Method for preparing multiple emulsions in one step by utilizing polyurethane amphiphilic block copolymer

Abstract

The invention belongs to the technical field of high polymer materials and emulsifiers, and provides a method for preparing multiple emulsions in one step by utilizing a polyurethane amphiphilic block copolymer. The method comprises the following steps: screening hydrophilic / hydrophobic chain segments, and carrying out addition reaction to synthesize a polyurethane block copolymer with an amphiphilic structure; further, the emulsion is used as an emulsifier to prepare an oil-water mixture, and a multi-emulsion system can be directly constructed through a one-step homogenization emulsification process. The polyurethane amphiphilic block copolymer is used for preparing the multiple emulsion for the first time, the synthesis process is simple and convenient, the cost is low, industrial production is easy, and wide application prospects are shown in the fields of cosmetics, food, biological medicine and the like.

Description

Technical Field

[0001] The present invention relates to the technical fields of polymer materials and emulsifiers, and particularly relates to a method for preparing multiple emulsions by using a polyurethane amphiphilic block copolymer in one step. Background Art

[0002] Multiple emulsions are composite systems that simultaneously contain O / W and W / O structures. Their three-phase two-film emulsification structure endows them with many unique properties and has broad application prospects in the fields of cosmetics, food, drug delivery, material manufacturing, etc. In the field of cosmetics, multiple emulsions make up for the deficiencies of O / W and W / O emulsions, have the characteristics of high-efficiency cleaning and low oiliness, and can effectively protect water-soluble active ingredients; in the food field, multiple emulsion products have a low fat content and at the same time have a unique taste and flavor; in the field of drug delivery, multiple emulsions can achieve drug slow release and effectively mask the unpleasant odor of drugs; in the field of material manufacturing, due to their unique structure, multiple emulsions can be used as soft templates and chemical microreactors for the preparation of hollow microspheres.

[0003] The preparation technologies of multiple emulsions mainly include two-step emulsification method, one-step emulsification method and microfluidic method, and their characteristics and limitations are different: ① The two-step emulsification method is widely used, but it is necessary to first prepare primary emulsions and then perform secondary emulsification. The process is cumbersome, which restricts its large-scale stability. ② The one-step emulsification method simplifies the process by mixing at one time, but has strict requirements for the matching degree of emulsifiers. ③ Microfluidic technology can accurately control the droplet size and monodispersity, but the equipment cost is high and the output is low, making it difficult to meet the requirements of industrial continuous production. The above methods for preparing multiple emulsions are restricted by the inherent defects of emulsifiers or the bottleneck of process costs, and there is an urgent need to develop a new emulsification system with both high efficiency, stability and low cost advantages.

[0004] Amphiphilic block copolymers have significant advantages in the stabilization and functional regulation of multiple emulsions: their hydrophilic-hydrophobic chain segments connected by chemical bonds can form a high-strength dense interfacial film at the oil-water interface, effectively inhibiting droplet coalescence, Ostwald ripening and hierarchical diffusion. The stabilization ability is far beyond that of traditional small molecule emulsifiers such as Span-80 and Tween-20; in addition, by precisely designing the segment ratio and functional groups, block copolymers can endow emulsions with intelligent release or targeted delivery capabilities, while traditional emulsifiers are limited by the space of chemical modification and it is difficult to achieve such functions. The synthesis process of traditional block copolymers is complex and the reaction requirements are strict, resulting in high costs; using polyurethane to synthesize block copolymers does not require strict deoxygenation or metal catalysts, and the raw materials are bulk industrial products, with significant cost advantages, providing a new idea for solving the above contradictions. The present invention designs amphiphilic polyurethane copolymers with different block structures. Using them as emulsifiers, W / O / W multiple emulsions can be constructed by a one-step method, opening up a new path for low-cost large-scale production and can be widely applied to various fields such as medicine, cosmetics, food packaging, etc.

[0005] At present, there have also been many reports on the method of preparing multiple emulsions with amphiphilic block copolymers. Hong et al. (Langmuir 2012, 28, 2332–2336) disclosed a method for preparing W / O / W multiple emulsions by a one-step method using an amphiphilic block copolymer (PEG-b-PS). This method uses block copolymers synthesized by atom transfer radical polymerization (ATRP) to stabilize the emulsion interface, but it has defects such as complex copolymer synthesis process and high industrialization cost, and the oil phase used is toluene, which limits the application range. CN104987515A discloses a method for preparing multiple emulsions by self-assembling micelles of amphiphilic random copolymers in one step. The copolymer synthesis process is complex, and it needs to be precipitated and dialyzed (for 4 days) many times during the reaction for purification, which is time-consuming and costly; at the same time, it relies on the toxic solvent DMF (dimethylformamide), and the residual solvent needs to be strictly treated. CN112336689A discloses a method for preparing multiple Pickering emulsions with crystalline block copolymer micelles. The method for preparing multiple emulsions is a two-step method, which requires the preparation of two kinds of micelle dispersions respectively, and the construction of multiple emulsions is completed by two shear mixings. The steps are redundant and the energy consumption is high, which is not easy for industrial production. Summary of the Invention

[0006] The present invention discloses a method for preparing multiple emulsions by one-step homogenization using a polyurethane amphiphilic block copolymer. Specifically, the present invention prepares a polyurethane amphiphilic block copolymer by designing and selecting functional hydrophilic and hydrophobic segments. Using this as an emulsifier, multiple emulsions can be prepared by one-step homogenization, with simple operation and low energy consumption. The prepared polyurethane amphiphilic block copolymer has excellent emulsifying performance and high pH sensitivity, and can stabilize oil phases with different polarities to form multiple emulsions. It has industrial value and can be applied to fields such as drug sustained release, cosmetics, and food.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing multiple emulsions by one-step using a polyurethane amphiphilic block copolymer, the specific steps are as follows:

[0009] (1) Select polyglycerol and glycerol polyether molecules as hydrophilic segments, and isocyanate and polyol copolymer as hydrophobic segments, and prepare a polyurethane amphiphilic block copolymer by an addition reaction;

[0010] (2) Configure the polyurethane amphiphilic block copolymer obtained in step (1) into an aqueous solution with a certain concentration and pH value, and mix it with a certain volume of oil phase for homogenization to obtain multiple emulsions.

[0011] Further, in step (1), the molar ratio of the hydrophilic segment to isocyanate is 1:1 - 1:3; the molar ratio of isocyanate to polyol is 1:1 - 3:1.

[0012] Furthermore, in step (2), the concentration of the polyurethane amphiphilic block copolymer is 5-20%, and the pH is 4-10.

[0013] The polyurethane amphiphilic block copolymer comprises the following raw materials in terms of mole parts:

[0014]

[0015] Among them, the hydrophilic segment polymer is selected from any one of diglycerol, triglycerol, tetraglycerol, hexaglycerol, octaglycerol, decaglycerol, and glycerol polyether.

[0016] The isocyanate is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), polymethylene polyphenyl polyisocyanate (PAPI), and triphenylmethane triisocyanate (TPTI).

[0017] The polyol is one or more of 2,2-dimethylolbutyric acid (DMBA), 2,2-dimethylolpropionic acid (DMPA), 1,4-butanediol (BDO), and trimethylolpropane (TMP).

[0018] The preparation method of the above-mentioned polyurethane amphiphilic block copolymer, the polyurethane amphiphilic block copolymer is synthesized by the following specific process:

[0019] (1) Using acetone as a solvent, fully dissolve the polyol, purge the reaction system with nitrogen to remove water, slowly add the dissolved polyol dropwise to a three-necked flask containing dibutyltin dilaurate and diisocyanate. After the addition is complete, control the temperature of the reaction system at 60-80 °C, and continuously stir under the condition of condensation reflux for 1-2 hours;

[0020] (2) Slowly add the prepolymer obtained from the reaction in step (1) dropwise to the hydrophilic segment polymer that has been dehydrated by high-temperature vacuum, and add dibutyltin dilaurate as a catalyst. Maintain the reaction temperature at 60-80 °C, and stir and react for 1-2 hours under the condition of condensation reflux;

[0021] (3) After distilling off acetone from the obtained product under reduced pressure, a polyurethane amphiphilic block copolymer is obtained.

[0022] A method for preparing multiple emulsions in one step using a polyurethane amphiphilic block copolymer, comprising the following steps:

[0023] Adjust the pH of the synthesized polyurethane amphiphilic block copolymer aqueous solution to 3 - 10, prepare an aqueous solution with a mass fraction of 5% - 20%, and mix it with the oil phase at a volume ratio of 3:7 - 7:3, and prepare a multiple emulsion through homogenization treatment.

[0024] Furthermore, the oil phase is selected from one or more of tributyrin, caprylic / capric triglyceride, glyceryl triacetate, glyceryl tri(ethylhexanoate), or squalane.

[0025] Furthermore, the homogenization treatment is carried out under the condition of 6 - 16Krpm for 3 - 7min.

[0026] The multiple emulsion prepared by the present invention using the polyurethane amphiphilic block copolymer in one step is a W / O / W type multiple emulsion, and the appearance of the emulsion is a milky white flowing liquid. Without adding any stabilizer, this emulsion system can be stably stored at 25°C for more than 60 days, so it has good application prospects in the preparation of cosmetics, drugs, and foods.

[0027] The present invention first prepares a multiple emulsion in one step using a polyurethane amphiphilic block copolymer as an emulsifier. This polyurethane material has both non-toxic characteristics and industrial production feasibility. At the same time, the process of preparing the multiple emulsion by one step has simple process steps, and the construction from the emulsifier to the multiple emulsion is suitable for industrial production.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention first uses a polyurethane amphiphilic block copolymer as a special emulsifier to prepare a multiple emulsion in one step. Its technical advantages are mainly reflected in: (1) The raw materials of this copolymer are easily available and the synthesis route is simple, and the production cost is lower than that of traditional amphiphilic block copolymers; (2) The emulsion construction is efficient, and a W / O / W type multiple emulsion can be realized in one step through a single homogenization treatment with the oil phase. Without adding any stabilizer, the emulsion system can be stably stored at 25°C for more than 60 days; (3) Relying on the excellent biocompatibility and pH response characteristics of the polyurethane material, this technology has great application potential in the fields of cosmetic sustained release, food embedding systems, and drug controlled release systems, etc. Description of the Drawings

[0030] Figure 1 It is the total reflection Fourier transform spectrogram of the polyurethane amphiphilic block copolymers GPE18 - IPDI - DMBA and PG10 - IPDI - DMBA in Example 1.

[0031] Figure 2 It is the sample pictures of PG10 - IPDI - DMBA, PG10 - HDI - DMBA, and PG10 - TDI - DMBA in the example.

[0032] Figure 3 The picture of the multiple emulsion formed by adding methyl blue water-soluble dye to the aqueous solution of PG10-IPDI-DMBA and constructing it with tributyrin in Example 1.

[0033] Figure 4 The microscopic images of the W / O / W emulsions prepared from polyurethane amphiphilic block copolymers with different degrees of polymerization of hydrophilic segments in Example 1: (a) PG3-IPDI-DMBA, (b) PG6-IPDI-DMBA, (c) PG8-IPDI-DMBA, (d) PG10-IPDI-DMBA, (e) GPE18-IPDI-DMBA, (f) GPE26-IPDI-DMBA. The scale bar in the figure is 20 μm.

[0034] Figure 5 The microscopic pictures of the multiple emulsions emulsified by PG10-IPDI-DMBA and different polar oil phases: (a) tributyrin, (b) caprylic / capric triglyceride, (c) tri(ethylhexanoate) glyceride, (d) triacetin in Example 1 (the scale bar in each figure is 20 μm) and their particle size distribution diagrams.

[0035] Figure 6 The emulsification result diagram of the polyurethane amphiphilic block copolymer prepared with different isocyanates and tributyrin in Example 2. The scale bar in the figure is 20 μm.

[0036] Figure 7 The microscopic images and emulsion photos of the emulsification of the aqueous solution of PG10-IPDI-DMBA with tributyrin at different pH values (4.02, 7.75, 9.42) in Example 3. The scale bar in the figure is 20 μm. Detailed implementation manners

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Those skilled in the art who make modifications or equivalent substitutions on the basis of understanding the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0038] Example 1:

[0039] (1) Preparation of polyurethane amphiphilic block copolymers PG3-IPDI-DMBA, PG6-IPDI-DMBA, PG8-IPDI-DMBA, PG10-IPDI-DMBA, GPE18-IPDI-DMBA, GPE26-IPDI-DMBA:

[0040] Preparation of PG3-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutyric acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutyric acid solution dropwise to a three-necked flask containing 0.05 mol of isophorone diisocyanate, and simultaneously add 0.000125 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of triglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer IPDI-DMBA dropwise to the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG3-IPDI-DMBA.

[0041] Preparation of PG6-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutyric acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutyric acid solution dropwise to a three-necked flask containing 0.05 mol of toluene diisocyanate, and simultaneously add 0.000125 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of hexaglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer IPDI-DMBA dropwise to the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG6-IPDI-DMBA.

[0042] Preparation of PG8-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutyric acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutyric acid solution dropwise to a three-necked flask containing 0.05 mol of isophorone diisocyanate, and simultaneously add 0.000125 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of octaglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer IPDI-DMBA dropwise to the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG8-IPDI-DMBA.

[0043] Preparation of PG10-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutanoic acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly drip the 2,2-dimethylolbutanoic acid solution into a three-necked flask containing 0.05 mol of isophorone diisocyanate, and at the same time add 0.000125 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of decaglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly drip the prepolymer IPDI-DMBA into the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG10-IPDI-DMBA.

[0044] Preparation of GPE18-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutanoic acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly drip the 2,2-dimethylolbutanoic acid solution into a three-necked flask containing 0.05 mol of isophorone diisocyanate, and at the same time add 0.000125 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of glycerol polyether-18 to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly drip the prepolymer IPDI-DMBA into the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain GPE18-IPDI-DMBA.

[0045] Preparation of GPE26-IPDI-DMBA: ① Dissolve 0.025 mol of 2,2-dimethylolbutanoic acid in 0.5 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutanoic acid solution dropwise into a three-necked flask containing 0.05 mol of isophorone diisocyanate, and simultaneously add 0.000125 mol of dibutyltin dilaurate as a catalyst. React for 2 hours under mechanical stirring at 70 °C and 200 rpm to obtain the prepolymer IPDI-DMBA. ② After subjecting 0.05 mol of glycerol polyether-26 to vacuum distillation to remove water, add it to the three-necked flask, and add 0.000125 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer IPDI-DMBA dropwise into the three-necked flask, and react for 2 hours under mechanical stirring at 80 °C and 200 rpm. The resulting product is subjected to vacuum distillation to remove acetone to obtain GPE26-IPDI-DMBA.

[0046] (2) Preparation of multiple emulsions:

[0047] Prepare an aqueous solution of PG3-IPDI-DMBA with a mass fraction of 10%, and adjust the pH to neutral with ammonia water. Take 10 mL of the PG3-IPDI-DMBA aqueous solution, and mix it with equal volumes of tributyrin, caprylic / capric triglyceride, glyceryl triacetate, and tri(ethylhexanoate) glycerol respectively, and homogenize at a speed of 10000 rpm for 5 minutes to prepare a W / O / W emulsion. Using the same method, prepare multiple emulsions using PG6-IPDI-DMBA, PG8-IPDI-DMBA, and PG10-IPDI-DMBA, GPE18-IPDI-DMBA, and GPE26-IPDI-DMBA as emulsifiers respectively.

[0048] Example 2:

[0049] (1) Preparation of polyurethane amphiphilic block copolymers PG10-TDI-DMBA and PG10-HDI-DMBA:

[0050] Preparation of PG10-TDI-DMBA: ① Dissolve 0.005 mol of 2,2-dimethylolbutyric acid in 1 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutyric acid solution dropwise to a three-necked flask containing 0.1 mol of toluene diisocyanate. Purge the reaction system with nitrogen to remove water, and simultaneously add 0.00025 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer TDI-DMBA. ② After subjecting 0.1 mol of decaglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.00025 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer TDI-DMBA dropwise to the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG10-TDI-DMBA.

[0051] Preparation of PG10-HDI-DMBA: ① Dissolve 0.005 mol of 2,2-dimethylolbutyric acid in 1 mol of acetone. After purging the reaction system with nitrogen to remove water, slowly add the 2,2-dimethylolbutyric acid solution dropwise to a three-necked flask containing 0.1 mol of hexamethylene diisocyanate, and simultaneously add 0.00025 mol of dibutyltin dilaurate as a catalyst. React at 70 °C with mechanical stirring at 200 rpm for 2 hours to obtain the prepolymer HDI-DMBA. ② After subjecting 0.1 mol of decaglycerol to vacuum distillation to remove water, add it to the three-necked flask, and add 0.00025 mol of dibutyltin dilaurate as a catalyst. After purging with nitrogen to remove water, slowly add the prepolymer HDI-DMBA dropwise to the three-necked flask, and react at 80 °C with mechanical stirring at 200 rpm for 2 hours. The resulting product is subjected to vacuum distillation to remove acetone to obtain PG10-HDI-DMBA.

[0052] (2) Preparation of multiple emulsions:

[0053] Prepare an aqueous solution of PG10-TDI-DMBA with a mass fraction of 5%, and adjust the pH to neutral with ammonia water. Take 10 mL of the PG10-TDI-DMBA aqueous solution, mix it with an equal volume of tributyrin respectively, and homogenize at a speed of 8000 rpm for 5 minutes to prepare a W / O / W emulsion. Using the same method, prepare multiple emulsions with PG10-HDI-DMBA as the emulsifier.

[0054] Example 3:

[0055] (1) Preparation of the polyurethane amphiphilic block copolymer PG10-IPDI-DMBA, with the method the same as in Example 1.

[0056] (2) Preparation of multiple emulsions:

[0057] Prepare an aqueous solution of PG10-IPDI-DMBA with a mass fraction of 10%, and divide it into 3 equal parts on average. Use ammonia water to adjust the pH of these 3 solutions to 4.02, 7.75, and 9.42 respectively. Take 10 mL of the PG10-IPDI-DMBA aqueous solution with the adjusted pH, and mix it with an equal volume of tributyrin respectively, and homogenize it at a speed of 10000 rpm for 5 minutes to prepare a W / O / W emulsion.

[0058] Figure 1 It is the total reflection Fourier transform spectrogram of the polyurethane amphiphilic block copolymer GPE18-IPDI-DMBA and PG10-IPDI-DMBA in Example 1. 260 - 2280 cm -1 There is no characteristic peak of isocyanate (-NCO) between them, and the absence of isocyanate proves that the polyurethane reaction is complete.

[0059] Figure 2 It is the sample pictures of PG10-IPDI-DMBA, PG10-HDI-DMBA, and PG10-TDI-DMBA in the example. Polyurethane emulsifiers (containing 50% water) prepared by reacting with IPDI, HDI, and TDI respectively with PG10 as the hydrophilic chain segment and DMBA as the chain extender have significant color differences for emulsifiers synthesized from different isocyanates.

[0060] Figure 3 It is the picture of the multiple emulsion constructed with tributyrin after adding methyl blue water-soluble dyeing agent to the PG10-IPDI-DMBA aqueous solution in Example 1. After introducing methyl blue dyeing agent into the PG10-IPDI-DMBA aqueous solution, the emulsion constructed with tributyrin presents a clear W / O / W structure (the outer aqueous phase is blue, the oil phase is transparent, and the inner aqueous phase is blue droplets), visually confirming the emulsion type.

[0061] Figure 4 It is the microscopic images of W / O / W emulsions prepared from polyurethane amphiphilic block copolymers synthesized with hydrophilic chain segments of different degrees of polymerization in Example 1. (a) PG3-IPDI-DMBA, (b) PG6-IPDI-DMBA, (c) PG8-IPDI-DMBA, (d) PG10-IPDI-DMBA, (e) GPE18-IPDI-DMBA, (f) GPE26-IPDI-DMBA. It is proved that emulsifiers synthesized from these hydrophilic chain segments with different degrees of polymerization can all prepare multiple emulsions in one step. Among them, GPE18-IPDI-DMBA and GPE26-IPDI-DMBA may have limited interfacial adsorption due to too long hydrophilic chain segments, resulting in less W / O / W prepared.

[0062] Figure 5Microscopic images and particle size distribution diagrams of multiple emulsions formed by PG10-IPDI-DMBA with different polar oil phases in Example 1: (a) tributyrin, (b) caprylic / capric triglyceride, (c) tri(ethylhexanoate) glyceride, (d) triacetin (scale bar in each figure is 20 μm). PG10-IPDI-DMBA shows good emulsifying performance for tributyrin (moderate polarity), forming a W / O / W emulsion with single droplets dispersed in the internal aqueous phase (average particle size 10 μm); while for highly polar triacetin, multiple droplets are dispersed in the internal aqueous phase of the emulsion, and the droplet size of the multiple emulsion systems obtained with caprylic / capric triglyceride and tri(ethylhexanoate) glyceride increases to 20 μm, indicating that the polarity of the oil phase also affects the size and structure of the multiple emulsion. It shows that multiple emulsions with different effects can be obtained by using oil phases with different polarities.

[0063] Figure 6 In Example 2, the emulsification results of polyurethane amphiphilic block copolymers prepared with different isocyanates and tributyrin are shown, indicating that multiple emulsions can also be obtained by using emulsifiers synthesized with different types of isocyanates.

[0064] Figure 7 In Example 3, microscopic images and emulsion photos of the emulsification of PG10-IPDI-DMBA aqueous solution with tributyrin at different pH values (4.02, 7.75, 9.42) are shown. The protonation / deprotonation of carboxyl groups on the chain segments of polyurethane amphiphilic block copolymers at lower or higher pH values affects the hydrophilicity of the molecules, resulting in a transformation of the emulsion type to O / W, confirming that this system has the function of regulating the emulsion type by pH.

Claims

1. A method for one-step preparation of multiple emulsions using polyurethane amphiphilic block copolymers, characterized in that, The specific steps are as follows: (1) Select polyglycerol and glycerol polyether molecules as hydrophilic chain segments, and isocyanate and polyol copolymer as hydrophobic chain segments, and prepare polyurethane amphiphilic block copolymer through an addition reaction; (2) Configure the polyurethane amphiphilic block copolymer obtained in step (1) into an aqueous solution, mix it with the oil phase and homogenize to obtain a multiple emulsion.

2. The method according to claim 1, characterized in that The polyurethane amphiphilic block copolymer described above comprises the following raw materials in terms of mole parts:

3. The method according to claim 2, wherein The hydrophilic chain segment polymer is selected from any one of diglycerol, triglycerol, tetraglycerol, hexaglycerol, octaglycerol, decaglycerol and glycerol polyether; the isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, triphenylmethane triisocyanate; the polyol is one or more of 2,2-dimethylolbutyric acid, 2,2-dimethylolpropionic acid, 1,4-butanediol, trimethylolpropane.

4. The method according to claim 1, wherein The polyurethane amphiphilic block copolymer is prepared by the following method: (1) Use acetone as a solvent, fully dissolve the polyol, purge the reaction system with nitrogen to remove water, slowly drop the dissolved polyol into a three-necked flask containing dibutyltin dilaurate and diisocyanate. After the dropping is completed, control the temperature of the reaction system at 60-80 °C, and continuously stir under the condition of condensing reflux for 1-2 hours; (2) Slowly drop the prepolymer obtained in step (1) into the hydrophilic chain segment polymer that has been dehydrated by high-temperature decompression, and add dibutyltin dilaurate as a catalyst, maintain the reaction temperature at 60-80 °C, and stir and react for 1-2 hours under the condition of condensing reflux; (3) After distilling off acetone from the obtained product under reduced pressure, obtain the polyurethane amphiphilic block copolymer.

5. The method according to claim 1, characterized in that In step (1), the molar ratio of the hydrophilic chain segment to the isocyanate is 1:1 - 1:3; the molar ratio of the isocyanate to the polyol is 1:1 - 3:

1.

6. The method according to claim 1, characterized in that, In step (2), the concentration of the polyurethane amphiphilic block copolymer aqueous solution is 5% - 20%, and the pH is 4 - 10.

7. The method according to claim 1, characterized in that In step (2), the oil phase is one or more of soybean oil, tributyrin, caprylic / capric triglyceride, triacetin, tri(ethylhexanoate) glycerol or squalane.

8. A polyurethane amphiphilic block copolymer prepared by the method described in claim 4.

9. A multiple emulsion prepared in one step using the polyurethane amphiphilic block copolymer described in any one of claims 1-7.

10. The application of the multiple emulsion prepared in one step using the polyurethane amphiphilic block copolymer described in claim 9 in cosmetics, drugs and foods.

Images