A method for preparing a high-stability W / O / W multiple Pickering emulsion based on Janus particles

Abstract

The application discloses a method for preparing a high-stability W / O / W type multiple Pickering emulsion based on Janus particles and belongs to the technical field of colloid and interface chemistry. Different chain length alkyl silane is used to modify SiO2 to prepare Janus particles with different hydrophilicity and hydrophobicity, the multiple emulsion is co-stabilized, different types of Janus particles are adsorbed on different oil-water interfaces, the interfacial activity and amphiphilicity of the Janus particles are fully exerted, and the high-stability multiple emulsion is prepared. The multiple emulsion has excellent stability, is stable under conditions of long-term storage, strong acid and strong base and high-concentration electrolyte, and can effectively expand the practical application of the multiple emulsion.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-stability W / O / W type multiple Pickering emulsion based on Janus particles, and belongs to the technical field of colloid and interface chemistry. Background Art

[0002] Multiple emulsions (MPEs), also known as composite emulsions, are multilayer emulsions formed by dispersing one emulsion in another continuous phase. They combine the advantages of traditional oil-in-water and water-in-oil emulsions, enabling the simultaneous encapsulation of both water-soluble and oil-soluble substances. Multiple emulsions are often classified as water-in-oil-in-water (W / O / W) and oil-in-water-in-oil (O / W / O) types. Their unique structure has led to their widespread application in the food industry, cosmetics, biomedicine, and agriculture. The stability of multiple emulsions is controlled by multiple factors, including their preparation process and emulsifiers, oil phase, and aqueous phase. Because multiple emulsions are more complex than single emulsions and their surface excess free energy is thermodynamically unstable, the preparation of stable and controllable multiple emulsions is key to their application.

[0003] Emulsifiers for multiple emulsions primarily include small-molecule surfactants, high-polymer emulsifiers, natural macromolecules, and colloidal particles. Multiple emulsions stabilized by small-molecule surfactants often lack stability. High-polymer emulsifiers offer excellent stabilization and swelling properties, significantly improving emulsion stability but exhibiting poor biosafety. Using natural macromolecules alone requires high concentrations to achieve stable multiple emulsions.

[0004] With the deepening of research on Pickering emulsions, Pickering emulsions stabilized by solid particles have higher stability because the particles adsorbed on the interface are not easy to desorb. Among them, amphiphilic Janus particles refer to colloidal particles with two different surface properties. The emulsions stabilized by them have excellent stability. Their adsorption energy at the oil-water interface is three times that of homogeneous particles. The surface asymmetry of Janus particles can accurately control their hydrophilicity and hydrophobicity. Some scholars have prepared Janus particles with medium wettability (θ ow ≈90°) to stabilize multiple emulsions in one step. Although this process is simple and convenient, there are some unfavorable factors such as the need to strictly control the wettability of the particles, the competition between the particles at the two interfaces, the poor reproducibility of the emulsion, and the difficulty in controlling the distribution of each phase (such as W1 / O / W2 type). Summary of the Invention

[0005] To solve the above problems, the application provides a method for preparing a high-stability multi-Pickering emulsion based on Janus particles. Different chain length alkyl silane is used to modify SiO2 to prepare Janus particles with different hydrophilic and hydrophobic properties, which are used to stabilize the multi-emulsion together, different types of Janus particles are adsorbed on different oil-water interfaces, the interfacial activity and amphiphilicity of the Janus particles are fully utilized, and a high-stability multi-emulsion is prepared, thereby effectively expanding the practical application of the multi-emulsion.

[0006] The first object of the application is to provide a method for preparing a multi-Pickering emulsion, which comprises the following steps:

[0007] (1) dispersing amino-silica particles (SiO2) in a toluene solution, adding octa-silane and triethylamine for reaction, and washing and drying to obtain hydrophilic Janus-SiO2 nanoparticles; wherein the mass ratio of the amino-silica particles, the octa-silane and the triethylamine is 1:2-3:1.2-1.5; and the dosage ratio of the amino-silica particles to the toluene solution is 1g:40-60mL;

[0008] dispersing amino-silica particles in a toluene solution, adding octadecyl silane and triethylamine for reaction, and washing and drying to obtain hydrophobic Janus-SiO2 nanoparticles; wherein the mass ratio of the amino-silica particles, the octadecyl silane and the triethylamine is 1:7-10:1.2-1.5; and the dosage ratio of the amino-silica particles to the toluene solution is 1g:40-60mL;

[0009] (2) mixing and dispersing the hydrophobic Janus-SiO2 nanoparticles with liquid paraffin, adding water, and homogenizing to obtain a water-in-oil primary emulsion (W / O primary emulsion); wherein the dosage ratio of the hydrophobic Janus-SiO2 nanoparticles, the liquid paraffin and the water is 1g:30-35mL:5-10mL;

[0010] (3) mixing and dispersing the hydrophilic Janus-SiO2 nanoparticles with water, adding the water-in-oil primary emulsion, and homogenizing to obtain a multi-Pickering emulsion (W / O / W emulsion); wherein the dosage ratio of the hydrophilic Janus-SiO2 nanoparticles, the water and the water-in-oil primary emulsion is 1g:80-100mL:80-100mL.

[0011] In an embodiment, the water can be deionized water.

[0012] In an embodiment, the preparation method of the amino-silica particles in step (1) comprises:

[0013] (1) dispersing silica particles in a cationic surfactant aqueous solution and ultrasonicating; adding paraffin wax, heating and melting, and homogenizing to obtain an oil-in-water emulsion; cooling the oil-in-water emulsion, washing, and drying to obtain paraffin-silica particle balls;

[0014] (2) dispersing paraffin-silica particles in a methanol solution, adding bisaminosilane, and reacting; adding chloroform to wash away the paraffin, washing, and drying to obtain amino-silica particles;

[0015] Optionally, the concentration of the cationic surfactant aqueous solution in step (1) is 0.05 to 0.1 g / L;

[0016] Optionally, in step (1), the ratio of the silicon dioxide particles, the cationic surfactant aqueous solution, and the paraffin wax is 1 g: 50-80 mL: 5-10 g;

[0017] Optionally, the homogenization in step (1) is performed at 13000-17000 rpm for 8-12 min;

[0018] Optionally, the heating and melting in step (1) is heating at 70-80° C. until the paraffin is completely melted;

[0019] Optionally, in step (2), the mass ratio of paraffin-silica particles to bisaminosilane is 1:180-200;

[0020] Optionally, in step (2), the ratio of paraffin wax-silica particles, methanol, and chloroform is 1 g: 2-6 mL: 10-15 mL;

[0021] Optionally, the reaction in step (2) is carried out at 150-250 rpm for 10-14 hours.

[0022] In one embodiment, the cationic surfactant in step (1) includes one or more of lauryltrimethylammonium bromide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and dihexadecyldimethylammonium chloride;

[0023] In step (1), the bisaminosilane includes one or more of N-aminoethyl-γ-aminopropyltrimethoxysilane, N-aminoethyl-γ-aminopropyltriethoxysilane, N-aminoethyl-3-aminopropylmethyldimethoxysilane, and N-(2-aminoethyl)-3-(trimethoxysilyl)propylamine;

[0024] The reaction in step (1) is carried out at room temperature for 2 to 4 hours.

[0025] In one embodiment, the octacarbosilane includes n-octyltrimethoxysilane, n-octyltriethoxysilane, trimethoxy(octyl)silane;

[0026] Octadecylsilane includes octadecyltrichlorosilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane.

[0027] In one embodiment, the homogenization in step (2) is carried out at 9000-13000 rpm for 2-3 min; and the homogenization in step (3) is carried out at 15000-17000 rpm for 2-3 min.

[0028] The second object of the present invention is to provide a multiple Pickering emulsion prepared by any of the above methods.

[0029] The third object of the present invention is to provide the use of the above-mentioned multiple Pickering emulsion in the preparation of food, medicine or cosmetics.

[0030] In one embodiment, the use in preparing food includes preparing emulsifiers and preservatives;

[0031] Applications in the preparation of medicines include the preparation of drug delivery carriers and drug solvents;

[0032] Applications in the preparation of cosmetics include the preparation of creams, lotions, and essences.

[0033] A fourth object of the present invention is to provide a method for simultaneously improving the stability, strong acid and alkali tolerance, and high-concentration electrolyte tolerance of a multiple Pickering emulsion, wherein the multiple Pickering emulsion is prepared using hydrophilic Janus-SiO2 nanoparticles and hydrophobic Janus-SiO2 nanoparticles, comprising the steps of:

[0034] (1) dispersing amination silica particles in a toluene solution, adding octacarbon silane and triethylamine to react, washing, and drying to obtain hydrophilic Janus-SiO2 nanoparticles; wherein the mass ratio of amination silica particles, octacarbon silane, and triethylamine is 1:2-3:1.2-1.5; and the amount ratio of amination silica particles to toluene solution is 1 g:40-60 mL;

[0035] The aminated silica particles are dispersed in a toluene solution, octadecylsilane and triethylamine are added for reaction, and the hydrophobic Janus-SiO2 nanoparticles are washed and dried. The mass ratio of the aminated silica particles, octadecylsilane, and triethylamine is 1:7-10:1.2-1.5. The amount ratio of the aminated silica particles to the toluene solution is 1 g:40-60 mL.

[0036] (2) mixing and dispersing hydrophobic Janus-SiO2 nanoparticles with liquid paraffin; adding water and homogenizing to obtain water-in-oil colostrum; wherein the amount ratio of hydrophobic Janus-SiO2 nanoparticles, liquid paraffin and water is 1 g: 30-35 mL: 5-10 mL;

[0037] (3) Mixing the hydrophilic Janus-SiO2 nanoparticles with water and dispersing them; adding water-in-oil colostrum and homogenizing to obtain a multiple Pickering emulsion; wherein the amount ratio of the hydrophilic Janus-SiO2 nanoparticles, water and water-in-oil colostrum is 1 g: 80-100 mL: 80-100 mL.

[0038] In one embodiment, the reaction in step (1) is carried out at room temperature for 2 to 4 hours;

[0039] In step (2), the homogenization is carried out at 9000-13000 rpm for 2-3 min; and in step (3), the homogenization is carried out at 15000-17000 rpm for 2-3 min.

[0040] Beneficial effects of the present invention:

[0041] (1) The present invention uses Janus particles with different hydrophilic and hydrophobic properties as emulsifiers to stabilize multiple emulsions. During the particle modification process, only the hydrophobic alkylsilane chain length is changed. Compared with the one-step stabilization of multiple emulsions by Janus particles, there is no need to strictly control the hydrophilic-lipophilic balance of the particles. The prepared multiple emulsions can regulate the properties of the internal and external aqueous phases.

[0042] (2) The multiple emulsions prepared by the present invention have a distinct structure, uniform particle size distribution, high internal phase content, and Janus particles of different hydrophilicity and hydrophobicity are arranged at different oil-water interfaces, fully utilizing the interfacial activity and amphiphilicity of the Janus particles. The prepared multiple emulsions have excellent stability and remain stable under conditions such as long-term storage, strong acid and strong base, and high electrolyte concentration, which can effectively expand the practical application of multiple emulsions.

[0043] Specifically:

[0044] (1) The particle size of the emulsion prepared by the present invention does not change significantly after storage at room temperature for 60 days;

[0045] (2) When the pH value of the emulsion prepared by the present invention is 1.51 and 13.06, the emulsion remains stable, does not break, and the multiple structures are clearly present;

[0046] (3) The emulsion prepared by the present invention is in a high concentration electrolyte (3.6×10 5 mg / L NaCl), the structural stability is not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the effect of the amount of octylsilane added on the contact angle of hydrophilic Janus-SiO2 particles;

[0048] Figure 2 The infrared spectra of the prepared hydrophilic and hydrophobic Janus-SiO2, amino-modified SiO2 and unmodified SiO2;

[0049] Figure 3 The thermogravimetric curves of the prepared hydrophilic and hydrophobic Janus-SiO2 and unmodified SiO2;

[0050] Figure 4 This is a microscopic image of the emulsion prepared after the oil and water phases were stained with Nile red and sodium fluorescein respectively, observed under an upright fluorescence microscope;

[0051] Figure 5 The appearance and microscopic image of the multiple emulsion after being placed at room temperature for 60 days;

[0052] Figure 6 The appearance and microscopic images of multiple emulsions under acidic and alkaline conditions;

[0053] Figure 7 The appearance and microscopic image of multiple emulsions at saturated NaCl concentration;

[0054] Figure 8 This is the effect of octadecylsilane addition on the contact angle and emulsification performance of hydrophobic Janus-SiO2 particles;

[0055] Figure 9 The appearance of W / O emulsions stabilized by Janus-SiO2 particles with different hydrophobicity concentrations;

[0056] Figure 10 Appearance and microscopic images of W / O / W multiple emulsions prepared for different hydrophilic Janus-SiO2 particle concentrations;

[0057] Figure 11 The charge of hydrophilic Janus-SiO2 particles at different pH values. DETAILED DESCRIPTION

[0058] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0059] Test method:

[0060] 1. Emulsion particle size detection method:

[0061] Take 10 μL of emulsion and disperse it in 3 mL of deionized water. Drop it on a glass slide and use an ultra-depth-of-field microscope to observe and photograph the droplet morphology. Use Nano Measurer software to calculate the emulsion particle size.

[0062] 2. Emulsion emulsification rate detection method

[0063] Measure the total height of the emulsion layer and the system respectively, and substitute into the formula EI=H e / H t ×100% to calculate the emulsification rate (EI); H e is the height of the upper emulsion, H t is the total height of the liquid.

[0064] 3. Particle infrared detection method

[0065] 30 mg of the particle powder was ground with KBr and then pressed into a pellet. The composition changes on the particle surface were analyzed using a Fourier transform infrared spectrometer.

[0066] 4. Particle thermogravimetric detection method

[0067] About 7 mg of the particles were weighed into a crucible, and the thermal stability of the particles was measured using a thermogravimetric analyzer in a nitrogen atmosphere by heating from 30° C. to 850° C. at a rate of 15° C. / min.

[0068] The raw materials used in the embodiment are:

[0069] Hexadecyltrimethylammonium bromide was purchased from MacLean Biochemical Technology Co., Ltd., CAS No. 57-09-0;

[0070] SiO2 was purchased from Aladdin Biochemical Technology Co., Ltd., CAS No. 7631-86-9;

[0071] Bisaminosilane was purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., CAS No. 1760-24-3;

[0072] Octacarbon silane was purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., CAS No. 3069-40-7;

[0073] Octadecanosilane was purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., CAS No. 112-04-9;

[0074] Triethylamine was purchased from Sinopharm Chemical Reagent Co., Ltd., CAS No. 121-44-8;

[0075] Liquid paraffin was purchased from Sinopharm Chemical Reagent Co., Ltd. with CAS number 8012-95-1.

[0076] Example 1: Preparation of hydrophilic Janus-SiO2

[0077] Prepare hydrophilic Janus-SiO2 as follows:

[0078] (1) 0.5 g of SiO2 was dispersed in 40 mL of 0.08 g / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonicated for 20 min. 5 g of sliced ​​paraffin was added and the mixture was completely melted in an 80°C water bath and homogenized at 15,000 rpm for 10 min to obtain an O / W emulsion. The paraffin was quickly solidified in an ice bath, and the residual CTAB and free SiO2 were washed to remove the residual CTAB and free SiO2. The mixture was then dried to obtain paraffin-silica particle spheres.

[0079] (2) 10 g of paraffin-silica granules were dispersed in 30 mL of methanol solution, 0.06 g of bisaminosilane was added, and the mixture was stirred slowly (200 rpm) for 12 h. The paraffin was washed away with 100 mL of chloroform, and the mixture was centrifuged and washed three times with ethanol. After drying, the aminated SiO2 powder was obtained.

[0080] (3) Take 0.1g of amino SiO2 and disperse it in 5mL of toluene solution, add 0.05g of octacarbon silane and triethylamine (the mass ratio of octacarbon silane and triethylamine is 1:1.5), react at room temperature (15-30℃) for 4h, wash it three times with toluene by centrifugation, and dry it to obtain hydrophilic Janus-SiO2 nanoparticles.

[0081] The effects of different addition amounts of octacarbon silane on the contact angle were tested. The results are as follows: Figure 1 As shown, the results show that with the increase of octacarbon silane, the hydrophobicity of the particles gradually increases. When the addition amount reaches 0.05g, the increase in the hydrophobic angle slows down, that is, 0.05g is taken as the optimal addition amount, at which time the particle-water-air contact angle value is 52.7°.

[0082] Example 2: Preparation of hydrophobic Janus-SiO2

[0083] Prepare hydrophobic Janus-SiO2 as follows:

[0084] (1) 0.5 g of SiO2 was dispersed in 40 mL of 0.08 g / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution and ultrasonicated for 20 min. 5 g of sliced ​​paraffin was added and the mixture was completely melted in an 80°C water bath and homogenized at 15,000 rpm for 10 min to obtain an O / W emulsion. The paraffin was quickly solidified in an ice bath, and the residual CTAB and free SiO2 were washed to remove the residual CTAB and free SiO2. The mixture was then dried to obtain paraffin-silica particle spheres.

[0085] (2) 10 g of paraffin-silica granules were dispersed in 30 mL of methanol solution, 0.06 g of bisaminosilane was added, and the mixture was stirred slowly (200 rpm) for 12 h. The paraffin was washed away with 100 mL of chloroform, and the mixture was centrifuged and washed three times with ethanol. After drying, the aminated SiO2 powder was obtained.

[0086] (3) Take 0.1g of amino SiO2 and disperse it in 5mL of toluene solution, add 0.015g of octadecylsilane and triethylamine (the mass ratio of octadecylsilane and triethylamine is 1:1.5), react at room temperature for 2h, centrifuge and wash three times with toluene, and dry to obtain hydrophobic Janus-SiO2 nanoparticles.

[0087] The contact angle of hydrophobic Janus-SiO2 nanoparticles was tested. The results showed that when the addition amount of octadecylsilane was 0.015 g, the particle-water-air contact angle value was 114.7°.

[0088] The amination SiO2 powder, hydrophilic Janus-SiO2 nanoparticles and hydrophobic Janus-SiO2 nanoparticles prepared in Example 1 and Example 2 were taken and their infrared spectra and thermogravimetric curves were detected. The results were as follows: Figure 2 and Figure 3 shown.

[0089] The infrared spectroscopy results showed that compared with the unmodified SiO2, the amino SiO2, hydrophilic and hydrophobic Janus-SiO2 showed a significant difference at 2850 cm -1 and 2929cm -1 The characteristic peaks at are the symmetric and antisymmetric stretching vibrations of the C-H bond. The thermogravimetric results show that before 200°C, the unmodified SiO2, the amino-treated SiO2 and the two Janus-SiO2 particles all show a relatively obvious weight loss, at which time the adsorbed water on the surface of the particles is lost. The weight loss of the two Janus-SiO2 particles around 300°C is mainly due to the decomposition of the amino group, and after 400°C, the alkyl chain decomposes, indicating that the diaminosilane and alkylsilane are successfully grafted on the SiO2 surface.

[0090] Example 3: Preparation of W / O / W Multiple Pickering Emulsion

[0091] 1. Prepare W / O / W multiple Pickering emulsions as follows:

[0092] (1) 0.18 g of the hydrophobic Janus-SiO2 prepared in Example 2 was added to 6 mL of liquid paraffin and ultrasonicated for 5 min until completely dispersed. 1.5 mL of deionized water (W2) was then added and homogenized at 13,000 rpm for 3 min to obtain W / O colostrum;

[0093] (2) Take 0.045 g of hydrophilic Janus-SiO2 prepared in Example 1 into 3 mL of deionized water (W1) and ultrasonic to completely disperse, then add 3 g of W / O primary emulsion, and homogenize at 16000 r / min for 2 min to obtain about 5 mL of W2 / O / W1 multiple emulsion.

[0094] 2. Emulsion property detection

[0095] (1) Particle size

[0096] Take the W2 / O / W1 multiple emulsion prepared in Example 3, and use a super-depth microscope to observe the droplet morphology, and use Nano Measurer 1.2 software to count the droplet particle size.

[0097] The results show that the particle size of the multiple emulsion is 52.4 μm, the emulsion particle size distribution is uniform, and the multiple structure is obvious.

[0098] (2) Emulsion type

[0099] Before emulsion preparation, deionized water is dyed with fluorescein sodium, and liquid paraffin is dyed with Nile red, and the dyeing agent concentration is 0.1 wt%, after homogenization, the emulsion is observed under a fluorescence microscope, and the excitation wavelength is 480 nm and 552 nm respectively.

[0100] The results are shown in Figure 4 , which show that the inner and outer phases of the emulsion are green, and the middle phase is red, indicating that the prepared emulsion has obvious W / O / W multiple structure.

[0101] (3) Long-term stability detection

[0102] Take the W2 / O / W1 multiple emulsion prepared in Example 3, and place it at room temperature for 60 days, during which the appearance and microstructure of the emulsion are observed, the total height of the emulsion layer and the liquid is measured, and the emulsification rate (EI) is calculated according to the formula EI = H e / H t × 100%, wherein H e is the height of the upper emulsion after the system is stable, and H t is the total height of the liquid.

[0103] The results are shown in Figure 5 , which show that the emulsion emulsification rate is 63.17%, which is lower than that of the freshly prepared emulsion (80.49%), but the average particle size of the emulsion is about 57.2 μm, which has not changed significantly, and the experimental results show that the prepared multiple emulsion has good long-term stability.

[0104] (4) Acid and alkali resistance detection

[0105] The pH of the water phase W1 and W2 was changed to 1.51 (as an acidic condition) and 13.06 (as an alkaline condition) respectively, and the acidic W / O / W multiple emulsion (prepared from the water phase with pH of 1.51, liquid paraffin, hydrophobic Janus-SiO2 and hydrophilic Janus-SiO2) and the alkaline W / O / W multiple emulsion (prepared from the water phase with pH of 13.06, liquid paraffin, hydrophobic Janus-SiO2 and hydrophilic Janus-SiO2) were prepared according to the steps of Example 1, Example 2 and Example 3, and the charging conditions of the emulsions at different pH were determined by using the Zeta potential and particle size analyzer.

[0106] The results are shown in Figure 6 , and the emulsions can be formed under both acidic and alkaline conditions, although some particles are precipitated (slightly turbid), the emulsion remains stable, does not break and the multiple structure is obvious. When the pH of the water phase is 1.51, the average particle size of the emulsion is 80.3 μm; when the pH of the water phase is 13.06, the average particle size of the emulsion is 65.7 μm.

[0107] The stability (agglomeration, precipitation) of the particles in the water phase is related to the absolute value of the zeta potential of the particles. The greater the absolute value, the greater the electrostatic repulsion between the particles, the more stable the particles are, and the closer the absolute value to 0, the easier the agglomeration and precipitation. The detection results of the zeta potential of the hydrophilic Janus-SiO2 nanoparticles are shown in Figure 11 . The results show that the absolute value of the zeta potential of the particles gradually decreases with the increase of the pH. When the pH is less than 9, the zeta potential value is greater than 10 mV, at this time the absolute value is large, and there is no particle precipitation in the emulsion system. When the pH is about 13, the zeta potential is about 0, at this time the electrostatic repulsion between the particles is small, and the particles are easy to agglomerate and precipitate, the water phase in the emulsion system is turbid, the number of particles in the emulsion layer is reduced, and the particle size is increased. Under the acidic condition of the water phase, the protonation of the amino group on the surface of the particles is enhanced, and the hydrophilicity is increased, which also causes the precipitation of the particles in the system. The results show that the W / O / W multiple emulsion prepared in Example 3 has excellent acid and alkali resistance.

[0108] (5) Resistance to electrolytes

[0109] On the basis of Example 3, the deionized water in steps (1) and (2) was changed to NaCl aqueous solution with a concentration of 10 3 , 10 4 , 10 5 , 3.6×10 5 mg / L (the solution with a concentration of 3.6×10 5 mg / L is a saturated solution), and the remaining steps were consistent with Example 3, to prepare W / O / W multiple emulsions containing different concentrations of electrolytes, and the appearance and particle size of the emulsions were detected.

[0110] When the NaCl concentration is 3.6×10 5 mg / L, the result is as follows Figure 7 As shown, the results showed that saturated NaCl concentration had no effect on emulsion formation, and the average droplet size was 62.3 μm, indicating that the prepared Janus particle-stabilized multiple Pickering emulsion had excellent electrolyte resistance.

[0111] Comparative Example 1: Changing the amount of octadecylsilane

[0112] On the basis of Example 2, the amount of octadecylsilane was changed to 0.005 g, 0.015 g, 0.022 g, and 0.04 g, and the remaining steps were consistent with Example 2 to prepare hydrophobic Janus-SiO2.

[0113] The hydrophobic Janus-SiO2 prepared in Comparative Example 1 and Example 2 was used to prepare an emulsion in the following steps:

[0114] 0.03 g of hydrophobized Janus-SiO2 was added to 3 mL of liquid paraffin and ultrasonicated until the particles were completely dispersed. Then 3 mL of deionized water was added and homogenized at 13000 r / min for 3 min.

[0115] The results are as follows Figure 8 As shown, the results show that when the addition amount is 0.005g, the particle-water-air contact angle is less than 90°, and the emulsion is of O / W type; when the addition amount is greater than 0.04g, the contact angle value is 137.6°. After the particle emulsifier prepared under this condition is homogenized at high speed, the oil and water phases are separated and no emulsion is formed; it can be seen that if the addition amount of octadecylsilane is too little or too much, a stable W / O emulsion cannot be formed.

[0116] Comparative Example 2: Changing the amount of hydrophobic Janus-SiO2 added

[0117] On the basis of Example 3, the addition amount of hydrophobic Janus-SiO2 in step (1) was changed to 0.06g, 0.12g, 0.18g, and 0.24g to obtain W / O emulsions with hydrophobic particle concentrations of 1wt%, 2wt%, 3wt%, and 4wt%, respectively. The remaining steps were consistent with Example 3.

[0118] Emulsion results such as Figure 9 As shown, the volume ratio of oil and water (i.e., liquid paraffin and deionized water W2) is kept unchanged (4:1). When the concentration of hydrophobic Janus-SiO2 particles is less than 3wt%, oil phase precipitates in the upper layer, and when it is greater than or equal to 3wt%, no water phase or oil phase precipitates; when the particle concentration is 4wt%, the emulsion viscosity is very high and there is no fluidity, which is not conducive to the removal of W / O colostrum. Taking all factors into consideration, the concentration of hydrophobic Janus-SiO2 particles is 3wt%.

[0119] Comparative Example 3: Change the amount of hydrophilic Janus-SiO2

[0120] On the basis of Example 3, the amount of hydrophilic Janus-SiO2 added in step (2) was changed to 0.0075 g, 0.015 g, 0.03 g, 0.045 g, and 0.0525 g, respectively, to obtain W / O / W multiple emulsions with hydrophilic particle concentrations of 0.25 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, and 1.75 wt%, respectively, and the remaining steps were consistent with Example 3.

[0121] The emulsion results are shown in Table 1. Figure 10 As shown in Table 1, the water emulsion mass ratio was fixed at 5:5, and the multiple emulsion was stable at a lower hydrophilic Janus-SiO2 particle concentration (0.25 wt%), at which the emulsion particle size was relatively large, about 93.7 μm, and the emulsion particle size gradually decreased with increasing particle concentration, and there was no significant change after 1.5 wt%. This condition was selected as the optimal dosage.

[0122] Comparative Example 4: W / O / W multiple emulsion prepared by conventional particles

[0123] On the basis of Example 3, the added hydrophilic and hydrophobic Janus-SiO2 was replaced by commercially available surface-uniformly modified SiO2 particles, in which the hydrophilic SiO2 was modified by hexadecylsilane with a C content of 0.9-1.8%, and the SiO2 surface hydroxyl was partially replaced, the hydrophilicity was reduced, but part of the silicon hydroxyl was still retained, and the whole was hydrophilic; the hydrophobic SiO2 was modified by dichlorodimethylsilane with a C content of 0.7-1.3%, and the silicon hydroxyl was very small, and the whole was lipophilic, and the remaining steps were consistent with Example 3, to prepare the emulsion.

[0124] The results show that the two kinds of particles are selected as emulsifiers to prepare multiple emulsions, which have no effect on the emulsion when the water phase pH is <7.6, but the emulsion prepared when the pH is ≥7.6 is unstable and quickly demulsifies.

[0125] By changing the NaCl concentration of the water phase, it is found that when c(NaCl)≤10 4 mg / L, the emulsion particle size increases significantly with increasing NaCl concentration, and greater than this concentration has a greater effect on the stability of the emulsion.

[0126] The results show that the multiple emulsion stabilized by the two kinds of particles together is not good in acid and alkali resistance and electrolyte resistance.

[0127] Although the present application has been disclosed with reference to the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a multiple Pickering emulsion, characterized in that: The method comprises the steps of: (1) Dispersing amination silica particles in a toluene solution, adding octacarbon silane and triethylamine to react, washing, and drying to obtain hydrophilic Janus-SiO2 nanoparticles; wherein the mass ratio of amination silica particles, octacarbon silane, and triethylamine is 1:2-3:1.2-1.5; and the amount ratio of amination silica particles to toluene solution is 1 g:40-60 mL; The aminated silica particles are dispersed in a toluene solution, octadecylsilane and triethylamine are added for reaction, and then washed and dried to obtain hydrophobic Janus-SiO2 nanoparticles. The mass ratio of the aminated silica particles, octadecylsilane, and triethylamine is 1:7-10:1.2-1.5, and the amount ratio of the aminated silica particles to the toluene solution is 1 g:40-60 mL. (2) Mixing and dispersing hydrophobic Janus-SiO2 nanoparticles with liquid paraffin; adding water and homogenizing to obtain water-in-oil colostrum; wherein the amount ratio of hydrophobic Janus-SiO2 nanoparticles, liquid paraffin and water is 1 g: 30-35 mL: 5-10 mL; (3) Mixing the hydrophilic Janus-SiO2 nanoparticles with water and dispersing them; adding water-in-oil colostrum and homogenizing to obtain a multiple Pickering emulsion; wherein the amount ratio of the hydrophilic Janus-SiO2 nanoparticles, water and water-in-oil colostrum is 1 g: 80-100 mL: 80-100 mL.

2. The method according to claim 1, characterized in that The preparation method of the amination-modified silica particles in step (1) comprises: (1) Dispersing silica particles in a cationic surfactant aqueous solution and ultrasonicating; adding paraffin wax, heating and melting, and homogenizing to obtain an oil-in-water emulsion; cooling the oil-in-water emulsion, washing, and drying to obtain paraffin-silica particle balls; (2) Disperse the paraffin-silica particles in a methanol solution, add diaminosilane, and react; add chloroform to wash away the paraffin, wash, and dry to obtain amino-silica particles.

3. The method according to claim 2, wherein The concentration of the cationic surfactant aqueous solution in step (1) is 0.05~0.1 g / L.

4. The method according to claim 2, wherein In step (1), the amount ratio of silica particles, cationic surfactant aqueous solution and paraffin is 1 g: 50-80 mL: 5-10 g.

5. The method according to claim 2, wherein In step (1), the homogenization is performed at 13,000 to 17,000 rpm for 8 to 12 minutes.

6. The method according to claim 2, characterized in that The heating and melting in step (1) is heating at 70-80°C until the paraffin wax is completely melted.

7. The method according to claim 2, characterized in that In step (2), the mass ratio of paraffin wax-silica particles to bisaminosilane is 1:180-200.

8. The method according to claim 2, wherein In step (2), the ratio of paraffin wax-silica particles, methanol, and chloroform is 1 g: 2-6 mL: 10-15 mL.

9. The method according to claim 2, wherein The reaction in step (2) is carried out at 150-250 rpm for 10-14 hours.

10. The method according to claim 2, characterized in that In step (1), the cationic surfactant includes one or more of lauryltrimethylammonium bromide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and dihexadecyldimethylammonium chloride; In step (1), the bisaminosilane includes one or more of N-aminoethyl-γ-aminopropyltrimethoxysilane, N-aminoethyl-γ-aminopropyltriethoxysilane, and N-aminoethyl-3-aminopropylmethyldimethoxysilane; The reaction in step (1) is carried out at room temperature for 2 to 4 hours.

11. The method according to claim 1, wherein Octacarbon silanes include n-octyltrimethoxysilane and n-octyltriethoxysilane; Octadecylsilane includes octadecyltrichlorosilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane.

12. The method according to claim 1, wherein In step (2), the homogenization is carried out at 9000-13000 rpm for 2-3 min; in step (3), the homogenization is carried out at 15000-17000 rpm for 2-3 min.

13. A multiple Pickering emulsion prepared by the method according to any one of claims 1 to 12.

14. Use of the multiple Pickering emulsion according to claim 13 in the preparation of food, medicine or cosmetics.

15. The use according to claim 14, characterized in that Applications in food preparation include preparation of emulsifiers and preservatives; Applications in the preparation of medicines include the preparation of drug delivery carriers and drug solvents; Applications in the preparation of cosmetics include the preparation of creams, lotions, and essences.

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