A polyazobenzene nanofiber and a preparation method thereof

Abstract

The present application relates to a kind of polybenzidine nanofiber and its preparation method, the polybenzidine nanofiber length is 43~67 μm, and the length-diameter ratio is 120~256.Its preparation method is as follows: benzidine is dissolved in solvent, when the system pH value is 3~6, benzidine and hydrogen peroxide occur oxidation polymerization reaction under the catalysis of divalent copper salt to obtain polybenzidine nanofiber.The polybenzidine nanofiber provided by the present application morphology is regular and controllable and has high length-diameter ratio, and conductivity is high, as a kind of semiconductor high polymer material has potential application prospect in battery, supercapacitor.

Description

Technical Field

[0001] This invention belongs to the field of nanostructure manufacturing or processing technology, specifically relating to a polybenzidine nanofiber and its preparation method. Background Technology

[0002] Polyaniline, as the first discovered conductive polymer, has attracted widespread attention due to its good environmental stability and simple synthesis methods. However, conventionally synthesized polyaniline is difficult to dissolve and has poor mechanical processability, which limits the practical application of polyaniline fibers.

[0003] Compared with conventionally synthesized polyaniline, polyaniline derivatives, especially aromatic diamine polymers, have shown significant improvements in solubility and conductivity. As an aromatic diamine polymer, polybenzidine nanofibers prepared from it have broad application prospects in fields such as nanosensors, antifouling and electromagnetic shielding materials.

[0004] Existing literature reports the use of interfacial polymerization to synthesize micro- and nano-sized polybenzidines using benzidine as a monomer and ammonium persulfate as an oxidant. However, the synthesized polybenzidines are short rod-shaped with poor fiber morphology regularity, and the subsequent processing of the generated ammonium salts is quite troublesome. In addition, some literature reports the use of hydrogen peroxide as an oxidant to catalyze the oxidation of aniline monomers to form polyaniline, but hydrogen peroxide has poor room temperature catalytic oxidation effect and low conversion efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a polybenzidine nanofiber and its preparation method. The nanofiber has a regular and controllable morphology, a high aspect ratio, and good electrical conductivity. Moreover, its preparation method is simple to operate, low in cost, and environmentally friendly.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A polybenzidine nanofiber is provided, with a length of 43–67 μm and an aspect ratio of 120–256.

[0008] The present invention also provides a method for preparing the above-mentioned polybenzidine nanofibers: benzidine is dissolved in a solvent, and at a system pH of 3 to 6, benzidine and hydrogen peroxide undergo an oxidative polymerization reaction under the catalysis of divalent copper salt to obtain polybenzidine nanofibers.

[0009] According to the above scheme, the benzidine is 3,3',5,5'-tetramethylbenzidine, 4,4'-diaminobiphenyl, or 3,3'-dimethylbenzidine.

[0010] According to the above scheme, the solvent is ethanol or methanol.

[0011] According to the above scheme, the divalent copper salt is copper nitrate or copper(II) perchlorate hexahydrate.

[0012] Preferably, the divalent copper salt is copper(II) hexahydrate. Copper(II) hexahydrate exhibits far superior catalytic performance compared to other divalent copper salts.

[0013] Preferably, the pH of the reaction system is adjusted using an acetate-sodium acetate buffer solution. The acetate-sodium acetate buffer solution is prepared by dissolving sodium acetate trihydrate in water to prepare a 10-15 mM sodium acetate solution, and then adjusting the pH of the sodium acetate solution to 3-6 with acetic acid solution to obtain the acetate-sodium acetate buffer solution. The acetate-sodium acetate buffer solution can adjust the pH of the system to acidic conditions, thereby regulating the rate of the oxidative polymerization reaction; when the solution is acidic, the reaction rate of the system is faster.

[0014] According to the above scheme, the oxidative polymerization reaction temperature is 25–35℃, and the reaction time is 12–48 h. Under these reaction conditions, the reaction is fastest and the product morphology is best. Increasing the reaction temperature is beneficial to the reaction, but if the temperature is too high, burst polymerization will occur, and the molecular chains will not be fully extended, thus reducing the fiber regularity. If the temperature is too low, fibers with high regularity cannot be obtained.

[0015] The specific steps of the above preparation method are as follows:

[0016] 1) Dissolve divalent copper salt in water to obtain a divalent copper salt solution, and dissolve benzidine in a solvent to obtain a benzidine solution;

[0017] 2) Hydrogen peroxide solution, divalent copper salt solution obtained in step 1), and benzidine solution are added sequentially to acetic acid-sodium acetate buffer solution. Oxidative polymerization reaction is carried out under stirring or standing conditions. After the reaction is completed, the reaction solution is filtered, and the resulting filter residue is washed and freeze-dried to obtain polybenzidine nanofibers.

[0018] According to the above scheme, the concentration of the divalent copper salt solution in step 1) is 2–10 mM (mmol / L). When the concentration is below 2 mM, the benzidine monomer cannot undergo continuous chain growth, resulting in an excessively long reaction time or the formation of short rod-shaped products. When the concentration is above 10 mM, the product undergoes peroxidation, producing a large number of cross-linking byproducts and reducing the molecular chain length.

[0019] According to the above scheme, the concentration of benzidine solution in step 1) is 2-10 mM. When the concentration is below 2 mM, the polymerization rate of benzidine monomer is too slow and the reaction time is too long; when the concentration of benzidine monomer is above 10 mM, the monomer polymerizes rapidly, with intense exothermic reaction, producing a large number of crosslinking byproducts, and the polybenzidine fiber has poor morphological regularity.

[0020] According to the above scheme, the concentration of the hydrogen peroxide solution in step 2) is 0.1–1 M. Theoretically, if too much oxidant is used, a relatively large number of hydroxyl radicals will be generated, which will further oxidize the main chain molecules, degrade them into smaller molecular chains, increase the degree of peroxidation, and decrease conductivity.

[0021] According to the above scheme, in step 2), the molar ratio of hydrogen peroxide in the hydrogen peroxide solution, copper in the divalent copper salt solution, and benzidine in the benzidine solution is 1:0.02-0.1:0.01-0.02, wherein the concentration of hydrogen peroxide in the acetic acid-sodium acetate buffer solution is 17-170 mM.

[0022] According to the above scheme, in step 2), the stirring speed is 200–1000 rpm, and the stirring time is 5–20 min. Under certain stirring speed and stirring time, it is beneficial for the rapid polymerization of monomer molecules, or the reaction can be allowed to proceed directly by static reaction.

[0023] This invention also provides the application of the above-mentioned polydiphenylamine nanofibers in the fields of battery cathode materials and supercapacitor thin film materials. Due to their conductivity, polydiphenylamine nanofibers can be used as conductive fillers, etc.

[0024] This invention relates to the oxidation of benzidine by cationic radicals from hydrogen peroxide under pH conditions of 3–6, followed by chain extension to produce polybenzidine via the catalytic generation of benzidine by divalent Cu ions. The applicant further investigated different divalent copper salts (copper nitrate, copper chloride, copper sulfate, copper(II) hexahydrate, etc.). Experimental results showed that copper chloride and copper sulfate did not produce a catalytic effect, copper nitrate had a poor catalytic effect, while copper(II) hexahydrate showed a significant advantage in catalyzing the oxidation of benzidine monomers by hydrogen peroxide under room temperature conditions.

[0025] The beneficial effects of this invention are as follows: 1. The polybenzidine nanofibers provided by this invention have a regular and controllable morphology and a high aspect ratio. They exhibit good solubility in the common solvent N,N-dimethylformamide (DMF), with a solubility of up to 46 mg / mL, and high conductivity (resistivity ρ≈1.47 kΩ·cm). As a semiconductor polymer material, they have potential applications in batteries and supercapacitors. 2. The raw materials used in this invention are inexpensive, the reaction conditions are mild, and the preparation method is simple, rapid, and environmentally friendly, making it suitable for large-scale preparation. Attached Figure Description

[0026] Figure 1 These are comparative photographs of the reaction solutions after the oxidation of benzidine with different copper salts catalyzed by the present invention.

[0027] Figure 2 SEM image of the polybenzidine nanofibers prepared in Example 1;

[0028] Figure 3 Here is a SEM image of the polybenzidine nanofibers prepared in Example 2;

[0029] Figure 4 Here is a SEM image of the polybenzidine nanofibers prepared in Example 3;

[0030] Figure 5 Here is a SEM image of the polybenzidine nanofibers prepared in Example 4;

[0031] Figure 6 Here is a SEM image of the polybenzidine nanofibers prepared in Example 5;

[0032] Figure 7 Fourier transform infrared spectra of copper(II) perchlorate hexahydrate, 3,3',5,5'-tetramethylbenzidine (TMB), and the prepared polybenzidine fiber in Example 5;

[0033] Figure 8 Here is a SEM image of the polybenzidine nanofibers prepared in Example 6;

[0034] Figure 9 This is a statistical comparison chart of the lengths of polybenzidine nanofibers obtained in Examples 4-7 after reacting for 120 min under different pH conditions. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0038] 1) Dissolve 102 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (100 mM);

[0039] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 4 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0040] 3) Dissolve 12.1 mg of copper nitrate trihydrate in 10 mL of water to obtain a copper salt solution (5 mM);

[0041] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0042] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 700 rpm for 10 min. Then the mixture was allowed to stand at 25 °C for 12 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was freeze-dried at -60 °C for 12 h to obtain polybenzidine nanofibers.

[0043] In step 3) of this embodiment, copper nitrate trihydrate is replaced with equimolar amounts of copper sulfate, copper chloride, and copper perchlorate (II) hexahydrate, while keeping all other conditions unchanged. The resulting reaction solution is illustrated in the photograph below. Figure 1 As shown, copper(II) hexahydrate has a better catalytic effect than other copper salts, the reaction is more complete, and the prepared product is fibrous.

[0044] Figure 2 The image shown is a scanning electron microscope image of the polybenzidine nanofibers prepared in this embodiment. The fibers produced using copper nitrate as a catalyst have poor morphological regularity.

[0045] Example 2

[0046] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0047] 1) Dissolve 21 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (20 mM);

[0048] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 4 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0049] 3) Dissolve 18.5 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (5 mM);

[0050] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0051] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 600 rpm for 10 min. Then the mixture was allowed to stand at 34 °C for 24 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was freeze-dried at -60 °C for 12 h to obtain polybenzidine nanofibers.

[0052] Figure 3The image shown is a scanning electron microscope image of the polybenzidine nanofibers prepared in this embodiment. It can be seen that under the condition that the molar ratio of benzidine monomer to hydrogen peroxide is 1:10 in this embodiment, the resulting fiber morphology has poor regularity and cannot be grown into polybenzidine fibers with a high aspect ratio.

[0053] Example 3

[0054] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0055] 1) Dissolve 1.02 mL of 30 wt% hydrogen peroxide solution in 10 mL of water to obtain hydrogen peroxide solution (1 M);

[0056] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 4 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0057] 3) Dissolve 37.1 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (10 mM);

[0058] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0059] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 700 rpm for 8 min. Then the mixture was allowed to stand at 30 °C for 24 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was freeze-dried at -60 °C for 12 h to obtain polybenzidine nanofibers.

[0060] Figure 4 The scanning electron microscope image of the polybenzidine nanofibers prepared in this embodiment shows that the fibers have good regularity.

[0061] Example 4

[0062] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0063] 1) Dissolve 102 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (100 mM);

[0064] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 3 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0065] 3) Dissolve 29.6 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (8 mM);

[0066] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0067] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 600 rpm for 8 min. Then the mixture was allowed to stand at 30 °C for 12 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was freeze-dried to obtain polybenzidine nanofibers.

[0068] Figure 5 The image shown is a scanning electron microscope image of the poly(biphenylamine) nanofibers prepared in this embodiment. It can be seen that the poly(biphenylamine) nanofibers have a regular morphology and a smooth surface.

[0069] Example 5

[0070] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0071] 1) Dissolve 102 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (100 mM);

[0072] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 4 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0073] 3) Dissolve 18.5 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (5 mM);

[0074] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0075] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 500 rpm for 5 min. Then the mixture was allowed to stand at 25 °C for 12 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was then freeze-dried to obtain polybenzidine nanofibers.

[0076] Figure 6The image shows a scanning electron microscope (SEM) image of the poly(biphenylamine) nanofibers prepared in this embodiment. As can be seen from the image, the fiber surface is smooth and has high regularity. The length of the poly(biphenylamine) nanofibers prepared in this embodiment is measured to be 43–67 μm and the aspect ratio is 120–256.

[0077] The Fourier transform infrared spectra of copper(II) perchlorate hexahydrate, 3,3',5,5'-tetramethylbenzidine (TMB), and the prepared polybenzidine fibers in this embodiment are as follows: Figure 7 As shown in Figure (c), the infrared spectrum of the polyphenylene aniline fiber is as follows: at a wavenumber of 3342 cm⁻¹ -1 The peak corresponds to the NH stretching vibration, with a wavenumber of 1570 cm⁻¹. -1 The peak corresponds to the C-C stretching vibration in the benzidine monomer, with a wavenumber of 1268 cm⁻¹. -1 The corresponding peak for CN stretching vibration is 1647 cm⁻¹. -1 The peak corresponds to the C=N stretching vibration of the quinone unit, with a wavenumber of 1389 cm⁻¹. -1 The peak corresponds to the NN stretching vibration between the two benzidine monomers, with a wavenumber of 10¹⁸ cm⁻¹. -1 Wavenumber 624cm -1 Corresponding to ClO4 -1 The doping of the polymer confirmed that the resulting product was polybenzidine fiber.

[0078] The polybenzidine fiber prepared in this embodiment has a high aspect ratio, which is beneficial to improving conductivity. Its resistivity was measured to be approximately 1.47 kΩ·cm. The fiber exhibits good solubility in the common solvent N,N-dimethylformamide (DMF), with a solubility of 46 mg / mL.

[0079] Example 6

[0080] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0081] 1) Dissolve 102 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (100 mM);

[0082] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 5 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0083] 3) Dissolve 18.5 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (5 mM);

[0084] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0085] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 400 rpm for 15 min. Then the mixture was allowed to stand at 28 °C for 24 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was freeze-dried to obtain polybenzidine nanofibers.

[0086] Figure 8 The image shown is a scanning electron microscope image of the poly(biphenylamine) nanofibers prepared in this embodiment. It can be seen that the poly(biphenylamine) nanofibers have a regular morphology and a smooth surface.

[0087] Example 7

[0088] A method for preparing polybenzidine nanofibers, the specific steps of which are as follows:

[0089] 1) Dissolve 102 μL of a 30 wt% hydrogen peroxide solution in 10 mL of water to obtain a hydrogen peroxide solution (100 mM);

[0090] 2) Dissolve 40.8 mg of sodium acetate trihydrate in 30 mL of water, adjust the pH to 6 with acetic acid solution (17.5 M), stir well to obtain acetic acid-sodium acetate buffer (10 mM);

[0091] 3) Dissolve 18.5 mg of copper(II) perchlorate hexahydrate in 10 mL of water to obtain a copper salt solution (5 mM);

[0092] 4) Dissolve 4.8 mg of 3,3',5,5'-tetramethylbenzidine in 10 mL of ethanol to obtain a benzidine solution (2 mM);

[0093] 5) The above hydrogen peroxide solution, copper salt solution and benzidine solution were added to the acetic acid-sodium acetate buffer solution in sequence and stirred at 350 rpm for 5 min. Then the mixture was allowed to stand at 30 °C for 12 h. After the reaction was completed, the reaction solution was filtered and the filter residue was washed with deionized water until the washing liquid was colorless. The washed product was then freeze-dried to obtain polybenzidine nanofibers.

[0094] Figure 9The graph shows the length of poly(benzidine) nanofibers obtained by sampling in acetate-sodium acetate buffer solutions at different pH values ​​for 120 min in Examples 4-7. The length of the fibers can reach several micrometers within 120 min of reaction. The poly(benzidine) fibers prepared under the conditions of Example 4 are about 1.835 μm long, the poly(benzidine) fibers prepared under the conditions of Example 5 are about 8.945 μm long, the poly(benzidine) fibers prepared under the conditions of Example 6 are about 3.617 μm long, and the poly(benzidine) fibers prepared under the conditions of Example 7 are about 1.198 μm long.

[0095] The final products prepared in Examples 3, 4 and 6, 7, polybenzidine nanofibers, have similar lengths and aspect ratios to those in Example 5.

Claims

1. A polyaniline nanofiber, characterized by, The length is 43-67 μm, and the length-diameter ratio is 120-256.

2. The method of claim 1, wherein the polyphenylamine nanofiber is prepared by the steps of: (a) dissolving a polyphenylamine in a solvent; (b) electrospinning the polyphenylamine solution; and (c) drying the electrospun polyphenylamine solution. The specific steps are as follows: 1) dissolving copper (II) perchlorate hexahydrate in water to obtain a divalent copper salt solution, the concentration of the divalent copper salt solution being 2-10 mM, and dissolving benzidine in a solvent to obtain a benzidine solution, the concentration of the benzidine solution being 2-10 mM; 2) adding a hydrogen peroxide solution with a concentration of 0.1-1 M, the divalent copper salt solution obtained in step 1), and the benzidine solution in sequence into an acetic acid-sodium acetate buffer solution with a pH value of 3-6, the molar ratio of hydrogen peroxide in the hydrogen peroxide solution, copper in the divalent copper salt solution, and benzidine in the benzidine solution being 1:0.02-0.1:0.01-0.02, wherein the concentration of hydrogen peroxide in the acetic acid-sodium acetate buffer solution is 17-170 mM, and performing an oxidative polymerization reaction under stirring or standing, the oxidative polymerization reaction temperature being 25-35 °C, the reaction time being 12-48 h, and after the reaction is completed, the reaction liquid is suction filtered, the obtained filter residue is washed and freeze-dried to obtain polybenzidine nanofibers.

3. The method for preparing polybenzidine nanofibers according to claim 2, characterized in that, In step 1), the benzidine is 3,3',5,5'-tetramethylbenzidine, 4,4'-diaminobiphenyl, or 3,3'-dimethylbenzidine, and the solvent is ethanol or methanol.

4. The method of claim 2, wherein the polyphenylamine nanofiber is prepared by the steps of: (a) dissolving a polyphenylamine in a solvent to prepare a solution; (b) electrospinning the solution to prepare a nanofiber; and (c) drying the nanofiber. In step 2), the preparation method of the acetic acid-sodium acetate buffer solution is as follows: dissolving sodium acetate trihydrate in water to prepare a sodium acetate solution with a concentration of 10-15 mM, and then adjusting the pH value of the sodium acetate solution to 3-6 with an acetic acid solution to obtain the acetic acid-sodium acetate buffer solution.

5. The polybenzidine nanofibers of claim 1 are applied in the fields of battery positive electrode materials and supercapacitor thin film materials.

Images