnetic shielding film, characterized in that: The preparation process comprises the following steps: Step 1: adding copper nanowires and cationic coordination monomers into deionized water and ultrasonically dispersing them uniformly; the S coordination atoms in the cationic coordination monomers form Cu-S coordination bonds with the nano-copper wires and are adsorbed on the surface of the nano-copper wires to obtain a positively charged copper nanowire dispersion; The chemical structure of the cationic coordination monomer is: ； Silver nanowires and anionic coordination monomers are added to deionized water and ultrasonically dispersed uniformly. The S coordination atoms in the anionic coordination monomers form Ag-S coordination bonds with the silver nanowires and are adsorbed on the surface of the silver nanowires to obtain a negatively charged silver nanowire dispersion. The chemical structure of the anionic coordination monomer is: ； The amount of positively charged species on the copper nanowires is greater than the amount of negatively charged species on the silver nanowires; The positively charged copper nanowire dispersion and the negatively charged silver nanowire dispersion are mixed to undergo an electrostatic self-assembly reaction to obtain a positively charged silver-copper composite nanowire dispersion exhibiting an interlaced and interconnected distribution; Step 2, preparing a negatively charged flexible substrate, wherein the preparation method is: using sodium allyl sulfonate to carry out a polymerization graft reaction with the flexible substrate under ultraviolet irradiation; Step 3: Immerse the negatively charged flexible substrate prepared in step 2 into the silver-copper composite nanowire dispersion prepared in step 1, and allow the silver-copper composite nanowires to spontaneously deposit on the flexible substrate through electrostatic adsorption force to obtain an electromagnetic shielding film with interlaced composite nanowires.

2. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The preparation method of the cationic coordination monomer comprises the following steps: firstly, a nanowire coordination monomer is synthesized by an esterification reaction between the carboxylic acid functional group of thioglycolic acid and the hydroxyl functional group of 3-dimethylamino-1-propanol; and then a cationic coordination monomer is synthesized by a quaternization reaction between the nanowire coordination monomer and 2-chloropropane.

3. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The preparation method of the anionic coordination monomer is as follows: the anionic coordination monomer is prepared by carrying out a nucleophilic substitution reaction between sodium 2-chloroethylsulfonate and thioglycolic acid under the catalysis of a phase transfer catalyst, triethylamine.

4. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The concentration of the copper nanowires in the positively charged copper nanowire dispersion is in the range of 0.5-3 mg / mL.

5. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The mass ratio of copper nanowires to cationic coordination monomers in the positively charged copper nanowire dispersion is (10-20):

1.

6. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The concentration of the silver nanowires in the negatively charged silver nanowire dispersion is in the range of 0.5-3 mg / mL.

7. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The mass ratio of the silver nanowires to the anionic coordination monomer in the negatively charged silver nanowire dispersion is (10-20):

1.

8. The process for preparing a composite nanowire interlaced electromagnetic shielding film according to claim 1, characterized in that: The amount of the positively charged substance on the copper nanowire and the amount of the negatively charged substance on the silver nanowire are (1.2-2):

1.

9. The composite nanowire interlaced electromagnetic shielding film prepared by the preparation process according to any one of claims 1 to 8, characterized in that: The electromagnetic shielding film enables a positively charged and cross-connected composite nanowire film to be spontaneously deposited on a negatively charged flexible substrate through electrostatic adsorption.

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