A high internal phase pickering emulsion and a preparation method and application thereof

Abstract

The present application relates to a kind of high internal phase Pickering emulsion and its preparation method and application, belong to emulsifier technical field.The high internal phase Pickering emulsion of the present application is oil-in-water high internal phase Pickering emulsion, include aqueous phase and oil phase;Aqueous phase includes amphiphilic random copolymer self-assembly aggregate;Amphiphilic random copolymer in amphiphilic random copolymer self-assembly aggregate is selected from poly (dodecyl methacrylate-co-methacrylic acid) and / or poly (octadecyl methacrylate-co-methacrylic acid) It is first to use amphiphilic random copolymer self-assembly aggregate as particle type emulsifier, successfully prepared O / W type high internal phase Pickering emulsion.Compared with the high internal phase Pickering emulsion prepared by traditional small molecule emulsifier or traditional Pickering emulsifier, this method can prepare 85% even 90% oil phase emulsion, with the advantages of low emulsifier consumption and high emulsion stability.

Description

Technical Field

[0001] This invention relates to the field of emulsifier technology, and in particular to a high internal phase Pickering emulsion, its preparation method, and its application. Background Technology

[0002] High internal phase emulsions (HIPEs) are emulsion systems with an internal phase volume fraction exceeding 74%. The dispersed phase droplets are tightly packed together and deformed into a polyhedral structure, forming a continuous gel-like network that gives them a semi-solid gel state. They have broad application prospects in food preservation coatings, cosmetic creams, functional foods, 3D printing, and tissue engineering.

[0003] Traditional HIPEs are mainly stabilized by low molecular weight surfactants such as hexadecyltrimethylammonium bromide (CTAB), Tween 20, Tween 80, and Span 80. However, HIPEs stabilized by these surfactants have the following drawbacks: (1) Large emulsifier dosage, usually requiring 5-50 wt% high concentration of surfactant to form stable HIPEs, significantly increasing production costs. (2) Poor biocompatibility, high concentrations of chemical surfactants have potential cytotoxicity and skin irritation, limiting their application in food, pharmaceuticals, and cosmetics. (3) Insufficient stability, the adsorption of surfactants at the oil-water interface is reversible, making it difficult to effectively resist droplet flocculation and Auschwitz ripening, and the emulsion is prone to phase separation. (4) Surfactants must be soluble in the continuous phase only, otherwise phase inversion will occur, resulting in harsh preparation process conditions.

[0004] High Internal Phase Pickering Emulsions (HIPPEs) utilize solid particles instead of traditional surfactants as emulsifiers, effectively overcoming the shortcomings of traditional HIPEs and offering advantages such as low emulsifier usage, good biocompatibility, excellent long-term stability, and unique rheological properties. Existing research indicates that the stability of HIPPEs is regulated by multiple factors, with the core dependence on the adsorption of solid particles at the oil-water interface. Simultaneously, the interfacial stabilizing film formed by particle aggregation and the continuous phase particle network structure can inhibit droplet coalescence. Furthermore, particle morphology, particle size, wettability, oil phase structure and viscosity, system pH, and ionic strength all directly affect the emulsion's stability.

[0005] Currently reported HIPPE emulsifiers are mainly divided into two categories: inorganic solid particles and macromolecular emulsifiers. Among them, metal oxides and metal particles such as silica and iron oxide require complex surface functionalization processes to adjust their wettability in order to effectively stabilize HIPPEs, increasing preparation costs and process complexity. Macromolecular emulsifiers mainly focus on amphiphilic block copolymers and graft copolymers. Currently, research on amphiphilic random copolymers as emulsifiers is relatively limited, and no technology has been reported for using the self-assembled aggregates of amphiphilic random copolymers as particulate emulsifiers to prepare high internal phase Pickering emulsions.

[0006] Therefore, developing such novel HIPPEs systems is expected to further reduce emulsifier costs, improve biocompatibility, and expand the application range of HIPPEs. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high internal phase Pickering emulsion, its preparation method, and its applications. The amphiphilic random copolymers of this invention use dodecyl methacrylate (LMA) or octadecyl methacrylate (SMA) as hydrophobic monomers and methacrylic acid (MAA) as a hydrophilic monomer to synthesize amphiphilic random copolymers poly(dodecyl methacrylate-co-methacrylic acid) (P(LMA-co-MAA)) and poly(octadecyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)). Self-assembled aggregates of these copolymers are prepared by direct dissolution combined with pH induction, thereby preparing an O / W type high internal phase Pickering emulsion system.

[0008] This invention uses the self-assembled aggregates (macromolecular micelles) of copolymers as Pickering emulsifiers to obtain a Pickering emulsion system with high internal phase, which has the characteristics of low emulsifier dosage, stable emulsion and high oil phase content. There are currently no related technologies reported worldwide.

[0009] This invention is achieved through the following technical solution:

[0010] The first objective of this invention is to provide a high internal phase Pickerling emulsion, wherein the high internal phase Pickerling emulsion is an oil-in-water type high internal phase Pickerling emulsion comprising an aqueous phase and an oil phase; wherein the aqueous phase comprises amphiphilic random copolymer self-assembled aggregates;

[0011] The amphiphilic random copolymer in the self-assembled aggregate is selected from poly(dodecyl methacrylate-co-methacrylic acid) and / or poly(octadecyl methacrylate-co-methacrylic acid).

[0012] In one embodiment of the present invention, the oil phase volume fraction of the high internal phase Pickering emulsion is 75%-90%.

[0013] In one embodiment of the present invention, the molar ratio of dodecyl methacrylate to methacrylic acid in the poly(dodecyl methacrylate-co-methacrylic acid) is 1:9-2:8.

[0014] And / or, the molar ratio of octadecyl methacrylate to methacrylic acid in the poly(octadecyl methacrylate-co-methacrylic acid) is 1:9-2:8.

[0015] In one embodiment of the present invention, the mass-volume fraction of the amphiphilic random polymer self-assembled aggregates in the aqueous phase is 0.5%-1.5%;

[0016] And / or, the pH of the aqueous phase is 5.0-11.0.

[0017] In one embodiment of the present invention, the oil phase is selected from one or more of caprylic / capric glyceride, white oil, silicone oil and olive oil; the silicone oil is decamethylcyclopentasiloxane or silicone oil with a viscosity range of 10 cst-50 cst.

[0018] A second objective of this invention is to provide a method for preparing the high internal phase Pickering emulsion, comprising the following steps:

[0019] (1) Dissolve the amphiphilic random polymer in an alkaline solution, adjust the pH, and obtain a solution of amphiphilic random polymer self-assembled aggregates;

[0020] The amphiphilic random polymer is selected from poly(dodecyl methacrylate-co-methacrylic acid) and / or poly(octadecyl methacrylate-co-methacrylic acid).

[0021] (2) Using the amphiphilic random polymer self-assembled aggregate solution obtained in step (1) as the aqueous phase, mix it with the oil phase and emulsify it to obtain the high internal phase Pickering emulsion.

[0022] In one embodiment of the present invention, in step (1), the poly(dodecyl methacrylate-co-methacrylic acid) is prepared by the following method: under a protective atmosphere, dodecyl methacrylate, methacrylic acid and an initiator are polymerized in a solvent to obtain the poly(dodecyl methacrylate-co-methacrylic acid); the molar ratio of dodecyl methacrylate to methacrylic acid is 1:9-2:8.

[0023] And / or, the poly(octadecyl methacrylate-co-methacrylic acid) is prepared by the following method: under a protective atmosphere, octadecyl methacrylate, methacrylic acid and an initiator are polymerized in a solvent to obtain the poly(octadecyl methacrylate-co-methacrylic acid); the molar ratio of octadecyl methacrylate to methacrylic acid is 1:9-2:8.

[0024] In one embodiment of the present invention, in step (1), the alkali in the alkaline solution is one or more of NaOH, NaHCO3, arginine and triethanolamine.

[0025] In one embodiment of the present invention, in step (1), the pH is 5-11.

[0026] In one embodiment of the present invention, in step (2), the emulsification conditions are: homogenization at 8000 rpm-10000 rpm for 1 min-2 min.

[0027] A third objective of this invention is to provide the application of the high internal phase Pickering emulsion in food preservation coatings, cosmetic creams, functional foods, 3D printing, or tissue engineering.

[0028] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0029] This invention provides a high internal phase Pickerling emulsion, its preparation method, and its applications. For the first time, an amphiphilic random copolymer self-assembled aggregate is used as a particulate emulsifier, successfully preparing an O / W type high internal phase Pickerling emulsion. Compared to high internal phase Pickerling emulsions prepared using traditional small molecule emulsifiers or traditional Pickerling emulsifiers, this method can prepare emulsions with 85% or even 90% oil phase, offering advantages such as low emulsifier usage (0.075% polymer, w / v) and high emulsion stability at 85% oil phase. Attached Figure Description

[0030] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0031] Figure 1 These are the infrared spectra of P(LMA-co-MAA) with different monomer molar ratios in this invention.

[0032] Figure 2 These are the 1H NMR spectra of P(LMA-co-MAA) with different monomer molar ratios in this invention;

[0033] Figure 3 The infrared spectrum and 1H NMR spectrum of P(SMA-co-MAA) with a monomer molar ratio of 1:9 in this invention are shown.

[0034] Figure 4 These are photographs of emulsions prepared under different pH aqueous phase and oil-water ratio conditions in this invention, using 0.5% (w / v) P(LMA-co-MAA) (LMA:MAA molar ratio 1:9 (a) and 2:8 (b)) as emulsifier and GTCC as oil phase.

[0035] Figure 5 These are TEM images of self-assembled aggregates of P(LMA-co-MAA) with a monomer molar ratio of 1:9 obtained under different pH conditions; and SEM images of cured oil droplets obtained by photocuring under 365 nm ultraviolet light.

[0036] Figure 6 These are TEM images of P(SMA-co-MAA) self-assembled aggregates at different pH values ​​in this invention;

[0037] Figure 7 This is a SEM image of O / W type emulsion-cured oil droplets obtained by P(SMA-co-MAA) self-assembled aggregates in this invention;

[0038] Figure 8 These are the pH and conductivity titration curves of P(LMA-co-MAA) in this invention;

[0039] Figure 9 These are digital photographs taken on days 1, 7, and 21 of emulsions prepared in this invention using 0.5% (w / v) P(LMA-co-MAA) as the aqueous phase and GTCC as the oil phase under different pH conditions and different oil-water volume ratios; wherein, (a) pH 5.0; (b) pH 7.0; (c) pH 9.0;

[0040] Figure 10 This is an inverted digital photograph on day 21 of emulsions prepared by P(LMA-co-MAA) self-assembled aggregates under different pH conditions in this invention.

[0041] Figure 11 These are digital photographs taken on days 1, 7, and 21 of emulsions prepared in this invention using 0.5% (w / v) P(SMA-co-MAA) as the aqueous phase and GTCC as the oil phase under different pH conditions and different oil-water volume ratios; where (a) pH 5.0; (b) pH 7.0; (c) pH 9.0; (d) 11.0;

[0042] Figure 12 These are inverted digital photographs taken on day 1 and day 21 of emulsions prepared by P(LMA-co-MAA) self-assembled aggregates under different pH conditions in this invention.

[0043] Figure 13These are fluorescence microscopy images of emulsions prepared with different pH values ​​and oil phase volume fractions in this invention, where 0.5% (w / v) P(LMA-co-MAA) is the aqueous phase and GTCC is the oil phase.

[0044] Figure 14 These are fluorescence microscopy images of emulsions prepared with different pH values ​​and oil phase volume fractions in this invention, where 0.5% (w / v) P(SMA-co-MAA) is the aqueous phase and GTCC is the oil phase.

[0045] Figure 15 These are ultra-depth-of-field microscopic images of HIPPEs stabilized at pH 5.0 with 0.5% (w / v) P(LMA-co-MAA) at different oil phase volume fractions (75%, 80%, 85%) on days 1, 7, and 21.

[0046] Figure 16 These are ultra-depth-of-field microscopic images of HIPPEs stabilized at pH 7.0 with 0.5% (w / v) P(LMA-co-MAA) at different oil phase volume fractions (75%, 80%, 85%) on days 1, 7, and 21.

[0047] Figure 17 These are ultra-depth-of-field microscopic images of HIPPEs stabilized at pH 9.0 with 0.5% (w / v) P(LMA-co-MAA) at different oil phase volume fractions (75%, 80%, 85%) on days 1, 7, and 21.

[0048] Figure 18 These are super depth-of-field microscopic images of HIPPEs stabilized with 0.5% (w / v) P(SMA-co-MAA) at (a) pH 7.0, (b) pH 9.0 and (c) pH 11.0.0 at different oil phase volume fractions (75%, 80%, 85%) on days 1, 7 and 21.

[0049] Figure 19 These are digital photos of HIPPEs stabilized with 0.5% (w / v) P(LMA-co-MAA) at different pH levels after centrifugation for 15 min at different centrifugation speeds, as described in this invention.

[0050] Figure 20 These are digital photos of HIPPEs stabilized with 0.5% (w / v) P (SMA-co-MAA) at different pH levels after centrifugation for 15 min at different centrifugation speeds, as described in this invention.

[0051] Figure 21 These are digital photographs taken after HIPPEs stabilized by P(LMA-co-MAA) at different pH levels were stored at different temperatures for 24 hours, according to the present invention.

[0052] Figure 22 These are digital photographs taken after HIPPEs stabilized by P(SMA-co-MAA) at different pH levels were stored at different temperatures for 24 hours, according to the present invention.

[0053] Figure 23 The graphs show the storage modulus (G') and loss modulus (G'') of P(LMA-co-MAA) stable HIPPEs (oil phase volume fraction of 85%) under different pH conditions, as well as the stress (a), frequency (b), viscosity and shear rate curves (c).

[0054] Figure 24 The graph (a) shows the storage modulus (G') and loss modulus (G'') of P(SMA-co-MAA) stable HIPPEs (oil phase volume fraction of 85%) as a function of frequency at different pH levels, and the viscosity and shear rate curve (b).

[0055] Figure 25 These are digital photographs of different oil phase emulsions stabilized by pH 7.0 0.5% (w / v) P(LMA-co-MAA) in this invention;

[0056] Figure 26 This is a fluorescence microscopy image of a HIPPEs emulsion with 0.5% (w / v) P(LMA-co-MAA) at pH 7.0 as a stabilizer, and (a) D10, (b) D50, (c) olive oil and (d) white oil as the oil phase, with an oil phase volume fraction of 85%.

[0057] Figure 27 These are images of emulsions produced in this invention, using 0.5% (w / v) P(SMA-co-MAA) at pH 9.0 as a stabilizer, with olive oil, white oil, D5, D10, D20, and D50 as the oil phase, and different volume fractions of the oil phase.

[0058] Figure 28 These are TEM images of P(St-co-MAA) with a St to MAA molar ratio of 6:4 in this invention, at pH 5.7 (a), 7.0 (b), 7.9 (c), and 9.1 (d).

[0059] Figure 29 These are photographs of the appearance of P(St-co-MAA) aqueous solutions at different pH values ​​under sunlight (a) and the corresponding Tyndall effect under laser pointer illumination (b) (pH values ​​from left to right are 12.0, 11.0, 10.0, 9.0, 8.2 and 7.3).

[0060] Figure 30These are the front view (a) and inverted view (b) of emulsions with different oil-water ratios, using P(St-co-MAA) with a monomer ratio of 6:4 at pH 7.0 as an interface stabilizer in this invention.

[0061] Figure 31 This is a fluorescence microscopy image of emulsions with different oil-water ratios, using P(St-co-MAA) at pH 7.0 and a monomer ratio of 6:4 as an interface stabilizer in this invention. Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0063] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0064] Table 1 Experimental Reagents

[0065]

[0066] Table 2 Experimental Instruments

[0067]

[0068] Example 1 Synthesis and Characterization of Random Copolymers

[0069] (1) Synthesis of P(LMA-co-MAA)

[0070] P(LMA-co-MAA) with a molar ratio of LMA and MAA monomers of 1:9 was prepared by solution polymerization: LMA, MAA, and AIBN (4% of the total monomer molars) were weighed and placed in a single-necked flask with isopropanol as the solvent (3 times the total monomer mass). After deoxygenation with N2, polymerization was carried out for 36 h at 70℃. After the polymerization reaction was completed and cooled to room temperature, the product was washed four times with petroleum ether. The precipitate was placed in a vacuum drying oven at room temperature and dried for 15 h. The resulting white granules were the polymer P(LMA-co-MAA) with a molar ratio of LMA and MAA monomers of 1:9.

[0071] P(LMA-co-MAA) with LMA and MAA monomer molar ratios of 2:8 and 3:7 were prepared according to the above method.

[0072] (2) Synthesis of P(SMA-co-MAA)

[0073] The synthesis method of P(SMA-co-MAA) is similar to step (1) of this embodiment, except that the monomer LMA is replaced with SMA to obtain P(SMA-co-MAA) with a monomer molar ratio of 1:9.

[0074] Characterization of P(LMA-co-MAA) and P(SMA-co-MAA) in Test Example 1

[0075] Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance spectroscopy were used. 1 The polymer prepared in Example 1 was characterized by 1H-NMR; the FTIR test was performed using the KBr pellet method, in which the polymer sample powder and potassium bromide (KBr) were mixed and ground uniformly at a mass ratio of 1:100 and then pressed into a test pellet. The scanning wavenumber range was 4000-600 cm⁻¹. -1 Fourier transform infrared spectroscopy characterization of copolymers P(LMA-co-MAA) with different monomer molar ratios is as follows: Figure 1 As shown. It can be seen that 3300-3700cm -1 The absorption peak at 2943 cm⁻¹ is relatively broad, mainly due to the stretching vibration of the OH bond; -1 and 2841 cm -1 CH stretching vibrations attributed to -CH3 and -CH2 respectively; 1612 cm -1 and 1174 cm -1 The stretching vibrations originate from C=O and CO in the MAA, respectively; the peak of the C=O stretching vibration in the LMA is located at 1722 cm⁻¹. -1 However, due to the lower proportion of LMA in P(LMA-co-MAA) with molar ratios of 1:9 and 2:8, this peak is overshadowed by the strong signal of the absorption peak of the C=O stretching vibration of MAA; 720 cm⁻¹ -1 The weak absorption peak at the point is attributed to the in-plane rocking vibration of -CH2- (with a consecutive number greater than 4) in long-chain aliphatic hydrocarbons, which proves that the copolymer P(LMA-co-MAA) was successfully prepared.

[0076] To determine the molar ratio of hydrophilic and hydrophobic units in the synthesized P(LMA-co-MAA), qualitative and quantitative analysis was performed using 1H NMR spectroscopy. 1 H-NMR analysis was performed using deuterated dimethyl sulfoxide (DMSO-d6) as the deuterated solvent. A polymer test solution with a concentration of 15 mg / mL was prepared, and the chemical shifts of hydrogen atoms in the polymer were determined to complete the structural analysis. The results are as follows: Figure 2As shown, the magnetic resonance signals of the -COOCH2- of the LMA unit and the -COOH of the MAA unit appear at 3.86 ppm and 12.28 ppm, respectively, indicating that the polymer contains LMA and MAA. Simultaneously, peak areas calculated using the normalization method show that the monomer molar ratios of LMA and MAA are approximately 0.95:9.00, 2.15:8.00, and 2.98:7.00, respectively, which are similar to feed ratios of 1:9, 2:8, and 3:7.

[0077] Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance (HNMR) spectra of P(SMA-co-MAA) 1 H-NMR (Figure) Figure 3 As shown in the figure, the target product was successfully synthesized.

[0078] Test Example 2: Emulsifying properties of P(LMA-co-MAA) and P(SMA-co-MAA)

[0079] (1) Emulsifying properties of P(LMA-co-MAA)

[0080] Because P(LMA-co-MAA) with a monomer molar ratio of 3:7 (LMA to MAA) is difficult to dissolve in aqueous polymer solutions, the emulsifying properties of P(LMA-co-MAA) with monomer molar ratios of 1:9 and 2:8 were subsequently investigated. Emulsions were prepared using 0.5% (w / v) P(LMA-co-MAA) aqueous solutions at pH 5.0, 7.0, and 9.0 as the aqueous phase and GTCC as the oil phase, at different oil phase volume fractions (10-90%, v / v). The appearance of the emulsions after standing for 24 h is shown below. Figure 4 As shown.

[0081] Depend on Figure 4 It is evident that when P(LMA-co-MAA) with a monomer molar ratio of 1:9 is used as a stabilizer, the height of the emulsion layer gradually increases with the increase of the oil phase proportion. When the oil phase volume fraction is 70%, a trace amount of aqueous phase is present at the bottom of the emulsion layer; when the oil phase accounts for 75%, 80%, and 85%, the emulsion does not separate into layers and forms a creamy consistency, preliminarily indicating the formation of O / W type HIPEs; when the oil phase volume fraction is 90%, a stable emulsion cannot be formed. At pH 5.0, 7.0, and 9.0, the polymer P(LMA-co-MAA) with a monomer molar ratio of 1:9 can stabilize emulsions with an oil phase content as high as 85% (v / v).

[0082] When P(LMA-co-MAA) with a monomer molar ratio of 2:8 is used as a stabilizer, an oil layer begins to precipitate on the upper layer of the emulsion prepared at pH 5.0 when the oil phase volume fraction is 80%. Under these conditions, the highest stable oil phase volume fraction emulsion is 75%. Emulsions prepared at pH 7.0 can stabilize emulsions with an oil phase volume fraction of up to 80%, and at pH 9.0, they can stabilize emulsion systems with an oil phase volume fraction of up to 85%, exhibiting emulsifying ability comparable to polymers with a monomer molar ratio of 1:9. This demonstrates that increasing the pH value of the system is beneficial for improving the hydrophilicity of the amphiphilic polymer, thereby enhancing its emulsifying ability.

[0083] It is evident that the emulsifying properties of amphiphilic random copolymers are related to the properties of hydrophilic and hydrophobic monomers, the monomer molar ratio, and the external environment (pH). Compared to a monomer molar ratio of 2:8, P(LMA-co-MAA) with a monomer molar ratio of 1:9 contains more hydrophilic units and exhibits better hydrophilicity, which is beneficial for the formation of O / W type HIPEs. Therefore, subsequent experiments all selected P(LMA-co-MAA) with a monomer molar ratio of 1:9.

[0084] Example 2 Preparation and characterization of P(LMA-co-MAA) and P(SMA-co-MAA) self-assembled aggregates

[0085] (1) Preparation of P(LMA-co-MAA) self-assembled aggregates

[0086] Weigh 0.5 g of P(LMA-co-MAA) with a monomer molar ratio of 1:9 from Example 1 and place it in a beaker. Add a certain amount of 0.1 mol / L NaOH aqueous solution, where the molar amount of NaOH is equal to the molar amount of -COOH in the polymer. After the polymer is completely dissolved, use 0.1 mol / L HCl to adjust the pH of the polymer aqueous solution to 5.0, 7.0, and 9.0, respectively, and then make up the volume to obtain P(LMA-co-MAA) aqueous solutions with a concentration of 0.5% (w / v) and pH values ​​of 5.0, 7.0, and 9.0.

[0087] (2) Preparation of P(SMA-co-MAA) self-assembled aggregates

[0088] P(SMA-co-MAA) aqueous solutions with a concentration of 0.5% (w / v) and pH values ​​of 5.0, 7.0, 9.0 and 11.0 were prepared by referring to step (1) of this embodiment.

[0089] Test Example 3: Characterization of P(LMA-co-MAA) and P(SMA-co-MAA) self-assembled aggregates

[0090] TEM: 10 µL of the polymer solutions prepared in Example 2 at various pH values ​​were dropped onto a copper grid, allowed to air dry, and then negatively stained with a 2% (w / v) phosphotungstic acid solution. The microstructure of the self-assembled aggregates induced at different pH values ​​was characterized using transmission electron microscopy at an accelerating voltage of 200 kV.

[0091] SEM: P(LMA-co-MAA) stabilized and cured emulsion droplets were tested at pH 5.0, 7.0, and 9.0. HDDA was used as the oil phase, and 0.5% (w / v) P(LMA-co-MAA) aqueous solutions (containing 1% (w / v) PVA) at different pH values ​​were used as the aqueous phase, with a fixed oil / water volume ratio of 1:10. Emulsification was performed using a high-speed disperser for 2 min to form a series of emulsions, which were then irradiated under 365 nm UV light for 3 min. 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) was used as a photoinitiator to initiate HDDA polymerization in the oil phase. The cured oil droplets in the emulsion were centrifuged at 1000 rpm and washed three times with anhydrous ethanol. The cured oil droplets were characterized using SEM at an accelerating voltage of 3.0 kV. P(SMA-co-MAA) cured emulsion droplets at pH 5.0, 7.0, 9.0, and 11.0 were also tested.

[0092] pKa determination of P(LMA-co-MAA) and P(SMA-co-MAA): P(LMA-co-MAA) with a molar ratio of LMA and MAA monomers of 1:9 was completely dissolved in an excess of 0.1 mol / L NaOH solution, and titrated with 0.1 mol / L HCl solution. The pH value and conductivity were monitored, and the titration curve was plotted.

[0093] P(SMA-co-MAA) with a SMA and MAA monomer molar ratio of 1:9 is the same as above.

[0094] Figure 5 Images (a), (b), and (c) are TEM images of self-assembled aggregates of P(LMA-co-MAA) with a monomer molar ratio of 1:9 obtained under different pH conditions. P(LMA-co-MAA) can form spherical self-assembled aggregates at pH 5.0, 7.0, and 9.0. Due to hydrophobic interactions, LMA segments aggregate to form the core, while MAA segments form the outer shell.

[0095] Using acid-base titration, by monitoring the pH value and conductivity during the titration process, a titration curve was plotted, and the pKa of the polymer was calculated to be 6.79. Figure 8Therefore, at pH 5.0, the -COOH groups of the MAA segments hardly dissociate, resulting in very little negative charge on the chains and a dominant hydrophobic effect. Simultaneously, hydrogen bonding between the -COOH groups of the outer shell MAA segments leads to relatively small aggregate sizes. As pH increases, the degree of dissociation of -COOH gradually increases, and the -COO... - The electrostatic repulsion between them gradually increases, and the aggregate size increases. At pH 7.0, this value is close to the pKa value of P(LMA-co-MAA), and the polymer is basically in a "semi-dissociated" state, with almost equal amounts of -COOH and -COO coexisting in the system. - Numerous studies have reported that fatty acids in a "semi-dissociated" state exhibit equal amounts of -COOH and -COO. - They can form dimers; therefore, under conditions of pH=pKa, fatty acid surfactants can generate vesicles. Equal amounts of -COOH and -COO... - The strong hydrogen bonding between the two promotes the formation of dense, large aggregates. However, when the pH increases to 9.0, -COOH has almost completely dissociated, and -COOH and -COO... - The hydrogen bond network between them almost disappears, and the strong electrostatic repulsion causes the aggregates to be highly loose.

[0096] Subsequently, using polymerizable HDDA as the oil phase and 1173 as the photoinitiator, O / W emulsions were prepared with 0.5% (w / v) P(LMA-co-MAA) at pH 5.0, 7.0, and 9.0 as the aqueous phase (containing 1% (w / v) PVA) at an oil-to-water volume ratio of 1:10. These emulsions were then photocured under 365 nm UV light. SEM images of the cured oil droplets are shown below. Figure 5As shown in (d), (e), and (f), the surface of the solidified oil droplets is covered with particles to varying degrees, i.e., self-assembled aggregates of P(LMA-co-MAA) formed at pH 5.0, 7.0, and 9.0. These particles act as particulate emulsifiers to stabilize the emulsion, which is consistent with the characteristics of Pickering emulsions. The figures show that at pH 9.0, the particles on the surface of the solidified oil droplets are dispersed. Due to the large number of negative charges on the surface of the P(LMA-co-MAA) self-assembled aggregates, electrostatic repulsion dominates, making it difficult for the self-assembled aggregates to aggregate. In contrast, at pH 7.0, the particles on the surface of the solidified oil droplets are tightly connected. This phenomenon is similar to the TEM observations; the strong interaction between the carboxyl groups and carboxylate groups of the MAA segments in P(LMA-co-MAA) promotes the tight connection between the self-assembled aggregates, forming a stable interfacial structure. At pH 5.0, the degree of interparticle connectivity on the surface of solidified oil droplets is lower than at pH 7.0. This is because the -COOH groups of MAA segments on the surface of P(LMA-co-MAA) self-assembled aggregates can form aggregates through hydrogen bonding. However, the strength of hydrogen bonding between -COOH groups at pH 5.0 is much lower than that at pH 7.0 when equal amounts of -COOH and -COO groups are bonded together. - The interaction between them.

[0097] Based on the SEM observations under different pH conditions and compared with TEM analysis, the conclusions of both studies on particle aggregation behavior and interface distribution patterns are basically consistent.

[0098] Figure 6 TEM images of P(SMA-co-MAA) self-assembled aggregates at different pH values ​​show that P(SMA-co-MAA) can form self-assembled aggregates under pH conditions of 5.0, 7.0, 9.0 and 11.0.

[0099] Figure 7 This is a SEM image of solidified oil droplets in an O / W type emulsion; the aqueous phase was a 0.5% (w / v) P(SMA-co-MAA) aqueous solution containing 1.0% (w / v) PVA, and the oil phase was HDDA. The results show that P(SMA-co-MAA) can form self-assembled aggregates and act as a particulate emulsifier to stabilize the emulsion, forming a Pickering emulsion, under pH conditions of 5.0, 7.0, 9.0, and 11.0.

[0100] Example 3: Preparation and characterization of high internal phase Pickering emulsion

[0101] (1) Preparation of high internal phase Pickering emulsion

[0102] P(LMA-co-MAA): A series of emulsions were obtained by emulsifying 0.5% (w / v) polymer aqueous solutions at pH 5.0, 7.0 and 9.0 as the aqueous phase and GTCC as the oil phase with an oil phase volume fraction of 10%-90% (10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%) using a high-speed disperser (10,000 rpm, homogenization for 2 min).

[0103] P(SMA-co-MAA): A series of emulsions were obtained by emulsifying 0.5% (w / v) polymer aqueous solutions at pH 5.0, 7.0, 9.0 and 11.0 as the aqueous phase and GTCC as the oil phase with an oil phase volume fraction of 10%-90% (10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%) using a high-speed disperser (10,000 rpm, homogenization for 2 min).

[0104] Test Example 4: pH-dependent storage stability test of high internal phase Pickering emulsion

[0105] To investigate the storage stability of the emulsion system obtained in Example 3, the sample was left to stand at room temperature, and the changes in the appearance of the emulsion on days 1, 7, and 21 were observed. The results are as follows: Figure 9 As shown in (a), (b), and (c) of the figure. The experimental results show that after 21 days of standing, the appearance of each emulsion sample did not change significantly, and they all maintained their initial milky white and homogeneous state. It is worth noting that when the oil phase volume fraction was 75%, 80%, and 85%, the emulsion system did not exhibit oil separation or stratification throughout the entire cycle, indicating that this series of emulsions has excellent storage stability at room temperature.

[0106] The macroscopic properties of the emulsion were further characterized by an inversion experiment, and the results are as follows: Figure 10 As shown, the emulsions did not flow when inverted. After 21 days of storage at room temperature, the series of emulsions still possessed complete self-supporting capabilities, which further demonstrates their excellent long-term stability. Simultaneously, this non-flowing phenomenon is a direct manifestation of the typical gel state formed by high internal phase emulsions, providing a structural basis for their subsequent use as templates or carrier materials.

[0107] like Figure 11As shown, 0.5% (w / v) P(SMA-co-MAA) aqueous solutions at pH 5.0, 7.0, 9.0, and 11.0 were used as the aqueous phase, and GTCC as the oil phase. A series of Pickering emulsions with oil phase volume fractions ranging from 10% to 90% were prepared. With increasing oil phase volume fraction, the emulsion layer height gradually increased at pH 7.0, 9.0, and 11.0, until the oil phase separated at an oil phase volume fraction of 90%. However, at pH 5.0, the oil phase gradually separated, with an oil volume fraction of 85%. This indicates that the P(SMA-co-MAA) self-assembled aggregates exhibit better emulsifying properties at pH 7.0, 9.0, and 11.0 than at pH 5.0. The emulsions were stored at room temperature, and changes in appearance were observed on days 1, 7, and 21. After 21 days, the appearance of the emulsions showed no significant change, remaining the initial milky white color. This demonstrates that Pickering emulsions stabilized by P(SMA-co-MAA) self-assembled aggregate particles have relatively good storage stability.

[0108] like Figure 12 As shown, emulsions with an oil phase volume fraction between 75% and 85% can be inverted. However, the emulsion at pH 5.0 with an oil phase volume fraction of 75% exhibited significant fluidity on day 21, while other emulsions showed no significant change after 21 days of storage and could still be inverted. At pH 5.0, the -COOH groups of the MAA fragments were almost non-ionized. The insufficient hydrophilicity of the self-assembled aggregate particles led to the instability of the Pickering emulsion. Experimental results indicate that emulsions prepared under pH conditions of 7.0, 9.0, and 11.0 exhibit better storage stability.

[0109] Test Example 4: Fluorescence Microscopy

[0110] 0.5% (w / v) P(LMA-co-MAA) aqueous solution with a monomer molar ratio of 1:9 was stained with fluorescein isothiocyanate (FITC). The microstructure of the emulsions at different pH (5.0, 7.0, and 9.0) and oil phase volume fractions (75%, 80%, and 85%) was observed using a fluorescence microscope (485 nm excitation wavelength). The emulsions were prepared with 0.5% (w / v) P(LMA-co-MAA) as the aqueous phase and GTCC as the oil phase. Fluorescence microscopy images of the emulsions prepared at different pH and oil phase volume fractions are shown below. Figure 13 As shown; 0.5% (w / v) P(SMA-co-MAA) is the aqueous phase, and GTCC is the oil phase. Fluorescence microscopy images of emulsions prepared with different pH values ​​and oil phase volume fractions are shown below. Figure 14 As shown.

[0111] like Figure 13 and 14As shown, the prepared emulsion is of the O / W type. At this point, the oil phase volume fraction is above 75%, exceeding the theoretical threshold of 74% for high internal phase emulsions (HIPEs), and the emulsion droplets exhibit a tightly packed, mutually compressed, irregular morphology, all consistent with the typical characteristics of HIPEs. Combined with... Figure 13 and Figure 14 This indicates that the emulsions prepared at pH 5.0, 7.0 and 9.0, 11.0, with an oil phase content of 75%-85%, are O / W type HIPPEs.

[0112] Test Example 5: Ultra-depth-of-field microscope

[0113] To further evaluate the stability of HIPPEs prepared from 0.5% (w / v) P(LMA-co-MAA) from a microscopic perspective, 100 µL of the emulsion was dropped onto a glass slide, and microscopic images of the emulsion were taken using a depth-of-field microscope. Deep-of-field micrographs of the emulsion were taken on days 1, 7, and 21 to evaluate its stability. The changes in droplet morphology over 21 days are shown below. Figure 15 , Figure 16 and Figure 17 The images shown are microscopic photographs of emulsion droplets at different pH values ​​(5.0, 7.0, and 9.0) and oil phase volume fractions (75%, 80%, and 85%).

[0114] On day 1, the droplets of the high internal phase emulsions under different pH conditions all exhibited irregular shapes with mutual compression, a typical microstructural feature of high internal phase emulsions, indicating that a tightly packed droplet network structure was formed in the initial stage. On day 7, the droplets of the emulsion prepared at pH 5.0 showed significant changes; the droplets were no longer tightly packed, and some droplets coalesced, indicating that the emulsion stability began to decline. In contrast, the droplet morphology of the emulsions at pH 7.0 and 9.0 remained stable for at least 21 days, demonstrating good storage stability.

[0115] The main reason for the above differences is that at pH 5.0, the -COOH group of the MAA segment in P(LMA-co-MAA) hardly dissociates, resulting in excessively hydrophobic self-assembled aggregates. This insufficient wettability of the self-assembled aggregate particles at the oil-water interface prevents effective stabilization of the interface, leading to instability in the Pickering emulsion and a tendency for aggregation. At pH 7.0 and 9.0, the -COOH group of the MAA segment can dissociate to form -COO. -The increased hydrophilicity of the self-assembled aggregates enhances their wettability at the oil-water interface, thereby improving emulsifying ability. Secondly, the enhanced electrostatic repulsion between the self-assembled aggregates effectively inhibits droplet aggregation, further improving emulsion stability. Under the combined effect of these mechanisms, the emulsion stability of P(LMA-co-MAA) at pH 7.0 and 9.0 is significantly better than that at pH 5.0.

[0116] Further analysis of the droplet size variation revealed that, under constant aqueous phase pH conditions, as the oil phase volume fraction increased (from 75% to 85%), the droplet size gradually decreased, and the droplet size distribution became more uniform. Furthermore, at the same oil phase volume fraction, the droplet size gradually decreased with increasing aqueous phase pH. These particle size variation patterns further confirm that P(LMA-co-MAA)-stable high-internal-phase Pickering emulsions exhibit excellent emulsifying properties at pH 7.0 and 9.0, and that pH and oil phase volume fraction have a synergistic regulatory effect on the microstructure of this high-internal-phase Pickering emulsion system.

[0117] Super-depth-of-field microscopic images of HIPPEs stable at pH 7.0, pH 9.0, and pH 11.0.0 with different oil phase volume fractions (75%, 80%, 85%) and 0.5% (w / v) P(SMA-co-MAA) at pH 7.0, pH 9.0, and pH 11.0.0 on days 1, 7, and 21 are shown below. Figure 18 As shown, the P(SMA-co-MAA)-stabilized high internal phase Pickering emulsion exhibits excellent emulsifying properties at pH 7.0, 9.0, and 11.0, which are basically consistent with the high internal phase Pickering emulsion constructed by P(LMA-co-MAA). pH and oil phase volume fraction have a synergistic regulatory effect on the microstructure of this high internal phase Pickering emulsion system.

[0118] Test Example 6 Centrifugation Stability Test

[0119] Emulsions with different pH values ​​(5.0, 7.0, and 9.0) and an oil phase volume fraction of 85% were placed in centrifuge tubes and centrifuged at 5000, 8000, and 11000 rpm for 15 min, respectively, to observe whether stratification occurred.

[0120] Results of HIPPEs stabilized with 0.5% (w / v) P(LMA-co-MAA) at different pH values ​​are as follows: Figure 19As shown, the emulsions with pH values ​​of 7.0 and 9.0 did not exhibit stratification at any of the three centrifugation speeds, remaining a uniform milky white state and demonstrating good centrifugal stability. However, at pH value of 5.0, the emulsion showed obvious stratification at 5000 rpm, with a clear aqueous phase on the upper layer, indicating poor centrifugal stability. This suggests that neutral or slightly alkaline conditions help improve the centrifugal stability of HIPPEs, a result consistent with... Figure 15 , Figure 16 and Figure 17 The results of the droplet morphology analysis using a super depth-of-field microscope are basically consistent.

[0121] Results of HIPPEs stabilized with 0.5% (w / v) P(SMA-co-MAA) at different pH values ​​are as follows: Figure 20 As shown, the emulsions with pH values ​​of 9.0 and 11.0 did not exhibit stratification at any of the three centrifugation speeds, remaining a uniform milky white state and demonstrating good centrifugal stability. However, at pH value of 7.0, the emulsion showed obvious stratification at 10,000 rpm, with a clear aqueous phase on the upper layer, indicating poor centrifugal stability. Therefore, neutral or slightly alkaline conditions help improve the centrifugal stability of HIPPEs.

[0122] Test Example 6 Temperature Stability Test

[0123] Emulsions with different pH values ​​(5.0, 7.0, and 9.0) and an oil phase volume fraction of 85% were placed at 4 ℃, 40 ℃, 60 ℃, and 80 ℃ for 24 h. Their appearance changes were observed, and upright and inverted photographs were taken. Digital photographs of P(LMA-co-MAA) stable HIPPEs at different pH values ​​after storage at different temperatures for 24 h are shown below. Figure 21 As shown in the figure, all exhibit excellent storage stability.

[0124] P(SMA-co-MAA) stabilized HIPPEs: Emulsions with different pH values ​​(5.0, 7.0 and 9.0, 11.0) and an oil phase content of 85% (v / v) were placed at 4 ℃, 40 ℃, 60 ℃, and 80 ℃ for 24 h. Their appearance changes were observed, and upright and inverted photographs were taken. The results are as follows: Figure 22 As shown in the figure, the emulsion did not separate into layers after 24 hours under either refrigeration or heating conditions, and remained stable even after inversion, indicating that the heating and cooling processes did not damage the emulsion structure. Generally, during heating, as the temperature rises, the Brownian motion of the droplets in the emulsion intensifies, making it easier for droplets to collide and coalesce, resulting in layering. However, in this experiment, the appearance of the emulsion did not change significantly, indicating that the high internal phase emulsion system has excellent storage stability.

[0125] Test Example 7: Rheological Property Test

[0126] Rheological properties provide textural information for P(LMA-co-MAA) stable HIPPEs and help reveal the regulatory role of pH on the interfacial interactions of self-assembled aggregates. Rheological properties of emulsions with different pH values ​​(5.0, 7.0, and 9.0) and an oil phase volume fraction of 85% were determined. The rheological behavior of HIPPEs was characterized using a rotational rheometer (equipped with a 2° cone plate with a diameter of 40 mm), and all tests were performed at 25 °C. The linear viscoelastic region of the emulsion was determined by amplitude scanning, with a fixed test frequency of 1 Hz and a stress scanning range of 0.01–100%. Based on this, frequency scanning was performed to record the changes in storage modulus (G') and loss modulus (G'') with frequency, with a test stress of 0.5% and a frequency range of 0.01–10 Hz. Furthermore, steady-state shear flow tests were used to determine the shear viscosity of the emulsion, with shear rates set from 0.01 to 800 s⁻¹. -1 .

[0127] Strain scanning test results as follows Figure 23 As shown in (a), it is evident that within the linear viscoelastic region, the storage modulus (G') of all samples is much higher than the loss modulus (G''), and the system exhibits gel behavior dominated by elasticity.

[0128] Frequency scan test results are as follows Figure 23 As shown in (b), pH effectively modulates the viscoelasticity of HIPPEs. Throughout the entire test angular frequency range, G' of each sample was consistently significantly higher than G'', and G' showed only a slight increasing trend with increasing angular frequency, exhibiting extremely weak frequency dependence. This indicates that the emulsion system primarily exhibits an elastic response, typically displaying strong gel behavior, and possesses excellent resistance to deformation and structural stability.

[0129] Shear scan curves of HIPPEs at different pH values ​​are shown below. Figure 23 As shown in (c), the apparent viscosity of all samples decreased significantly with increasing shear rate, exhibiting typical shear-thinning behavior, which is also one of the typical characteristics of high internal phase Pickering emulsions. This phenomenon can be attributed to the deformation of the tightly packed droplets in the emulsion or the disruption of the droplet cluster structure when the shear rate increases, leading to a decrease in the system viscosity.

[0130] It should be noted that although the samples under all pH conditions exhibited strong gelation properties, the underlying structure formation mechanisms were not the same.

[0131] Storage modulus (G') and loss modulus (G'') of P(SMA-co-MAA) stable HIPPEs (85% oil phase by volume) as a function of frequency at different pH levels, and viscosity versus shear rate curves are shown below. Figure 24As shown, it can be seen that it also has strong gel properties and shear-thinning characteristics, which are consistent with the basic characteristics of high internal phase Pickering emulsions.

[0132] Example 4: Effect of oil phase lipophilicity on high internal phase emulsion

[0133] The oil-water partition coefficient (Log P) is the logarithmic ratio of the concentrations of a substance at equilibrium in the n-octanol and water phases, and is commonly used to characterize the lipophilicity or hydrophilicity of a substance. Generally, the larger the Log P value, the stronger the lipophilicity of the substance and the lower its solubility in the aqueous phase. However, for oils with even stronger lipophilicity, such as white oil (Log P = 7.42), silicone oil (Log P > 8.0), and olive oil (Log P = 23.29), their hydrophobicity differs significantly from that of GTCC, posing a greater challenge to the stabilizing ability of emulsifiers. Therefore, it is necessary to further investigate whether P(LMA-co-MAA) self-assembled aggregates, as particulate emulsifiers, can stabilize these highly lipophilic oils to form Pickering emulsions.

[0134] Therefore, a series of emulsions were subsequently prepared using a 0.5% (w / v) P(LMA-co-MAA) aqueous solution at pH 7.0 as the aqueous phase and silicone oil (D10, D50), olive oil, and white oil as the oil phase, respectively, at different oil phase volume fractions (10~90%). Figure 25 As shown, at pH 7.0, 0.5% (w / v) P(LMA-co-MAA) can emulsify all four oil phases to form stable Pickering emulsions. The emulsion layer height varies with the oil phase volume fraction. For silicone oils (D10, D50) and olive oil, emulsions can still be formed at an oil phase volume fraction of 85%; while for the white oil system, emulsification can still be achieved at an oil phase volume fraction as high as 90%. When the oil phase volume fraction is 75%, 80%, and 85%, the internal phase volume of the emulsion exceeds 74.05%, indicating that under pH 7.0 conditions, all four oil phases can be stably formed into HIPPEs by the self-assembled aggregates of P(LMA-co-MAA). This result further confirms the wide applicability of this copolymer aggregate as a particulate emulsifier, effectively stabilizing high internal phase emulsion systems even when faced with multiple oil phases with significantly different lipophilicities.

[0135] To verify whether the above emulsions were O / W type HIPPEs, FITC was used to stain the P(LMA-co-MAA) aqueous solution, and the microstructure of the four emulsions was observed using a fluorescence microscope. The oil phases of these four emulsions were silicone oil (D10, D50), olive oil, and white oil, with an oil phase volume fraction of 85%.

[0136] like Figure 26As shown, the continuous phase is an aqueous phase stained with FITC, exhibiting green fluorescence; the dispersed phase consists of unstained oil droplets, appearing black under bright field. The oil droplets deform due to their dense accumulation, exhibiting a typical high internal phase emulsion structure. Therefore, the four emulsions with an oil phase content of 75-85% (v / v) are O / W type HIPPEs.

[0137] D10 and D50 are two polydimethylsiloxanes with different degrees of polymerization, both containing siloxane structures; olive oil is a vegetable oil rich in unsaturated fatty acids; white oil is a mineral oil, mainly composed of saturated hydrocarbons. The four oil phases have significantly different chemical structures, but are all lipophilic oil phases, and these oils have wide applications in cosmetics, food, and industrial manufacturing. However, obtaining stable emulsions containing such oils, especially stable O / W type HIPPEs, usually requires complex and high-concentration emulsifier formulations. In contrast, this study used a 0.5% (w / v) P(LMA-co-MAA) aqueous solution (i.e., P(LMA-co-MAA) accounted for 0.075% (w / v) of the total emulsion system content) to obtain O / W type HIPPEs with an oil phase volume fraction as high as 85%. In some oil-phase types, the oil phase content exceeds 90%. That is, even with P(LMA-co-MAA) at a total concentration of 0.05% (w / v) in the emulsion system, O / W type HIPPEs with an oil phase volume fraction as high as 90% can still be obtained. These results demonstrate that P(LMA-co-MAA) exhibits excellent emulsifying ability even at extremely low concentrations.

[0138] Using 0.5% (w / v) P(SMA-co-MAA) at pH 9.0 as a stabilizer, and with olive oil, white oil, D5, D10, D20, and D50 as the oil phase, the appearance images of the emulsions with different oil phase volume fractions are shown below. Figure 27 As shown, P(SMA-co-MAA) can form stable high-internal-phase Pickering emulsions in six different oil-phase emulsions. Specifically, using a 0.5% (w / v) P(SMA-co-MAA) aqueous solution (i.e., P(SMA-co-MAA) content in the entire emulsion system is 0.075% (w / v)) yields O / W type HIPPEs with an oil phase volume fraction as high as 85%. In some oil-phase types, the oil phase content exceeds 90%, meaning that even with a P(SMA-co-MAA) content of 0.05% (w / v) in the entire emulsion system, O / W type HIPPEs with an oil phase volume fraction as high as 90% can also be obtained.

[0139] Therefore, P(LMA-co-MAA) and P(SMA-co-MAA) can form high internal phase Pickering emulsions for a variety of oils.

[0140] In summary, amphiphilic random copolymers P(LMA-co-MAA) and P(SMA-co-MAA) were synthesized via solution polymerization, and then analyzed using FIIR... 1 HNMR and APC characterization confirmed P(LMA-co-MAA) polymers with LMA and MAA monomer molar ratios of 1:9, 2:8 and 3:7, and P(SMA-co-MAA) with a monomer molar ratio of 1:9.

[0141] Emulsions were prepared using P(LMA-co-MAA) self-assembled aggregates as stabilizers and GTCC as the oil phase. The effects of monomer molar ratio, pH, and oil phase volume fraction on the emulsifying properties of P(LMA-co-MAA) were investigated, and the optimal monomer molar ratio of P(LMA-co-MAA) for preparing the emulsion was determined to be 1:9.

[0142] When the oil phase volume fraction was 75%, 80%, and 85%, and the pH was 5.0, 7.0, and 9.0, respectively, the P(LMA-co-MAA)-stabilized emulsion systems were all O / W type HIPPEs. Microstructure observation of the emulsions at room temperature over 21 days using a super-depth-of-field microscope showed that the emulsifying performance of P(LMA-co-MAA) at pH 7.0 and 9.0 was significantly better than that at pH 5.0. Storage stability tests (4-80 °C) and centrifugation tests indicated that the stability of HIPPEs prepared at pH 7.0 and 9.0 was also significantly better than that at pH 5.0. Rheological tests showed that at pH 5.0, 7.0, and 9.0, the HIPPEs exhibited shear-thinning characteristics and elastic-dominant gel behavior.

[0143] When the oil phase volume fraction was 75%, 80%, and 85%, and the pH was 7.0, 9.0, and 11.0, respectively, the P(SMA-co-MAA)-stabilized emulsion systems were all O / W type HIPPEs. Microstructure observation of the emulsions at room temperature over 21 days using ultra-depth-of-field microscopy showed that the emulsifying performance of P(SMA-co-MAA) at pH 9.0 and 11.0 was superior to that at pH 7.0. Storage stability tests (4-80 °C) and centrifugation tests indicated that the stability of HIPPEs prepared at pH 11.0 and 9.0 was also significantly better than that at pH 7.0. Rheological tests showed that at pH 7.0, 9.0, and 11.0, the HIPPEs exhibited shear-thinning characteristics and elastic-dominant gel behavior.

[0144] When the oil phase was replaced with highly lipophilic polydimethylsiloxane (D10, D50), olive oil, and white oil, an aqueous solution of 0.5% (w / v) P(LMA-co-MAA) at pH 7.0 as the aqueous phase could yield O / W type HIPPEs with an oil phase volume fraction as high as 85%, meaning that the content of P(LMA-co-MAA) in the entire emulsion system was 0.075% (w / v), demonstrating the excellent emulsifying properties of P(LMA-co-MAA).

[0145] Comparative Example

[0146] This comparative example provides a method for preparing poly(styrene-co-methacrylic acid) (P(St-co-MAA)), which is similar to Example 1, except that LMA and MAA in a molar ratio of 1:9 are replaced with styrene (St) and MAA in a molar ratio of 6:4 to obtain P(St-co-MAA) with a monomer molar ratio of 6:4.

[0147] Following the method in step (1) of Example 2, aqueous solutions of P(St-co-MAA) with a concentration of 1.0% (w / v) and pH values ​​of 5.7, 7.0, 7.3, 7.9, 8.2, 9.0, 9.1, 10.0, 11.0, and 12.0 were prepared. The microstructure of the self-assembled aggregates induced at different pH values ​​(pH 5.7, pH 7.0, pH 7.9, pH 9.1) was characterized by TEM using the method described in Test Example 3. The results are as follows: Figure 28 As shown in the image, at pH 5.7, the particle size of the random copolymer self-assembled aggregates is small, only 10 nm; when the pH is increased to 7.0, the particle size is 57 nm. This indicates a significant increase in aggregate particle size when the pH is increased from 5.7 to 7.0. Subsequently, when the pH is increased from 7.0 to 7.9, the copolymer aggregate particle size continues to increase (63 nm). However, when the pH is adjusted to 9.1, almost no self-assembled aggregate particles are visible in the TEM image, only a faint linear trace, indicating that the copolymer aggregates have depolymerized.

[0148] Photographs of the appearance of P(St-co-MAA) aqueous solutions at pH 7.3, pH 8.2, pH 9.0, pH 10.0, pH 11.0, and pH 12.0 under sunlight and laser pointer illumination, along with the corresponding Tyndall effect (from left to right, pH values ​​are 12.0, 11.0, 10.0, 9.0, 8.2, and 7.3). Figure 29 As shown, it can also be seen that when the pH exceeds 9.0, there are no self-assembled aggregates in the solution, while opalescence appears at 7.3 (the transparency is very low when the pH is less than 6, and it is impossible to judge by appearance and Tyndall effect). Further TEM is needed to determine the self-assembly status of the copolymer.

[0149] Because the emulsions prepared by FITC staining using a single aqueous phase yielded poor results, both the aqueous and oil phases were stained simultaneously. The aqueous phase consisted of a 1.0% (w / v) P(St-co-MAA) aqueous solution at pH 7.0 after FITC staining, and the oil phase consisted of Nile Red-stained GTCC. The oil-water ratio was 1:9–9:1, with a total oil-water mass of 4.00 g. The emulsions were incubated at 10000 rpm for 2 min to obtain a series of staining emulsions with different oil-water ratios. The appearance and inversion test were observed, and the microstructure of the emulsions with different oil-water ratios was observed using a fluorescence microscope at an excitation wavelength of 485 nm. Figure 30 As shown in the figure, it is clear that the emulsion exhibits different macroscopic structures as the oil-to-water ratio increases. When the oil-to-water ratio is 1:9-5:5, the emulsion shows obvious stratification, and the emulsion is an O / W emulsion. When the oil-to-water ratio is 6:4-9:1, although there is no obvious precipitation of oil or water phase, the appearance color of the 6:4 and 7:3 emulsions is different from that of the 8:2 and 9:1 emulsions. The 6:4 and 7:3 emulsions are orange, while the 8:2 and 9:1 emulsions are red. This indicates that the microscopic structure of the emulsion has changed significantly. The 6:4 and 7:3 emulsions are bicontinuous Pickering emulsions, while the 8:2 and 9:1 emulsions are W / O emulsions. Furthermore, inverted images of the emulsions reveal that both the 6:4 and 7:3 emulsions remained at the bottom of the sample vials before and after inversion, exhibiting no significant flow. This demonstrates the unique gelation properties of the bicontinuous Pickering emulsion and confirms the formation of bicontinuous emulsion gels (Bijels). Visually, it is clearly different from P(LMA-co-MAA) and P(SMA-co-MAA). P(St-co-MAA), when used as an interface stabilizer, failed to form an O / W type high internal phase Pickering emulsion.

[0150] Fluorescence microscopy was used to image emulsions with different oil-to-water ratios. Water-soluble and oil-soluble dyes were excited at an excitation wavelength of 485 nm, resulting in green and red fluorescence, respectively. The results are as follows: Figure 31As shown, when the oil-to-water ratio is 1:9 to 5:5, the emulsion is of the O / W or W / O / W type, and the droplet size increases with the increase of the oil-to-water volume ratio. The emulsion droplets all exhibit anisotropic characteristics, typical of Pickering emulsions. When the oil-to-water ratio is 6:4 and 7:3, the emulsion exhibits a bicontinuous structure, forming a bicontinuous emulsion. When the oil-to-water ratio increases to 8:2 and 9:1, the emulsion is a W / O emulsion. This is because the emulsion type depends not only on the surface hydrophilicity / hydrophobicity of the particulate emulsifier but also on the oil-to-water ratio of the emulsion. When the volume fraction of the oil phase in the emulsion increases, the size and number of emulsion droplets also increase, which forces droplet aggregation and interfacial fusion, causing the initial internal phase to transform into a new external phase. It can be demonstrated that emulsions prepared with different monomer ratios of P(St-co-MAA) will undergo emulsion type conversion with increasing pH.

[0151] It should be noted that when the molar ratio of styrene (St) to MAA is 1:9, 2:8, or 3:7, it is impossible to dissolve and form a solution and self-assembled aggregates, let alone obtain a high internal phase emulsion.

[0152] In summary, it can be seen that the emulsions prepared using P(St-co-MAA) are not high internal phase emulsions.

[0153] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high internal phase Pickering emulsion, characterized in that, The high internal phase Pickerling emulsion is an oil-in-water type high internal phase Pickerling emulsion, comprising an aqueous phase and an oil phase; the aqueous phase comprises amphiphilic random copolymer self-assembled aggregates; The amphiphilic random copolymer in the self-assembled aggregate is selected from poly(dodecyl methacrylate-co-methacrylic acid) and / or poly(octadecyl methacrylate-co-methacrylic acid).

2. The high internal phase Pickering emulsion according to claim 1, characterized in that, The oil phase volume fraction of the high internal phase Pickering emulsion is 75%-90%.

3. The high internal phase Pickering emulsion according to claim 1, characterized in that, The molar ratio of dodecyl methacrylate to methacrylic acid in the poly(dodecyl methacrylate-co-methacrylic acid) is 1:9-2:

8. And / or, the molar ratio of octadecyl methacrylate to methacrylic acid in the poly(octadecyl methacrylate-co-methacrylic acid) is 1:9-2:

8.

4. The high internal phase Pickering emulsion according to claim 1, characterized in that, The mass-volume fraction of the amphiphilic random polymer self-assembled aggregates in the aqueous phase is 0.5%-1.5%.

5. The high internal phase Pickering emulsion according to claim 1, characterized in that, The pH value of the aqueous phase is 5.0-11.

0.

6. The high internal phase Pickering emulsion according to claim 1, characterized in that, The oil phase is selected from one or more of caprylic / capric glycerides, white oil, silicone oil, and olive oil; the silicone oil is decamethylcyclopentasiloxane or silicone oil with a viscosity range of 10 cst-50 cst.

7. A method for preparing the high internal phase Pickering emulsion according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Dissolve the amphiphilic random polymer in an alkaline solution, adjust the pH, and obtain a solution of amphiphilic random polymer self-assembled aggregates; The amphiphilic random polymer is selected from poly(dodecyl methacrylate-co-methacrylic acid) and / or poly(octadecyl methacrylate-co-methacrylic acid). (2) Using the amphiphilic random polymer self-assembled aggregate solution obtained in step (1) as the aqueous phase, mix it with the oil phase and emulsify it to obtain the high internal phase Pickering emulsion.

8. The preparation method according to claim 7, characterized in that, In step (1), the alkali in the alkaline solution is one or more of NaOH, NaHCO3, arginine and triethanolamine.

9. The preparation method according to claim 7, characterized in that, In step (1), the pH is 5-11.

10. The use of the high internal phase Pickering emulsion according to any one of claims 1-6 in food preservation coatings, cosmetic creams, functional foods, 3D printing, or tissue engineering.

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