Core-shell particle of double-bond silicon dioxide coated polymer and synthesis method of core-shell particle

Abstract

The invention relates to the technical field of preparation of functional nano composite materials, in particular to core-shell particles of a double-bond silicon dioxide coated polymer and a synthesis method of the core-shell particles. According to the preparation method, tetraethyl orthosilicate and triethoxyvinylsilane are subjected to co-hydrolysis to generate silicon dioxide particles with double-bond functional groups, a polymer shell layer is coated under the emulsion polymerization condition, surface double bonds are introduced through tetraethyl orthosilicate, the interface affinity between an organic monomer and an inorganic core is enhanced, and continuous film forming of the shell layer is promoted; the shell thickness can be controlled between dozens of nanometers and hundreds of nanometers by adjusting the monomer type and the cross-linking agent ratio; the method has good process universality and is suitable for different types of monomer systems; the obtained particles are excellent in dispersity and uniform in morphology, and can be used for preparing an amorphous structural color coating material, and the mechanical stability of the coating material is remarkably improved. The core-shell particles prepared by the method have application potential in the fields of amorphous structural colors, intelligent response coatings, anti-counterfeiting films and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional nanocomposite material preparation. BACKGROUND

[0002] Core-shell composite nanoparticles have important value in frontier application fields such as coatings, sensors, anti-counterfeiting identification and photonic structural color, due to the structural rigidity of inorganic core and the functional adjustability of polymer shell. For example, in the application of anti-counterfeiting and photonic structural color, silica-polymer particles produce unique structural color effect through disordered arrangement, which can present high saturation, low angle dependence and non-fading optical appearance without dye, meeting the dual needs of security and beauty for high-end commodities, bills and certificates.

[0003] However, the emulsion polymerization method commonly used in the prior art has obvious technical problems in constructing inorganic / organic core-shell particles. Specifically, this method usually adopts the process of "dispersion first and polymerization later", that is, the inorganic particles are first dispersed in the aqueous phase, and then the organic monomer and surfactant are introduced for free radical polymerization, so that the polymer is deposited on the surface of the inorganic particles to form a shell. However, for inorganic particles such as silica which lack active sites on the surface, the traditional emulsion polymerization method has the following three shortcomings: First, nucleation is uncontrollable: monomers are prone to homogeneous polymerization in solution, forming "grape cluster" type polymer agglomerates, making it difficult to ensure uniform polymer coating on the surface of single particles; Second, the shell thickness is difficult to accurately adjust: due to the high interfacial energy between hydrophobic monomers and hydrophilic silica surface, the polymer deposition is significantly affected by kinetics, resulting in large fluctuations in shell thickness, with batch-to-batch differences of tens of nanometers; Third, the interfacial bonding force is insufficient: the polymer shell and silica core mainly rely on van der Waals force or hydrogen bonding, which is not firm, and is prone to falling off during subsequent high-temperature curing, solvent washing or mechanical rubbing, resulting in decreased structural color stability.

[0004] Therefore, when synthesizing silica-coated polymer core-shell structure materials, the existing emulsion polymerization method is difficult to simultaneously achieve single particle dispersity, nanoscale controllability of shell thickness and strong interfacial bonding force, which is a key technical problem restricting its large-scale application. SUMMARY

[0005] The purpose of the present application is to avoid the shortcomings of the prior art and provide a kind of double bond silica-coated polymer core-shell particle and its synthesis method, which realizes efficient coating and structure regulation of silica particles through effective functionalization strategy.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is a synthesis method of double bond silica-coated polymer core-shell particles, comprising the following steps: Step one, tetraethyl orthosilicate and triethoxysilane vinyl silane are added to the alcohol-water-ammonia reaction system, heated to 40-60℃, stirred for 1-3 hours, then centrifuged, washed, and freeze-dried to obtain silica particles with double bonds on the surface; The molar ratio of tetraethyl orthosilicate to triethoxysilane vinyl silane is (5-15):1. The alcohol-water-ammonia reaction system includes anhydrous ethanol, deionized water and ammonia water in a mass ratio of (1-2):(1-3):(0.5-1.5), the total liquid volume of the reaction system is 100-500 mL, and the pH value is 10-12. Step two, the silica particles with double bonds on the surface are added to a mixed solvent of ethanol and deionized water, dispersed by ultrasonic vibration, and stirred with a surfactant to obtain a mixed solution. The volume ratio of ethanol to deionized water is (1-5):(1-10), and the amount of surfactant added is 0.5-5wt% of the mass of silica particles. Step three, monomers and initiators are added to the mixed solution, heated to 60-80℃ in an inert atmosphere, and polymerized for 10-24 hours to form polymer core-shell particles. The total amount of monomers is 0.5-5 times the mass of silica particles, and the amount of initiator is 0.5-2wt% of the mass of monomers. Step four, the polymer core-shell particles are washed and dried to obtain double-bond silica-coated polymer core-shell particles.

[0007] Further, the molar ratio of tetraethyl orthosilicate to triethoxysilane vinyl silane in step one is 10:1; the triethoxysilane vinyl silane is added to the alcohol-water-ammonia reaction system in a dropwise manner, and the dropwise addition time is 10-60 min. The centrifugal speed during centrifugation is 8000-15000 rpm, and the centrifugation time is 5-30 min; the washing solvent during washing is anhydrous ethanol, and the washing frequency is 2-5 times; the freeze-drying temperature during freezing is -50 to -70℃, and the drying time is 12-48h.

[0008] Further, the alcohol-water-ammonia reaction system in step one includes anhydrous ethanol, deionized water and ammonia water, the total liquid volume of the reaction system is 100-500 mL, and the pH value is 10-12; the mass ratio of anhydrous ethanol, deionized water and ammonia water is (1-2):(1-3):(0.5-1.5), the reaction temperature is 40-60℃, the stirring speed is 300-600 rpm, and the reaction time is 2h; obtained under the conditions of reaction temperature 40-60℃, stirring speed 300-600 rpm, and reaction time 2-4h.

[0009] Furthermore, in step two, the vibration power of the ultrasonic vibration during dispersion is 100-400 W, the ultrasonic time is 10-60 min, and the frequency is 20-40 kHz. The surfactant is an anionic or nonionic surfactant, and the stirring speed is 200-600 rpm, and the stirring time is 0.5-2 h.

[0010] Furthermore, the surfactant is sodium dodecyl sulfate, polyvinylpyrrolidone, or polyethylene glycol.

[0011] Furthermore, in step three, the added monomer is one or a combination of methyl methacrylate, butyl acrylate, methyl acrylate, and ethyl acrylate. The initiator is potassium persulfate, ammonium persulfate, or sodium persulfate. The polymerization reaction is heated at 70°C and the polymerization reaction time is 12 h.

[0012] Furthermore, in step four, when washing and drying the polymer core-shell particles, the washing solvent is a mixture of ethanol and water with a volume ratio of 1:1 to 3:1, the washing number is 3 to 6 times, the centrifugation speed is 8000 to 15000 rpm, and the washing time is 5 to 15 min. The drying methods are freeze drying or vacuum drying. The temperature conditions for freeze drying are -50 to -70℃, and the time is 12-36 h; while the temperature conditions for vacuum drying are 40-60℃, and the time is 12-24 h.

[0013] The present invention also provides a method for synthesizing core-shell particles of double-bonded silica-coated polymer as described above. The core-shell particles of the double-bonded silica-coated polymer include a silica particle core having surface allyl double bond functional groups, and a polymer shell formed by in-situ polymerization on the surface of the silica particle core. The organic polymer shell is copolymerized from methacrylate and / or acrylate monomers.

[0014] Furthermore, the average particle size of the silica particles is 200-550 nm, and the thickness of the organic polymer shell is 50-300 nm.

[0015] Furthermore, the organic polymer shell and the silica particle core are covalently bonded to form a structurally stable core-shell interface.

[0016] The beneficial effects of this invention are as follows: This invention introduces polymerizable vinyl double bonds on the surface of silica, that is, by co-hydrolyzing tetraethyl orthosilicate and triethoxyvinylsilane to generate silica particles with double bond functional groups, and then coating them with a polymer shell under emulsion polymerization conditions. By introducing surface double bonds through tetraethyl orthosilicate, the interfacial reactivity of the inorganic core is significantly improved, enabling organic monomers to be grafted and polymerized in situ on the particle surface to form a stable chemically bonded shell, enhancing the interfacial affinity between the organic monomers and the inorganic core, and promoting continuous film formation of the shell. Meanwhile, by controlling the feeding ratio of monomers and silica involved in polymerization, the shell thickness can be precisely adjusted, which can control the shell thickness between tens and hundreds of nanometers. It has good process versatility and is applicable to different types of monomer systems. It also effectively suppresses secondary nucleation and agglomeration, thereby preparing double-bonded silica-coated polymer core-shell particles with a near-monodisperse particle size distribution, uniform shell, and strong bonding. This fundamentally solves the limitations of emulsion polymerization in the existing technology. The resulting particles have excellent dispersion and uniform morphology, and can be used to prepare amorphous structural color coatings or thermally responsive smart materials. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the reaction process and structure of double-bond functionalized silica particles according to the present invention; Figure 2 The infrared spectrum of the double-bonded functionalized silica particles of this invention is shown at 1635 cm⁻¹. -1 The peaks attributable to the C=C double bond vibrations of vinyl groups prove that vinyl-modified double-bonded silica particles have been synthesized. Figure 3 The microstructure of the silica-polyacrylic acid core-shell particles of the present invention is shown. In the figure: (a) is a scanning electron microscope image; (b) is a transmission electron microscope image; (c) is an energy-dispersive X-ray spectrometer image; Figure 4 The structural color materials were obtained by spraying polymer shell core-shell particles coated with double-bonded silica and double-bonded silica onto a thin film substrate, respectively. In the figure, (a) is a photo of the structural color material before folding, and (b) is a photo of the structural color material after folding. Detailed Implementation

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] To achieve the above objectives, the present invention provides the following specific embodiments: Example 1: As Figure 1 , Figure 2As shown, a method for synthesizing double-bond functionalized silica-coated polymer shell core-shell particles includes the following steps: Step 1: Add tetraethyl orthosilicate and triethoxyvinylsilane to the alcohol-water-ammonia reaction system, heat to 40-60℃, stir for 1-3 hours, and obtain silica particles with double bonds on the surface by centrifugation, washing, and freeze-drying; the reaction process and structural schematic diagram are shown below. Figure 1 As shown; its infrared structural characterization is as follows Figure 2 As shown, at 1635 cm -1 The peaks attributable to the C=C double bond vibrations of vinyl groups prove that vinyl-modified double-bonded silica particles have been synthesized. The molar ratio of tetraethyl orthosilicate to triethoxyvinylsilane is (5-15):1, preferably 10:1; the triethoxyvinylsilane is added by dropping, and the dropping time is 10-60 min. An alcohol-water-ammonia reaction system includes anhydrous ethanol, deionized water, and ammonia. The total liquid volume of the reaction system is 100-500 mL, and the pH value is 10-12. The mass ratio of anhydrous ethanol, deionized water, and ammonia is (1-2):(1-3):(0.5-1.5). The reaction temperature is 40-60℃, the stirring speed is 300-600 rpm, and the preferred reaction time is 2 h. The centrifugation speed is 8000-15000 rpm, and the centrifugation time is 5-30 min; the washing solvent is anhydrous ethanol, and the washing number is 2-5 times; the freeze-drying temperature is -50 to -70℃, and the drying time is 12-48 h.

[0020] Step 2: Add the obtained silica particles to a mixed solvent of ethanol and deionized water, disperse them by ultrasonic vibration, add a surfactant and stir. Specifically: The volume ratio of ethanol to deionized water is (1-5):(1-10); the ultrasonic vibration for dispersion has a vibration power of 100-400 W, an ultrasonic time of 10-60 min, and a frequency of 20-40 kHz; the surfactant is anionic or nonionic, and its addition amount is 0.5-5 wt% of the mass of the silica particles; the stirring conditions are 200-600 rpm and a stirring time of 0.5-2 h. The surfactant is preferably sodium dodecyl sulfate, polyvinylpyrrolidone, or polyethylene glycol.

[0021] Step 3: Add monomers and initiators, and heat to 60-80℃ under an inert atmosphere to carry out the polymerization reaction for 10-24 hours to form polymer core-shell particles; The added monomers are methyl methacrylate, butyl acrylate, methyl acrylate, ethyl acrylate, or combinations thereof, and the total amount of monomers is 0.5-5 times the mass of silica particles; the initiator is potassium persulfate, ammonium persulfate, or sodium persulfate, and the amount of initiator is 0.5-2 wt% of the monomer mass; the polymerization reaction heating temperature is selected as 70℃, and the time is preferably 12 h.

[0022] Step 4: Wash and dry the polymer core-shell particles to obtain polymer core-shell particles coated with double-bonded silica, specifically as follows: The polymer core-shell particles are washed and dried: the washing solvent is a mixture of ethanol and water, with a volume ratio of ethanol to water of 1:1-3:1, and the washing is performed 3-6 times. The centrifugation speed is 8000-15000 rpm and the time is 5-15 min. The drying method is freeze drying or vacuum drying. The freeze drying conditions are -50 to -70℃ for 12-36 h, and the vacuum drying conditions are 40-60℃ for 12-24 h.

[0023] Example 2: The present invention also provides a core-shell particle of double-bonded silica coated with polymer prepared by the method of Example 1, comprising a silica particle core having surface allyl double bond functional groups, and a polymer shell formed by in-situ polymerization on the surface of the silica particle core, wherein the organic polymer shell is copolymerized from methacrylate and / or acrylate monomers.

[0024] The average particle size of the silica particles is 200-550 nm, and the thickness of the organic polymer shell is 50-300 nm.

[0025] Furthermore, the organic polymer shell and the silica particle core are bonded together by covalent bonds to form a structurally stable core-shell interface.

[0026] like Figure 3 , Figure 4 As shown, to further illustrate the technical solution and technical effects of the present invention, the following specific examples are provided: Specific Example 1: Preparation of double-bond functionalized silica particles. 78.9 g of anhydrous ethanol, 125.1 g of deionized water, 61.2 g of ammonia, and 52.1 g of tetraethyl orthosilicate (TEOS) were sequentially added to a three-necked flask. After stirring in a 40°C water bath for 5 minutes, 4.75 g of triethoxyvinylsilane (TEVS) was added dropwise, and the reaction continued for 4 hours. The resulting product was centrifuged at 8000 rpm, washed with ethanol, and freeze-dried to obtain silica powder with allyl double bonds on its surface.

[0027] Specific Example 2: Construction of Core-Shell Particles. Taking a combination of methyl methacrylate (MMA) and butyl acrylate (BA) as the shell monomers as an example, 1 g of double-bond functionalized silica particles were dispersed in an aqueous solution of 15 g ethanol and 0.01 g sodium dodecyl sulfate (SDS), and a homogeneous suspension was formed by sonication. A mixture of 0.1 g potassium persulfate (KPS), 10 g deionized water, and monomers was added, with a mass ratio of MMA:BA = 2:1 and a total mass of 1 g. The mixture was heated to 70°C under a nitrogen atmosphere and polymerized for 10 hours. After the reaction, the particles were centrifuged, washed, and freeze-dried to obtain polymer-coated core-shell particles.

[0028] Experimental verification showed that the silica coating experiment without TEVS treatment was repeated in Specific Example 2 above, but using pure silica particles that had not undergone TEVS treatment, while keeping other conditions the same. The results showed that the shell film was uneven, the particles were significantly aggregated, and the shell thickness varied greatly.

[0029] Comparing different monomer types, Example 2 was repeated using acrylic acid (PAA) and MMA as shell monomer systems, and both could form a complete core-shell structure. Figure 3 The microstructure of the obtained silica-polyacrylic acid core-shell particles is shown in (a) as a scanning electron microscope image, which shows that the particles have a uniform morphology and an adhesion layer belonging to PAA between the particles; (b) as a transmission electron microscope image, which shows that the particles have a distinct core-shell structure with a shell thickness of about 15 nm; (c) as the X-ray energy dispersive spectroscopy analysis corresponding to (b), where red represents silicon and green represents carbon, showing that the core is mainly silicon and the shell is mainly carbon.

[0030] Specific Example 3: To prepare structural color materials by spraying the obtained particles onto a substrate, weigh 0.05 g of silica particles or core-shell particles, 0.5 g of anhydrous ethanol, and 1% of carbon black by mass of the particle powder. Use a CNC ultrasonic cleaner to ultrasonically treat the particles for 30 min and mix them evenly to obtain a particle suspension for later use.

[0031] The obtained particle / carbon black / anhydrous ethanol suspension was added to a spray gun and sprayed onto the substrate surface under a pressure of 0.04 MPa. The spray gun was about 2 cm away from the substrate, and the spray gun moving speed was about 1 cm / s. The spraying was stopped after the suspension in the spray gun was used up, resulting in a structural color film.

[0032] Figure 4 The structural color materials were obtained by spraying polymer-shell core-shell particles coated with double-bonded silica onto a thin film substrate, respectively. (a) shows the structural color material before folding; (b) shows the structural color material after folding. It can be seen that the sprayed structural color is bright and vivid, and the structural color material with polymer-shell core-shell particles does not show obvious peeling after folding, indicating a significant improvement in mechanical stability.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synthesizing core-shell particles of polymers coated with double-bonded silica, characterized in that, Includes the following steps: Step 1: Add tetraethyl orthosilicate and triethoxyvinylsilane to the alcohol-water-ammonia reaction system, heat to 40-60℃, stir for 1-3 hours, and then obtain silica particles with double bonds on the surface by centrifugation, washing and freeze drying. The molar ratio of tetraethyl orthosilicate to triethoxyvinylsilane is (5-15):

1. The alcohol-water-ammonia reaction system includes anhydrous ethanol, deionized water and ammonia in a mass ratio of (1-2):(1-3):(0.5-1.5), the total liquid volume of the reaction system is 100-500 mL, and the pH value is 10-12. Step 2: Add silica particles with double bonds on their surface to a mixed solvent of ethanol and deionized water, disperse them by ultrasonic vibration, add a surfactant and stir to obtain a mixed solution; The volume ratio of ethanol to deionized water is (1-5):(1-10); the amount of surfactant added is 0.5-5 wt% of the mass of the silica particles. Step 3: Add monomers and initiators to the mixed solution, and heat to 60-80℃ under an inert atmosphere to carry out the polymerization reaction for 10-24 hours to form polymer core-shell particles; The total amount of monomers is 0.5-5 times the mass of silica particles; the amount of initiator is 0.5-2 wt% of the monomer mass. Step 4: Wash and dry the polymer core-shell particles to obtain polymer core-shell particles coated with double-bonded silica.

2. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 1, characterized in that, In step one, the molar ratio of tetraethyl orthosilicate to triethoxyvinylsilane is 10:1; the triethoxyvinylsilane is added to the alcohol-water-ammonia reaction system by dropping, and the dropping time is 10-60 min. The centrifugation speed is 8000-15000 rpm and the centrifugation time is 5-30 min; the washing solvent is anhydrous ethanol and the washing is performed 2-5 times; the freeze-drying temperature is -50 to -70℃ and the drying time is 12-48 h.

3. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 1, characterized in that, The alcohol-water-ammonia reaction system described in step one includes anhydrous ethanol, deionized water, and ammonia. The total liquid volume of the reaction system is 100-500 mL, and the pH value is 10-12. The mass ratio of anhydrous ethanol, deionized water, and ammonia is (1-2):(1-3):(0.5-1.5). The reaction temperature is 40-60℃, the stirring speed is 300-600 rpm, and the reaction time is 2 h. This is obtained under the conditions of a reaction temperature of 40-60℃, a stirring speed of 300-600 rpm, and a reaction time of 2-4 h.

4. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 1, characterized in that, In step two, the ultrasonic vibration power for dispersion is 100-400 W, the ultrasonic time is 10-60 min, and the frequency is 20-40 kHz. The surfactant is an anionic or nonionic surfactant, and the stirring speed is 200-600 rpm, and the stirring time is 0.5-2 h.

5. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 4, characterized in that, The surfactant is sodium dodecyl sulfate, polyvinylpyrrolidone, or polyethylene glycol.

6. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 1, characterized in that, In step three, the added monomer is one or a combination of methyl methacrylate, butyl acrylate, methyl acrylate, and ethyl acrylate. The initiator is potassium persulfate, ammonium persulfate, or sodium persulfate. The polymerization reaction is heated at 70°C and the polymerization reaction time is 12 h.

7. The method for synthesizing core-shell particles of a polymer coated with double-bonded silica as described in claim 1, characterized in that, In step four, when washing and drying the polymer core-shell particles, the washing solvent is a mixture of ethanol and water with a volume ratio of 1:1 to 3:1, the washing is performed 3 to 6 times, the centrifugation speed is 8000 to 15000 rpm, and the washing time is 5 to 15 minutes. The drying methods are freeze drying or vacuum drying. The temperature conditions for freeze drying are -50 to -70℃, and the time is 12-36 hours; while the temperature conditions for vacuum drying are 40-60℃, and the time is 12-24 hours.

8. A core-shell particle of a double-bonded silica-coated polymer prepared by a method for synthesizing core-shell particles of a double-bonded silica-coated polymer as described in any one of claims 1 to 7, characterized in that, It includes a silica particle core with surface allyl double bond functional groups, and a polymer shell formed by in-situ polymerization on the surface of the silica particle core, wherein the organic polymer shell is copolymerized from methacrylate and / or acrylate monomers.

9. The core-shell particles of a polymer coated with double-bonded silica as described in claim 8, characterized in that, The average particle size of the silica particles is 200-550 nm, and the thickness of the organic polymer shell is 50-300 nm.

10. The core-shell particles of a polymer coated with double-bonded silica as described in claim 8, characterized in that, The organic polymer shell and the silica particle core are covalently bonded to form a structurally stable core-shell interface.

Images