Method for preparing polyphenyl ether with controllable molecular weight through electro-catalysis

Abstract

The invention discloses a method for preparing molecular weight controllable polyphenyl ether through electro-catalysis, which comprises the following steps: 1) preparing an electrode: preparing a series of Prussian blue doped with different metals, and respectively using the Prussian blue for an anode and a cathode; 2) material preparation: adding 2, 6-dimethylphenol into an aqueous solution containing carbonate and alkali with a certain concentration, and stirring until the 2, 6-dimethylphenol is completely dissolved to prepare a substrate solution; 3) electrocatalytic polymerization: putting the cathode and the anode into an electrolytic bath containing a substrate solution, introducing air, performing electrochemical polymerization reaction at constant temperature, and regulating the molecular weight of polyphenyl ether by changing direct current voltage; and 4) product purification: after the reaction is finished, carrying out centrifugal separation, carrying out graded washing on precipitates obtained by centrifugation, and finally, carrying out vacuum drying to obtain the polyphenyl ether. Compared with the prior art, the method has the advantages that the polyphenyl ether is synthesized through electro-catalysis, the reaction selectivity can be improved, the generation amount of a by-product dibenzoquinone in the reaction process is reduced, the substrate utilization rate is increased, the molecular weight of the polyphenyl ether can be accurately regulated and controlled, and the polyphenyl ether with uniform molecular weight distribution is obtained; polyphenyl ether is synthesized in water, which is green and environment-friendly; the method avoids the use of a metal catalyst, so that the dielectric property of the polyphenyl ether is improved; alcohol washing and water washing are adopted in the purification process, the washing steps are simple, resources are saved, and the environment is protected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer synthesis, and particularly relates to a method for electrocatalytically preparing polyphenyl ether with controllable molecular weight. BACKGROUND

[0002] Polyphenyl ether is one of the five important general engineering plastics, and has the advantages of non-toxicity, small relative density, good heat resistance, chemical corrosion resistance, and mechanical strength. Different molecular weight polyphenyl ethers have different applications, and medium and high molecular weight polyphenyl ethers have wide applications in household appliances, office automation machinery, automobiles, aviation and military industries. With the development of the 5G era, electronic communication has developed towards higher frequency and faster signal transmission frequency. Low molecular weight polyphenyl ether not only has the above advantages, but also can solve the problems of poor processing performance, high melt viscosity and difficulty in mixing with other materials of high molecular weight polyphenyl ether, and can be used for copper-clad plate substrate materials.

[0003] The traditional polyphenyl ether synthesis method uses homogeneous catalysts to catalyze the oxidative polymerization of 2,6-dimethylphenol in organic solvents. The polyphenyl ether washing method is dissolution and precipitation to remove the residual copper and by-products in the polyphenyl ether. For example, US11041046B2 uses metal salt-amine and quaternary ammonium salt as catalyst to catalyze the polymerization of monohydric phenol in a non-polar solvent, and oxygen is continuously introduced during the process, obtaining polyphenyl ether with a single peak distribution and a characteristic viscosity of 0.5-2.0 dL / g. Chinese patent CN114015041B uses a copper-containing metal organic framework compound as a catalyst and oxygen as an oxidizing agent to catalyze the polymerization of substituted phenol compounds in a polyphenyl ether good solvent, obtaining polyphenyl ether with low metal impurity content. However, even if an organic framework compound is used as a catalyst, a part of the metal is still left in the polyphenyl ether, affecting its dielectric properties. At the same time, there is an explosion hazard when oxygen is introduced into the organic solvent, and the use of organic solvents has problems such as high cost, great harm, and complicated recovery. Therefore, it is necessary to develop a new, efficient and green method for preparing polyphenyl ether.

[0004] The method for controlling the molecular weight of polyphenyl ether includes solvent method, redistribution method, etc. For example, Chinese patent CN115477748B uses the redistribution method to synthesize low molecular weight dihydroxy polyphenyl ether, i.e. in the presence of an initiator and a molecular chain regulator, high molecular weight polyphenyl ether and dihydric phenol are subjected to redistribution reaction, thereby obtaining polyphenyl ether with a number average molecular weight less than 4000. However, polyphenyl ether with a molecular weight greater than 4000 cannot be synthesized, and the molecular weight range of the synthesized polyphenyl ether is narrow, which cannot meet the demand for other molecular weight polyphenyl ethers. Therefore, it is necessary to develop a new method for precisely controlling the molecular weight of polyphenyl ether.

[0005] In view of the above problems, it is necessary to develop an efficient and environmentally friendly method for electrocatalytically preparing polyphenyl ether with controllable molecular weight. SUMMARY

[0006] The present application aims at the deficiencies of the prior art, and provides a method for electrochemically catalyzing 2,6-dimethylphenol, so as to obtain polyphenyl ether with controllable molecular weight by changing voltage, so as to synthesize polyphenyl ether with different molecular weights; the electrocatalytic synthesis avoids the use of organic solvents and organic ligands, is green, safe and environmentally friendly; the electrocatalytic synthesis of polyphenyl ether can avoid the use of metal catalysts, so that there is no metal residue in the polyphenyl ether, thereby improving the dielectric property thereof; the purification step is first alcohol washing and second water washing, so that the use of organic solvents such as chloroform is avoided, compared with the repeated dissolution-reprecipitation purification step in the traditional synthesis method, so that the process is simplified, resources are saved, and the environment is protected.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] According to a first aspect of the present application, the present application provides a method for electrochemically catalyzing polyphenyl ether with controllable molecular weight, comprising the following steps:

[0009] S1, preparing electrodes: a series of Prussian blue doped with different metals are prepared, and the materials are coated on carbon paper to prepare anode and cathode for electrocatalysis;

[0010] S2, preparing materials: 2,6-dimethylphenol is added into an aqueous solution containing a certain concentration of carbonate and alkali, and stirring is performed until the 2,6-dimethylphenol is completely dissolved, so as to prepare a substrate solution;

[0011] S3, electrocatalytic polymerization: the cathode and the anode are placed into an electrolytic cell containing the substrate solution, air is introduced, and electrochemical polymerization reaction is performed at constant temperature, and the molecular weight of polyphenyl ether is regulated by changing direct current voltage;

[0012] S4, product purification: after the reaction is completed, centrifugal separation is performed, the precipitate obtained by centrifugal separation is subjected to fractional washing, and finally vacuum drying is performed, so as to obtain polyphenyl ether.

[0013] Preferably, in step S1, the metal doped Prussian blue is preferably doped with cobalt, nickel, copper or manganese.

[0014] Preferably, in step S2, the concentration of carbonate is 0.01M-2M, and more preferably 0.5M-1M.

[0015] Preferably, in step S2, the alkali is preferably NaOH and KOH, the concentration of alkali is 0.5M-2M, and the concentration of 2,6-dimethylphenol is 0.5M-1M.

[0016] Preferably, in step S3, the air rate is 1-10mL / min. -1 .

[0017] Preferably, in step S3, the polymerization temperature is 30℃-70℃, and the polymerization time is 6h-12h.

[0018] Preferably, in step S4, the fractional washing is divided into a first alcohol washing and a second water washing.

[0019] The first alcohol washing uses solvents such as methanol and ethanol to wash away unreacted 2,6-dimethylphenol and by-products diphenylquinone in the crude product.

[0020] The second water washing uses deionized water to wash away carbonates present in the crude product.

[0021] Compared with the prior art, the method for electrocatalytically preparing polyphenyl ether with controllable molecular weight provided by the application has at least the following beneficial effects:

[0022] (1) The method provided by the application uses water as a solvent, which is economical, green, and environmentally friendly, and has greatly reduced danger compared with organic solvents.

[0023] (2) The method provided by the application has high selectivity for the oxidative polymerization of 2,6-dimethylphenol, and the yield of the by-product diphenylquinone obtained in the reaction is very low.

[0024] (3) The method provided by the application can realize precise control by changing the voltage to regulate the molecular weight of the synthesized polyphenyl ether. At the same time, the method can reduce the molecular weight distribution index of the polyphenyl ether and synthesize polyphenyl ether with uniform molecular weight distribution. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The infrared spectrum of the product obtained in Example 1 of the application.

[0026] Figure 2 The thermogravimetric analysis diagram of Example 2 of the application.

[0027] Figure 3 The differential scanning calorimetry analysis diagram of Example 3 of the application. DETAILED DESCRIPTION

[0028] To make the technical solutions and advantages of the application clearer, the technical solutions of the application will be described in detail below with specific examples. Obviously, the described examples are only part of the examples of the application, rather than all the examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0029] Example 1

[0030] A method for electrocatalytically preparing polyphenyl ether with controllable molecular weight, comprising the following steps:

[0031] (1) Preparation of electrodes: copper-doped Prussian blue and nickel-doped Prussian blue were prepared by a hydrothermal method, and the materials were coated on carbon paper to prepare electrocatalytic anodes and cathodes.

[0032] (2) Preparation of materials: 1 g of sodium hydroxide and 2.65 g of sodium carbonate were dissolved in 50 mL of water, and stirred until all the solids were completely dissolved to obtain an alkali solution; then 3.05 g of 2, 6-dimethylphenol was added to 50 mL of the alkali solution, and stirred until all the 2, 6-dimethylphenol was dissolved to obtain a substrate solution.

[0033] (3) Electro-catalytic polymerization: copper-doped Prussian blue was used as the cathode, and nickel-doped Prussian blue was used as the anode, which were placed in an electrolytic cell containing the substrate solution, 1 mL min -1 of air was introduced, and the temperature was kept at 50°C, the voltage was set to 1.8V, and the electrochemical polymerization reaction was carried out for 6h.

[0034] (4) Product purification: after the reaction was completed, centrifugal separation was carried out, and the precipitate obtained by centrifugation was subjected to fractional washing, the first alcohol washing used methanol solvent to wash away the unreacted 2, 6-dimethylphenol and byproduct diphenylquinone in the crude product; the second water washing used deionized water to wash away the carbonates present in the crude product. Finally, vacuum drying was carried out, and a grayish white polyphenyl ether was obtained.

[0035] Example 2

[0036] A method for electro-catalytically preparing polyphenyl ether with controllable molecular weight, comprising the following steps:

[0037] (1) Preparation of electrodes: manganese-doped Prussian blue and nickel-doped Prussian blue were prepared by a hydrothermal method, and the materials were coated on carbon paper to prepare electrocatalytic anodes and cathodes.

[0038] (2) Preparation of materials: 1 g of sodium hydroxide and 2.65 g of sodium carbonate were dissolved in 50 mL of water, and stirred until all the solids were completely dissolved to obtain an alkali solution; then 3.05 g of 2, 6-dimethylphenol was added to 50 mL of the alkali solution, and stirred until all the 2, 6-dimethylphenol was dissolved to obtain a substrate solution.

[0039] (3) Electro-catalytic polymerization: manganese-doped Prussian blue was used as the cathode, and nickel-doped Prussian blue was used as the anode, which were placed in an electrolytic cell containing the substrate solution, 1 mL min -1 of air was introduced, and the temperature was kept at 50°C, the voltage was set to 2.4V, and the electrochemical polymerization reaction was carried out for 6h.

[0040] (4) Product purification: After the reaction is completed, centrifugal separation is carried out, and the precipitate obtained by centrifugation is subjected to fractional washing. First alcohol washing selects methanol solvent to wash away unreacted 2,6-dimethylphenol and byproduct diphenylquinone in the crude product; second water washing uses deionized water to wash away carbonate existing in the crude product. Finally, vacuum drying is carried out, and grayish white polyphenyl ether is obtained.

[0041] Example 3

[0042] A method for electrocatalytically preparing polyphenyl ether with controllable molecular weight, comprising the following steps:

[0043] (1) Preparation of electrode: manganese-doped Prussian blue and nickel-doped Prussian blue are prepared by a hydrothermal method, and the materials are coated on carbon paper to prepare an electrocatalytic anode and cathode.

[0044] (2) Preparation of materials: 1.4 g of potassium hydroxide and 3.46 g of potassium carbonate are dissolved in 50 mL of water, and stirring is performed until all the solids are completely dissolved to obtain an alkali solution; then 3.05 g of 2,6-dimethylphenol is added to 50 mL of the alkali solution, and stirring is performed until the 2,6-dimethylphenol is completely dissolved to obtain a substrate solution.

[0045] (3) Electrochemical polymerization: manganese-doped Prussian blue is used as the cathode, and nickel-doped Prussian blue is used as the anode, which are placed in an electrolytic cell containing the substrate solution, 2 mL min -1 of air is introduced, constant temperature is maintained at 60°C, the voltage is set to 3.0 V, and electrochemical polymerization reaction is carried out for 12 h.

[0046] (4) Product purification: After the reaction is completed, centrifugal separation is carried out, and the precipitate obtained by centrifugation is subjected to fractional washing. First alcohol washing selects methanol solvent to wash away unreacted 2,6-dimethylphenol and byproduct diphenylquinone in the crude product; second water washing uses deionized water to wash away carbonate existing in the crude product. Finally, vacuum drying is carried out, and grayish white polyphenyl ether is obtained.

[0047] The intrinsic viscosity, molecular weight, and molecular weight distribution of the polyphenyl ether synthesized in the examples are measured using an Ubbelohde viscometer and a gel permeation chromatograph, and the data are shown in Table 1.

[0048] Table 1 Performance parameters of polyphenyl ether synthesized in the examples

[0049]

[0050] Those skilled in the art can make various modifications and variations to the above embodiments based on the disclosure and teachings of this specification. Therefore, the present application should not be limited to the above specific embodiments, and any obvious modifications, replacements or variations made by those skilled in the art based on the present application shall fall within the scope of the present application. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation on the present application.

Claims

1. A method for electrocatalytically preparing polyphenylene ether with controllable molecular weight, characterized in that: (1) the electrocatalytic synthesis of polyphenylene ether has high catalytic efficiency, and the electrode material can be reused; (2) the number average molecular weight of the synthesized polyphenylene ether is 1000-10000, and the molecular weight can be accurately controlled by changing the reaction conditions; (3) the synthesis steps are: S1, preparing electrodes: preparing a series of Prussian blue doped with different metals, and coating the materials on carbon paper to prepare anodic and cathodic electrodes for electrocatalysis; S2, preparing materials: adding 2,6-dimethylphenol into an aqueous solution containing a certain concentration of carbonate and alkali, stirring until the 2,6-dimethylphenol is completely dissolved, and preparing a substrate solution; S3, electrocatalytic polymerization: placing the cathode and anode into an electrolytic cell containing the substrate solution, passing in air, and performing electrochemical polymerization reaction at constant temperature, and adjusting the molecular weight of polyphenylene ether by changing the direct current voltage; S4, product purification: after the reaction is completed, centrifugal separation is performed, the precipitate obtained by centrifugation is subjected to fractional washing, and finally vacuum drying is performed, thereby obtaining polyphenylene ether. In step S1, the metal-doped Prussian blue preferably contains cobalt, nickel, copper, or manganese. In step S2, the concentration of carbonate is 0.5M-1M. In step S2, the alkali is preferably NaOH and KOH, the concentration of alkali is 0.5M-2M, and the concentration of 2,6-dimethylphenol is 0.5M-1M. In step S3, the polymerization temperature is 30℃-70℃, and the polymerization time is 6h-12h. In step S4, the fractional washing is divided into primary alcohol washing and secondary water washing. The primary alcohol washing uses solvents such as methanol and ethanol to wash away unreacted 2,6-dimethylphenol and byproduct diphenylquinone in the crude product. The secondary water washing uses deionized water to wash away the carbonate present in the crude product.

2. The method for electrocatalytically preparing polyphenylene ether with controllable molecular weight according to claim 1, characterized in that: ​ 3. The method for electrocatalytically preparing polyphenylene ether with controllable molecular weight according to claim 1, characterized in that: ​ 4. The method of claim 1, wherein the method is characterized by: ​ 5. The method of claim 1, wherein the method is characterized by: In step S3, the air rate is 1-10 mL min -1 .

6. The method of claim 1, wherein the method is an electrocatalytic method for the preparation of polyphenylene ether with controlled molecular weight. ​ 7. The method of claim 1, wherein the method is characterized by: ​ ​ ​

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