Hybrid shell polymer nanoparticles with high interfacial activity and preparation method and application thereof

Abstract

The present invention relates to hybrid-shell polymer nanoparticles with high interfacial activity, as well as their preparation method and application. The preparation method specifically comprises the following steps: first, separately polymerizing two or more diblock copolymers, adding a crosslinking agent to a common good solvent for the two or more diblock copolymers, and inducing micellization of the block copolymers by covalently crosslinking nucleating segments to prepare hybrid-shell polymer nanoparticles with high interfacial activity. The hybrid-shell particles have a stable structure, a preparation efficiency approaching 100%, and can be prepared on a large scale at high concentrations. The preparation process is simple and the preparation method has a certain degree of universality, making it applicable to the construction of various functional hybrid-shell particles. The obtained hybrid-shell particles exhibit high interfacial activity comparable to Janus particles, can effectively reduce interfacial tension, and are suitable for emulsion stabilization and solubilization of polymer blend systems.

Description

Technical Field

[0001] The invention belongs to the field of polymer nano functional materials, and in particular relates to mixed shell polymer nano particles with high interfacial activity, and a preparation method and application thereof. Background Art

[0002] Polymer Janus particles are an important research area in materials science and have important application value in the fields of biomedicine, heterogeneous catalysis, emulsion stabilization, and solubilization of polymer blend systems. In particular, due to the properties of the asymmetric structure of Janus particles, they have extremely excellent interfacial activity and interfacial stability and have been widely used to stabilize many types of incompatible multiphase mixture systems, such as oil-water emulsion stabilization and interfacial stabilization between incompatible phases in polymer blend systems (i.e., acting as a solubilizer for the blend system). Although existing research has developed a series of methods for preparing polymer Janus particles, such as various block copolymer assembly methods, asymmetric modification methods, and polymer coprecipitation phase separation methods, and polymer Janus particles with a series of morphologies such as rods, discs, snowmen, and tadpoles have been constructed, their complex preparation process, poor process scalability, and low yield greatly increase their preparation costs, making their industrial application greatly limited.

[0003] The idea of ​​preparing core-shell polymer nanoparticles (non-multicomponent mixed shell) by cross-linking-induced micellization is reported in Macromolecules 2003, 36, 2576-2578. At the same time, patents CN1200030C, WO2003066712A1, EP1472309A1 and US 7166306B2 disclose a one-step method for preparing structurally stable, high-concentration polymer nanomicelles with a core-shell structure. The specific scheme is to dissolve a block copolymer having a cross-linkable block in a common solvent for the copolymer, then add a cross-linking agent for cross-linking, and stir appropriately during cross-linking to obtain a polymer nanomicelle solution and solid powder in which the cross-linked block is the core and the uncross-linked portion is the shell. The use of cross-linking-induced micellization to prepare mixed-shell polymer nanoparticles was first proposed in Macromolecules 2005, 38, 5834-5837. However, this work only prepared and characterized a single type of mixed-shell polymer nanoparticle: PS-b-P2VP / PEO-b-P2VP. Furthermore, no research was conducted on the regulation of structural parameters or the relationship between micelle structure parameters and emulsion stability.

[0004] Based on the current status of existing technologies, developing a simple preparation method for preparing polymer particles with high interfacial activity on a large scale, efficiently and at high concentration can effectively address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of the present invention is to provide a mixed shell polymer nanoparticle with high interfacial activity and its preparation method and application. The method of the present invention can prepare polymer particles with high interfacial activity on a large scale, efficiently and at high concentration, which can well address the shortcomings of the existing technology.

[0006] Based on the understanding of the conformational transition of shell chains at the interface in hybrid shell polymer particles, the present invention has developed a simple preparation method for the scalable, efficient and high-concentration preparation of polymer particles with high interfacial activity. Not only can the hybrid shell particles be customized to achieve high interfacial activity at the interfaces of various compatible systems, but the preparation process is simple and has strong scalability, and can achieve scalable, efficient and high-concentration preparation in various customized hybrid shell particle systems.

[0007] The preparation concept of the mixed-shell polymer nanoparticles with high interfacial activity provided by the present invention is: two (or more) diblock copolymers are obtained by separate polymerization, a crosslinking agent is added to their common good solvent, and the block copolymers are induced to micellize by covalently crosslinking the nucleating segments, thereby realizing the efficient preparation of mixed-shell polymer nanoparticles. The mixed-shell particles can be uniformly dispersed in the two phases of the corresponding incompatible system. When located at the interface, the mixed-shell particles exhibit a Janus conformation, can be firmly fixed to the interface, and have high interfacial activity and stability. Taking the oil-water system as an example, the mixed-shell particles can be stably dispersed in oil and water respectively, that is, in water, the hydrophilic chains stretch and the lipophilic chains collapse; in oil, the lipophilic chains stretch and the hydrophilic chains collapse. When located at the interface, the shell molecular chains obtain a Janus conformation through asymmetric conformational changes on both sides. In addition to the oil-water system, it can also be used for interfacial stabilization of any incompatible polymer blend system (that is, acting as an interfacial solubilizer).

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The present invention provides a method for preparing mixed-shell polymer nanoparticles with high interfacial activity. Specifically, the method comprises the following steps: firstly separately polymerizing to obtain two or more diblock copolymers; adding a crosslinking agent to a common good solvent of the two or more diblock copolymers; and inducing micellization of the block copolymers by covalently crosslinking nucleation segments to obtain mixed-shell polymer nanoparticles with high interfacial activity.

[0010] The method provided by this invention enables the efficient preparation of mixed-shell polymer nanoparticles. The particle powder mass and the polymer feed mass are essentially the same, with a preparation efficiency approaching 100%. Furthermore, the method can be scalably prepared at high concentrations. The preparation method is simple and universal, and can be used to construct a variety of functional mixed-shell particles.

[0011] In one embodiment of the present invention, a method for preparing mixed-shell polymer nanoparticles with high interfacial activity comprises the following steps:

[0012] (1) preparing a diblock copolymer by any one or more methods selected from reversible addition-fragmentation chain transfer polymerization (RAFT), atom transfer radical polymerization (ATRP), and anionic polymerization;

[0013] (2) dissolving two or more diblock copolymers in a common good solvent, adding a small molecule crosslinker, and inducing micellization of the block copolymers through the reaction of the small molecule crosslinker with the nucleation block of the diblock copolymer to obtain a mixed shell polymer nanoparticle dispersion with high interfacial activity;

[0014] (3) After sedimentation separation, mixed shell polymer nanoparticle powder with high interfacial activity is obtained.

[0015] In one embodiment of the present invention, in step (1), the first block of the diblock copolymer is a cross-linkable core segment, which is polymerized from monomers that can covalently react with a cross-linking agent, and the monomers are selected from one or more of 4-vinylpyridine, dimethylaminoethyl methacrylate, acrylic acid, methacrylic acid, isoprene or hydroxyethyl methacrylate; the second block is a functional shell segment, and the polymerized monomers are selected from one or more of ethylene oxide, N,N-dimethylacrylamide, N-isopropylacrylamide, dimethylaminoethyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, methyl methacrylate or styrene.

[0016] In one embodiment of the present invention, in step (2), the molar ratio of the number of repeating units of the functional shell segments to the number of repeating units of the cross-linkable core segments in the diblock copolymer solution is 1.3-6.6.

[0017] In one embodiment of the present invention, in step (1), the degree of polymerization of the first block of the diblock copolymer is between 100-500, the degree of polymerization of the second block is between 50-1500, and the number average molecular weight of the diblock copolymer is in the range of 12000-80000 g / mol.

[0018] In one embodiment of the present invention, in step (2), the good solvent for the diblock copolymer is selected from one or more of N,N-dimethylformamide, tetrahydrofuran, chloroform, dichloromethane, 2-butanone or 1,4-dioxane.

[0019] In one embodiment of the present invention, in step (2), the concentration of the two or more diblock copolymers in the good solvent is 10-150 mg / mL.

[0020] In one embodiment of the present invention, in step (2), the small molecule cross-linking agent is selected from one or more of hexamethylene diisocyanate, 1,4-dibromobutane, 1,4-diiodobutane, 1,5-dibromopentane, 1,5-diiodopentane or 1,6-hexanedithiol.

[0021] In one embodiment of the present invention, in step (2), the molar ratio of the small molecule cross-linking agent to the number of repeating units of the cross-linkable nucleating segment in the diblock copolymer is 0.2-1.0.

[0022] In one embodiment of the present invention, in step (2), the reaction time of the nucleation block reaction is 6-48 hours, and the reaction temperature is 20-90°C.

[0023] The present invention further provides highly interfacially active hybrid-shell polymer nanoparticles prepared using the aforementioned preparation method. The highly interfacially active hybrid-shell polymer nanoparticles prepared by the present method have a particle size distribution ranging from 10 to 80 nm, are uniform in size, and exhibit excellent structural stability, maintaining their core-shell morphology in various solvents. The highly interfacially active hybrid-shell polymer nanoparticles prepared by the present method exhibit high interfacial activity comparable to that of Janus particles, effectively reduce interfacial tension, and are suitable for emulsion stabilization and solubilization of polymer blend systems.

[0024] The present invention further provides applications of hybrid shell polymer nanoparticles with high interfacial activity prepared based on the above preparation method. The hybrid shell polymer nanoparticles with high interfacial activity are used in the fields of petroleum industry, drug sustained release, heterogeneous catalysis, emulsion stabilization, and solubilization of blended systems.

[0025] The present invention explored multiple systems and varied their structural parameters, achieving efficient preparation of hybrid-shell polymer nanoparticles. Based on this, the present invention provides a specific method for preparing hybrid-shell polymer nanoparticles and statistically analyzes the preparation efficiency of hybrid-shell polymer nanoparticles, which approaches 100%.

[0026] Compared with the prior art, the advantages and positive effects of the present invention are:

[0027] Based on the understanding of the conformational transition of the shell chains at the interface in mixed-shell polymer particles, the present invention has developed a simple preparation method for preparing polymer particles with high interfacial activity on a large scale, efficiently and at high concentration. Not only can the mixed shell particles be customized to achieve high interfacial activity at the interface of various compatible systems, but the preparation process is simple and has strong scalability, and can be prepared on a large scale, efficiently and at high concentration in various customized mixed-shell particle systems. The preparation idea is to separately polymerize two or more diblock copolymers, add a cross-linking agent to their common good solvent, and induce the micellization of the block copolymers by covalently cross-linking the nucleating segments to achieve efficient preparation of mixed-shell polymer nanoparticles. The mixed shell particles can be uniformly dispersed in the two phases of the corresponding incompatible system. When located at the interface, the mixed shell particles exhibit a Janus conformation, can be firmly fixed to the interface, and have high interfacial activity and stability. Taking an oil-water system as an example, hybrid shell particles can be stably dispersed in both oil and water. In water, the hydrophilic chains expand while the lipophilic chains collapse; in oil, the lipophilic chains expand while the hydrophilic chains collapse. At the interface, the shell molecular chains achieve a Janus conformation through asymmetric conformational changes on both sides. Beyond oil-water systems, this technology can also be used to stabilize the interface of any incompatible polymer blend (i.e., act as an interfacial solubilizer).

[0028] The preparation method of the present invention is simple, highly reproducible, and capable of scalable, efficient, and high-concentration production. Furthermore, the preparation method of the present invention is highly scalable, enabling the preparation of customized hybrid shell particles with varying composition and structural parameters according to application requirements. The preparation of these hybrid shell particles is highly controllable and exhibits excellent structural stability. The resulting hybrid shell particles exhibit high interfacial activity comparable to Janus particles, effectively reducing interfacial tension and being suitable for emulsion stabilization and solubilization of polymer blends. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Flow chart for the preparation of core-crosslinked hybrid-shell polymer particles.

[0030] Figure 2 TEM images and size distribution diagram of a group of PAA-b-PDMA / PAA-b-PnBA mixed-shell polymer particles prepared in Example 1. The mixed-shell particles are uniform in size, with a particle size of 27.1±7.2 nm.

[0031] Figure 3 Schematic diagram of the PAA-b-PDMA / PAA-b-PnBA mixed shell polymer particles located at the interface of two immiscible phases in Example 1.

[0032] Figure 4This is the oil-water interfacial tension test curve of the PAA-b-PDMA / PAA-b-PnBA mixed shell polymer particles in Example 1. DETAILED DESCRIPTION

[0033] To better understand the technical solutions of the present invention, embodiments of the present invention are described in detail below. It should be noted that the embodiments described are only a portion of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, those skilled in the art may make various changes and improvements without departing from the conceptual framework of the present invention. These all fall within the scope of protection of the present invention.

[0034] Example 1. Preparation of polyacrylic acid-b-poly(N,N-dimethylacrylamide) / polyacrylic acid-b-poly-n-butyl acrylate (PAA-b-PDMA / PAA-b-PnBA) mixed-shell polymer particles and interfacial activity test of the mixed-shell particles.

[0035] First, tert-butyl acrylate (PAA) was synthesized as the first block by RAFT polymerization. After multiple sedimentation and purification steps, it was used as a macromolecular chain transfer agent to synthesize poly(tert-butyl acrylate)-b-poly(N,N-dimethylacrylamide) (PtBA-b-PDMA) and poly(tert-butyl acrylate)-b-poly(n-butyl acrylate) (PtBA-b-PnBA). After separate sedimentation and purification, the tert-butyl ester in PtBA was hydrolyzed in trifluoroacetic acid in dichloromethane to obtain PAA-b-PDMA and PAA-b-PnBA, respectively. The chain transfer agent was trithiocarbonate; the initiator was azobisisobutyronitrile; the solvents were 2-butanone and 1,4-dioxane, respectively; the sedimentation agents were diethyl ether and water, respectively; and the reaction temperature was 70°C. Due to variations in polymerization time, solvent, and other preparation techniques among different sample batches, the resulting polymerization degrees of polymerization (DPs) of PAA ranged from 100 to 500, while those of PDMA and PnBA ranged from 50 to 1500.

[0036] PAA-b-PDMA and PAA-b-PnBA were dissolved in the good solvent N,N-dimethylacrylamide, and a certain amount of hexamethylene diisocyanate (crosslinker) was added. The reaction was carried out at 25°C for 24 hours to obtain mixed shell particles. The molar ratio of the crosslinker to the number of repeating units of the crosslinkable nucleating segment was 0.2. The preparation concentration was 20 mg / mL. The preparation process is shown in the figure below. Figure 1 As shown. The obtained mixed shell particles are uniform in size. Taking one group of mixed shell particles as an example, the particle size is 27.1±7.2nm by TEM observation. Figure 2 shown.

[0037] Furthermore, the hanging drop method was used to test Figure 2The interfacial tension of the mixed shell particles at the n-decane / water interface. When located at the oil-water interface, the mixed shell particles exhibit a Janus conformation, such as Figure 3 The interfacial tension of n-decane / water without mixed shell particles was 46.3 mN / m. After adding 2 mg / mL mixed shell particles, the interfacial tension was significantly reduced to 20.8 mN / m (as shown in Figure 2). Figure 4 This indicates that the hybrid shell particles have high interfacial activity.

[0038] Example 2. Preparation process of poly (4-vinylpyridine)-b-poly (N,N-dimethylacrylamide) / poly (4-vinylpyridine)-b-poly (n-butyl acrylate) (P4VP-b-PDMA / P4VP-b-PnBA) mixed shell polymer particles and interfacial activity test of the mixed shell particles.

[0039] The polymerization process of P4VP-b-PDMA and P4VP-b-PnBA is similar to that of Example 1. RAFT polymerization of poly-4-vinylpyridine as the first block was selected. After multiple sedimentation and purification, P4VP-b-PDMA and P4VP-b-PnBA were synthesized using this as a macromolecular chain transfer agent. The chain transfer agent was trithiocarbonate; the initiator was azobisisobutyronitrile; the solvent was N,N-dimethylformamide; the sedimentation agent was diethyl ether; the reaction temperature was 70°C; due to different preparation processes such as polymerization time and solvent in different sample batches, the polymerization degree of P4VP obtained by polymerization was between 100-500, and the polymerization degree of PDMA and PnBA was between 50-1500.

[0040] The process of preparing hybrid shell particles by covalent crosslinking is similar to that in Example 1.

[0041] P4VP-b-PDMA and P4VP-b-PnBA were dissolved in a good solvent, N,N-dimethylacrylamide, and a certain amount of 1,4-dibromobutane (cross-linker) was added thereto. The reaction was carried out at a reaction temperature of 40°C for 48 hours to obtain mixed shell particles. The molar ratio of the cross-linker to the number of repeating units of the cross-linkable nucleating segment was 0.2. The preparation concentration was 20 mg / mL. The obtained mixed shell particles were uniform in size. Taking one group of mixed shell particles as an example, the particle size was observed to be 25.0±3.0 nm by TEM. The interfacial tension at the n-decane / water interface was tested using the hanging drop method, and a significant reduction in the interfacial tension as shown in Example 1 was also achieved, indicating that the mixed shell particles have high interfacial activity.

[0042] Example 3. Preparation of poly (4-vinylpyridine)-b-polyethylene oxide / poly (4-vinylpyridine)-b-poly (n-butyl acrylate) (P4VP-b-PEO / P4VP-b-PnBA) mixed-shell polymer particles and test of the interfacial activity of the mixed-shell particles.

[0043] The polymerization process of P4VP-b-PnBA is consistent with that of Example 2. P4VP-b-PEO is polymerized by ATRP. Monomethyl-terminated polyethylene oxide is reacted with 2-chloropropionyl chloride and triethylamine is used as an acid-binding agent. After reacting overnight and settling multiple times, PEG-Cl macroinitiator is obtained. On this basis, 4-vinylpyridine, catalyst CuCl, tri[2-(methylamino)ethyl]amine and solvent isopropanol are added. After sufficient freeze-thaw deoxygenation, the reaction is carried out at 45°C for 6 hours to obtain P4VP-b-PEO. The settling agent is ether; due to different preparation processes such as polymerization time and solvent in different sample batches, the polymerization degree of P4VP obtained by polymerization is between 100-500, the polymerization degree of PEO is between 113 and 226, and the polymerization degree of PnBA is between 50-1500.

[0044] The preparation of mixed shell particles by covalent crosslinking is similar to that of Example 2. P4VP-b-PEO and P4VP-b-PnBA were dissolved in a good solvent, N,N-dimethylacrylamide, and a certain amount of 1,4-dibromobutane (crosslinker) was added thereto. The reaction was carried out at a reaction temperature of 40°C for 48 hours to obtain mixed shell particles. The molar ratio of the crosslinker to the number of repeating units of the crosslinkable nucleating segment was 0.2. The preparation concentration was 20 mg / mL. The obtained mixed shell particles were uniform in size. Taking one group of mixed shell particles as an example, the particle size was observed to be 22.4±2.7 nm by TEM. The interfacial tension at the n-decane / water interface was tested using the hanging drop method, and a significant reduction in the interfacial tension as shown in Example 1 was also achieved, indicating that the mixed shell particles have high interfacial activity.

[0045] Example 4. Preparation of poly (4-vinylpyridine)-b-polystyrene / poly (4-vinylpyridine)-b-methyl methacrylate (P4VP-b-PS / P4VP-b-PMMA) mixed shell polymer particles, which effectively reduces the size of the PS / PMMA blend domain.

[0046] The polymerization process for P4VP-b-PS and P4VP-b-PMMA was similar to that in Example 2. RAFT polymerization was used to prepare a poly(4-vinylpyridine) macromolecular transfer agent, from which P4VP-b-PS and P4VP-b-PMMA were synthesized. The chain transfer agent was trithiocarbonate; the initiator was azobisisobutyronitrile; the solvent was N,N-dimethylformamide; the precipitant was diethyl ether; and the reaction temperature was 70°C. Due to variations in the polymerization time, solvent, and other preparation processes among different sample batches, the resulting P4VP polymerization degrees ranged from 100 to 500, while those of PDMA and PnBA ranged from 50 to 1500.

[0047] The process of preparing mixed shell particles by covalent crosslinking is similar to that in Example 2. P4VP-b-PS and P4VP-b-PMMA were dissolved in a good solvent N,N-dimethylacrylamide, a certain amount of 1,4-diiodobutane was added thereto, and the mixture was reacted at a reaction temperature of 40°C for 48 hours to obtain mixed shell particles. The molar ratio of the crosslinker to the number of repeating units of the crosslinkable nucleating segment is 0.2. The preparation concentration is 20 mg / mL. The obtained mixed shell particles are of uniform size. The above-mentioned mixed shell particles are used to blend two incompatible polymers, PS and PMMA, and the size of the obtained PS / PMMA blend phase region is significantly reduced, indicating that it has high interfacial activity when located at the interface between PS and PMMA.

[0048] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing mixed-shell polymer nanoparticles with high interfacial activity, characterized in that: It is polyacrylic acid- b -Poly( N,N -Dimethylacrylamide) / Polyacrylic acid- b -Polybutyl acrylate mixed shell polymer particles, The specific preparation includes the following steps: (1) RAFT polymerization was used to synthesize the first block of poly(tert-butyl acrylate), which was then used as a macromolecular chain transfer agent to synthesize poly(tert-butyl acrylate)- b -Poly( N,N -dimethylacrylamide) and poly-tert-butyl acrylate- b -polybutyl acrylate, after precipitation and purification, hydrolyzed in a dichloromethane solution of trifluoroacetic acid to remove P t tert-butyl esters in BA to obtain PAA- b -PDMA and PAA- b -P n BA, wherein the chain transfer agent is trithiocarbonate; the initiator is azobisisobutyronitrile; the solvents are 2-butanone and 1,4-dioxane; the sedimentation agents are ether and water; the reaction temperature is 70 o C; The polymerization degree of PAA obtained by polymerization is 100-500, PDMA and P n BA degree of polymerization is between 50-1500; (2) PAA- b -PDMA and PAA- b -P n BA dissolved in a good solvent N,N - dimethyl acrylamide, in which hexamethylene diisocyanate was added, at 25 o C reaction temperature for 24 hours to obtain mixed shell particles with a particle size distribution of 10-80 nm, a molar ratio of the crosslinker to the number of repeating units of the crosslinkable nucleating segment of 0.2-1.0, and a molar ratio of the number of repeating units of the functional shell segment to the number of repeating units of the crosslinkable nucleating segment in the diblock copolymer solution of 1.3-6.6; The hybrid shell particles are uniformly dispersed in the two phases of the corresponding incompatible system. When located at the interface, the hybrid shell particles exhibit a Janus conformation, are firmly fixed to the interface, and have high interfacial activity and stability; in water, the hydrophilic chains stretch and the lipophilic chains collapse; in oil, the lipophilic chains stretch and the hydrophilic chains collapse. When located at the interface, the shell molecular chains obtain a Janus conformation through asymmetric conformational changes on both sides.

2. The use of the mixed-shell polymer nanoparticles with high interfacial activity prepared by the preparation method according to claim 1, characterized in that: The mixed shell polymer nanoparticles with high interfacial activity are used in the fields of petroleum industry, drug sustained release, heterogeneous catalysis, emulsion stabilization, and blend system solubilization.

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