Efficient compound emulsifier based on hydrophilic polyelectrolyte

Abstract

The invention relates to an efficient compound emulsifier based on hydrophilic polyelectrolyte, and belongs to the field of colloid and interface chemistry. The composite emulsifier is composed of a hydrophilic polyelectrolyte and an ionic surfactant, and the hydrophilic polyelectrolyte and the ionic surfactant have the same charges in a water phase. The compound emulsifier is an efficient O / W type emulsifier. Wherein the effective concentration of the polyelectrolyte can be as low as 0.001 wt.% of the mass fraction of the polyelectrolyte in a water phase, and the effective concentration of the ionic surfactant can be as low as 0.01 times of the critical micelle concentration (cmc) of the ionic surfactant. The composite emulsifier has good biocompatibility and can be safely used in the fields of food, medicine, cosmetics and the like. The efficient compound emulsifier can greatly reduce the use amount and emission of the surfactant, and has extremely high economic benefits and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of colloid and interface chemistry, and more specifically to a highly efficient composite emulsifier for stabilizing oil-in-water (O / W) emulsions. Background Technology

[0002] An emulsion is a multiphase dispersion system in which a liquid is dispersed in the form of droplets in another immiscible liquid. To obtain a stable emulsion, an emulsifier is usually added. Based on the type of emulsifier used, emulsions can be mainly classified into the following categories: conventional emulsions stabilized by surfactants or polymers adsorbed at the interface to form a monolayer; Pickering emulsions stabilized by amphiphilic solid (colloidal) particles adsorbed at the interface to form a particulate film; and, in recent years, Oil-in-dispersion (OID) emulsions, which are synergistically stabilized by ionic surfactants with the same charge and inorganic nanoparticles. Compared with other systems, OID emulsion systems exhibit extremely high emulsifying efficiency, significantly reducing the amount and emission of surfactants.

[0003] However, OID emulsion systems still face significant limitations in practical applications: on the one hand, their core component, inorganic nanoparticles, needs to be fully dispersed (e.g., high-intensity ultrasonic homogenization) before emulsion preparation, a process that is complex, energy-intensive, and requires sophisticated equipment. On the other hand, inorganic nanoparticles pose potential risks of biotoxicity, irritation, or difficulty in metabolism in fields such as food, cosmetics, and pharmaceuticals, where biosafety and material compatibility are critical, thus severely limiting their application.

[0004] Therefore, although OID emulsions have made significant progress in reducing emulsifier usage, it is of great practical significance to develop a high-efficiency composite emulsifier that can replace inorganic nanoparticles, has ultra-low usage characteristics, and possesses better biocompatibility, lower processing costs, and is environmentally friendly. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a novel, highly efficient composite emulsifier and its applications. This invention employs a composite of a strongly hydrophilic polyelectrolyte and an ionic surfactant carrying the same charge. This composite emulsifier can efficiently stabilize O / W emulsions at ultra-low concentrations, providing a safer, lower-cost, and more environmentally friendly emulsification solution for fields with extremely high safety requirements, such as food, cosmetics, and pharmaceuticals. This invention utilizes the synergistic effect between an ultra-low concentration of the strongly hydrophilic polyelectrolyte and the surfactant carrying the same charge. The composite emulsifier can efficiently stabilize O / W emulsions with droplet diameters between 150 μm and 1 μm, requiring only about one-hundredth to one-thousandth of the concentration used in conventional emulsifiers.

[0006] The first objective of this invention is to provide a composite emulsifier composed of a hydrophilic polyelectrolyte and an ionic surfactant, wherein the hydrophilic polyelectrolyte and the ionic surfactant carry the same charge in the aqueous phase; wherein the hydrophilic polyelectrolyte is used to thicken the aqueous phase and, through electrostatic interaction, synergistically stabilizes the oil-water interface with the ionic surfactant. Furthermore, the effective concentration of the polyelectrolyte is from 0.001 wt.% to 1.0 wt.% of its mass fraction in the aqueous phase.

[0007] Furthermore, the effective concentration of the ionic surfactant is from 0.01 cmc to 0.1 cmc.

[0008] Polyelectrolytes are macromolecular electrolytes containing ionizable groups. They possess excellent water dispersibility, high viscosity, and ease of modification, and are widely used in wastewater treatment, papermaking, and coatings. Some amphiphilic polyelectrolytes can independently stabilize emulsions; however, strongly hydrophilic polyelectrolytes are difficult to stabilize emulsions on their own.

[0009] In this invention, the same charge refers to the same type of charge, such as both being positive charges or both being negative charges, and the amount of charge they carry may be equal or unequal.

[0010] In some embodiments, the composite emulsifier comprises a positively charged polyelectrolyte and a cationic surfactant in water, or a negatively charged non-polyelectrolyte and anionic surfactant in water.

[0011] In some embodiments, the effective concentration of the polyelectrolyte is 0.001 wt.% to 1.0 wt.% of its mass fraction in the aqueous phase. Optionally, it is 0.001 wt.% to 1.0 wt.%, 0.001 wt.% to 0.8 wt.%, 0.001 wt.% to 0.5 wt.%, 0.0001 wt.% to 0.1 wt.%, 0.001 wt.% to 0.05 wt.%; further, it is optional to be 0.005 wt.% to 1.0 wt.%, 0.01 wt.% to 1.0 wt.%, 0.05 wt.% to 0.5 wt.%, 0.1 wt.% to 0.5 wt.%, etc.

[0012] In some embodiments, the polyelectrolyte can be any one or a combination of the following: cationic polyelectrolytes include polyethyleneimine, cationic polyacrylamide, polydimethyldiallylammonium chloride, and chitosan; anionic polyelectrolytes include anionic polyacrylamide, sodium polyacrylate, sodium alginate, carboxymethyl cellulose, heparin, etc.

[0013] In some embodiments, the effective concentration of the ionic surfactant is from 0.01 cmc to 0.1 cmc, where cmc is the critical micelle concentration of the corresponding ionic surfactant in pure water.

[0014] In some embodiments, the ionic surfactant may be any one or a combination of the following: cationic surfactants include quaternary ammonium salts, pyridine ammonium salts, and imidazoline ammonium salts; anionic surfactants include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfonates, and fatty acid salts (soap), preferably with a main alkyl chain length of C. 12 -C 18 Amphoteric surfactants include imidazoline surfactants, betaine surfactants, amino acid surfactants, and amine oxide surfactants, preferably with an alkyl chain length of C. 12 -C 18 .

[0015] In some preferred embodiments, the ionic surfactant is a quaternary azobenzene (C4AzoC6N); its molecular formula is C 25 H 38 N3OBr.

[0016] In some embodiments, the "aqueous phase" carrying the same charge in the aqueous phase refers to the aqueous phase present in the emulsion prepared when the composite emulsifier is used.

[0017] A second aspect of the present invention provides a stimulus-responsive composite emulsifier, which is formed by combining a stimulus-responsive hydrophilic polyelectrolyte with an ionic surfactant, wherein the stimulus-responsive hydrophilic polyelectrolyte and the ionic surfactant carry the same charge in the aqueous phase.

[0018] In some embodiments, the stimulus-responsive hydrophilic polyelectrolyte is a pH-responsive, oxygen-temperature-responsive, or CO2 / N2-responsive polyelectrolyte.

[0019] In some embodiments, the stimulus-responsive hydrophilic polyelectrolyte is a surfactant having reversible protonating / deprotonating groups.

[0020] In some preferred embodiments, the stimulus-responsive hydrophilic polyelectrolyte is chitosan.

[0021] A third objective of this invention is to provide a dispersion system containing the composite emulsifier of this invention.

[0022] In some embodiments, the dispersion system comprises a dispersed phase and a continuous phase: wherein the continuous phase contains a polyelectrolyte, and an ionic surfactant is adsorbed at the interface between the dispersed phase and the continuous phase; and the polyelectrolyte and the ionic surfactant carry the same charge in the aqueous phase.

[0023] A fourth objective of this invention is to provide an O / W type emulsion comprising an oil phase, an aqueous phase, and the composite emulsifier of this invention.

[0024] In some embodiments, the oil phase is selected from alkanes, aromatics, triglycerides, silicone oils, or fragrance oils; In some embodiments, the emulsion is an O / W type emulsion, which may be formed by emulsifying substances such as gasoline, kerosene or diesel.

[0025] In some embodiments, the volume fraction of the oily substance in the emulsion is from 1% to 75%.

[0026] In some embodiments, the diameter of the oil droplets in the O / W emulsion is between 150 μm and 1 μm, with most being between 100 μm and 200 μm. The emulsion is stable at room temperature for at least six months.

[0027] A fifth object of the present invention is to provide a food, cosmetic, pharmaceutical, pesticide, or emulsion explosive composition comprising or in emulsion form, wherein the composite emulsifier of the present invention is used as the emulsifier.

[0028] In some embodiments, the food may be bread, ice cream, cream, etc.

[0029] This invention also claims protection for the application of the composite emulsifier in the preparation of O / W type oil-water dispersion systems, as well as its application in the food, cosmetics, pharmaceutical, pesticide, oil transportation, machining, material synthesis (emulsion polymerization), and emulsion explosive industries.

[0030] In some implementations, it is used in the fields of pesticides, oil transportation, machining, emulsion polymerization, or emulsion explosives. In some preferred embodiments, the hydrophilic polyelectrolyte is applied in food, cosmetics, or pharmaceutical products due to its high biocompatibility and biodegradability.

[0031] In some embodiments, the application in the food industry can be as a food additive; it can play a role in emulsification, dispersion, lubrication, and stabilization during the mixing and blending of raw materials, or it can improve the quality and stability of food. For example, it can be used in bread making to maintain the soft texture of bread and as an emulsifier to prevent starch retrogradation, or in the manufacture of cold foods to increase the product's overrun, or in the production of margarine, etc.

[0032] In some embodiments, the application in the materials synthesis industry includes using emulsion polymerization with emulsifiers to synthesize products such as coatings and adhesives.

[0033] In some implementations, large quantities of explosives are required in blasting operations such as mining, construction blasting, and rock excavation. Traditional explosives suffer from problems such as inconvenience in carrying and a high risk of safety accidents. Emulsion explosives, in addition to ensuring good explosive effects, have advantages such as good emulsification, good storage stability, and suitability for long-term storage at high and extremely cold temperatures, thus solving the safety hazards during transportation, carrying, and use. The composite emulsifier of this invention can be used to emulsion explosives and to prepare emulsion explosive compositions.

[0034] In some embodiments, the application in the oil transportation industry involves using the composite emulsifier of this invention to emulsify oil products, thereby facilitating oil transportation, reducing the equipment requirements for oil transportation, and improving the safety of oil transportation. If necessary, certain measures can be taken to demulsify the oil after it arrives at its destination.

[0035] In some embodiments, the application includes preparing an emulsion using the composite emulsifier of the present invention. When demulsification is required, another ionic surfactant with the same charge as the existing ionic surfactant and the opposite charge to the polyelectrolyte is added to the emulsion and mixed evenly, which can lead to rapid demulsification of the emulsion.

[0036] In some embodiments, the application further includes restabilizing and recycling the demulsified emulsion; specifically, after demulsification, an ionic surfactant with the same charge (the charge amount may be equal or unequal) as the ionic surfactant in the initial emulsion is added to the system (the type of ionic surfactant may be the same or different from the original one), and after homogenization and emulsification, a stable emulsion is formed again. This cycle can be repeated, allowing the emulsion to switch between demulsification and restabilization multiple times.

[0037] In some embodiments, the stimulus-responsive hydrophilic polyelectrolyte has reversible protonated / deprotonated groups. By introducing CO2 or N2 gas, the charge density of the polyelectrolyte can be changed, thereby altering the electrostatic repulsion between oil droplets and between oil droplets and the polyelectrolyte, thus achieving demulsification and restabilization of the emulsion. This process can be repeated, allowing the emulsion to switch between demulsification and restabilization multiple times.

[0038] In some embodiments, the emulsifier of the present invention employs a strongly hydrophilic polyelectrolyte that carries a charge in the aqueous medium, such as anionic polyacrylamide (negatively charged in acidic water) and cationic chitosan polyelectrolyte (positively charged in acidic water), combined with an ionic surfactant carrying the same charge, such as anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant quaternary azobenzene (C4AzoC6N), to form a composite emulsifier. The ionic surfactant adsorbs at the oil / water interface, reducing the interfacial tension and imparting a surface charge to the oil droplets, enabling electrostatic repulsion when the droplets approach each other. Meanwhile, the polyelectrolyte is distributed in a disordered, extended conformation within the aqueous phase (continuous phase), increasing the viscosity of the aqueous phase and further preventing the oil droplets from approaching each other. The synergistic effect between the polyelectrolyte and the surfactant effectively prevents flocculation and aggregation between oil droplets, maintaining the dynamic stability of the emulsion.

[0039] Beneficial effects: (1) The present invention provides a composite emulsifier, which works by the synergistic effect of a hydrophilic polyelectrolyte and an ionic surfactant with the same charge. The surfactant is adsorbed at the interface to reduce tension and impart charge, while the polyelectrolyte is dispersed in the aqueous phase to increase the viscosity of the system and provide a kinetic barrier. The synergistic effect of the two stabilizes the emulsion. (2) Achieving ultra-low dosage; the effective concentration of the surfactant in this invention can be as low as 0.01 to 0.1 times its critical micelle concentration (cmc), and the dosage is reduced by 10-100 times compared with traditional emulsifiers; the polyelectrolyte concentration is as low as 0.001 wt.%; which greatly reduces raw material costs and environmental emissions; (3) The polyelectrolyte used in the composite emulsifier of this invention has good biocompatibility, making it safe for use in food, medicine, cosmetics and other fields. At the same time, when applied to the preparation of emulsions, the preparation process is simpler and the energy consumption is lower (avoiding the high energy consumption of ultrasonic dispersion treatment for particulate systems); (4) Intelligent stimulus response function: When using stimulus-responsive hydrophilic polyelectrolytes such as pH, temperature, or CO2 / N2, the composite emulsifier of this invention enables the emulsion to possess corresponding intelligent response performance. This provides a new option for developing intelligent products with controllable release and on-demand demulsification; Attached Figure Description

[0040] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. Figure 1 Here is a photograph of the appearance of the n-octane (3 mL) / water (3 mL) emulsion prepared in Example 1; wherein, Figure 1 a represents emulsions with different concentrations of chitosan polyelectrolyte that are individually stable; Figure 1Figure b shows emulsions stabilized by C4AzoC6N alone at different concentrations, photographed after 24 hours; Figure c shows emulsions stabilized by 0.01 wt.% chitosan polyelectrolyte combined with C4AzoC6N at different concentrations, photographed after 24 hours. Figure 2 Micrographs of the emulsion prepared in Example 1; Figure a shows the emulsion stabilized by C4AzoC6N alone at concentrations of 0.6, 1.0, and 3.0 (mM); Figure b shows the emulsion stabilized by 0.01 wt.% chitosan polyelectrolyte combined with different concentrations of C4AzoC6N, with C4AzoC6N concentrations of 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0 (mM), taken after 24 hours.

[0041] Figure 3 The appearance (a) and micrographs (b) of the emulsions formed by emulsifying chitosan polyelectrolytes of different concentrations with n-octane in 0.01 mM C4AzoC6N aqueous solution are shown after 24 hours. Figure 4 The test results for Example 3 are as follows: Figure 4 (a) The interfacial tension of n-octane / water at different CP concentrations; Figure 4 (b) The interfacial tension of C4AzoC6N and C4AzoC6N / CPs (0.01 wt.%) at different C4AzoC6N concentrations; Figure 5 (a) Viscosities of aqueous solutions with different CP concentrations, and (b) Viscosities of CPs / C4AzoC6N-stabilized emulsions with different CP concentrations; Figure 6 Figure (a) and (b) are digital photographs and photomicrographs of an emulsion stable in C4AzoC6N (0.01 mM) / CPs (0.01 wt.%) after emulsification and homogenization (H) following the introduction of N2 or CO2 (25 mL / min), taken 24 hours later; Figure (c) is a schematic diagram of the emulsion mechanism in response to CO2 / N2. Figure 7The images show the appearance of n-octane (3 mL) / water (3 mL) emulsions. Figures ac and d show emulsions stabilized by different types of polyelectrolytes individually; where a is cationic polyacrylamide (CPAM), b is polyethyleneimine (PEI), and c is anionic polyacrylamide (APAM). Figures d and f show emulsions stabilized by the polyelectrolytes in Figure ac with ionic surfactants of the same charge, respectively: d is CPAM and C4AzoC6N, e is PEI and C4AzoC6N, and f is APAM and SDS. The polyelectrolyte concentrations (ac) from left to right are: 0.01, 0.05, 0.1, 0.2, and 0.5 (wt%). The surfactant concentrations (df) from left to right are: 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0 (mM). Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents and instruments described, unless otherwise specified, are commercially available.

[0043] Some of the raw materials used in the specific implementation method: Sodium dodecyl sulfate (SDS, > 99%) is a commercially available surfactant purchased from Adamas.

[0044] C4AzoC6N was prepared in-house by our team. The preparation method can be found in "Stimulus-responsive surfactants and reversible self-assembly of nanoparticles at the oil-water interface". Chitosan polyelectrolytes (CPs, degree of deacetylation >95%, molecular weight 120~260 kDa) were purchased from Macklin; Cationic polyacrylamide (CPAM, analytical grade), anionic polyacrylamide (APAM, analytical grade), and polyethyleneimine (PEI, > 99%) were purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd. The performance testing methods used in the specific implementation are as follows: (1) Take microscopic photographs of the emulsion using an optical microscope, and use Image J to statistically analyze the particle size of the emulsion.

[0045] (2) Interfacial tension was determined using an optical contact angle meter. 20 mL of n-octane (oil phase) was added to a glass dish. A droplet of an aqueous surfactant solution (containing CPs or CPs / C4AzoC6N) was slowly released into the oil phase, with the droplet volume reaching at least 80% of its initial volume when detached from the needle. The droplet was allowed to equilibrate with the oil phase in a pendant form for at least 30 minutes. Then, photographs were taken using an optical contact angle meter (OCA 40), and the oil / water interfacial tension was calculated using the Young-Laplace equation. The measurement temperature was typically 25 ± 0.5 °C.

[0046] (3) The viscosities of the aqueous solutions and emulsions were determined using a rotational rheometer (DHR-3 type). A concentric cylinder was used for testing the viscosity of the CPs aqueous solution, and a 40 mm aluminum plate clamp was used for testing the viscosity of the emulsion. The test temperature was set to 25 ℃, the mode was selected as steady-state rheological mode, and the shear rate variation range was 0.01-100 s. -1 .

[0047] (4) The effect of changes in CPs charge density on emulsion was investigated by introducing CO2 or N2.

[0048] In the examples, mM = mmol / L; Example 1: Stabilization of octane-water emulsion by chitosan polyelectrolyte and C4AzoC6N composite emulsifier This embodiment mainly explores the effect of surfactant C4AzoC6N concentration; Octane was used as the oil phase, and an emulsion was prepared with pure water (pH=4.0) at a volume ratio of 1:1 (3 mL oil / 3 mL water). The emulsion was homogenized and emulsified at 11,000 rpm for 2 minutes using a homogenizer (IKAT18 basic model, S18N-10G rotor). The emulsifiers were different concentrations of single chitosan polyelectrolyte, different concentrations of single C4AzoC6N, and a complex of 0.01 wt.% chitosan polyelectrolyte and different concentrations of C4AzoC6N.

[0049] The experiment consisted of three groups: (1) Emulsions that are individually stabilized by chitosan polyelectrolytes of different concentrations, with chitosan polyelectrolyte concentrations of 0.01, 0.05, 0.1, 0.2, and 0.5 (wt%) respectively; (2) Different concentrations of C4AzoC6N stabilized the emulsions alone. The C4AzoC6N concentrations were: 0.001, 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0 (mM); (3) 0.01 wt.% chitosan polyelectrolyte and C4AzoC6N of different concentrations stabilized emulsions; the C4AzoC6N concentrations were 0.001, 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0 (mM).

[0050] Figure 1 Experimental results are given; such as Figure 1 As shown in (a), a single chitosan polyelectrolyte cannot stabilize the emulsion in the concentration range of 0.01 wt.% to 0.5 wt.%. Figure 1 As shown in (b), a single C4AzoC6N can stabilize O / W emulsions, but the C4AzoC6N concentration needs to be greater than or equal to 0.6 mM (cmc = 0.6 mM). Figure 1 As shown in (c), when 0.01 wt.% of chitosan polyelectrolyte was added to an aqueous solution of C4AzoC6N, a stable emulsion could be formed in the composite system when the concentration of C4AzoC6N was as low as 0.001 mM, demonstrating a significant synergistic effect between the polyelectrolyte and the surfactant with the same charge.

[0051] Figure 2 Micrographs of octane / water emulsions stabilized by C4AzoC6N alone are presented, along with micrographs of emulsions stabilized by a composite emulsifier. It can be seen that as the concentration of C4AzoC6N increases, the diameter of the oil droplets decreases. Figure 2 As shown in (a), except for the oil droplet diameter reaching approximately 100 μm at C4AzoC6N concentrations of 0.01–0.03 mM, the oil droplet diameter is less than 50 μm at other concentrations. At higher C4AzoC6N concentrations, the oil droplet diameter is similar to that of oil droplets stably produced by C4AzoC6N alone (>0.6 mM). This indicates that the composite emulsifier of the present invention can achieve emulsification effects similar to, or even better than, those of a single surfactant at high concentrations (≥ cmc) even at ultra-low surfactant concentrations.

[0052] Example 2: Stabilization of octane-water emulsion by chitosan polyelectrolyte and C4AzoC6N composite emulsifier This embodiment mainly explores the effect of chitosan polyelectrolyte concentration; With the C4AzoC6N concentration fixed at 0.01 mM, the concentration of the polyelectrolyte was varied to 0.001, 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, and 0.3 (wt.%), respectively, and emulsification experiments were conducted; the homogenization method was the same as in Example 1. like Figure 3 As shown, Figure 3The macroscopic photograph in (a) shows that when the surfactant concentration is fixed at 0.01 mM, a stable O / W emulsion can be formed when the concentration of chitosan polyelectrolyte reaches 0.003 wt.% or higher (no obvious stratification after standing for 24 hours). Figure 3 The micrographs in (b) further show that within the effective concentration range of CPs (0.003 wt.% to 0.3 wt.%), the droplet diameters of the formed emulsions are mostly between 30 and 100 μm, and within this concentration range, the droplet diameter does not change significantly with increasing CPs concentration. This indicates that effective emulsification can be achieved by adding a trace amount of polyelectrolyte with the same charge (≥0.003 wt.%) in the presence of extremely low concentrations of surfactant (0.01 mM, approximately 1.7% of its cmc), and the concentration of polyelectrolyte has little effect on the droplet size of the emulsion over a wide range.

[0053] Example 3: Effect of concentration on the n-octane-water interfacial tension of CPs and C4AzoC6N / CPs This embodiment aims to investigate the ability of single-component and composite systems to reduce the oil / water interface tension by measuring the oil / water interfacial tension; it includes three sets of experiments: (1) The concentrations of chitosan polyelectrolyte were 0 (pure water), 0.01, 0.1, and 0.5 (wt%), respectively; (2) Different concentrations of C4AzoC6N stabilized the emulsions individually. The C4AzoC6N concentrations were: 0.001, 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0 (mM); (3) 0.01wt.% chitosan polyelectrolyte and different concentrations of C4AzoC6N stabilized emulsion, with the C4AzoC6N concentration set as in group (2).

[0054] like Figure 4 As shown in (a), the interfacial tension between the aqueous solution of chitosan polyelectrolytes (CPs) and n-octane did not change much over time in the concentration range of 0.01 to 0.5 wt.%, and even high concentrations of CPs were difficult to reduce the oil-water interfacial tension, indicating that the ability of CPs to reduce the oil / water interfacial tension is very limited. Figure 4(b) compares the interfacial tension at the oil / water interface when a single C4AzoC6N solution and a C4AzoC6N / CPs (0.01 wt.%) composite system reach equilibrium at different C4AzoC6N concentrations. The results show that within a range where the C4AzoC6N concentration is below its critical micelle concentration (cmc = 0.6 mM), the interfacial tension of the composite system is consistently lower than that of the single C4AzoC6N system at the same concentration, with a difference of approximately 2–3 mN / m. This indicates that the presence of a polyelectrolyte carrying the same charge promotes the adsorption of the cationic surfactant C4AzoC6N at the oil / water interface, enabling it to more effectively reduce the oil / water interfacial tension.

[0055] Example 4: Effect of CPs concentration on the viscosity of aqueous phase and emulsion; Different concentrations of CPs aqueous solutions and emulsions were prepared, and their viscosity was tested using a DHR-3 rotational rheometer. A concentric cylinder was used for viscosity testing of the CPs aqueous solution, while a 40 mm aluminum plate fixture was used for viscosity testing of the emulsion.

[0056] This embodiment includes two sets of experiments: (1) Viscosities of aqueous solutions with different CPs concentrations, wherein the chitosan polyelectrolyte concentrations are 0.001, 0.003, 0.006, 0.01, 0.03, 0.1, and 0.3 (wt%), respectively; (2) When the concentration of C4AzoC6N was fixed at 0.1 mM, the concentrations of CPs were 0.001, 0.003, 0.006, 0.01, 0.03, 0.1, and 0.3 (wt%). The viscosity of the CPs / C4AzoC6N stable emulsion was tested at different CPs concentrations.

[0057] like Figure 5 As shown in (a), the viscosity of the aqueous solution increases with increasing CP concentration; however, the viscosity does not change significantly with increasing shear rate. This is particularly evident when the shear rate ranges from 1 to 1000 s⁻¹. -1 Within a certain range, its viscosity remains essentially constant and does not change with shear rate, exhibiting Newtonian fluid behavior. For example... Figure 5 As shown in (b), the emulsion stabilized by the CPs / C4AzoC6N complex exhibits a viscosity that increases with increasing CPs concentration, while also displaying significant shear-thinning characteristics, classifying it as a non-Newtonian fluid. This indicates that in this composite emulsion system, increasing CPs concentration leads to an increase in the viscosity of both the continuous phase (aqueous phase) and the emulsion layer. By increasing these viscosity, the emulsion's long-term stability is enhanced, suppressing droplet collision-induced aggregation and stratification due to density differences.

[0058] Figure 5The data demonstrates the dual function of highly hydrophilic polyelectrolytes in the composite emulsion system of this invention: on the one hand, they provide a crucial kinetic barrier for the emulsion by efficiently thickening the continuous phase; on the other hand, their electrostatic repulsion with surfactants at the interface jointly ensures the stability of the emulsion.

[0059] Example 5: Effect of introducing CO2 or N2 on the stability of emulsions This embodiment aims to verify that the composite emulsifier system of the present invention can reversibly control the stability of the emulsion by altering the aqueous phase environment through external stimuli. This responsiveness stems from the change in the charge state of the polyelectrolyte in response to external stimuli.

[0060] (1) Preparation of initial emulsion: Using the same method as in Example 1, an octane / water emulsion stabilized by 0.01 wt.% chitosan polyelectrolyte and 0.01 mM C4AzoC6N was prepared with an initial pH of 5.2; (2) Stable emulsion system: Carbon dioxide was introduced into the above system at a flow rate of 25 mL / min for 5 minutes. Chitosan formed polyelectrolyte chains in the form of carbonates, and the pH value of the system decreased (pH 4.5). During the process, the positive charge of CPs increased, and a stable emulsion was prepared.

[0061] (3) Emulsion instability process: In the demulsified system treated with N2 and homogenized, nitrogen gas was introduced at a flow rate of 25 mL / min for 2 minutes to remove dissolved CO2 from the aqueous phase, causing the pH value of the system to rise (pH 4.9). During the process, the positive charge of CPs decreased, which weakened the electrostatic repulsion synergy and triggered emulsion instability; nitrogen gas (N2) was introduced at a flow rate of 25 mL / min for 2 minutes, and all CO2 in the system was removed, the pH of the system returned to 5.2, the positive charge of CPs further decreased or even became electrically neutral, and the emulsion was completely demulsified.

[0062] (4) Restabilization process: In the demulsified system treated with CO2 and homogenized, carbon dioxide was introduced at a flow rate of 25 mL / min for 5 minutes to form carbonic acid, and the pH value of the system decreased (pH 4.5). The amino groups of chitosan were reprotonated, restoring its cationic polyelectrolyte properties and emulsifying ability.

[0063] like Figure 6 As shown, Figure 6Macroscopic and microscopic photographs (a) and (b) visually demonstrate the reversible behavior of the n-octane / water emulsion stabilized by the CPs / C4AzoC6N composite emulsifier after the introduction of CO2 or N2. The initially stable emulsion (pH 5.2, unstable emulsion) became a stable emulsion after the introduction of CO2 (25 mL / min, 5 min) and homogenization; the emulsion became unstable after the introduction of N2 (25 mL / min, 2 min) and homogenization; the emulsion completely demulsified and separated into oil and water after the continued introduction of N2 (25 mL / min, 2 min) and homogenization. Figure 6 The mechanism diagram in (c) illustrates its molecular mechanism: The introduction of CO2 acidifies the aqueous phase, protonating the amino groups of CPs to become positively charged, which synergistically stabilizes the emulsion with the similarly positively charged C4AzoC6N. The introduction of N2 removes the CO2, deprotonating the CPs, weakening or eliminating the synergistic effect, thereby initiating droplet aggregation, increased particle size, and eventual demulsification. Reintroduction of CO2 reprotonates the CPs, restoring emulsion stability. This demonstrates that the composite emulsifier system possesses the characteristic of achieving a reversible cycle of emulsion stabilization and demulsification through external stimulation.

[0064] Example 6: Validation of different oil phases and different polyelectrolyte / surfactant combinations Using the same emulsification method as in Example 1 (oil-to-water volume ratio 1:1, homogenization at 11,000 rpm for 2 minutes), the emulsification effects of different combinations of strongly hydrophilic polyelectrolytes and ionic surfactants with the same charge on n-octane were tested.

[0065] (1) Cationic system: Cationic polyacrylamide (CPAM) and polyethyleneimine (PEI) were used as polyelectrolytes and compounded with cationic surfactant C4AzoC6N.

[0066] (2) Anionic system: Polyacrylamide (APAM) is used as a polyelectrolyte and combined with sodium dodecyl sulfate (SDS), an anionic surfactant.

[0067] In all experiments, the concentration of the polyelectrolyte in the aqueous phase was kept constant at 0.01 wt.%, and the surfactant concentration gradients were set as follows: 0.003, 0.006, 0.01, 0.03, 0.06, 0.1, 0.3, 0.6, 1.0, 3.0 (mM). A control group was also included, consisting of emulsification experiments of n-octane with a single polyelectrolyte (0.01, 0.05, 0.1, 0.2, 0.5 wt.%).

[0068] like Figure 7 The figure shows the stabilizing effect of different types of polyelectrolytes, alone and in combination with surfactants of the same charge, on n-octane / water (3 mL / 3 mL) emulsions. Control group ( Figure 7Neither of the ac) groups could form a stable emulsion. The experimental group (Figure df) with a fixed polyelectrolyte concentration of 0.01 wt.% could form a stable O / W type emulsion at extremely low surfactant concentrations (above 0.01 mM).

[0069] Figure 7 The results show that the composite emulsifier constructed by combining a strong hydrophilic polyelectrolyte with an ionic surfactant of the same charge in this invention can achieve efficient emulsification at ultra-low surfactant concentrations, regardless of the specific types of polyelectrolyte and surfactant, as long as the charges are the same.

[0070] In summary, this invention provides a novel emulsifier composed of a hydrophilic polyelectrolyte and an ionic surfactant carrying the same charge. Through a novel synergistic stabilization mechanism, it achieves ultra-low dosage while completely avoiding the safety and processing challenges of inorganic nanoparticles, and endows the system with intelligent stimulus responsiveness, representing a significant breakthrough in safety, functionality, and application breadth.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A composite emulsifier, characterized in that, It is composed of a hydrophilic polyelectrolyte and an ionic surfactant, wherein the hydrophilic polyelectrolyte and the ionic surfactant carry the same charge in the aqueous phase; The hydrophilic polyelectrolyte is used to thicken the aqueous phase and stabilizes the oil-water interface in synergy with the ionic surfactant through electrostatic interaction. The effective concentration of the polyelectrolyte is from 0.001 wt.% to 1.0 wt.% of its mass fraction in the aqueous phase. The effective concentration of the ionic surfactant is from 0.01 cmc to 0.1 cmc.

2. The composite emulsifier according to claim 1, characterized in that, The polyelectrolyte is a hydrophilic cationic polyelectrolyte or a hydrophilic anionic polyelectrolyte; The cationic polyelectrolyte is selected from one or a combination of polyethyleneimine, cationic polyacrylamide, polydimethyldiallylammonium chloride, and chitosan; The anionic polyelectrolyte includes one or a combination of anionic polyacrylamide, sodium polyacrylate, sodium alginate, carboxymethyl cellulose, and heparin.

3. The composite emulsifier according to claim 1, characterized in that, The ionic surfactant is selected from cationic surfactants, anionic surfactants, amphoteric surfactants, or combinations thereof; The cationic surfactant is selected from one or a combination of quaternary ammonium salts, pyridine ammonium salts, and imidazoline ammonium salts; The anionic surfactant is selected from one or a combination of alkyl sulfates, alkylbenzene sulfonates, alkyl sulfonates, and fatty acid salts; The amphoteric surfactants include one or a combination of imidazoline surfactants, betaine surfactants, amino acid surfactants, and amine oxide surfactants.

4. A stimulus-responsive composite emulsifier, characterized in that, It is formed by combining a stimulus-responsive hydrophilic polyelectrolyte and an ionic surfactant, wherein the stimulus-responsive polyelectrolyte and the ionic surfactant carry the same charge in the aqueous phase.

5. The stimulus-responsive composite emulsifier according to claim 4, characterized in that, The stimulus-responsive polyelectrolyte is a pH-responsive, temperature-responsive, or CO2 / N2-responsive hydrophilic polyelectrolyte.

6. The stimulus-responsive composite emulsifier according to claim 4, characterized in that, The stimulus-responsive polyelectrolyte is a polyelectrolyte with reversible protonation / deprotonation groups.

7. An O / W type emulsion, characterized in that, It comprises an oil phase, an aqueous phase, and a composite emulsifier as described in any one of claims 1 to 7.

8. The O / W type emulsion according to claim 7, characterized in that, The oil phase is selected from alkanes, aromatics, triglycerides, silicone oils, or fragrance oils; and / or, The volume fraction of the oil phase in the emulsion is 1% to 75%; and / or, The diameter of the oil droplets in the O / W type emulsion is between 100 μm and 1 μm.

9. The use of the composite emulsifier according to any one of claims 1 to 6 in the preparation of O / W type oil-water dispersion systems.

10. The application according to claim 9, characterized in that, Applications include pesticides, oil transportation, machining, emulsion polymerization, and emulsion explosives, and / or... Based on the high biocompatibility and biodegradability of the hydrophilic polyelectrolyte, it can be applied in food, cosmetics or pharmaceutical products.

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