Preparation method and application of small-size homopolymer nanoparticles

Abstract

The invention discloses a preparation method and application of small-size homopolymer nanoparticles, and relates to the technical field of polymer materials.The preparation method comprises the following steps that S1, rigid hydrophobic groups with the strong pi-pi stacking effect are introduced into a polymerization initiation / chain transfer system, a good solvent is added, hydrophilic monomer polymerization is initiated, the polymerization concentration is 20%-100%, and a hydrophilic monomer is obtained; the terminal of the amphiphilic homopolymer is a rigid hydrophobic group, the molecular weight of the amphiphilic homopolymer is 1000-100000g / mol, and the molecular weight distribution is 1.0-20.0; and S2, preparing the homopolymer into an aqueous solution with the concentration of 0.05-80%, and carrying out ultrasonic treatment to obtain the small-size polymer nanoparticles, thereby solving the problems that the small-size polymer nanoparticles are complex in preparation system, difficult to prepare and unfavorable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer materials, in particular to a preparation method of small-size homopolymer nanoparticles and application thereof. BACKGROUND

[0002] Polymer nanoparticles show a wide application prospect in the fields of new materials, biological medicine, aerospace, etc. The performance or function will change significantly with the size, for example, different sizes of polymer nanoparticles exhibit different biochemical behaviors in the body, and the effects are also different when used as fillers to enhance the mechanical properties of materials. When the size of polymer nanoparticles is small enough, the performance of many materials can be significantly improved. However, at present, although there are some reports on the synthesis method of polymer nanoparticles less than 20 nm, the number of such methods is relatively limited, and the synthesis process is relatively complex, and there are still many challenges in realizing industrial-scale production.

[0003] For example: the patent document with publication number "CN114989459A" discloses "a preparation method of polymer fluorescent nanoparticles", which prepares polymer fluorescent nanoparticles with a size of less than 10 nm by nano-precipitation method. However, this method needs to use capillary to generate continuous droplets under the action of pump and purging gas, and at the same time, external field (ultrasound, magnetic stirring) is used to strengthen mixing. The operation is complex, and the capillary flux is low, which is difficult to realize large-scale production. For example, the patent application document with publication number "CN117126353A" discloses "a single-chain nanoparticle, a preparation method and application thereof, and a polymer composite and a preparation method". In this method, a large amount of solvent is used to configure the polymer into an extremely dilute solution (0.5~5mg / ml), and then ultraviolet light is used for a long time (>7h) to cause intramolecular photo-crosslinking of the polymer to form nanoparticles. The preparation of extremely dilute solution and long-time ultraviolet light greatly increases the preparation cost and efficiency of the particles. For example, the patent document with publication number "CN115010962A" discloses "a method for preparing small-size polymer Janus particles using mixed shell particles as templates", which can prepare small-size (5~30 nm) polymer Janus particles. This method needs to be realized through complex operation steps and precise condition control. For example, the patent document with publication number "CN115109175A" discloses "a preparation method of small-size polymer nanoparticles". This scheme realizes the preparation of various 15 nm or less polystyrene and polymethacrylate polymer nanoparticles on the basis of existing microemulsion polymerization, by using a part of good solvent to replace the monomer reactant, and cooperating with a series of precise control of reaction conditions. However, this method needs to introduce a large amount of small molecule surfactant to limit the growth and coalescence of nanoparticles, and it is also a great challenge to remove the small molecule surfactant in the nanoparticles efficiently and at low cost.

[0004] Therefore, it is of great significance to develop a simple and efficient method for preparing small-size (especially 20 nm or less) polymer nanoparticles for both nanoscience research and nanomaterial industrialization. SUMMARY

[0005] The purpose of the present application is to solve the problems of complex preparation system and difficulty in preparing small-size polymer nanoparticles, which are not conducive to industrial production, and to provide a preparation method of small-size homopolymer nanoparticles.

[0006] The present application is realized by the following technical scheme: A preparation method of small-size homopolymer nanoparticles, comprising the following steps: S1, introducing monomers with rigid hydrophobic groups having strong π-π stacking effect into a polymerization initiation / chain transfer system, adding a good solvent, initiating polymerization of hydrophilic monomers, polymerization concentration is 20-100%, forming amphiphilic homopolymer with rigid hydrophobic groups at the end, the molecular weight of the amphiphilic homopolymer is 1000-100000 g / mol, and the molecular weight distribution is 1.0-20.0; S2, configuring the homopolymer into an aqueous solution with a concentration of 0.05-80%, and obtaining small-size polymer nanoparticles by ultrasonic treatment.

[0007] Further, in step S1, the rigid hydrophobic groups with strong π-π stacking effect include azobenzene, biphenyl, stilbene, naphthalene and anthracene with π-π groups.

[0008] Further, in step S1, the polymerization initiation / chain transfer system includes a chain initiation system or a chain transfer system corresponding to active anion and cation polymerization, free radical polymerization or ring-opening polymerization method.

[0009] Further, in step S1, the hydrophilic monomer includes one or more of methacrylic acid and its salt, acrylic acid and its salt, hydrophilic amide, hydrophilic methacrylate, hydrophilic acrylate, hydrophilic vinyl derivative and hydrophilic styrene derivative.

[0010] Further, in step S1, the hydrophilic monomer includes one or more of N-isopropyl acrylamide, N,N-dimethyl acrylamide, methacrylic acid, sodium methacrylate, acrylic acid and sodium acrylate.

[0011] Further, in step S1, the good solvent includes one or more of water, tetrahydrofuran or dioxane.

[0012] Further, in step S1, the polymerization concentration is preferably 50%. If the polymerization concentration is too low, it is not conducive to improving the particle preparation efficiency; if the polymerization concentration is too high, the solubility of the initiation system is poor, and the molecular weight distribution of the polymer is wide.

[0013] Further, in step S1, the molecular weight of the amphiphilic homopolymer is preferably 2000-10000 g / mol; and the molecular weight distribution is preferably 1.0-3.0. If the molecular weight distribution is too high, the particle size dispersion is large and not uniform.

[0014] Further, in step S2, the concentration of the homopolymer aqueous solution is preferably 20-50%. If the polymer concentration is too low, it is not conducive to improving the particle preparation efficiency; if the polymer concentration is too high, it is not conducive to improving the dispersion efficiency.

[0015] Further, in step S2, the ultrasonic power is 1 W~10 kW, preferably 100~200 W; the ultrasonic time is 5 s~2 h, preferably 3~5 min. If the ultrasonic power is too low, the ultrasonic time needs to be greatly prolonged, which is not conducive to improving the particle preparation efficiency; if the ultrasonic power is too high, the equipment requirement is high. If the ultrasonic time is too short, the ultrasonic power needs to be greatly increased to strengthen the dispersion; if the ultrasonic time is too long, it is not conducive to improving the particle preparation efficiency.

[0016] The application of the small-size homopolymer nanoparticles obtained by the preparation method according to any one of the preceding embodiments in preparing Pickering emulsion.

[0017] Further, in the application of the small-size homopolymer nanoparticles in preparing Pickering emulsion, water and oil substances are added to the small-size homopolymer nanoparticles, the nanoparticle concentration is controlled to be 0.0005~20%, preferably 0.001%~5%, and the water / oil ratio is (1:0.1)~(10:0.1), preferably (1:3)~(1:0.5). If the nanoparticle concentration is too low, the emulsion stability is not good; if the nanoparticle concentration is too high, the raw material consumption is increased, and the cost is high. After oscillation stirring, the Pickering emulsion is obtained by standing.

[0018] The application of the small-size homopolymer nanoparticles obtained by the preparation method according to any one of the preceding embodiments in preparing polymer materials for aerospace and daily chemical industry, wherein the small-size homopolymer nanoparticles have a particle size of ≤20 nm.

[0019] Compared with the prior art, the present application has the following advantages and beneficial effects: Firstly, in the present application, a small-size homopolymer nanoparticle preparation method is developed through ingenious molecular structure design. The method is based on the synthesis of small-scale amphiphilic polymer nanoparticles through self-assembly of homopolymers. The method can realize efficient preparation of small-size particles without complex post-polymerization steps, especially particles with a particle size of less than 20 nm. The preparation process is simple, does not require complex additives or complex processing equipment, and can realize the preparation of high-concentration (50% solid content) nanoparticles, which is convenient for scale-up and batch production.

[0020] Secondly, in the present application, the preparation method can be applied to the preparation of Pickering emulsifiers, and a stable oil-in-water emulsion system under the condition of low particle addition amount is successfully constructed. The method realizes long-term kinetic stability of the emulsion system by precisely controlling the interfacial interaction mechanism while significantly reducing the amount of nanoparticles, which provides a new solution for the industrial application of efficient and green emulsification technology.

[0021] Thirdly, in the present application, the small-size homopolymer nanoparticles, especially particles with a particle size of less than 20 nm, can be widely used in the fields of new materials, aerospace, daily chemical industry, etc. Attached Figure Description

[0022] Figure 1 This is the molecular structure and NMR spectrum of the AzCTA chain transfer agent in Example 1.

[0023] Figure 2 This is the molecular formula and gel permeation chromatography characterization chromatogram of the PDMA-Az polymer in Example 1.

[0024] Figure 3 This is a transmission electron microscope image of the PDMA-Az homopolymer nanoparticles in Example 1.

[0025] Figure 4 This is a magnified micrograph of the Pickering emulsion prepared from PDMA-Az homopolymer nanoparticles in Example 1.

[0026] Figure 5 These are photographs of Pickering emulsions with different concentrations of PDMA-Az homopolymer nanoparticles in Example 1.

[0027] Figure 6 This is the molecular structure and NMR spectrum of the StbCTA chain transfer agent in Example 2.

[0028] Figure 7 This is the molecular formula and gel permeation chromatography characterization of the PNIPAMAm-Stb polymer.

[0029] Figure 8 This is a photograph of the Pickering emulsion prepared from the PNIPAAm-Stb homopolymer nanoparticles in Example 2.

[0030] Figure 9 This is a magnified micrograph of the Pickering emulsion prepared from PNIPAAm-Stb homopolymer nanoparticles in Example 2. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0032] Example 1 A method for preparing small-sized homopolymer nanoparticles includes the following steps: Step S1: Synthesis of homopolymers with rigid end units.

[0033] Azobisisobutyronitrile (AIBN, 0.5 g, 0.003 mol) initiator and AzCTA chain transfer agent (molecular structure and NMR characterization are shown in Appendix) were used. Figure 1, 11 g, 0.015 mol), 30 g N, N-dimethylacrylamide monomer (DMA, 30 g, 0.303 mol), 1,4-dioxane (10 g) were added into a three-necked flask, and nitrogen was bubbled. After stirring for 30 min, the three-necked flask was placed in a 70 °C oil bath for 12 h. Then, the product was dried in vacuum.

[0034] In this step, by adjusting the ratio of DMA monomer and AzCTA, a series of PDMA-Az homopolymers with different molecular weights were obtained. The gel permeation chromatography characterization and molecular weight information of the homopolymers are shown in Figure 2 .

[0035] Step S2: Preparation of small-size homopolymer nanoparticles.

[0036] 1 g of PDMA-Az homopolymer was added to 5 g of water, and 100 W ultrasonic treatment was performed for 2 min to obtain a PDMA-Az homopolymer nanoparticle aqueous solution. The transmission electron microscope (TEM) image of the nanoparticles prepared from the PDMA-Az homopolymer is shown in Figure 3 .

[0037] As can be seen from Figure 3 , the homopolymer in this embodiment self-assembles in water to form particles with a size of about 10 nm.

[0038] Different molecular weight PDMA-Az homopolymers can form nanoparticles with different sizes, and the characterization results are shown in the dynamic light scattering (DLS) data in Table 1. The sample numbers in Table 1 correspond one-to-one to the sample numbers in Figure 2 .

[0039] Table 1

[0040] Application Example 1 The small-size homopolymer nanoparticles prepared in Example 1 were used as Pickering emulsifiers to prepare Pickering emulsions.

[0041] The PDMA-Az homopolymer was added to a water / n-decane liquid with a water / oil ratio of 1:0.5, and after shaking and stirring for 30 min, a stable Pickering emulsion was obtained after standing for 12 h.

[0042] The optical micrograph of the Pickering emulsion obtained in this application example is shown in Figure 4 .

[0043] As can be seen from Figure 4 , the PDMA-Az homopolymer nanoparticles successfully stabilized n-decane in water and formed oil droplets with an average diameter of about 8 microns.

[0044] Pickering emulsions prepared using different concentrations of PDMA-Az homopolymer nanoparticles are shown in Figure 5. By Figure 5 It can be seen that when the nanoparticle concentration is 0.01%, good stability and emulsification effect can still be achieved.

[0045] Example 2 This example is different from Example 1 in that the rigid unit is stilbene and the hydrophilic monomer is N-isopropyl acrylamide.

[0046] Step S1: Synthesis of homopolymer with rigid unit at the end. Azo diisobutyronitrile initiator (AIBN, 0.5 g, 0.003 mol), StbCTA chain transfer agent (molecular structure and NMR characterization are shown in the following Figure 6 , 11 g, 0.015 mol), 42.4 g N-isopropyl acrylamide (NIPAAm, 42.4 g, 0.374 mol), 1,4-dioxane (10 g) were added to a three-necked flask, nitrogen was bubbled, and after stirring for 30 minutes, the three-necked flask was placed in a 70°C oil bath and reacted for 12 hours, then taken out and vacuum dried.

[0047] In this example, by adjusting the ratio of NIPAAm monomer and StbCTA, a series of PNIPAAm-Stb homopolymers with different molecular weights can be obtained, and their gel permeation chromatography characterization and molecular weight information are shown in the following Table 1. Figure 7 .

[0048] Step S2: Preparation of small-size homopolymer nanoparticles.

[0049] 1 g of PNIPAAm-Stb homopolymer was added to 5 g of water, and 100 W ultrasonic treatment was performed for 2 min to obtain a PDMA-Az homopolymer nanoparticle aqueous solution. By adjusting the molecular weight of the PNIPAAm-Stb homopolymer, a series of particles with a size less than 20 nm were obtained, and the following Table 2 is referred to.

[0050] Table 2: Dynamic light scattering data of PNIPAAm-Stb homopolymer nanoparticles. The sample numbers in Table 2 correspond one-to-one to the sample numbers in Figure 7 .

[0051]

[0052] Application Example 2 The small-size homopolymer nanoparticles prepared in Example 2 were used as Pickering emulsifiers to prepare Pickering emulsions.

[0053] The PNIPAAm-Stb homopolymer was added to water / n-decane liquid with a water / oil ratio of 1:0.5, and after shaking and stirring for 30 minutes, a stable Pickering emulsion was obtained by standing for 12 hours. The actual photo of the Pickering emulsion obtained in this application example is shown in Figure 8, the optical micro-magnification photo is shown in Figure 9 .

[0054] Example 3 The difference between the present example and Example 1 is that the rigid base unit is biphenyl unit, the hydrophilic monomer is α-methyl acrylic acid, and the preparation process is the same as that of Example 1.

[0055] It is found that the size of the obtained homopolymer nanoparticles is 12.5 nm, and PDI=0.213. Among them, the number average molecular weight of the homopolymer is 11.2k, and the molecular weight distribution is 1.21.

[0056] Examples 3-5 verify the specific information of the nanoparticles prepared by different monomers. Among them, PDI reflects the uniformity of the particle size, and the smaller the PDI, the better the uniformity of the particles.

[0057] Example 4 The difference between the present example and Example 1 is that the rigid base unit is biphenyl unit, the hydrophilic monomer is N, N-dimethyl acrylamide, and the preparation process is the same as that of Example 1.

[0058] It is found that the size of the obtained homopolymer nanoparticles is 10.3 nm, and PDI=0.198. Among them, the number average molecular weight of the homopolymer is 9.7k, and the molecular weight distribution is 1.19.

[0059] Example 5 The difference between the present example and Example 1 is that the rigid base unit is biphenyl unit, the hydrophilic monomer is α-methyl acrylic acid, and the preparation process is the same as that of Example 1.

[0060] It is found that the size of the obtained homopolymer nanoparticles is 15.8 nm, and PDI=0.116. Among them, the number average molecular weight of the homopolymer is 14.9k, and the molecular weight distribution is 1.25.

[0061] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change based on the technical essence of the present application to the above embodiments falls within the protection scope of the present application.

Claims

1. A method for preparing small-sized homopolymer nanoparticles, characterized in that, Includes the following steps: S1. Introduce rigid hydrophobic groups with strong π-π stacking interaction into the polymerization initiation / chain transfer system, add a good solvent to initiate the polymerization of hydrophilic monomers, the polymerization concentration is 20~100%, and an amphiphilic homopolymer with rigid hydrophobic groups at the end is formed. The molecular weight of the amphiphilic homopolymer is 1000~100000 g / mol, and the molecular weight distribution is 1.0~20.

0. S2. Prepare an aqueous solution of homopolymer with a concentration of 0.05~80% and sonicate it to obtain small-sized polymer nanoparticles.

2. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the rigid hydrophobic groups with strong π-π stacking include azobenzene, biphenyl, diphenylethylene, naphthalene, and anthracene groups that have π-π groups.

3. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the polymerization initiation / chain transfer system includes the chain initiation system or chain transfer system corresponding to the living cationic / anionic polymerization, free radical polymerization, or ring-opening polymerization method.

4. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the hydrophilic monomer includes one or more of the following: methacrylic acid and its salts, acrylic acid and its salts, hydrophilic amides, hydrophilic methacrylates, hydrophilic acrylates, hydrophilic ethylene derivatives, and hydrophilic styrene derivatives.

5. The method for preparing small-sized homopolymer nanoparticles according to claim 4, characterized in that: In step S1, the hydrophilic monomer includes one or more of N-isopropylacrylamide, N,N-dimethylacrylamide, methacrylic acid, sodium methacrylate, acrylic acid, and sodium acrylate.

6. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the good solvent includes one or more of water, tetrahydrofuran, or dioxane.

7. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the polymerization concentration is 50%.

8. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S1, the molecular weight of the amphiphilic homopolymer is 2000~10000 g / mol; the molecular weight distribution is 1.0~3.

0.

9. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S2, the concentration of the homopolymer aqueous solution is 20-50%.

10. The method for preparing small-sized homopolymer nanoparticles according to claim 1, characterized in that: In step S2, the ultrasonic power is 1W~10kW; the ultrasonic time is 5s~2h.

11. The method for preparing small-sized homopolymer nanoparticles according to claim 10, characterized in that: In step S2, the ultrasonic power is 100~200W; the ultrasonic time is 3~5min.

12. The application of small-sized homopolymer nanoparticles in the preparation of Pickering emulsions, characterized in that: The small-sized homopolymer nanoparticles are obtained by the preparation method described in any one of claims 1 to 11.

13. The application according to claim 12, characterized in that: Water and oil were added to small-sized homopolymer nanoparticles, and the concentration of nanoparticles was controlled at 0.0005~20%, and the water-oil ratio was (1:0.1)~(10:0.1). After shaking and stirring, the mixture was allowed to stand to obtain Pickering emulsion.

14. The application according to claim 13, characterized in that: Water and oil were added to small-sized homopolymer nanoparticles, and the concentration of nanoparticles was controlled at 0.001~5% and the water-oil ratio was (1:3)~(1:0.5). After shaking and stirring, the mixture was allowed to stand to obtain Pickering emulsion.

15. The application of small-sized homopolymer nanoparticles in the preparation of polymer materials for aerospace and daily chemical industries, characterized by: The small-sized homopolymer nanoparticles are obtained by the preparation method described in any one of claims 1 to 10.

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