Method for preparing high-stability W / O / W type multiple Pickering emulsion based on Janus particles

Abstract

The invention 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. According to the preparation method, the Janus particles with different hydrophilic and hydrophobic properties are prepared by using alkylsilane modified SiO2 with different chain lengths, the multiple emulsion is stabilized together, different types of Janus particles are adsorbed on different oil-water interfaces, and the interface activity and amphipathicity of the Janus particles are fully exerted to prepare the high-stability multiple emulsion. The multi-emulsion provided by the invention has excellent stability, keeps stable under the conditions of long-term storage, strong acid, strong alkali, high-concentration electrolyte and the like, and can effectively expand the practical application of the multi-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 (MPE), also known as composite emulsions, are multilayer emulsions formed by dispersing one emulsion in another continuous phase. They have the advantages of both traditional water-in-oil and oil-in-water emulsions, and can carry both water-soluble and oil-soluble substances. Multiple emulsions are often divided into water-in-oil-in-water (W / O / W) and oil-in-water-in-oil (O / W / O) types. Their unique structure makes them widely used in the food industry, cosmetics, biomedicine, and agriculture. The stability of multiple emulsions is controlled by their preparation process and multiple factors such as emulsifiers, oil phase, and water phase. Since multiple emulsions have a more complex system than single emulsions, the surface excess free energy is thermodynamically unstable, so the preparation of stable and controllable multiple emulsions is the key to their application.

[0003] The emulsifiers of multiple emulsions are mainly small molecule surfactants, high polymer emulsifiers, natural macromolecules and colloidal particles. Multiple emulsions stabilized by small molecule surfactants often have poor stability; high polymer emulsifiers have excellent stability and swelling properties, which can greatly improve the stability of emulsions, but their biological safety is poor; using natural macromolecules alone requires a high concentration to obtain 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 emulsion stabilized by them has excellent stability, and its 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 the 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 on 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 present invention provides a method for preparing a high-stability multiple Pickering emulsion based on Janus particles. SiO 2Janus particles with different hydrophilicity and hydrophobicity are prepared to jointly stabilize multiple emulsions. Different types of Janus particles are adsorbed on different oil-water interfaces to give full play to the interfacial activity and amphiphilicity of Janus particles to prepare highly stable multiple emulsions, effectively expanding the practical applications of multiple emulsions.

[0006] A first object of the present invention is to provide a method for preparing a multiple Pickering emulsion, the method comprising the steps of:

[0007] (1) The aminated silica particles (SiO 2 ) was dispersed in a toluene solution, octacarbon silane and triethylamine were added to react, and the hydrophilic Janus-SiO 2 Nanoparticles; wherein the mass ratio of the aminated silica particles, octacarbon silane and triethylamine is 1:2-3:1.2-1.5; the amount ratio of the aminated silica particles to the toluene solution is 1g:40-60mL;

[0008] The aminated silica particles were dispersed in toluene solution, octadecylsilane and triethylamine were added to react, and the hydrophobic Janus-SiO 2 Nanoparticles; wherein the mass ratio of the amination silica particles, octadecylsilane and triethylamine is 1:7-10:1.2-1.5; the amount ratio of the amination silica particles to the toluene solution is 1g:40-60mL;

[0009] (2) Hydrophobic Janus-SiO 2 Nanoparticles are mixed with liquid paraffin and dispersed; water is added and homogenized to obtain water-in-oil colostrum (W / O colostrum); wherein the hydrophobic Janus-SiO 2 The dosage ratio of nanoparticles, liquid paraffin and water is 1 g: 30-35 mL: 5-10 mL;

[0010] (3) Hydrophilic Janus-SiO 2 Nanoparticles are mixed with water and dispersed; water-in-oil colostrum is added and homogenized to obtain a multiple Pickering emulsion (W / O / W emulsion); among them, the hydrophilic Janus-SiO 2 The dosage ratio of nanoparticles, water and water-in-oil colostrum is 1g:80-100mL:80-100mL.

[0011] In one embodiment, the water may be deionized water.

[0012] In one embodiment, the method for preparing the amination silica particles in step (1) comprises:

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

[0014] (2) dispersing paraffin-silica particle balls in a methanol solution, adding bisaminosilane, 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 is 1 g: 50-80 mL: 5-10 g;

[0017] Optionally, in step (1), the homogenization is carried out 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 particle balls to bisaminosilane is 1:180-200;

[0020] Optionally, in step (2), the ratio of the paraffin-silica particle ball, 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 lauryl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and dihexadecyl dimethyl ammonium 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 octacarbon silane includes n-octyltrimethoxysilane, n-octyltriethoxysilane, trimethoxy(octyl)silane;

[0026] The 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] The application in the preparation of cosmetics includes the preparation of creams, lotions and essences.

[0033] The 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 multiple Pickering emulsions by using a hydrophilic Janus-SiO 2 Nanoparticles and hydrophobic Janus-SiO 2 Nanoparticles are prepared into multiple Pickering emulsions, comprising the steps of:

[0034] (1) The aminated silica particles are dispersed in a toluene solution, octacarbon silane and triethylamine are added to react, and then washed and dried to obtain a hydrophilic Janus-SiO 2 Nanoparticles; wherein the mass ratio of the aminated silica particles, octacarbon silane and triethylamine is 1:2-3:1.2-1.5; the amount ratio of the aminated silica particles to the toluene solution is 1g:40-60mL;

[0035] The aminated silica particles were dispersed in toluene solution, octadecylsilane and triethylamine were added to react, and the hydrophobic Janus-SiO 2 Nanoparticles; wherein the mass ratio of the amination silica particles, octadecylsilane and triethylamine is 1:7-10:1.2-1.5; the amount ratio of the amination silica particles to the toluene solution is 1g:40-60mL;

[0036] (2) Hydrophobic Janus-SiO 2Nanoparticles are mixed with liquid paraffin and dispersed; water is added and homogenized to obtain water-in-oil colostrum; among them, hydrophobic Janus-SiO 2 The dosage ratio of nanoparticles, liquid paraffin and water is 1 g: 30-35 mL: 5-10 mL;

[0037] (3) Hydrophilic Janus-SiO 2 Nanoparticles are mixed with water and dispersed; oil-in-water colostrum is added and homogenized to obtain multiple Pickering emulsions; among them, hydrophilic Janus-SiO 2 The dosage ratio of nanoparticles, water and water-in-oil colostrum is 1g:80-100mL:80-100mL.

[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 hydrophilicity and hydrophobicity as emulsifiers to stabilize multiple emulsions. During the particle modification process, only the hydrophobic alkyl silane 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 water phases.

[0042] (2) The multiple emulsion prepared by the present invention has a distinct structure, uniform particle size distribution, high internal phase content, and Janus particles with different hydrophilicity and hydrophobicity are arranged on different oil-water interfaces, making full use of the interfacial activity and amphiphilicity of the Janus particles; the prepared multiple emulsion has excellent stability and remains stable under conditions such as long-term storage, strong acid and strong alkali, and high-concentration electrolytes, 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 being stored at room temperature for 60 days;

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

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

[0047] Figure 1 Effect of octylsilane addition on hydrophilic Janus-SiO 2 Particle contact angle influence diagram;

[0048] Figure 2 To prepare hydrophilic and hydrophobic Janus-SiO 2 、Amination SiO 2 And unmodified SiO 2 Infrared spectrum of

[0049] Figure 3 To prepare hydrophilic and hydrophobic Janus-SiO 2 And unmodified SiO 2 Thermogravimetric curve of

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

[0051] Figure 5 The appearance and microscopic picture 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 Effect of octadecylsilane addition on hydrophobicity of Janus-SiO 2 Particle contact angle and emulsification performance influence diagram;

[0055] Fig. 9 Janus-SiO with different hydrophobicity 2 Appearance of particle concentration-stable W / O emulsion;

[0056] Fig.10 Janus-SiO with different hydrophilicity 2 Particle concentration Preparation of W / O / W multiple emulsion appearance and microscopic images;

[0057] Fig.11 Hydrophilic Janus-SiO 2 The charge of particles at different pH values. DETAILED DESCRIPTION

[0058] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0059] Test method:

[0060] 1. Emulsion particle size detection method:

[0061] Take 10 μL of the 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 the droplet morphology and take pictures. Use Nano Measurer software to count 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%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 pressed into tablets, and 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 examples are:

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

[0070] SiO 2 Purchased from: Aladdin Biochemical Technology Co., Ltd., CAS number 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., CAS No. 8012-95-1.

[0076] Example 1: Preparation of hydrophilic Janus-SiO 2

[0077] Preparation of hydrophilic Janus-SiO 2 , the steps are as follows:

[0078] (1) 0.5 g SiO 2 Dispersed in 40mL 0.08g / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution, ultrasonicated for 20min; added 5g sliced ​​paraffin, completely melted in 80℃ water bath, homogenized at 15000r / min for 10min to obtain O / W type emulsion; paraffin was quickly solidified in ice bath, and residual CTAB and free SiO were removed by washing. 2 , drying to obtain paraffin-silica particle balls;

[0079] (2) 10 g of paraffin-silica particles were dispersed in 30 mL of methanol solution, 0.06 g of bisaminosilane was added, and the mixture was reacted for 12 h under slow stirring (200 r / min). The paraffin was washed away with 100 mL of chloroform, and centrifuged and washed three times with ethanol. After drying, the amino SiO 2 powder;

[0080] (3) Take 0.1g of amino SiO 2 Dispersed in 5 mL toluene solution, 0.05 g octacarbon silane and triethylamine (the mass ratio of octacarbon silane to triethylamine is 1:1.5) were added, reacted at room temperature (15-30 ° C) for 4 h, washed three times by centrifugation with toluene, and dried to obtain hydrophilic Janus-SiO 2 Nanoparticles.

[0081] The effect of different addition amounts of octacarbon silane on the contact angle was 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-SiO 2

[0083] Preparation of hydrophobic Janus-SiO 2 , the steps are as follows:

[0084] (1) 0.5 g SiO 2Dispersed in 40mL 0.08g / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution, ultrasonicated for 20min; added 5g sliced ​​paraffin, completely melted in 80℃ water bath, homogenized at 15000r / min for 10min to obtain O / W type emulsion; paraffin was quickly solidified in ice bath, and residual CTAB and free SiO were removed by washing. 2 , drying to obtain paraffin-silica particle balls;

[0085] (2) 10 g of paraffin-silica particles were dispersed in 30 mL of methanol solution, 0.06 g of bisaminosilane was added, and the mixture was reacted for 12 h under slow stirring (200 r / min). The paraffin was washed away with 100 mL of chloroform, and centrifuged and washed three times with ethanol. After drying, the amino SiO 2 powder;

[0086] (3) Take 0.1g of amino SiO 2 Dispersed in 5 mL toluene solution, 0.015 g octadecylsilane and triethylamine (the mass ratio of octadecylsilane to triethylamine was 1:1.5) were added, reacted at room temperature for 2 h, washed three times by centrifugation with toluene, and dried to obtain hydrophobic Janus-SiO 2 Nanoparticles.

[0087] Detection of hydrophobic Janus-SiO 2 The contact angle of the nanoparticles showed that when the addition amount of octadecylsilane was 0.015 g, the particle-water-air contact angle value was 114.7°.

[0088] Take the amino SiO prepared in Example 1 and Example 2 2 Powder, hydrophilic Janus-SiO 2 Nanoparticles and hydrophobic Janus-SiO 2 Nanoparticles, detect their infrared spectrum and thermogravimetric curve, the results are as follows Figure 2 and Figure 3 shown.

[0089] Infrared spectroscopy results show that compared with unmodified SiO 2 In comparison, the amino SiO 2 , hydrophilic and hydrophobic Janus-SiO 2 At 2850cm -1 and 2929cm -1 The characteristic peaks at are the symmetric and antisymmetric stretching vibrations of the CH bond; the thermogravimetric results show that before 200℃, the unmodified SiO 2 and aminated SiO 2 , two kinds of Janus-SiO 2The particles all showed obvious weight loss, which was caused by the loss of adsorbed water on the surface of the particles. 2 The particle weight loss at around 300℃ was mainly due to the decomposition of the amino group, and the decomposition of the alkyl chain after 400℃ indicated that the bisaminosilane and alkylsilane 2 The surfaces were successfully grafted.

[0090] Example 3: Preparation of W / O / W multiple Pickering emulsion

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

[0092] (1) Take 0.18 g of the hydrophobic Janus-SiO prepared in Example 2 2 Add to 6 mL of liquid paraffin and sonicate for 5 min until completely dispersed, then add 1.5 mL of deionized water (W2), and homogenize at 13000 r / min for 3 min to obtain W / O colostrum;

[0093] (2) Take 0.045 g of the hydrophilic Janus-SiO prepared in Example 1 2 The mixture was added to 3 mL of deionized water (W1) and ultrasonicated until completely dispersed. Then, 3 g of W / O colostrum was added and homogenized at 16000 r / min for 2 min to obtain about 5 mL of W2 / O / W1 multiple emulsion.

[0094] 2. Emulsion property testing

[0095] (1) Particle size

[0096] The W2 / O / W1 multiple emulsion prepared in Example 3 was taken, and the droplet morphology was observed using an ultra-depth microscope, and the droplet particle size was counted using Nano Measurer 1.2 software.

[0097] The results showed that the particle size of the multiple emulsion was 52.4 μm, the particle size distribution of the emulsion was uniform, and it had an obvious multiple structure.

[0098] (2) Emulsion type

[0099] Before preparing the emulsion, deionized water was stained with sodium fluorescein and liquid paraffin was stained with Nile red at a dye concentration of 0.1 wt %. After homogenization, the emulsion was observed under an upright fluorescence microscope at excitation wavelengths of 480 nm and 552 nm, respectively.

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

[0101] (3) Long-term stability testing

[0102] The W2 / O / W1 multiple emulsion prepared in Example 3 was placed at room temperature for 60 days. During this period, the appearance and microscopic conditions of the emulsion were observed, and the total height of the emulsion layer and the liquid was measured. According to the formula EI = H e / H t ×100% to calculate the emulsification rate (EI), where H e is the height of the upper emulsion after the system is stabilized, H t is the total height of the liquid.

[0103] The results are as follows Figure 5 As shown, the results show that the emulsification rate of the emulsion 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 at this time, and there is no obvious change. The experimental results show that the prepared multiple emulsion has good long-term stability.

[0104] (4) Acid and alkali resistance test

[0105] The pH of the aqueous phases W1 and W2 were changed to 1.51 (as an acidic condition) and 13.06 (as an alkaline condition), respectively, and an acidic W / O / W multiple emulsion (composed of an aqueous phase with a pH of 1.51, liquid paraffin, and hydrophobic Janus-SiO 2 and hydrophilic Janus-SiO 2 prepared) and alkaline W / O / W multiple emulsions (composed of an aqueous phase with a pH of 13.06, liquid paraffin, hydrophobic Janus-SiO 2 and hydrophilic Janus-SiO 2 The zeta potential and particle size analyzer were used to determine the charge status at different pH values.

[0106] The results are as follows Figure 6 As shown in the figure, the emulsion can be formed under both acidic and alkaline conditions. Although some particles settle (slightly turbid), the emulsion remains stable, does not break, and multiple structures are obviously present. When the pH of the aqueous phase is 1.51, the average particle size of the emulsion is 80.3μm; when the pH of the aqueous phase is 13.06, the average particle size of the emulsion is 65.7μm.

[0107] The stability (agglomeration, sedimentation) of particles in water phase is related to the absolute value of the zeta potential of the particles. The larger the absolute value, the greater the electrostatic repulsion between the particles and the more stable they are. When the absolute value is closer to 0, the particles are prone to aggregation and sedimentation. 2 The Zeta potential test results of nanoparticles are as follows: Fig.11As shown, the results show that with the increase of pH, the absolute value of the Zeta potential of the particles gradually decreases. When the pH is less than 9, the Zeta potential value is greater than 10mV. At this time, the absolute value is large and there is no particle sedimentation in the emulsion system. When the pH is around 13, the Zeta potential is about 0. At this time, the electrostatic repulsion between particles is small, and agglomeration and sedimentation are easy to occur. The water phase in the emulsion system is turbid, and the number of particles in the emulsion layer is reduced, resulting in an increase in particle size. Under the condition of acidic water phase, the protonation of the amino group on the particle surface is enhanced, the hydrophilicity is increased, and the particle sedimentation in the system is also caused. In summary, the W / O / W multiple emulsion prepared in Example 3 has excellent acid and alkali resistance.

[0108] (5) Electrolyte resistance

[0109] On the basis of Example 3, the deionized water in step (1) and step (2) was changed to a concentration of 10 3 , 10 4 , 10 5 , 3.6×10 5 mg / L (concentration is 3.6×10 5 The remaining steps were the same as those in Example 3 to prepare W / O / W multiple emulsions containing electrolytes at different concentrations, and the appearance and particle size of the emulsions were tested.

[0110] When the NaCl concentration is 3.6×10 5 When mg / L, the result is Figure 7 As shown, the results show that saturated NaCl concentration has no effect on emulsification and the average droplet size is 62.3 μm, indicating that the multiple Pickering emulsions stabilized by the prepared Janus particles have 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-SiO 2 .

[0113] The hydrophobic Janus-SiO prepared in Comparative Example 1 and Example 2 2 , prepare the emulsion, the steps are as follows:

[0114] Take 0.03 g of hydrophobized Janus-SiO 2 Add to 3 mL of liquid paraffin, sonicate until the particles are completely dispersed, then add 3 mL of deionized water, and homogenize 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 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 too little or too much octadecylsilane addition cannot form a stable W / O emulsion.

[0116] Comparative Example 2: Changing the hydrophobicity of Janus-SiO 2 Addition amount

[0117] Based on Example 3, the hydrophobic Janus-SiO 2 The addition amounts were 0.06 g, 0.12 g, 0.18 g, and 0.24 g, to obtain W / O emulsions with hydrophobic particle concentrations of 1 wt%, 2 wt%, 3 wt%, and 4 wt%, respectively. The remaining steps were consistent with Example 3.

[0118] Emulsion results such as Fig. 9 As shown in the figure, the volume ratio of oil and water (i.e., liquid paraffin and deionized water W2) is kept constant (4:1). 2 When the particle concentration 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 has a high viscosity and no fluidity, which is not conducive to the removal of W / O colostrum. Considering the hydrophobicity of Janus-SiO 2 The particle concentration was 3 wt%.

[0119] Comparative Example 3: Changing the hydrophilicity of Janus-SiO 2 Addition amount

[0120] Based on Example 3, the hydrophilic Janus-SiO 2 The addition amounts were 0.0075 g, 0.015 g, 0.03 g, 0.045 g and 0.0525 g, respectively obtaining 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%, and the remaining steps were the same as in Example 3.

[0121] Emulsion results such as Fig.10 As shown, the water-emulsion mass ratio is fixed at 5:5. 2 The multiple emulsions can be stabilized at a particle concentration of 0.25wt%. At this time, the emulsion particle size is relatively large, about 93.7μm. As the particle concentration increases, the emulsion particle size gradually decreases, and there is no obvious change after 1.5wt%. This condition is selected as the optimal dosage.

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

[0123] On the basis of Example 3, the hydrophilic and hydrophobic Janus-SiO 2 Replaced with commercially available surface uniformly modified SiO 2 Particles, in which hydrophilic SiO 2 Modified by hexadecylsilane, C content is 0.9-1.8%, SiO 2 The surface hydroxyl groups are partially replaced, the hydrophilicity is reduced, but some silicon hydroxyl groups are still retained, and the whole is hydrophilic; hydrophobic SiO 2 Modified by dichlorodimethylsilane, the C content is 0.7-1.3%, the silanol group is very small, and the whole is lipophilic. The remaining steps are consistent with Example 3 to prepare an emulsion.

[0124] The results show that the selection of these two particles as emulsifiers to prepare multiple emulsions has no effect on the emulsions when the pH of the aqueous phase is less than 7.6, but when the pH is ≥ 7.6, the prepared emulsions are unstable and demulsification occurs quickly.

[0125] By changing the NaCl concentration in the aqueous phase, it was found that c(NaCl)≤10 4 When the concentration of NaCl increases to 0.17477 mg / L, the particle size of the emulsion increases significantly, and when the concentration is greater than this, it has a greater impact on the stability of the emulsion.

[0126] The results show that the multiple emulsions stabilized by these two types of particles have poor acid, alkali and electrolyte resistance.

[0127] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a multiple Pickering emulsion, characterized in that: The method comprises the steps of: (1) dispersing the aminated 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 the aminated silica particles, octacarbon silane and triethylamine is 1:2-3:1.2-1.5; and the amount ratio of the aminated silica particles to the 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; wherein the mass ratio of the aminated silica particles, octadecylsilane and triethylamine is 1:7-10:1.2-1.5; and the dosage ratio of the aminated silica particles to the toluene solution is 1 g:40-60 mL; (2) mixing hydrophobic Janus-SiO2 nanoparticles with liquid paraffin and dispersing them; 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 method for preparing the amination-modified silicon dioxide particles in step (1) comprises: (1) dispersing silica particles in an aqueous solution of a cationic surfactant, and ultrasonicating; adding paraffin, heating to melt, and homogenizing to obtain an oil-in-water emulsion; cooling the oil-in-water emulsion, washing, and drying to obtain paraffin-silicon dioxide particle balls; (2) dispersing paraffin-silica particle balls in a methanol solution, adding bisaminosilane, reacting; adding chloroform to wash away the paraffin, washing, and drying to obtain amino-silica particles; Optionally, the concentration of the cationic surfactant aqueous solution in step (1) is 0.05 to 0.1 g / L; Optionally, in step (1), the ratio of the silicon dioxide particles, the cationic surfactant aqueous solution and the paraffin is 1 g: 50-80 mL: 5-10 g; Optionally, in step (1), homogenization is performed at 13000-17000 rpm for 8-12 min; Optionally, the heating and melting in step (1) is heating at 70-80° C. until the paraffin is completely melted; Optionally, in step (2), the mass ratio of paraffin-silica granules to bisaminosilane is 1:180-200; Optionally, in step (2), the ratio of the paraffin-silica particle ball, methanol and chloroform is 1 g: 2-6 mL: 10-15 mL; Optionally, the reaction in step (2) is carried out at 150-250 rpm for 10-14 hours.

3. The method according to claim 2, characterized in that In step (1), the cationic surfactant includes one or more of lauryl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and dihexadecyl dimethyl ammonium 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.

4. The method according to claim 1, characterized in that: Octacarbon silanes include n-octyltrimethoxysilane and n-octyltriethoxysilane; The octadecylsilane includes octadecyltrichlorosilane, octadecyltrimethoxysilane and octadecyltriethoxysilane.

5. The method according to claim 1, characterized in that 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.

6. The multiple Pickering emulsion prepared by the method according to any one of claims 1 to 5.

7. Use of the multiple Pickering emulsion according to claim 6 in the preparation of food, medicine or cosmetics.

8. The use according to claim 7, characterized in that: Applications in food preparation include preparation of emulsifiers, preservatives; Applications in the preparation of medicines include the preparation of drug delivery carriers and drug solvents; The application in the preparation of cosmetics includes the preparation of creams, lotions and essences.

9. A method for simultaneously improving the stability, strong acid and alkali tolerance, and high-concentration electrolyte tolerance of multiple Pickering emulsions, characterized in that: The method of preparing a multiple Pickering emulsion using hydrophilic Janus-SiO2 nanoparticles and hydrophobic Janus-SiO2 nanoparticles comprises the following steps: (1) dispersing the aminated 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 the aminated silica particles, octacarbon silane and triethylamine is 1:2-3:1.2-1.5; and the amount ratio of the aminated silica particles to the 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; wherein the mass ratio of the aminated silica particles, octadecylsilane and triethylamine is 1:7-10:1.2-1.5; and the dosage ratio of the aminated silica particles to the toluene solution is 1 g:40-60 mL; (2) mixing hydrophobic Janus-SiO2 nanoparticles with liquid paraffin and dispersing them; 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.

10. The method according to claim 9, characterized in that The reaction in step (1) is carried out at room temperature for 2 to 4 hours; the homogenization in step (2) is carried out at 9000 to 13000 rpm for 2 to 3 minutes; and the homogenization in step (3) is carried out at 15000 to 17000 rpm for 2 to 3 minutes.

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