Two-dimensional layered piezoelectric material, preparation method thereof and application of two-dimensional layered piezoelectric material in atom transfer radical polymerization

Abstract

The invention relates to a two-dimensional layered piezoelectric material, a preparation method thereof and application of the two-dimensional layered piezoelectric material in atom transfer radical polymerization, and belongs to the technical field of piezoelectric materials. The preparation method comprises the following steps: S1, dispersing few-layer molybdenum disulfide and polyvinylpyrrolidone in an organic solvent to obtain a few-layer molybdenum disulfide colloidal solution; s2, dispersing a metal precursor and thiourea in water, and standing to obtain a metal / thiourea complex solution; and S3, reacting the few-layer molybdenum disulfide colloidal solution with the metal / thiourea complex solution to obtain the two-dimensional layered piezoelectric material. Under the action of external mechanical force such as ultrasound, lattice distortion of the material can be induced to generate internal piezoelectric potential, and the generated piezoelectric potential directly drives a variable valence metal active center to generate reversible valence state conversion, so that a catalytic reaction is efficiently initiated, and further, the catalytic reaction efficiency is greatly improved under the condition that a consumable metal complex does not need to be additionally added as an activating agent. And an active / controllable atom transfer radical polymerization process is driven.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric materials, and in particular relates to a two-dimensional layered piezoelectric material, a preparation method thereof, and an application thereof in atom transfer radical polymerization. Background Art

[0002] In recent years, with the increasing demand for functional polymers, living controlled radical polymerization techniques such as atom transfer radical polymerization (ATRP) have attracted widespread attention due to their high conversion rates, low molecular weight distribution, and good reaction controllability. ATRP offers advantages such as fast reaction speed, a wide temperature range, and compatibility with a variety of monomers. By controlling reaction time and feed ratio, the chain segment composition and molecular weight of the polymer can be precisely adjusted to meet the design requirements of high-performance polymers. ATRP has potential applications in materials science, coatings, drug delivery systems, and biomedicine.

[0003] Building upon traditional thermally initiated atom transfer radical polymerization (ATRP), researchers have developed novel initiation methods, including photocatalysis, electricity, and ultrasound. Among these, the piezoelectric effect, initiated by ultrasound-activated piezoelectric catalysts, has attracted considerable attention due to its high efficiency. However, currently, piezoelectric materials used in ATRP systems are limited to zinc oxide and barium titanate. These materials suffer from relatively low charge carrier mobility, requiring the addition of high doses of catalyst to compensate for their insufficient electron transfer efficiency. Furthermore, as the polymerization reaction proceeds, increasing monomer conversion leads to the gradual oxidation of the low-valent metal ligand activator to a high-valent state, which remains in the final polymer product. This conversion can easily terminate the polymerization reaction. To maintain the reaction, the metal ligand complex must be continuously replenished. Furthermore, after the reaction is complete, the residual metal ligand complex is difficult to remove, affecting product purity and potentially causing environmental pollution. Therefore, there is an urgent need to develop new piezoelectric materials that combine efficient piezoelectric response with catalytic and activation functions to overcome the bottlenecks faced by existing technologies.

[0004] Molybdenum disulfide, a typical two-dimensional layered material, possesses excellent piezoelectric properties. It has also been widely studied due to its adjustable number of atomic layers, outstanding flexibility, ability to withstand large strains, and small band gap. Currently, MoS2 has been used in the field of polymerization, but problems such as difficulty in controlling polymer molecular weight and instability during the polymerization process have limited its further application. Therefore, modifying MoS2 catalysts to achieve better controllable polymerization is of great significance.

[0005] Therefore, there is an urgent need to develop new piezoelectric materials that not only have efficient piezoelectric response but also integrate catalytic and activation functions to overcome the bottlenecks faced by existing technologies. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a two-dimensional layered piezoelectric material, a preparation method thereof and an application in atom transfer radical polymerization. First, a high-temperature solvent thermal reaction is used to prepare multilayer molybdenum disulfide, followed by using a reducing agent to peel off the multilayer molybdenum disulfide to obtain a few-layer molybdenum disulfide containing sulfur vacancies on the surface, and then a variable-valence metal active site is introduced through the sulfur vacancies to obtain a few-layer molybdenum disulfide containing a variable-valence metal. At the same time, with the help of ultrasonic drive, functional polymer materials with a narrow molecular weight distribution and precise structural control can be efficiently synthesized under mild conditions. This modification method not only avoids dependence on high temperature and high-energy light sources, but also systematically solves key problems such as low material efficiency, residual transition metal catalysts and high energy consumption in traditional technologies, providing new ideas and methods for the application of molybdenum disulfide in the field of controlled polymerization.

[0007] The first object of the present invention is to provide a method for preparing a two-dimensional layered piezoelectric material, comprising the following steps:

[0008] S1, dispersing a few-layer molybdenum disulfide and polyvinyl pyrrolidone in an organic solvent to obtain a few-layer molybdenum disulfide colloidal solution;

[0009] S2, dispersing the metal precursor and thiourea in water, and allowing to stand to obtain a metal / thiourea complex solution;

[0010] S3. Mixing the few-layer molybdenum disulfide colloidal solution described in S1 and the metal / thiourea complex solution described in S2 and reacting them, and washing to obtain the two-dimensional layered piezoelectric material.

[0011] In one embodiment of the present invention, in S1, the preparation of the few-layer molybdenum disulfide comprises the following steps:

[0012] S11, dissolving a molybdenum source and a sulfur source in water, reacting at 190° C.-210° C. for 22 h-26 h, drying, and annealing to obtain a multilayer molybdenum disulfide; the annealing is performed under a protective atmosphere at 78° C.-820° C. for 1.5 h-2.5 h;

[0013] S12, dissolving the multilayer molybdenum disulfide and reducing agent described in S11 in a solvent, performing a stripping reaction for 5 h to 7 h, and obtaining a few-layer molybdenum disulfide by centrifugation, washing, and drying.

[0014] In one embodiment of the present invention, the molybdenum source is selected from ammonium molybdate and / or sodium molybdate;

[0015] The sulfur source is selected from one or more of thiourea, elemental sulfur and sodium sulfide;

[0016] The molar ratio of molybdenum atoms in the molybdenum source to sulfur atoms in the sulfur source is 1:(4.8-5.2);

[0017] The reducing agent is selected from hydrazine hydrate and / or sodium lauryl sulfate;

[0018] The mass ratio of the multilayer molybdenum disulfide to the reducing agent is 60:(39-41).

[0019] In one embodiment of the present invention, in S1, the concentration of the few-layer molybdenum disulfide in the few-layer molybdenum disulfide colloidal solution is 0.8 mg / mL-1.2 mg / mL, and the concentration of polyvinyl pyrrolidone is 0.8 mg / mL-1.2 mg / mL.

[0020] In one embodiment of the present invention, in S2, the metal precursor is selected from one or more of iron salts, nickel salts and copper salts;

[0021] The concentration of the metal precursor in the metal / thiourea complex solution is 55 mmol / L-65 mmol / L, and the concentration of thiourea is 145 mmol / L-155 mmol / L.

[0022] In one embodiment of the present invention, in S3, the volume ratio of the few-layer molybdenum disulfide colloid solution to the metal / thiourea complex solution is (9.5-10.5):1;

[0023] The reaction temperature is 155° C.-165° C., and the reaction time is 14 h-18 h.

[0024] The second object of the present invention is to provide a two-dimensional layered piezoelectric material prepared by the method described above.

[0025] The third object of the present invention is to provide an application of the two-dimensional layered piezoelectric material in atom transfer radical polymerization, wherein the application process is as follows: under a protective atmosphere, methacrylate monomers, two-dimensional layered piezoelectric materials and initiators are subjected to atom transfer radical polymerization in a solvent to obtain a polymer material.

[0026] In one embodiment of the present invention, the methacrylate monomer is selected from one or more of methyl methacrylate, hydroxyethyl methacrylate and butyl methacrylate;

[0027] The initiator is selected from benzyl bromide and / or ethyl α-bromoisobutyrate;

[0028] The solvent is selected from one or more of tetrahydrofuran, N,N-dimethylformamide and cyclopropanone;

[0029] The molar ratio of the methacrylate monomer to the initiator is 100:(0.5-1.5);

[0030] The mass ratio of the two-dimensional layered piezoelectric material to the methacrylate monomer is 1:(50-200).

[0031] In one embodiment of the present invention, the power of the atom transfer radical polymerization is 300W-600W, and the frequency is 40kHz-80kHz.

[0032] In one embodiment of the present invention, before performing atom transfer radical polymerization, three freeze-evacuation-thaw-air intake cycles are performed in a liquid nitrogen bath to remove air until no bubbles are generated, and then a protective atmosphere is introduced to put the reaction system in a water-free and oxygen-free state, and then the system is transferred to an ultrasonic machine for piezoelectrically driven atom transfer radical polymerization.

[0033] The technical solution of the present invention has the following advantages over the prior art:

[0034] (1) The preparation method described in the present invention converts multilayer molybdenum disulfide into a few-layered sheet structure, exposing more sulfur vacancies on its surface. These sulfur vacancies provide a good platform for functionalization, enabling the transition metal activation centers commonly used in atom transfer radical polymerization systems to be directly combined with the molybdenum disulfide substrate, thereby serving as efficient activation centers.

[0035] (2) The two-dimensional layered piezoelectric material of the present invention utilizes sulfur vacancies on the surface of two-dimensional few-layer MoS2 to introduce reversibly variable valence metals, and the piezoelectric potential generated by ultrasonically induced two-dimensional layered MoS2 directly drives the reversibly variable valence metals (such as Fe 2+ / Fe 3+ 、Cu + / Cu 2+ ) valence state transition, a process that efficiently triggers atom transfer radical polymerization. Compared to traditional systems that rely on exogenous transition metal complexes, this endogenous valence state transition is more efficient and allows for better control of polymerization activity. Furthermore, the synergistic effect of the piezoelectric effect of the two-dimensional layered MoS2 and the reversible valence metal significantly enhances the activity of the catalytic system.

[0036] (3) The two-dimensional layered piezoelectric material described in the present invention directly combines the transition metal active center with the piezoelectric catalyst to form an efficient and environmentally friendly catalytic system. Under the action of external mechanical forces such as ultrasound, the material lattice distortion can be induced to generate internal piezoelectric potential. The generated piezoelectric potential directly drives the valence-variable metal active center to undergo a reversible valence state transition, thereby efficiently initiating the catalytic reaction, and then driving the "active / controllable" atom transfer radical polymerization process without the need for additional consumable metal complexes as activators. Since the transition metal active center is fixed on the piezoelectric catalyst, the metal ion residues that are difficult to remove in the solvent system after the reaction are avoided, which significantly improves the greenness and sustainability of the reaction. This combination not only improves the catalytic efficiency, but also reduces pollution to the environment, showing good synergistic effects and application prospects.

[0037] (4) Compared with the prior art, the two-dimensional layered piezoelectric material of the present invention requires significantly less catalyst under the same polymerization reaction conditions, thereby reducing costs and potential environmental pollution. This effectively solves the problems of low piezoelectric induction efficiency and residual transition metal catalyst in the prior art. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples are not intended to limit the present invention.

[0039] In the present invention, unless otherwise specified, the preparation of the few-layer molybdenum disulfide used in the embodiments of the present invention specifically includes the following steps: S1, according to the molar ratio of molybdenum atoms to sulfur atoms of 1:5, the ammonium molybdate tetrahydrate aqueous solution and the thiourea aqueous solution are mixed evenly, and then added to a 50mL polytetrafluoroethylene reactor, and reacted at 200°C for 24h; then dried and annealed in an argon environment at 800°C for 2h to obtain a multilayer molybdenum disulfide;

[0040] S2. Take 600 mg of multilayer molybdenum disulfide in a reaction tube, add 40 mL of water / isopropanol (volume ratio 7:3) and 400 μL of hydrazine hydrate, sonicate for 6 hours, then centrifuge three times at 1500 rpm, adjust the pH to 7 with hydrochloric acid, wash three times with deionized water, freeze with liquid nitrogen, and dry in a freeze dryer to obtain a few-layer molybdenum disulfide.

[0041] Example 1

[0042] The two-dimensional layered piezoelectric material and the preparation method thereof of this embodiment specifically include the following steps:

[0043] S1, add 60 mg of synthesized few-layer molybdenum disulfide, 60 mg of polyvinyl pyrrolidone and 60 mL of methanol / chloroform (volume ratio 1:3) into a reaction tube and ultrasonically disperse for 1 h to obtain a few-layer molybdenum disulfide colloidal solution;

[0044] S2. 5 mmol of thiourea, 2 mmol of copper chloride dihydrate, and 33 mL of deionized water were added to a centrifuge tube in sequence, and ultrasonically dispersed for 5 minutes, and then allowed to stand for 12 hours to obtain a copper / thiourea ligand complex;

[0045] S3. Add 40 mL of a few-layer molybdenum disulfide colloidal solution and 4 mL of a copper / thiourea ligand complex into a reactor, react at 160° C. for 16 h, and then wash three times with deionized water to obtain a two-dimensional layered piezoelectric material, namely, copper-coordinated few-layer molybdenum disulfide.

[0046] Example 2

[0047] The two-dimensional layered piezoelectric material and the preparation method thereof of this embodiment specifically include the following steps:

[0048] S1, add 60 mg of synthesized few-layer molybdenum disulfide, 60 mg of polyvinyl pyrrolidone and 60 mL of methanol / chloroform (volume ratio 1:3) into a reaction tube and ultrasonically disperse for 1 h to obtain a few-layer molybdenum disulfide colloidal solution;

[0049] S2. 5 mmol of thiourea, 2 mmol of ferric chloride hexahydrate, and 33 mL of deionized water were added to a centrifuge tube in sequence, and ultrasonically dispersed for 5 minutes, and then allowed to stand for 12 hours to obtain an iron / thiourea ligand complex;

[0050] S3. Add 40 mL of a few-layer molybdenum disulfide colloidal solution and 4 mL of an iron / thiourea ligand complex into a reactor, react at 160° C. for 16 h, and then wash three times with deionized water to obtain a two-dimensional layered piezoelectric material, i.e., iron-coordinated few-layer molybdenum disulfide.

[0051] Example 3

[0052] The two-dimensional layered piezoelectric material and the preparation method thereof of this embodiment specifically include the following steps:

[0053] S1, add 60 mg of synthesized few-layer molybdenum disulfide, 60 mg of polyvinyl pyrrolidone and 60 mL of methanol / chloroform (volume ratio 1:3) into a reaction tube and ultrasonically disperse for 1 h to obtain a few-layer molybdenum disulfide colloidal solution;

[0054] S2. 5 mmol of thiourea, 2 mmol of nickel chloride dihydrate, and 33 mL of deionized water were sequentially added to a centrifuge tube and ultrasonically dispersed for 5 minutes, and then allowed to stand for 12 hours to obtain a nickel / thiourea ligand complex;

[0055] S3. Add 40 mL of a few-layer molybdenum disulfide colloidal solution and 4 mL of a nickel / thiourea ligand complex into a reactor, react at 160° C. for 16 h, and then wash three times with deionized water to obtain a two-dimensional layered piezoelectric material, namely, nickel-coordinated few-layer molybdenum disulfide.

[0056] Comparative Example 1

[0057] Piezoelectric material zinc oxide.

[0058] Comparative Example 2

[0059] Piezoelectric material barium titanate.

[0060] Comparative Example 3

[0061] Piezoelectric material few-layer molybdenum disulfide.

[0062] Test Example 1

[0063] 20 mg of the piezoelectric material of Example 1-3 and Comparative Example 1-3, 0.11 mmol (16 μL) of initiator ethyl α-bromoisobutyrate, 11 mmol of methacrylate monomer hydroxyethyl methacrylate and 2 mL of N, N-dimethylformamide were added to the Schlenk reaction tubes and uniformly dispersed (specifically, about 0.07 mmol of copper chloride and 30 μL of tris(2-pyridylmethyl)amine were additionally added during the piezoelectrically driven atom transfer radical polymerization of Comparative Example 1-3), and then three freeze-pump-thaw-air intake cycles were performed in a liquid nitrogen bath (77K) to remove the air in the reaction tube until no bubbles were generated. Nitrogen was then introduced to place the reaction system in an inert gas protection state, and the reaction system was transferred to an ultrasonic machine (42 kHz, 300 W) for piezoelectrically driven atom transfer radical polymerization for 12 h. After the reaction was completed, it was precipitated by anhydrous ether to obtain a polymer material.

[0064] According to the GB / T 36214.1-2018 method, the number average molecular weight and molecular weight distribution of the polymer material obtained by piezoelectrically driven atom transfer radical polymerization were characterized by gel permeation chromatography (GPC). Specifically, the polymer material was mixed with tetrahydrofuran to prepare a 10 mg / L polymer solution, which was injected into the gel permeation chromatograph through an injector with an injection volume of 1.0 mL. Tetrahydrofuran was selected as the mobile phase, the flow rate was set to 1.0 mL / min, and polymethyl methacrylate was selected as the internal standard substance. The number average molecular weight and molecular weight distribution of the prepared polymer material were tested. The results are shown in Table 1:

[0065] Table 1

[0066] Group Number average molecular weight Molecular weight distribution Example 1 213400 1.24 Example 2 183200 1.21 Example 3 164200 1.25 Comparative Example 1 124600 1.13 Comparative Example 2 89400 1.14 Comparative Example 3 131300 1.15

[0067] As can be seen from Table 1, the performance of transition metal-coordinated few-layer molybdenum disulfide in polymerization reactions is significantly better than that of traditional commercial piezoelectric materials. This indicates that after combining the transition metal active center with the catalytic center, a significant synergistic effect is generated between the two, thereby significantly improving the catalytic activity and polymerization reaction rate. In addition, compared with the few-layer molybdenum disulfide without transition metal coordination in Comparative Example 3, the transition metal-coordinated few-layer molybdenum disulfide still shows significant advantages, further demonstrating that the design of integrating the transition metal active center with the catalytic center is significantly better than the uncombined system, and this integrated approach has a significant enhancement effect on catalytic performance.

[0068] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional layered piezoelectric material, characterized in that: The following steps are involved: S1, dispersing a few-layer molybdenum disulfide and polyvinyl pyrrolidone in an organic solvent to obtain a few-layer molybdenum disulfide colloidal solution; S2, dispersing the metal precursor and thiourea in water, and allowing to stand to obtain a metal / thiourea complex solution; S3. Mixing the few-layer molybdenum disulfide colloidal solution described in S1 and the metal / thiourea complex solution described in S2 and reacting them, and washing to obtain the two-dimensional layered piezoelectric material.

2. The method for preparing a two-dimensional layered piezoelectric material according to claim 1, wherein: In S1, the preparation of the few-layer molybdenum disulfide comprises the following steps: S11, dissolving a molybdenum source and a sulfur source in water, reacting at 190° C.-210° C. for 22 h-26 h, drying, and annealing to obtain a multilayer molybdenum disulfide; the annealing is performed under a protective atmosphere at 78° C.-820° C. for 1.5 h-2.5 h; S12, dissolving the multilayer molybdenum disulfide and reducing agent described in S11 in a solvent, performing a stripping reaction for 5 h to 7 h, and obtaining a few-layer molybdenum disulfide by centrifugation, washing, and drying.

3. The method for preparing a two-dimensional layered piezoelectric material according to claim 2, wherein: The molybdenum source is selected from ammonium molybdate and / or sodium molybdate; The sulfur source is selected from one or more of thiourea, elemental sulfur and sodium sulfide; The molar ratio of molybdenum atoms in the molybdenum source to sulfur atoms in the sulfur source is 1:(4.8-5.2); The reducing agent is selected from hydrazine hydrate and / or sodium lauryl sulfate; The mass ratio of the multilayer molybdenum disulfide to the reducing agent is 60:(39-41).

4. The method for preparing a two-dimensional layered piezoelectric material according to claim 1, wherein: In S1, the concentration of the few-layer molybdenum disulfide in the few-layer molybdenum disulfide colloidal solution is 0.8 mg / mL-1.2 mg / mL, and the concentration of polyvinyl pyrrolidone is 0.8 mg / mL-1.2 mg / mL.

5. The method for preparing a two-dimensional layered piezoelectric material according to claim 1, wherein: In S2, the metal precursor is selected from one or more of iron salts, nickel salts and copper salts; The concentration of the metal precursor in the metal / thiourea complex solution is 55 mmol / L-65 mmol / L, and the concentration of thiourea is 145 mmol / L-155 mmol / L.

6. The method for preparing a two-dimensional layered piezoelectric material according to claim 1, wherein: In S3, the volume ratio of the few-layer molybdenum disulfide colloidal solution to the metal / thiourea complex solution is (9.5-10.5):1; The reaction temperature is 155° C.-165° C., and the reaction time is 14 h-18 h.

7. A two-dimensional layered piezoelectric material prepared by the method according to any one of claims 1 to 6.

8. Use of the two-dimensional layered piezoelectric material according to claim 7 in atom transfer radical polymerization, characterized in that: The application process is: under a protective atmosphere, methacrylate monomers, two-dimensional layered piezoelectric materials and initiators are subjected to atom transfer radical polymerization in a solvent to obtain a polymer material.

9. The method for preparing a two-dimensional layered piezoelectric material according to claim 8, wherein: The methacrylate monomer is selected from one or more of methyl methacrylate, hydroxyethyl methacrylate and butyl methacrylate; The initiator is selected from benzyl bromide and / or ethyl α-bromoisobutyrate; The solvent is selected from one or more of tetrahydrofuran, N,N-dimethylformamide and cyclopropanone; The molar ratio of the methacrylate monomer to the initiator is 100:(0.5-1.5); The mass ratio of the two-dimensional layered piezoelectric material to the methacrylate monomer is 1:(50-200).

10. The method for preparing a two-dimensional layered piezoelectric material according to claim 8, characterized in that: The power of the atom transfer radical polymerization is 300W-600W, and the frequency is 40kHz-80kHz.