Water-in-water nanocellulose Pickering emulsion with uniform and controllable size and preparation method of water-in-water nanocellulose Pickering emulsion

Abstract

The invention relates to a preparation method of a water-in-water nanocellulose Pickering emulsion with uniform and controllable size, which comprises the following steps: S1, preparing an aqueous two-phase system, and respectively preparing a water-based continuous phase and a dispersed phase of a water-soluble polymer with compatible type, concentration and molecular weight; s2, preparing an aqueous continuous phase suspension containing 5%-8% of cellulose nanocrystal (CNC) particles; s3, assembling a micro-channel device which comprises a two-water-phase two-channel angle-designable feeding pipe, a length-dependent composite pipe for regulating and controlling the size of a dispersed phase, a lead-in pipe for introducing the particle suspension and the composite pipe according to a set angle, and a spiral pipe for forcibly assembling and optimizing particles on a two-phase interface and adaptively regulating and controlling the length / screw pitch / diameter; s4, preparing a water-in-water emulsion with stable CNC particles; according to the method, two-water-phase compounding and particle interface assembling are strengthened through micro-channel design, the flow speed and the air pressure interruption time are regulated and controlled, accurate control over the emulsion size and the droplet distance is achieved, and the common problems that the emulsion size is not uniform and the particle coverage degree is not high are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of emulsion production and preparation, and relates to a water-in-water nanocellulose Pickering emulsion with uniform and controllable size and a preparation method thereof. Background Art

[0002] Water-in-water nanocellulose Pickering emulsions have attracted the attention of researchers due to their ease of preparation, strong stability, and environmental friendliness. Unlike traditional emulsions, the formation and stabilization of Pickering emulsions do not require the addition of molecular surfactants. Instead, the solid microparticles or nanoparticles at the interface between the liquid and liquid phases act as emulsion stabilizers, thereby improving the emulsion droplet's resistance to demulsification. Furthermore, compared to traditional industrial emulsion formation methods involving stirring or the addition of surfactants, Pickering emulsions stabilized with solid particles can minimize the impact on the activity of bioactive molecules (such as enzymes) and offer the advantages of being economical, green, and environmentally friendly.

[0003] Nanocellulose, an emerging stabilizer for Pickering emulsions, has attracted considerable attention due to its high biosafety, renewable and biodegradable nature, widespread availability, diverse extraction methods, and irreversible adsorption at the oil-water interface. Cellulose nanocrystals (CNCs), with their high crystallinity, ordered distribution of hydrophilic and hydrophobic facets on their surface, and aspect ratios that complement their high rigidity, have proven to be ideal stabilizers for food-grade Pickering emulsions. However, most researchers have focused on CNC stabilization of water-oil two-phase systems. However, the potential environmental impact of the oil phase in these systems, coupled with the uneven shear distribution of the emulsification system, hinder the application of CNCs. Existing preparation methods, however, result in uneven size and low particle coverage in the resulting water-in-water nanocellulose Pickering emulsions, which in turn limits their application. Therefore, preparing water-in-water nanocellulose Pickering emulsions with uniform particle size and high particle coverage is a challenge.

[0004] In 2021, Liu Shilin's team developed a new strategy for constructing W / W Pickering emulsions in one step based on impinging stream technology. Figure 1The method shown innovatively pre-disperses the solid particle stabilizer in the continuous phase, and then introduces the dispersed phase into the highly turbulent region through the strong shear force field generated by the collision of two continuous phases, thereby achieving in situ assembly of solid particles at the liquid-liquid interface and emulsion stabilization. This continuous preparation process effectively overcomes the problem that traditional W / W emulsions are difficult to produce on a large scale. This method can generate water-in-water nanocellulose Pickering emulsions in one step through the shear force generated by a magnetic stirrer or oscillation process, but there is an uneven distribution of shear force in this process, which leads to the problems of uneven size of the generated water-in-water nanocellulose Pickering emulsions and low particle coverage, which to a certain extent limits their application.

[0005] like Figure 2 As shown, Niki Abbasi et al. prepared monodisperse water-in-water emulsions using a PDMS passive microfluidics platform via flow focusing. They then exploited the spontaneous distribution of carboxylated particles to the PEG-Dex aqueous two-phase interface and the spatial confinement of the particles by the PDMS platform to achieve particle adsorption at the water-water interface. These particle-stabilized water-in-water emulsions exhibited good particle adsorption under shear forces and could flow in narrow microchannels. Particle-stabilized water-in-water emulsions have inherent biocompatibility advantages and are ideal alternatives to traditional particle-stabilized oil-in-water emulsions. However, although Niki Abbasi et al. successfully prepared monodisperse water-in-water emulsions using microfluidics, they were unable to achieve high particle coverage due to the need for particles to flow in narrow microchannels, thus limiting the stability of the water-in-water emulsions and their high encapsulation performance for bioactive substances. Summary of the Invention

[0006] In view of this, the present invention provides a water-in-water nanocellulose Pickering emulsion with uniform and controllable size and a preparation method thereof in order to solve the problems of uneven emulsion size and low particle coverage in the preparation process of water-in-water nanocellulose Pickering emulsion in the prior art, which limit its performance and effect in practical applications.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a water-in-water nanocellulose Pickering emulsion with uniform and controllable size, characterized by comprising the following steps:

[0009] S1. Prepare a two-phase aqueous system: prepare an aqueous continuous phase and an aqueous dispersed phase containing 10-15% by mass of a water-soluble polymer of compatible type and molecular weight, which can be designed and controlled;

[0010] S2. Preparing a cellulose nanocrystal (CNC) particle suspension: dispersing CNC particles in the aqueous continuous phase prepared in step S1 to prepare a CNC particle suspension containing 5-8% by mass;

[0011] S3. Design and assemble a microchannel composite and forced particle interface assembly device: The device includes independent multi-channel flow rate controllers for fluids, a dual-channel feed tube with a programmable angle between the two aqueous phases, a length-dependent composite tube for controlling the size of the dispersed phase, an inlet tube connecting the particle suspension and the composite tube at a set angle, and a spiral tube with adaptable length, pitch, and diameter for forced and optimized particle assembly at the interface between the two aqueous phases.

[0012] S4. Prepare a water-in-water nanocellulose Pickering emulsion that stabilizes CNC particles: inject the aqueous continuous phase prepared in step S1 into the syringe of the dispensing machine and control the flow rate at 100-200 μL / min. Inject the aqueous dispersed phase prepared in step S1 into one side of the air pump. Adjust the air pump pressure to 20-26 kPa, the closing time to 0.5-1.2 s, and the opening time to 2.0-4.0 s. Inject the CNC particle suspension into the inlet tube at the connection between the composite tube and the spiral tube through a syringe at a flow rate of 30-35 μL / min.

[0013] Furthermore, the method for obtaining the aqueous continuous phase and the aqueous dispersed phase in step S1 is specifically as follows: two aqueous solutions containing water-soluble polymers with different solubility parameters are blended, stirred or homogenized until uniform, and allowed to stand to separate into two phases, wherein the upper layer is the aqueous continuous phase and the lower layer is the aqueous dispersed phase.

[0014] Furthermore, in step S1, the solubility parameter of the water-soluble polymer in the aqueous continuous phase is greater than the solubility parameter of the water-soluble polymer in the aqueous dispersed phase, and the difference is greater than 0.5.

[0015] Furthermore, in step S1, the water-soluble polymer in the aqueous continuous phase is one or more of polyethylene glycol, starch, konjac glucomannan, carrageenan, guar gum, and chitosan with a molecular weight of 8000 to 20000, and the water-soluble polymer in the aqueous dispersed phase is one or more of pullulan, dextran, gelatin, collagen, and casein with a molecular weight of 20000 to 50000.

[0016] Furthermore, in step S3, the dual-channel feeding tube includes a square glass tube whose end is stretched by a needle puller and a cylindrical glass tube cross-connected to the square glass tube. The composite angle of the square glass tube and the cylindrical glass tube is adjustable, which is convenient for regulating the shear field of the mutual mixing of the aqueous continuous phase and the aqueous dispersed phase; the cylindrical glass tube away from one end of the square glass tube is connected to an air pump for controlling the liquid flow rate, and the end of the square glass tube away from the cylindrical glass tube is sequentially connected to a composite tube and a spiral tube for facilitating length control. The spiral tube makes the shear field of mutual mixing controllable and the effects of capillary force and friction force under diameter change more prominent. The composite tube close to the spiral tube is connected to an inlet tube for injecting CNC particle suspension, and the inlet tube and the composite tube are connected in an angle-adjustable manner mainly with a vertical cross, which is convenient for regulating the mutual mixing shear field.

[0017] Furthermore, in step S3, the inner diameter of the cylindrical glass tube is 0.35-0.55 mm; after the end of the square glass tube is stretched, the tip forms a nozzle with a size range of 100-400 μm, and the inner diameter of the square glass tube is 1-2 mm.

[0018] Furthermore, in step S3, the spiral tube is a PVC plastic tube wound on three parallel glass rods as a basic structure. The length of the spiral tube is designed and assembled to be 2 to 3 meters. The corresponding PVC plastic tube used is 2.5 to 3.75 meters long and has an inner diameter of 1.2 to 2.4 mm. It is wound on the three glass rods at a pitch of 1 cm. The pitch of the PVC plastic tube on the glass rod where the free end of the spiral tube is located gradually increases, and the PVC plastic tube and the glass rod are fixed with transparent epoxy resin.

[0019] Furthermore, in step S3, the dual-channel feed pipe, composite pipe, introduction pipe, and spiral pipe are connected using silicone tubes with an inner diameter of 1.2 to 2.4 mm according to the size of each pipe. These four parts are connected together on the same horizontal plane, and transparent epoxy resin is applied to each connection to seal it.

[0020] The water-in-water nanocellulose Pickering emulsion prepared by the preparation method of the water-in-water nanocellulose Pickering emulsion has uniform and controllable size.

[0021] The water-in-water nanocellulose Pickering emulsion controls the flow rates of the aqueous continuous phase and the aqueous dispersed phase and the air pressure interruption time by controlling the microflow, thereby controlling the size of the water-in-water nanocellulose Pickering emulsion and the distance between the water-in-water Pickering droplets to obtain water-in-water droplets with uniform size and monodisperse.

[0022] The beneficial effects of the present invention are:

[0023] The present invention discloses a method for preparing a water-in-water nanocellulose Pickering emulsion with uniform and controllable size. The core of the method lies in the design of a novel forced interfacial assembly composite device for cellulose nanocrystal particles. This device cleverly integrates a dual-channel microchannel device with a programmable angle between the two aqueous phases, a composite tube, an inlet tube, and a spiral tube, achieving the synergistic control of multiple force fields, including shear, capillary, and frictional forces. The angle of the dual-channel feed tube is adjustable, facilitating the control of the shear field during the mixing of the aqueous continuous and dispersed phases. The length of the composite tube is determined by the size control requirements of the dispersed phase. During the preparation process, a suspension of cellulose nanocrystals (CNCs), an important type of nanocellulose, is introduced into the device through the inlet tube. The inlet tube and the composite tube are connected at a programmable angle, primarily perpendicular to each other, facilitating the control of the shear field during the mixing. The spiral tube configuration allows for controllable shear fields during the mixing and enhances the effects of capillary and frictional forces as the diameter varies. Within the spiral tube, the CNC particles are significantly affected by Dean vortices, achieving large-area contact with the water-in-water droplets. This unique design enables CNC particles to uniformly and efficiently cover the surface of water-in-water droplets at the interface between the two aqueous phases, thereby preparing a monodisperse water-in-water nanocellulose Pickering emulsion with high particle coverage. The entire preparation method achieves a high degree of uniformity and controllability in the size of the water-in-water nanocellulose Pickering emulsion by leveraging the control technology of microchannel composite and forced particle interface assembly. At the same time, the Dean vortex in the spiral tube significantly improves the particle mass transfer process, greatly increasing the contact area between the particles and the droplet surface, ensuring complete coverage of the CNC particles on the water-in-water droplet surface, and significantly improving the stability and performance of the emulsion.

[0024] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0026] Figure 1 Schematic diagram of a two-phase system composed of two biocompatible water-soluble polymers forming a W / W emulsion in the background art;

[0027] Figure 2 Schematic diagram of the generation of water-in-water emulsion by flow focusing method on PDMS passive microfluidic platform in the background art;

[0028] Figure 3 A photo of the microchannel composite and forced particle interface assembly device of the present invention (left) and a microscopic image of the cone mouth (right);

[0029] Figure 4 Schematic diagram of the device for microchannel composite and forced particle interface assembly of the present invention;

[0030] Figure 5 (a) is an optical image of a water-in-water droplet formed at the cone mouth of the present invention. Figure 5 (b) is an optical image of a water-in-water droplet flowing in a capillary tube according to the present invention;

[0031] Figure 6 This is an optical microscopy image of the water-in-water nanocellulose Pickering emulsion stabilized by the CNC particles of the present invention;

[0032] Figure 7 Diameter distribution diagram of the water-in-water nanocellulose Pickering emulsion stabilized by the CNC particles of the present invention;

[0033] Figure 8 is the optical microscopy of a pair of droplets in the absence or presence of BSA-GP particles on the surface of the present invention as a function of time;

[0034] Figure 9 (a) is a graph showing the function of the water-in-water droplet size versus the dispersed phase pressure of the present invention, Figure 9 (b) is a graph showing the water-in-water droplet size as a function of the program switching time of the present invention;

[0035] Figure 10 (a) is a graph showing the spacing between water-in-water droplets as a function of the flow rate of the continuous phase of the present invention. Figure 10 (b) is a graph showing the function of the distance between water-in-water droplets and the total time of program switching according to the present invention. DETAILED DESCRIPTION

[0036] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] The method for preparing the water-in-water nanocellulose Pickering emulsion with uniform and controllable size comprises the following steps:

[0038] Preparation of S1. PEG (polyethylene glycol) / Dex (dextran) aqueous two-phase system: First, weigh 30 g of each of PEG (8 kDa) and Dex (500 kDa) and disperse them in 240 g of deionized water in a 500 mL beaker. A magnetic stirrer was placed in the beaker and the stirrer was adjusted to an appropriate speed for a period of time until complete dissolution. Next, the completely dissolved PEG and Dex aqueous solutions were mixed and homogenized by rotation until uniform. The mixture was then allowed to stand at room temperature for at least 24 h to allow for complete phase separation. The solution formed two layers: an upper PEG-rich phase and a lower Dex-rich phase. The upper and lower phases were extracted with a syringe to obtain 10% PEG-rich and 10% Dex-rich phases, respectively. The mixture was stored in a 50 mL centrifuge tube, sealed, and refrigerated at 4°C.

[0039] S2. Preparation of CNC (cellulose nanocrystal) particle suspension: Weigh 4.7 g of the 10% PEG-enriched phase obtained in (1) into a 15 mL screw-cap bottle. Then weigh 0.3 g of CNC and disperse it in the previously prepared PEG-enriched phase to obtain a 6% CNC particle suspension. Seal the screw-cap bottle and place it in a refrigerator at 4°C.

[0040] S3. Design and assemble a microchannel composite and forced particle interface assembly device: Use a needle puller (PN 30) to pull the end of a square glass tube (1 mm inner diameter, 1.2 mm outer diameter) to form a nozzle with a size range of 100 to 400 μm at the tip. Subsequently, on a glass slide, this square glass tube and a cylindrical glass tube (0.55 mm inner diameter, 0.96 mm outer diameter) are embedded in the needle of a dispensing machine, ensuring that both are stable and accurately positioned. Use transparent epoxy resin as a sealing material and apply it to the required location to create a microchannel device, such as Figure 3 As shown. Among them, Figure 3 The left picture is a real picture of the microchannel composite and forced particle interface assembly device. Figure 3 The picture on the right is a microscopic image of the cone mouth of the microchannel device.

[0041] S4. Design and Fabrication of Length-Dependent Composite Tubes: To further optimize the performance of the microchannel composite and forced particle interface assembly system, a composite tube design was introduced. A length-dependent composite tube, controlling the dispersed phase size, was connected to the tip of a square glass capillary tube, ensuring that it would not intrude into the internal space of the dispenser needle. An inlet tube for injecting the CNC particle suspension was connected to the composite tube near the spiral tube. The inlet tube and composite tube were connected in a perpendicular cross-section to facilitate the control of the mixing shear field. The joints were then sealed with transparent epoxy resin to ensure the stability and sealing of the entire system.

[0042] S5. Design and Fabrication of a Spiral Tube: Three parallel glass rods served as the base structure and were secured with transparent epoxy resin. A 2.5-meter-long PVC tube (1.2 mm inner diameter, 2.7 mm outer diameter) was then tightly wound around the three glass rods at a 1-centimeter pitch. To effectively prevent droplet coalescence in the tube, the pitch of the PVC tube on the final glass rod was gradually increased. Finally, transparent epoxy resin was again used to securely secure the PVC tube to the glass rods, completing the design and fabrication of the spiral tube.

[0043] S6. Assembly of microchannel composite device: Figure 4 As shown in the figure, in order to integrate the microchannel device, composite tube, introduction tube and spiral tube into an efficient and compact system, silicone tube (inner diameter 1.2 mm, outer diameter 2.2 mm) was selected as the connecting medium to connect the four parts together on the same horizontal plane. At the same time, transparent epoxy resin was applied to each joint to seal it. After natural air drying, a new microchannel composite device was obtained.

[0044] S7. Preparation of a CNC particle-stabilized water-in-water emulsion: A 10% PEG-enriched phase was drawn into a 10 mL syringe as the external phase. A syringe pump was used to control the flow rate at 200 μL / min. 7 mL of a 10% Dex-enriched phase solution was then placed into a screw-cap bottle as the internal phase. This was connected via an air pump with an air pressure of 26 kPa, a closing time of 1.2 s, an opening time of 4.0 s, and a spiral tube length of 2.0 m. In the microchannel device, the dispersed and continuous phases met at the tip of the inner capillary tube. Because the air pump connected to the dispersed phase provided intermittent air pressure, the dispersed phase column was sheared into uniformly sized droplets by the continuous phase during liquid backdraw, generating a Dex-in-PEG monodisperse emulsion. At the same time, the pre-prepared CNC particle suspension was injected into a 10 mL syringe equipped with a small rotor (E10 mm). The suspension was injected into the introduction tube using a syringe pump at a flow rate of 35 μL / min. A magnetic stirrer was fixed above the syringe and the speed was adjusted to 400 rpm to prevent the suspension from settling, so that the particles were evenly injected into the microchannel introduction tube. As the preparation process progressed, it was observed that the CNC particles were gradually adsorbed to the surface of the droplet under the drive of the Dean vortex in the spiral tube, and finally formed a water-in-water emulsion stabilized by the CNC particles, as shown in Figure 2. Figure 5 As shown. Among them, Figure 5 (a) is the optical image of a water-in-water droplet formed at the cone mouth. Figure 5 (b) is an optical image of a water-in-water droplet flowing in a capillary tube. The emulsion was received by a PEG-enriched phase, and its morphology was observed by optical microscopy and its monodispersity was evaluated, as shown in Figure 2. Figure 6 shown. Figure 7The diameter distribution diagram of the water-in-water nanocellulose Pickering emulsion stabilized by CNC particles shows that the diameter distribution of the water-in-water nanocellulose Pickering emulsion conforms to the normal distribution, and the average particle size is 581.2±3.9μm.

[0045] The present invention solves the problems of uneven size and low particle coverage of water-in-water nanocellulose Pickering emulsion. By controlling the microflow mode, regulating the flow rate of the continuous phase and the dispersed phase and the air pressure interruption time, the size of the water-in-water nanocellulose Pickering emulsion can be controlled. Figure 9 ) and the water-in-water Pickering droplet spacing ( Figure 10 ), thereby preparing uniform-sized, monodisperse water-in-water droplets; wherein Figure 9 (a) is a graph showing the function of water-in-water droplet size to dispersed phase air pressure. It can be seen that under the same experimental conditions, as the air pressure provided by the air pump connected to the dispersed phase increases, the droplet diameter of the water-in-water nanocellulose Pickering emulsion prepared increases. Figure 9 (b) is a graph showing the water-in-water droplet size as a function of the program switching time. It can be seen that under the same experimental conditions, as the opening time of the air pump connected to the dispersed phase increases, the droplet diameter of the water-in-water nanocellulose Pickering emulsion increases; in addition, as the closing time of the air pump connected to the dispersed phase increases, the droplet diameter of the water-in-water nanocellulose Pickering emulsion decreases.

[0046] Figure 10 (a) is a graph showing the function of the distance between water-in-water droplets and the flow rate of the continuous phase. It can be seen that under the same experimental conditions, the droplet diameter of the water-in-water nanocellulose Pickering emulsion increases with the increase of the flow rate of the aqueous continuous phase. Figure 10 (b) is a graph showing the function of the distance between water-in-water droplets to the total time of the program switch. It can be seen that under the same experimental conditions, the droplet diameter of the water-in-water nanocellulose Pickering emulsion prepared increases with the increase of the total time of the program switch.

[0047] The present invention utilizes the improvement of mass transfer by Dean vortices in the spiral tube to expand the contact area between the particles and the droplet surface, achieving complete coverage of the CNC particles on the surface of the water-in-water droplets and preparing a monodisperse water-in-water nanocellulose Pickering emulsion. The water-in-water droplets covered with CNC particles can remain monodisperse for up to 2 days. Figure 8As shown; in addition, the coverage of particles on the droplet surface can be controlled by changing the length of the spiral tube. The breakthrough of water-in-water nanocellulose Pickering emulsion in particle coverage is conducive to expanding wider application scenarios; the entire system is a fully aqueous system, and there is no need to consider the biocompatibility interference of organic reagents, and the CNC particles are biodegradable and biocompatible, ensuring the high biocompatibility of the system; moreover, all reagents involved in the entire system are non-toxic and green and environmentally friendly; the CNC particles prepared by the present invention have stable particle coverage, high monodispersity, and have broad application prospects in the fields of food, biomedicine, cosmetics, etc.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a water-in-water nanocellulose Pickering emulsion with uniform and controllable size, characterized in that: The following steps are involved: S1. Prepare a two-phase aqueous system: prepare an aqueous continuous phase and an aqueous dispersed phase containing 10-15% by mass of a water-soluble polymer of compatible type and molecular weight, which can be designed and controlled; S2. Preparing a cellulose nanocrystal (CNC) particle suspension: dispersing CNC particles in the aqueous continuous phase prepared in step S1 to prepare a CNC particle suspension containing 5-8% by mass; S3. Design and assemble a microchannel composite and forced particle interface assembly device: The device includes independent multi-channel flow rate controllers for fluids, a dual-channel feed tube with a programmable angle for composite of the two aqueous phases, a length-dependent composite tube for controlling the size of the dispersed phase, an inlet tube connecting the particle suspension and the composite tube at a set angle, and a spiral tube with adaptable length, pitch, and diameter for forced and optimized particle assembly at the interface between the two aqueous phases. S4. Prepare a water-in-water nanocellulose Pickering emulsion that stabilizes CNC particles: inject the aqueous continuous phase prepared in step S1 into the syringe of the dispensing machine and control the flow rate at 100-200 μL / min. Inject the aqueous dispersed phase prepared in step S1 into one side of the air pump. Adjust the air pump pressure to 20-26 kPa, the closing time to 0.5-1.2 s, and the opening time to 2.0-4.0 s. Inject the CNC particle suspension into the inlet tube at the connection between the composite tube and the spiral tube through a syringe at a flow rate of 30-35 μL / min.

2. The method for preparing a water-in-water nanocellulose Pickering emulsion according to claim 1, wherein The method for obtaining the aqueous continuous phase and the aqueous dispersed phase in step S1 is specifically as follows: two aqueous solutions containing water-soluble polymers with different solubility parameters are blended, stirred or homogenized until uniform, and allowed to stand to separate into two phases, wherein the upper layer is the aqueous continuous phase and the lower layer is the aqueous dispersed phase.

3. The method for preparing a water-in-water nanocellulose Pickering emulsion according to claim 2, wherein: In step S1, the solubility parameter of the water-soluble polymer in the aqueous continuous phase is greater than the solubility parameter of the water-soluble polymer in the aqueous dispersed phase, and the difference is greater than 0.

5.

4. The method for preparing a water-in-water nanocellulose Pickering emulsion according to claim 2, wherein In step S1, the water-soluble polymer in the aqueous continuous phase is one or more of polyethylene glycol, starch, konjac glucomannan, carrageenan, guar gum, and chitosan with a molecular weight of 8,000 to 20,000, and the water-soluble polymer in the aqueous dispersed phase is one or more of pullulan, dextran, gelatin, collagen, and casein with a molecular weight of 20,000 to 50,000.

5. The method for preparing the water-in-water nanocellulose Pickering emulsion according to claim 1, wherein In step S3, the dual-channel feeding tube includes a square glass tube whose end is stretched by a needle puller and a cylindrical glass tube cross-connected to the square glass tube. The composite angle of the square glass tube and the cylindrical glass tube is adjustable, which is convenient for regulating the shear field of the mutual mixing of the aqueous continuous phase and the aqueous dispersed phase; the cylindrical glass tube away from one end of the square glass tube is connected to an air pump for controlling the liquid flow rate, and the end of the square glass tube away from the cylindrical glass tube is sequentially connected to a composite tube and a spiral tube for facilitating length control. The spiral tube makes the shear field of mutual mixing controllable and the effects of capillary force and friction force under diameter change more prominent. The composite tube close to the spiral tube is connected to an inlet tube for injecting CNC particle suspension. The inlet tube and the composite tube are connected in an angle-adjustable manner mainly with a vertical cross, which is convenient for regulating the mutual mixing shear field.

6. The method for preparing the water-in-water nanocellulose Pickering emulsion according to claim 5, wherein: In step S3, the inner diameter of the cylindrical glass tube is 0.35-0.55 mm; after the end of the square glass tube is stretched, the tip forms a nozzle with a size range of 100-400 μm, and the inner diameter of the square glass tube is 1-2 mm.

7. The method for preparing a water-in-water nanocellulose Pickering emulsion according to claim 5, wherein: In step S3, the spiral tube is a PVC plastic tube wrapped around three parallel glass rods as a basic structure. The length of the spiral tube is designed and assembled to be 2 to 3 meters. The corresponding PVC plastic tube used is 2.5 to 3.75 meters long and has an inner diameter of 1.2 to 2.4 mm. It is wrapped around the three glass rods at a pitch of 1 cm. The pitch of the PVC plastic tube on the glass rod where the free end of the spiral tube is located gradually increases, and the PVC plastic tube and the glass rod are fixed with transparent epoxy resin.

8. The method for preparing a water-in-water nanocellulose Pickering emulsion according to claim 6, wherein: In step S3, the dual-channel feed pipe, composite pipe, introduction pipe, and spiral pipe are connected using silicone tubes with an inner diameter of 1.2 to 2.4 mm corresponding to the size of each pipe. These four parts are connected together on the same horizontal plane, and transparent epoxy resin is applied to each connection to seal it.

9. The water-in-water nanocellulose Pickering emulsion with uniform and controllable size prepared by the method for preparing the water-in-water nanocellulose Pickering emulsion according to claim 7 or 8.

10. The water-in-water nanocellulose Pickering emulsion according to claim 9, characterized in that By controlling the microflow, the flow rate of the aqueous continuous phase and the aqueous dispersed phase and the air pressure interruption time are regulated, thereby controlling the size of the water-in-water nanocellulose Pickering emulsion and the distance between the water-in-water Pickering droplets to obtain water-in-water droplets with uniform size and monodisperse.

Images