CN103435731A - Preparation method of porous polymer microspheres - Google Patents

Abstract

The invention provides a preparation method of porous polymer microspheres, which comprises the steps of: mixing an oil-soluble monomer, a crosslinking agent and an emulsifier to obtain an oil phase; mixing the oil phase with water to prepare a double emulsion; Initiate the polymerization reaction of the double emulsion to obtain porous polymer microspheres. The double emulsion in the preparation method of the porous polymer microsphere provided by the present invention has high stability, and does not need to add electrolyte and stabilizer to increase the stability of the double emulsion; the porous polymer microsphere obtained by polymerization has high yield, regular shape, The pores have good penetration; the size of the microspheres has good monodispersity, the size adjustment range is wide, and the post-processing of the obtained final product is simple.

Description

A kind of preparation method of porous polymer microsphere

technical field

The invention relates to the field of porous microsphere materials, in particular to a preparation method of porous polymer microspheres.

Background technique

High Internal Phase Emulsion (High Internal Phase Emulsion, HIPE) refers to the emulsion whose volume fraction of the internal phase (dispersed phase) is more than 74%. microporous) porous material. This material has good application prospects. For example, due to its high specific surface area, it can be used as a catalyst carrier or as a catalyst itself; it has adjustable pore size and can be used in the field of separation and filtration; in addition, porous materials can be used in tissue cell culture, drug release, etc. and other biological fields have good prospects.

High internal phase emulsions can be divided into water-in-oil (W/O) type and oil-in-water (O/W) type. Depending on the nature of the monomer, the types of emulsions that are suitable are also different. Among them, the oil-in-water (O/W) high internal phase emulsion refers to a high internal phase emulsion that uses an organic solvent as a dispersed phase and a solution containing a water-soluble monomer as a continuous phase. Water-in-oil (W/O) type high internal phase emulsion is a high internal phase emulsion with aqueous solution as dispersed phase and oil phase containing hydrophobic monomer as continuous phase.

Compared with common methods for preparing porous materials, such as reverse phase method, phase separation method, solvent-induced pore method, etc., the high internal phase emulsion template method has the advantage that the size and distribution of pore diameter and channel diameter can be precisely controlled, and it generally initiates polymerization first. The continuous phase containing the monomer, and the polymer material with porous structure can be obtained after removing the dispersed phase and emulsifier. Due to the continuous phase polymerization, the shape of the high internal phase polymer porous material (polyHIPEs) obtained after polymerization is consistent with the shape of the reactor. For example, a test tube as a reactor will obtain a cylindrical block material, which is not conducive to The removal of impurities such as unpolymerized monomers, emulsifiers, and electrolytes in the system is also inconvenient in practical applications.

和Krajnc等(React.Funct.Polym.2005,65,37)先制备好含氯苯乙烯的油包水(W/O)反相高内相乳液，然后将高内相乳液分散到PVP水溶液中，再悬浮聚合得到polyHIPEs多孔聚合物微珠。但这种方法的缺点是高内相乳液是一种高粘度的乳液，将其分散比较困难，即使能够分散也难以形成规则的球形，并且由含有内水相含有电解质，内外水相形成渗透压导致形成的双重乳液不稳定；Gokmen等(Macromolecules2009,42,9289)用微流体技术将制备好的反相高内相乳液分散到PVA水溶液中，通过紫外引发聚合获得多孔聚合物粒子(球和棒)。但是采用的微流体技术目前只能在实验室里实现，很难应用到实际工业生产中。U.S. Patent Application No. 5,583,162 reported that the high internal phase emulsion was transferred to molds of different shapes, and millimeter-scale porous balls in shapes such as spheres, ellipses, and cylinders were obtained, but the mold design and manufacturing costs of this method were too high. The smallest size can only be controlled to a few millimeters;

(React.Funct.Polym.2005,65,37) and Krajnc et al. (React.Funct.Polym.2005,65,37) first prepared the water-in-oil (W/O) reverse phase high internal phase emulsion containing chlorostyrene, and then dispersed the high internal phase emulsion into the PVP aqueous solution , and resuspension polymerization to obtain polyHIPEs porous polymer microbeads. But the disadvantage of this method is that the high internal phase emulsion is a high viscosity emulsion, it is difficult to disperse it, even if it can be dispersed, it is difficult to form a regular spherical shape, and the internal water phase contains electrolytes, and the internal and external water phases form osmotic pressure. The double emulsion that causes formation is unstable; Gokmen et al. (Macromolecules2009,42,9289) disperses the prepared inverse high internal phase emulsion into the PVA aqueous solution by microfluidic technology, and obtains porous polymer particles (spheres and rods) by UV-induced polymerization. ). However, the microfluidic technology used can only be realized in the laboratory at present, and it is difficult to apply it to actual industrial production.

Therefore, how to prepare a low-cost, easy-to-prepare, and spherical porous polymer has become an urgent problem to be solved in this field.

Contents of the invention

In view of this, the present invention provides a method for preparing porous polymer microspheres with low cost, simple preparation and high yield.

To achieve the above object, the invention provides a method for preparing porous polymer microspheres, which comprises the steps of:

(1) Mix the oil-soluble monomer, cross-linking agent and emulsifier to obtain the oil phase;

(2) Mix the oil phase obtained in step (1) with water under stirring to prepare a double emulsion;

(3) Initiating the polymerization reaction of the double emulsion prepared in step (2) to obtain porous polymer microspheres.

Preferably, the mass ratio of the oil-soluble monomer, the crosslinking agent and the emulsifier in the step (1) is (3-8):(1-4):(1-3).

Preferably, the general formula of the oil-soluble monomer is CH ₂ =CR ₁ R ₂ , wherein R ₁ is hydrogen or methyl, R ₂ is aryl, ester or COOR ₃ , and R ₃ is alkyl or haloalkyl .

Preferably, the general formula of the crosslinking agent is R ₄ (CR ₅ =CH ₂ ) _n , wherein R ₄ is aryl, alkyl, ether-containing or ester-containing, R ₅ is hydrogen or methyl, n It is an integer of 2 to 4.

Preferably, the structural formula of the emulsifier is Where X is NH ₄ ⁺ , Na ⁺ , K ⁺ or amine salt, R is a saturated or unsaturated aliphatic hydrocarbon group or aryl group, a is an integer of 6-14, b is 1 or 2, and c is an integer of 3-14 .

Preferably, a porogen is further added to the oil phase in the step (1), and the mass ratio of the porogen to the oil phase is (0-5):5.

Preferably, the step (1) further includes adjusting the pH value of the oil phase to 6-9.

Preferably, the mass ratio of the oil phase to water in the step (2) is 1:(12-25).

Preferably, the polymerization reaction in the step (3) is initiated by γ-ray radiation.

Preferably, the polymerization reaction in step (3) is initiated by a free radical initiator.

The preparation method of the porous polymer microsphere provided by the present invention has the following characteristics: the double emulsion prepared by the present invention has high stability, and does not need to add electrolyte and stabilizer to increase the stability of the double emulsion; the porous polymer microsphere obtained by polymerization produces High efficiency, regular shape, good penetration of pores; good size monodispersity of microspheres, wide range of size adjustment, and easy post-processing of the obtained final product.

Description of drawings

Fig. 1 is the schematic diagram of the mechanism of the emulsion type formed by different hydrophilic-lipophilic emulsifiers and different oil-water ratios;

Figure 2 is an optical microscope photo of the emulsion formed by S1 in different water phase ratios, where a is the water phase mass fraction of 60wt% (the scale length is 100 μm), b is the water phase mass fraction of 76wt% (the scale length is 100 μm), c is the water phase mass fraction 92wt% (the scale length is 100 μm), d is the water phase mass fraction 92wt% (the scale length is 50 μm);

Fig. 3 is the change graph of the electrical conductivity of the emulsion that S1 forms in different water phase ratios with the water phase mass fraction;

Figure 4 is a scanning electron micrograph of S1;

Figure 5 is a scanning electron micrograph of S2;

Figure 6 is a scanning electron micrograph of S3;

Fig. 7 is the change curve graph of the aqueous phase mass fraction of the emulsion phase transition point along with the pH value;

Figure 8 is an optical micrograph of the double emulsion at different pH values, where a is pH=6, b is pH=7, c is pH=8, d is pH=9, and the scale length is 200 μm;

Fig. 9 is a scanning electron micrograph of S8;

Fig. 10 is the optical micrograph of the double emulsion obtained under different rotating speeds, wherein a is 300r/min (scale length is 200 μm), b is 600r/min (scale length is 200 μm), c is 800r/min (scale length is 100 μm ), d is 1000r/min (scale length is 100μm);

Figure 11 is a scanning electron micrograph of S12;

Fig. 12 is a scanning electron micrograph of S13.

Detailed ways

In order to make the above objects, features and advantages of the invention more obvious and comprehensible, specific implementations of the invention will be described in detail below.

In the following description, a lot of specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described here, and those skilled in the art can do it without departing from the meaning of the present invention. By analogy, the present invention is therefore not limited to the specific examples disclosed below.

As shown in Figure 1, the preparation method of the porous polymer microsphere proposed by the present invention utilizes the phenomenon of "phase inversion" (phase inversion) of the emulsion, and the transformation process is as indicated by the arrow, when the water-in-oil (W/O) reverse phase When the volume fraction of the internally dispersed aqueous phase of the emulsion increases to a certain extent, the type of the emulsion will change, that is, from a water-in-oil (W/O) inverse emulsion to a water-in-oil-in-water (W/O/W) Double lotion. If the oil phase contains polymerizable monomers, porous polymer microspheres can be obtained by initiating polymerization.

The invention provides a kind of preparation method of porous polymer microsphere, comprises the steps:

Step 1: Mix the oil-soluble monomer, cross-linking agent and emulsifier to obtain the oil phase. Those skilled in the art know easily that the ratio of oil-soluble monomer, cross-linking agent and emulsifier can be selected according to actual conditions. Preferably, the mass ratio of oil-soluble monomer, cross-linking agent and emulsifier is (3～8): (1～4):(1～3), more preferably, the mass ratio of oil-soluble monomer, crosslinking agent and emulsifier is (9～13):(4～6):(3～5).

The general formula of the oil-soluble monomer is preferably CH ₂ =CR ₁ R ₂ , wherein R ₁ is hydrogen or methyl, R ₂ is aryl, ester or COOR ₃ , R ₃ is alkyl or haloalkyl, more Preferred are styrene, 4-methylstyrene, 4-ethylstyrene, chlorostyrene, chloromethylstyrene, butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate, etc. at least one of .

The cross-linking agent can not only accelerate the polymerization speed, but also improve the mechanical strength of the porous polymer microsphere, and can introduce functional groups, and its general formula is preferably R ₄ (CR ₅ =CH ₂ ) _n , wherein R ₄ is an aryl group, an alkyl group, an ether group or an ester group, R ₅ is hydrogen or methyl, and n is an integer of 2 to 4; more preferably ethylene glycol dimethacrylate, octapentyl glycol acrylate , at least one of pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and divinylbenzene.

其中X为NH₄ ⁺、Na⁺、K⁺或胺盐，R为饱和或不饱和的脂肪烃基或芳基，a为6～14的整数，b为1或2，c为3～14的整数。上述乳化剂为Y型乳化剂，其结构特点为长链脂肪酸上带有一个或两个酯基的支链，其中长链脂肪酸的碳链长度为12～24；更优选的乳化剂的结构通式为

其中X为NH₄ ⁺或Na⁺或K⁺或胺盐，R为饱和或不饱和脂肪烃基或芳基，例如CH₃或CH=CH₂或C₆H₅或CH₂CH₂CH₃或CH₂CH₂CH₂CH₂CH₃；再优选地，所述乳化剂为12-丙烯酰氧基-9-十八碳烯酸(AOA，12-acryloxy-9-octadecenoic acid)，其结构式如下所示：The emulsifier is an ionic surfactant, and its properties can be adjusted by the pH value and electrolyte concentration. It can stabilize the normal phase emulsion, stabilize the reverse phase emulsion, and stabilize the high internal phase emulsion. Its preferred structural formula is

Where X is NH ₄ ⁺ , Na ⁺ , K ⁺ or amine salt, R is a saturated or unsaturated aliphatic hydrocarbon group or aryl group, a is an integer of 6-14, b is 1 or 2, and c is an integer of 3-14 . Above-mentioned emulsifying agent is Y type emulsifying agent, and its structural characteristic is to have the branched chain of one or two ester groups on the long-chain fatty acid, wherein the carbon chain length of long-chain fatty acid is 12～24; The structure of more preferred emulsifying agent is generally Formula is

Where X is NH ₄ ⁺ or Na ⁺ or K ⁺ or amine salt, R is saturated or unsaturated aliphatic hydrocarbon group or aryl group, such as CH ₃ or CH=CH ₂ or C ₆ H ₅ or CH ₂ CH ₂ CH ₃ or CH ₂ CH ₂ CH ₂ CH ₂ CH ₃ ; more preferably, the emulsifier is 12-acryloxy-9-octadecenoic acid (AOA, 12-acryloxy-9-octadecenoic acid), whose structural formula is as follows Show:

AOA has active double bonds, which can participate in the polymerization of monomers and cross-linking agents, so there is no need to remove the emulsifier, which greatly simplifies the post-processing of the product; the emulsifier has a carboxyl group at the end, which can be adjusted by adjusting the pH value and electrolyte concentration. Hydrophilic and lipophilic (HLB), so it can stabilize both the normal phase emulsion and the reverse phase emulsion; in addition, this emulsifier has a special Y-shaped structure that can increase steric hindrance at the interface, while the ionized terminal group Due to the strong electrostatic repulsion, the group can greatly improve the strength of the interface film.

In order to increase the specific surface area and permeability of the material, a porogen can also be added to the oil phase. Those skilled in the art can select the amount of porogen added according to actual needs. Preferably, the mass ratio of the porogen to the oil phase is (0-5):5; more preferably, the mass ratio of the porogen to the oil phase is (1-4):5. In the present invention, the porogen is preferably a non-polar organic solvent, more preferably, the porogen is at least one of toluene, chlorobenzene, chloroform, carbon tetrachloride and the like.

In the present invention, in order to adjust the phase transition time and the size of the double emulsion, the pH value of the oil phase obtained in the first step can be adjusted and then mixed with water. Changing the pH value will cause the phase transition to advance or delay, and the phase transition can be detected by monitoring the change in the conductivity of the mixture. The higher the pH, the smaller the mass fraction of water phase required for a sudden change in conductivity, and the earlier the phase transition occurs; the lower the pH, the larger the mass fraction of water phase required for a sudden change in conductivity, and the later the phase transition occurs. The larger the pH value, the smaller the size of the double emulsion droplet; when the pH is in the weak alkaline range, it is beneficial to form a stable double emulsion. Those skilled in the art can select different pH values according to actual needs. Preferably, the pH value of the oil phase is adjusted to 6-9; more preferably, the pH value of the oil phase is adjusted to 7.5-8.5. In addition, the base used for pH adjustment can also be flexibly selected according to actual needs, such as ammonia water, NaOH aqueous solution, triethylamine and other organic bases.

The second step: under the condition of stirring, the oil phase obtained in the first step is mixed with water to prepare a double emulsion. Those skilled in the art can easily know that the mixing of oil phase and water can choose to add water to the oil phase or add the oil phase to water, wherein when water is added to the oil phase to undergo a phase transition, a double emulsion is obtained, and the oil phase is added to the water phase Double emulsions can also be obtained. The phase transition refers to the process in which the type of emulsion transforms from an oil-in-water (W/O) high internal phase emulsion to a water-in-oil-in-water (W/O/W) double emulsion, which can be observed by observing a sudden change in conductivity or an optical microscope. Judging by appearance changes. Before the phase transition of the W/O high internal phase emulsion, the electrical conductivity is very low because the oil phase is the continuous phase; after the phase transition, the water phase is the continuous phase, and the electrical conductivity will suddenly increase by an order of magnitude. In addition, there are obvious differences in morphology between high internal phase emulsions and double emulsions. High internal phase emulsions have a densely packed structure of dispersed droplets, while double emulsions are composed of many large droplets containing many small droplets inside. The two structures They are all on the micron scale and can be observed with an optical microscope.

In the present invention, stirring is beneficial to accelerate the formation of the double emulsion and make the droplets of the double emulsion more uniform, preferably, the rotating speed is 200r/min to 1000r/min; more preferably, the rotating speed is 300r/min to 500r/min .

In the second step, the mass ratio of the oil phase to water can be selected according to actual needs. When water is added to the oil phase, the water can be added in two times. The emulsion is reduced in size and homogenized. After the homogenization of the double emulsion, the viscosity of the system is still very large, and the high viscosity is not conducive to polymerization. You can continue to add water to reduce the viscosity of the system, and continue to add water under stirring. The mass ratio of the oil phase to water is preferably 1:(12～ 25), more preferably 1:(15-20). When the oil phase is added to the water, it can be added all at once or dropwise. The mass ratio of the oil phase to water is also preferably 1:(12-25), more preferably 1:(15-20).

The third step: initiating the polymerization reaction of the double emulsion prepared in the second step to obtain porous polymer microspheres. In this step, any method known in the art can be used to initiate the polymerization reaction, preferably by γ-ray radiation, more preferably cobalt 60 radiation source, the absorbed dose rate is 10-160 Gy·min ^-1 , the absorbed dose 30-100KGy, and the irradiation temperature is room temperature.

In the present invention, the initiation of the polymerization reaction can also be initiated by a free radical initiator, and the free radical initiator is preferably a peroxide, azo or redox initiator, such as benzoyl peroxide (BPO) , Azobisisobutyronitrile (AIBN), etc. When selecting an oil-soluble free radical initiator, the free radical initiator can be added to the oil phase in the first step, preferably, the mass ratio of the free radical initiator to the oil phase is (0.5～3.5):100; When soluble free radical initiator, free radical initiator can be added in water, preferably, the mass ratio of free radical initiator and oil phase is (0.5～3.5):100; When selecting redox class free radical initiator for use, can Its oil-soluble initiator is added in the oil phase, and the water-soluble initiator is added in water. Preferably, the molar ratio of oxidizing and reducing radical initiators is 1:1, and the mass ratio of its total mass to the oil phase is (0.5～ 3.5): 100. In a specific embodiment, the polymerization is initiated by a free radical initiator, preferably an oil soluble initiator.

The particle size of the porous polymer microspheres prepared by the method of the present invention can reach 30 μm to 6 mm, and the specific surface area can reach 13.6 to 325.8 m ² /g. In the range of 30 μm to 300 μm, the particle size of porous polymer microspheres prepared by polymerization initiated by free radical initiators can be 60 μm to 6 mm, and the size of microspheres prepared by γ-ray radiation and polymerization initiated by free radical initiators has both good.

Styrene (98%), toluene (analytical grade), ammonia water (25%), and ethanol produced by Sinopharm Chemical Reagent Co., Ltd. are used in the examples, divinylbenzene (80%) of Aldrich-Sigmal is used, and Fluka Ethylene glycol dimethacrylate (95%), using 12-acryloyloxy-9-octadecenoic acid (AOA) produced by HKUST Innovation Company;

Adopt the D2010W type constant speed mechanical stirrer that Shanghai Sile Instrument Co., Ltd. produces to stir in the embodiment; Adopt the DDS-307 type conductivity meter that Shanghai Lei Magnetic Company produces to detect the conductivity of double emulsion, adopt the Leica company's The DM1000 optical microscope was used to observe the emulsion droplets, and the JEOL JSM-6700 scanning electron microscope of Hitachi Company was used to detect the morphology and size of the porous polymer microspheres. The specific surface area of the ball was measured.

Example 1

(1) Add 2.25g of styrene, 0.75g of ethylene glycol dimethacrylate and 0.75g of 12-acryloyloxy-9-octadecenoic acid into a 100ml beaker, and use a syringe to take a certain amount of ammonia water to adjust pH to 8, after mixing evenly, a light yellow viscous opaque liquid is obtained, which is the oil phase;

(2) Add 60.0g of distilled water dropwise to the oil phase under stirring at 300r/min to prepare a double emulsion;

(3) Transfer the double emulsion to a 100ml wide-mouth bottle, and after 30 minutes of nitrogen gas to remove the oxygen in the system, the sealed container is sent into the cobalt source radiation to initiate polymerization, and the dose rate is kept at 30.2Gy·min ^-1 , and it is taken out after 48 hours The product was sieved, washed twice with distilled water, and then washed with ethanol. After drying, the porous polymer microsphere S1 was obtained, and the yield could reach 70%.

As shown in Figure 2 and Figure 3, only inverse emulsions will be produced after the initial drop of distilled water (see Figure 2a); when the water phase mass fraction is less than 90.5%, the conductivity of the emulsion is less than 5μS/cm, when the water phase mass fraction When the fraction is greater than 74%, the emulsion formed is a viscous inverse high internal phase emulsion (see Figure 2b); when the mass fraction of the aqueous phase is greater than 90.5%, the conductivity suddenly increases to greater than 30 μS/cm, and double emulsions can be observed formation (see Figures 2c and 2d).

As shown in Figure 4, the surface and interior of S1 have a through-hole structure, the average size of the microspheres is 60 μm, and the specific surface area is 18.6 m ² /g.

Example 2

Repeat Example 1 with the following difference: replace "ethylene glycol dimethacrylate" with "divinylbenzene".

Finally, porous polymer microspheres S2 were obtained with a yield of up to 70%.

As shown in Figure 5, the surface and internal pores of S2 are closed, the average size of the microspheres is 52 μm, and the specific surface area is 13.6 m ² /g.

Example 3

Repeat Example 1 with the following difference: 3.0 g of toluene was also added as a porogen in step (1).

Finally, porous polymer microspheres S3 were obtained with a yield of up to 65%.

As shown in Figure 6, the surface of S3 has many nanoscale pores, the average size of the microspheres is 41 μm, and the specific surface area is 325.8 m ² /g.

Example 4

Repeat Example 1 with the following differences: adjust the pH value to 6 with ammonia water.

Finally, the porous polymer microsphere S4 was obtained.

As shown in Fig. 8a, the average size of the formed double emulsion droplets is 397 μm.

Example 5

Repeat Example 1 with the following differences: the pH value is adjusted to 7 with ammonia water.

Finally, the porous polymer microsphere S5 was obtained.

As shown in Fig. 8b, the average size of the formed double emulsion droplets is 115 μm.

Example 6

Repeat Example 1 with the following differences: adjust the pH value to 8 with ammonia water.

Finally, the porous polymer microsphere S6 was obtained.

As shown in Fig. 8c, the average size of the formed double emulsion droplets is 52 μm.

Example 7

Repeat Example 1 with the following differences: adjust the pH value to 9 with ammonia water.

Finally, the porous polymer microsphere S7 was obtained.

As shown in Fig. 8d, the average size of the formed double emulsion droplets is 30 μm.

As shown in Figure 7, the larger the pH, the smaller the mass fraction of the water phase required for a sudden change in conductivity, and the earlier the phase transition occurs; the smaller the pH, the larger the mass fraction of the water phase required for a sudden change in conductivity, and the faster the phase transition occurs. Night.

As shown in Figure 8, the droplet size of the double emulsion decreases with the increase of pH. When the pH is 6, 7, 8, and 9, the average sizes of the formed double emulsion droplets are 397 μm, 115 μm, 52 μm, and 30 μm, respectively. The average size of the polymer microspheres obtained by this polymerization also becomes smaller.

Example 8

(1) Add 2.25g of styrene, 0.75g of ethylene glycol dimethacrylate and 0.75g of 12-acryloyloxy-9-octadecenoic acid into a 100ml beaker, and use a syringe to take a certain amount of ammonia water to adjust pH to 8, after mixing evenly, a light yellow opaque mixed liquid is obtained, which is the oil phase;

(2) Add the oil phase dropwise to 60.0g of distilled water under the condition of stirring at 300r/min to prepare a double emulsion;

(3) Transfer the double emulsion to a 100ml wide-mouthed bottle, blow nitrogen for 30 minutes to remove the oxygen in the system, put the sealed container into cobalt source radiation to initiate polymerization, and keep the dose rate at 30.2Gy·min ^-1 , after 48 hours The product was taken out, sieved, washed twice with distilled water, and then washed with ethanol. After drying, the porous polymer microsphere S8 was obtained, and the yield could reach 75%.

As shown in Figure 9, the surface and interior of S8 have a through-hole structure, the average particle size of the microspheres is 169 μm, and the specific surface area is 20.2 m ² /g.

As shown in Fig. 10a, the average size of the formed double emulsion droplets is 198 μm.

Example 9

Example 8 was repeated, with the following differences: the rotational speed in the control step (2) was 600 r/min.

Finally, the porous polymer microsphere S9 was obtained.

As shown in Fig. 10b, the average size of the formed double emulsion droplets is 98 μm.

Example 10

Example 8 was repeated with the following differences: the rotational speed in the control step (2) was 800 r/min.

Finally, the porous polymer microsphere S10 was obtained.

As shown in Fig. 10c, the average size of the formed double emulsion droplets was 78 μm.

Example 11

Example 8 was repeated with the following differences: the rotational speed in the control step (2) was 1000 r/min.

Finally, the porous polymer microsphere S11 was obtained.

As shown in Fig. 10d, the average size of the formed double emulsion droplets is 55 μm.

As shown in Figure 10, the size of the double emulsion droplets will change accordingly when the stirring rate is changed. The average size of the polymer microspheres obtained by polymerization will also become smaller.

Example 12

(1) Add 2.25g styrene, 0.75g ethylene glycol dimethacrylate, 0.75g 12-acryloyloxy-9-octadecenoic acid and 0.13g azobisisobutyronitrile (AIBN) to In a 100ml beaker, use a syringe to take a certain amount of ammonia water to adjust the pH to 8, and mix well to obtain a light yellow viscous opaque liquid, which is the oil phase;

(2) Add 60.0g of distilled water dropwise to the oil phase under stirring at 300r/min to prepare a double emulsion;

(3) Transfer the double emulsion to a 125ml three-neck flask, under the protection of nitrogen, react in a 70°C water bath at 200rpm for 24h, take out the product and sieve it, wash it twice with distilled water, then wash it with ethanol, and dry it Thus, porous polymer microspheres S12 were obtained.

As shown in Figure 11, the microstructure of S12 has a porous structure, the average size of microspheres is 456 μm, and the specific surface area is 15.8 m ² /g.

Example 13

Example 12 was repeated with the following differences: in step (2), the oil phase was added dropwise to 60.0 g of distilled water.

Finally, porous polymer microspheres S13 were obtained.

As shown in Figure 12, the microstructure of S13 has a porous structure, the average size of microspheres is 2.97 mm, and the specific surface area is 14.6 m ² /g.

Although the present invention is described in conjunction with the above embodiments, the present invention is not limited to the above embodiments, but is only limited by the appended claims, and those skilled in the art can easily modify and change it, but without departing from the spirit and scope of the present invention.

Claims (10)

1. a preparation method of porous polymer microspheres, is characterized in that, comprises the steps: (1) Mix the oil-soluble monomer, cross-linking agent and emulsifier to obtain the oil phase; (2) Mix the oil phase obtained in step (1) with water under stirring to prepare a double emulsion; (3) Initiating the polymerization reaction of the double emulsion prepared in step (2) to obtain porous polymer microspheres. 2. The method for preparing porous polymer microspheres according to claim 1, wherein the mass ratio of the oil-soluble monomer, crosslinking agent, and emulsifier in the step (1) is (3-8):( 1～4): (1～3). 3. The preparation method of porous polymer microspheres according to claim 1, wherein the general formula of the oil-soluble monomer is CH ₂ =CR ₁ R ₂ , wherein R ₁ is hydrogen or methyl, R ₂ is an aryl group, an ester group or COOR ₃ , and R ₃ is an alkyl group or a haloalkyl group. 4. The preparation method of porous polymer microspheres according to claim 1, characterized in that, the general formula of the crosslinking agent is R ₄ (CR ₅ =CH ₂ ) _n , wherein R ₄ is aryl, alkane Group, containing ether group or containing ester group, R ₅ is hydrogen or methyl, n is an integer of 2-4. 5. the preparation method of porous polymer microsphere according to claim 1 is characterized in that, the structural formula of described emulsifying agent is

Where X is NH ₄ ⁺ , Na ⁺ , K ⁺ or amine salt, R is a saturated or unsaturated aliphatic hydrocarbon group or aryl group, a is an integer of 6-14, b is 1 or 2, and c is an integer of 3-14 . 6. The method for preparing porous polymer microspheres according to claim 1, wherein a porogen is added to the oil phase in the step (1), and the mass ratio of the porogen to the oil phase is For (0～5):5. 7 . The method for preparing porous polymer microspheres according to claim 1 , wherein the step (1) further comprises adjusting the pH value of the oil phase to 6-9. 8 . The method for preparing porous polymer microspheres according to claim 1 , wherein the mass ratio of the oil phase to water in the step (2) is 1:(12-25). 9. The preparation method of porous polymer microspheres according to claim 1, characterized in that, the polymerization reaction in the step (3) is initiated by γ-ray radiation. 10 . The method for preparing porous polymer microspheres according to claim 1 , wherein the polymerization reaction in step (3) is initiated by a free radical initiator. 11 .

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