Disc-shaped multi-hollow polymer particle and preparation method thereof

Abstract

The invention relates to the field of polymer particles, and provides a disc-shaped multi-hollow polymer particle and a preparation method thereof. The appearance of the disc-shaped multi-hollow polymer particle has a disc shape which can be identified by a scanning electron microscope; a plurality of mutually isolated hollow areas which can be identified by a transmission electron microscope are arranged in the shell; the average diameter is 1.5 to 6.0 [mu] m, preferably 1.7 to 2.4 [mu] m; the average thickness is 100 to 600 nm, preferably 200 to 400 nm; the preparation method comprises the following steps: preparing spherical polystyrene (PS) microspheres by a dispersion polymerization method; the preparation method comprises the following steps: preparing PS / poly (2-ethylhexyl methacrylate) (PEHMA) / decane composite microspheres through a seed dispersion polymerization method; and removing the PEHMA / decane component by using n-butyl alcohol to obtain disc-shaped polymer particles with a multi-hollow structure inside. The prepared particle has a disc-shaped appearance and a multi-hollow internal structure for the first time, the preparation conditions are relatively flexible, and the prepared particle is expected to be applied to the fields of drug release, cosmetics and the like.

Description

Technical Field

[0001] The invention relates to the field of polymer particles, in particular to a disc-shaped multi-hollow polymer particle and a preparation method thereof. Background Art

[0002] Non-spherical shape is an inherent functional property of colloidal particles, which can give different properties from spherical particles in terms of optics, rheology, touch, etc. In the past few decades, people have prepared a variety of non-spherical (e.g., raspberry-shaped, surface wrinkled, golf ball-shaped, disc-shaped) polymer particles.

[0003] Compared with other non-spherical polymer particles, there are still few studies on disc-shaped polymer particles. For example, Okubo et al. used micron-sized polystyrene (PS) microspheres as seeds and prepared hamburger-shaped PS / PEHMA / decane composite microspheres (PS phase in the middle and PEHMA / decane phases on both sides) by seed dispersion polymerization of 2-ethylhexyl methacrylate (EHMA) in the presence of decane. During the seed polymerization process, the PS microspheres were swollen by decane in a methanol / water mixed solvent, and the PEHMA generated by the polymerization was insoluble in the mixed solvent and thus located on the surface of the PS microspheres. Under the action of phase separation, the PS microspheres could be squeezed into a disc shape; subsequently, a large amount of n-butanol was added to remove the PEHMA / decane component, thus obtaining disc-shaped PS particles (Colloid Polym. Sci. 2005, 283, 793-798; Langmuir 2007, 23, 7958-7962). It is worth noting that the seed dispersion polymerization described in this method is carried out by horizontal shaking rather than magnetic stirring, and the conditions for forming disc-shaped particles are relatively strict (methanol / water mass ratio 80 / 20-90 / 10, stirring time must reach 24h, and shaking rate must reach more than 60 laps / min), and the internal structure of the microspheres has not been studied. In addition, Liu Bing et al. prepared disc-shaped PS particles using magnetic stirring (Langmuir 2012, 28, 6436–6440). This method is to magnetically stir the aqueous dispersion of sulfate-stabilized PS microspheres in the presence of water-soluble or oil-soluble organic solvents. Sacanna et al. used polymerizable 3-(trimethoxysilyl) propyl methacrylate (TPM) as a sacrificial template to prepare disc-shaped PS microspheres (Nat. Comm. 2013, 4, 1688). The method includes the following steps: first, PS microspheres with negative surface charge are dispersed in alkaline TPM oil droplets, so that the TPM oil droplets are nucleated on two opposite surfaces of the PS microspheres; then, the PS microspheres are liquefied by adsorbing a small amount of toluene and deformed under the action of surface tension; then, the toluene is removed and the TPM is polymerized to obtain dumbbell-shaped PS-pTPM particles; finally, the pTPM component is removed by selective dissolution to obtain disc-shaped PS particles. Liu Bing et al. also proposed a framework-guided synthesis strategy to prepare polymer discs. This method uses annular SiO2 colloids as a framework, first coating the surface of the SiO2 ring with a polymer to form a SiO2 / polymer core / shell ring; then, a good solvent for the polymer is added to liquefy it; due to the presence of the framework, the shrinkage instability of the liquid on the framework leads to the formation of oblate droplets; after the solvent in the droplets evaporates, polymer discs are formed (J.Am.Chem.Soc.2021,143,1790-1797).

[0004] On the other hand, multi-hollow polymer microspheres are a special type of hollow microspheres, which have the advantages of large specific surface area, large internal space and mutual isolation, and low density, and have been widely studied. The preparation methods can be mainly divided into two categories: post-treatment of the formed polymer microspheres and polymerization. Post-treatment of the formed polymer microspheres includes alkali treatment, heat treatment, solvent treatment and other methods. For example, Okubo et al. heated the aqueous dispersion of micron-sized PS microspheres containing sulfate groups to T g After a certain period of time, multi-hollow PS microspheres are obtained (Langmuir 2017, 33, 3468-3475). This is because during the heating process, the PS microspheres containing water themselves further absorb water under the action of the osmotic pressure caused by the sulfate groups they contain, and the water-containing areas undergo growth and merging. Under appropriate conditions, multi-hollow microspheres can be formed. The polymerization method mainly includes seed emulsion polymerization and one-step emulsion polymerization. For example, Okubo et al. used micron-sized PS microspheres containing sulfate groups inside as seeds, and obtained multi-hollow PS microspheres through seed emulsion polymerization of styrene (Langmuir 2007, 23, 8703–8708). Similar to the above-mentioned heat treatment method, during the seed polymerization process, the PS microspheres containing water themselves further absorb water under the action of the osmotic pressure caused by the sulfate groups they contain, and the water-containing areas undergo growth and merging. Under appropriate conditions, multi-hollow microspheres can be formed.

[0005] Disc-shaped multi-hollow polymer particles have the advantages of disc-shaped polymer particles and multi-hollow polymer microspheres, and are expected to be used in the fields of drug release, cosmetics, etc. However, there are no public reports on disc-shaped multi-hollow polymer particles. Summary of the invention

[0006] The present invention aims to provide a disc-shaped multi-hollow polymer particle and a preparation method thereof.

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

[0008] In a first aspect, the present application provides a disc-shaped multi-hollow polymer particle, comprising:

[0009] a. The particles have a disc-shaped appearance that can be identified by scanning electron microscopy;

[0010] b. The particles have a plurality of mutually isolated hollow regions identifiable by transmission electron microscopy;

[0011] c. The average diameter of the particles is 1.5 to 6.0 μm, preferably 1.7 to 2.4 μm; the average thickness is 100 to 600 nm, preferably 200 to 400 nm.

[0012] In a second aspect, the present application provides a method for preparing the disc-shaped multi-hollow polymer particles described in the first aspect, comprising the following three steps:

[0013] Step 1: Prepare spherical PS microspheres by dispersion polymerization. Spherical PS microspheres are prepared using styrene as a monomer, ethanol or a mixture of ethanol and water as a solvent, polyvinyl pyrrolidone (PVP) as a stabilizer, and azobisisobutyronitrile (AIBN) as an initiator.

[0014] Step 2: Prepare PS / PEHMA / decane composite microspheres by seed dispersion polymerization. 2-Ethylhexyl methacrylate (EHMA) is used as a monomer, the spherical PS microspheres are used as seeds, a mixture of methanol and water is used as a solvent, PVP is used as a stabilizer, and decane is used as a swelling agent. The mixture is heated to 60°C after magnetic stirring for 30 minutes under a nitrogen atmosphere, and then a methanol solution of AIBN initiator is added. Then, the mixture is polymerized at 60°C at a certain speed for a certain period of time.

[0015] Step 3: Add a large amount of n-butanol to the aqueous dispersion of the PS / PEHMA / decane composite microspheres to remove the PEHMA / decane components, thereby forming disc-shaped hollow polymer particles.

[0016] Preferably, in the step 1, the diameter of the prepared spherical PS microspheres is 1.0 to 3.0 μm (average diameter measured by scanning electron microscopy).

[0017] Preferably, in the step 2, the mass ratio of methanol / water in the mixture of methanol and water is 50 / 50 to 100 / 0; the certain rotation speed during stirring is 80 to 360 rpm; and the certain polymerization time is 2 to 24 h.

[0018] The characteristics of the present invention are: (1) the prepared particles have both a disc-shaped appearance and a multi-hollow internal structure; (2) the conditions for forming the disc-shaped particles are relatively flexible. Therefore, compared with the prior art, the beneficial effects of the present invention are: for the first time, it is clarified that the prepared particles have both a disc-shaped appearance and a multi-hollow internal structure, the preparation conditions are relatively flexible, and the prepared disc-shaped multi-hollow polymer particles are expected to be used in the fields of drug release, cosmetics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope photograph of the spherical PS microspheres prepared in step 1 of Example 1.

[0020] Figure 2 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 1.

[0021] Figure 3 This is a transmission electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 1.

[0022] Figure 4 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 2.

[0023] Figure 5 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 3.

[0024] Figure 6 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 4.

[0025] Figure 7 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 5.

[0026] Figure 8 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 6.

[0027] Fig. 9 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 7.

[0028] Fig.10 This is a scanning electron microscope photograph of the spherical PS microspheres prepared in step 1 of Example 8.

[0029] Fig.11 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 8.

[0030] Fig.12 This is a transmission electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 8. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0032] Embodiment 1:

[0033] The preparation method of the disk-shaped hollow polymer particles involved in this embodiment includes the following three steps:

[0034] Step 1: Prepare spherical PS seed microspheres by dispersion polymerization. Take 2.0g styrene as monomer, 0.378g PVP as stabilizer, 14.0g anhydrous ethanol as solvent, put into a 50mL three-necked round-bottom flask equipped with a condenser, a nitrogen gas device and a magnetic stirrer, mix and stir for 30min, then heat the oil bath to 65°C, inject 0.02g AIBN initiator in 4.0g anhydrous ethanol to initiate polymerization, and then continue to stir and polymerize at 65°C for 24h, wherein the condenser and the nitrogen gas device are in the open state throughout the above reaction. After the reaction stops, the obtained product is centrifuged and washed three times (centrifugal speed 6000rpm, 30 minutes each time), the supernatant is replaced with water after the first two centrifugations, and the obtained product is vacuum freeze-dried after the third centrifugation to obtain spherical PS microspheres; the average diameter of the prepared PS microspheres measured by scanning electron microscopy is 1.20μm.

[0035] Step 2: Prepare PS / PEHMA / decane composite microspheres by seed dispersion polymerization. Take 0.05g spherical PS microspheres as seeds, 0.34g EHMA as monomer, 0.1g PVP as stabilizer, 4.0g methanol and 2.0g water as solvents, 1.25g decane as swelling agent, put into a 50mL three-necked round-bottom flask equipped with a condenser, a nitrogen gas device and a magnetic stirrer and mix and stir for 30min, then heat the oil bath to 60°C, inject and add 25mg AIBN solution in 4.0g methanol to initiate polymerization, and then continue to stir and polymerize at 60°C at 120rpm for 24h. Among them, the condenser and nitrogen gas device are in the open state throughout the above reaction.

[0036] Step 3: Prepare disc-shaped polymer particles by removing PEHMA and decane components. After the above polymerization is completed, a large amount of n-butanol is added to the polymerization reaction product. The resulting product is centrifuged and washed 3 times (centrifugal speed 6000rpm, 15 minutes each time), and the supernatant is replaced with n-butanol after each centrifugation, and then the resulting product is dispersed in n-butanol. Scanning electron microscopy observation found that the prepared particles are disc-shaped, with an average diameter of 2.0μm and an average thickness of 260nm. Transmission electron microscopy observation found that the prepared particles have a multi-hollow internal structure, so the prepared polymer particles are disc-shaped multi-hollow particles.

[0037] Figure 1 This is a scanning electron microscope photograph of the spherical PS microspheres prepared in step 1 of Example 1; Figure 2 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 1; Figure 3 This is a transmission electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 1.

[0038] Embodiment 2:

[0039] Referring to the operation of step 2 in Example 1, 1.0 g of methanol and 5.0 g of water were used as solvents, and the rest remained unchanged. Scanning electron microscope observation showed that the prepared particles were disc-shaped, with an average diameter of 2.4 μm and an average thickness of 200 nm. Figure 4 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 2.

[0040] Embodiment 3:

[0041] Referring to the operation of step 2 in Example 1, 6.0 g of methanol was used as the solvent, and the rest remained unchanged. Scanning electron microscopy showed that the prepared particles were disc-shaped, with an average diameter of 1.7 μm and an average thickness of 400 nm. Figure 5 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 6.

[0042] Embodiment 4:

[0043] Referring to the operation of step 2 in Example 1, the polymerization was continued with stirring at 120 rpm at 60° C. for 2 h, and other conditions remained unchanged. Scanning electron microscopy showed that the prepared particles were disc-shaped, with an average diameter of 1.7 μm and an average thickness of 400 nm. Figure 6 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 7.

[0044] Embodiment 5:

[0045] Referring to the operation of step 2 in Example 1, the polymerization was continued at 60° C. and 120 rpm for 24 hours, and other conditions remained unchanged. The prepared particles were observed under a scanning electron microscope to be disc-shaped with an average diameter of 2.2 μm and an average thickness of 240 nm. Figure 7 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 8.

[0046] Embodiment 6:

[0047] Referring to the operation of step 2 in Example 1, the polymerization was continued at 60° C. and 80 rpm for 12 h, and other conditions remained unchanged. The prepared particles were observed under a scanning electron microscope to be disc-shaped with an average diameter of 2.3 μm and an average thickness of 220 nm. Figure 8 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 9.

[0048] Embodiment 7:

[0049] Referring to the operation of step 2 in Example 1, the polymerization was continued at 60° C. and 360 rpm for 12 h, and other conditions remained unchanged. The prepared particles were observed under a scanning electron microscope to be disc-shaped with an average diameter of 2.2 μm and an average thickness of 240 nm. Fig. 9This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 10.

[0050] Embodiment 8:

[0051] Step 1: Preparation of spherical PS seed microspheres by dispersion polymerization. Take 0.5g PVP as a stabilizer, a mixture of 47.25g anhydrous ethanol and 2.75g water as a solvent, put it into a 100mL three-necked round-bottom flask equipped with a condenser, a nitrogen gas device and a magnetic stirrer, mix and stir for 30min, then heat the oil bath to 60°C, inject 0.05g AIBN initiator in 5.0g styrene to initiate polymerization, and then continue to stir and polymerize at 60°C for 24h, wherein the condenser and the nitrogen gas device are in the open state throughout the above reaction. After the reaction stops, the obtained product is centrifuged and washed 3 times (centrifugal speed 6000rpm, 30 minutes each time), the supernatant is replaced with water after the first 2 centrifugations, and the obtained product is vacuum freeze-dried after the third centrifugation to obtain spherical PS microspheres. The average diameter of the prepared PS microspheres measured by scanning electron microscopy is 1.30μm.

[0052] Step 2 and step 3 are the same as in Example 1. Scanning electron microscopy showed that the prepared particles were disc-shaped, with an average diameter of 2.2 μm and an average thickness of 240 nm. Transmission electron microscopy showed that the prepared particles had a multi-hollow internal structure, so the prepared polymer particles were disc-shaped multi-hollow particles.

[0053] Fig.10 This is a scanning electron microscope photograph of the spherical PS microspheres prepared in step 1 of Example 8; Fig.11 This is a scanning electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 8; Fig.12 This is a transmission electron microscope photograph of the disc-shaped PS particles prepared in step 3 of Example 8.

[0054] The above embodiments of the present invention are intended to illustrate the present invention rather than to limit the present invention. Any changes within the equivalent meaning and scope of the claims of the present invention should be considered to be included in the scope of the claims.

Claims

1. A disc-shaped multi-hollow polymer particle, characterized in that: include: a. The particles have a disc-shaped appearance that can be identified by scanning electron microscopy; b. The particles have a plurality of mutually isolated hollow regions identifiable by transmission electron microscopy; c. The average diameter of the particles is 1.5 to 6.0 μm, and the average thickness is 100 to 600 nm.

2. The method for preparing the disc-shaped hollow polymer particles according to claim 1, characterized in that: The steps include: Step 1: Preparation of spherical PS microspheres by dispersion polymerization; Spherical PS microspheres were prepared by dispersion polymerization, using styrene as a monomer, ethanol or a mixture of ethanol and water as a solvent, polyvinyl pyrrolidone (PVP) as a stabilizer, and azobisisobutyronitrile (AIBN) as an initiator. Step 2, preparing PS / PEHMA / decane composite microspheres by seed dispersion polymerization; 2-Ethylhexyl methacrylate (EHMA) is used as a monomer, the spherical PS microspheres are used as seeds, a mixture of methanol and water is used as a solvent, PVP is used as a stabilizer, and decane is used as a swelling agent. The mixture is heated to 60° C. by magnetic stirring for 30 minutes under a nitrogen atmosphere, and then a methanol solution of an AIBN initiator is added, followed by stirring at 60° C. at a certain speed for a certain time to polymerize. Step 3: Add a large amount of n-butanol to the aqueous dispersion of the PS / PEHMA / decane composite microspheres to remove the PEHMA / decane components, thereby forming disc-shaped hollow polymer particles.

3. The method for preparing the disc-shaped hollow PS particles according to claim 1, characterized in that: In the step 2, the mass ratio of methanol / water in the mixture of methanol and water is 50 / 50 to 100 / 0.

4. The method for preparing the disc-shaped hollow PS particles according to claim 1, characterized in that: In the step 2, the certain rotation speed during stirring is 80 to 360 rpm.

5. The method for preparing the disc-shaped hollow PS particles according to claim 1, characterized in that: In the step 2, the polymerization time is 2 to 24 hours.

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