A kind of temperature-sensitive polymer microsphere with self-regulating spherical shell permeability and preparation method thereof

Abstract

The present invention discloses a thermosensitive spherical shell permeability self-regulating polymer microsphere and a preparation method, specifically, thermosensitive bidirectional shape memory nanoparticles are compounded in the spherical shell to act as a "micro switch", and the shrinkage / recovery effect generated by the spherical shell in response to temperature rise / fall is used to increase / decrease the pore size in the spherical shell, thereby regulating the spherical shell permeability. In this way, the pore size of the spherical shell can be increased without destroying the spherical shell structure to improve the water vapor permeability during high-temperature drying and accelerate the water dissipation rate of the microsphere kernel; the pore size of the spherical shell is reduced at room temperature after drying, ensuring the mechanical properties and optical properties required for the application of core-shell polymer microspheres. The present invention can significantly improve the drying efficiency of water-containing core-shell polymer microspheres and help high-throughput manufacturing of polymer hollow microspheres.

Description

Technical Field

[0001] The invention relates to the field of functional polymer materials, and in particular to a temperature-sensitive polymer microsphere with self-regulated spherical shell permeability and a preparation method thereof. Background Art

[0002] Polymer hollow microspheres are microspheres with a high molecular polymer material as the shell (such as PS, PAMS, PVC) and a cavity structure inside. Compared with polymer solid microspheres, polymer hollow microspheres have the characteristics of high specific surface area, light weight, low density and heat insulation, which give polymer hollow microspheres many unique physical and chemical properties. Due to the difference between the shading coefficient of the shell layer of polymer hollow microspheres and the shading coefficient of the cavity part, polymer hollow microspheres can be used as shading materials in aerospace and architectural coatings; furthermore, polymer hollow microspheres can absorb ultraviolet rays and reduce radiation, so they are also used in the fields of biomedicine and cosmetics; on the other hand, there is a cavity structure inside the polymer hollow microspheres, and the cavity part can be used as a reaction container, such as a microchemical reactor. In addition, since the inside of polymer hollow microspheres can be coated with other materials or filled with active substances, they are now widely used in many fields such as food, catalysis, chemical industry and biochemical medicine. In view of the huge demand for polymer hollow microspheres, the realization of mass preparation of high-quality hollow microspheres is a necessary prerequisite for improving their application performance or developing new application fields.

[0003] At present, polymer hollow microspheres are usually prepared by microemulsion encapsulation technology, and its preparation process is divided into three important stages: first, water / oil / water double emulsion is prepared by microfluidic chip (production process); then, the preform is collected in a rotary evaporation bottle to remove the organic solvent to obtain a hard polymer microsphere preform (curing process); finally, the internal phase water is dried to obtain the polymer hollow microsphere (drying process). The drying method used is to place the polymer microsphere preform in a static constant temperature thermal environment at normal pressure and slightly above room temperature, so that the water in the microsphere core evaporates and diffuses out. However, the permeability of the preform spherical shell based on high molecular polymer (such as polystyrene, polypropylene, poly-α-methylstyrene) is extremely low, resulting in a very slow dissipation rate of the inner core water during the drying process, which seriously restricts the improvement of the drying efficiency of the polymer microsphere preform, thereby greatly limiting the yield of polymer hollow microspheres. If the drying rate is increased by increasing the drying temperature, the structural stress of the spherical shell will be damaged, causing cracks on the surface of the spherical shell, and the application performance requirements cannot be met. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a thermosensitive spherical shell permeability self-regulating polymer microsphere and preparation method for improving the drying efficiency of the microsphere preform in view of the above-mentioned deficiencies in the prior art. The core-shell polymer microsphere of the present invention combines thermosensitive bidirectional shape memory polymer nanoparticles in the spherical shell as a "micro switch", and uses the shrinkage / recovery effect generated by the response to temperature rise / fall to increase / decrease the pore size in the spherical shell, thereby intelligently regulating the spherical shell permeability, improving the drying speed of the water-containing core-shell polymer microspheres, and facilitating the high-throughput manufacturing of polymer hollow microspheres.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] The present invention first provides a thermosensitive polymer microsphere with self-regulated spherical shell permeability, comprising an inner core and an outer shell wrapping the inner core, and characterized in that: the outer shell is compounded with thermosensitive bidirectional shape memory polymer nanoparticles; the thermosensitive bidirectional shape memory polymer nanoparticles produce a contraction effect when the temperature rises, thereby increasing the pore size in the outer shell; the thermosensitive bidirectional shape memory polymer nanoparticles produce a recovery effect when responding to a decrease in temperature, thereby reducing the pore size in the outer shell, thereby intelligently regulating the permeability of the outer shell.

[0007] The microsphere of the present invention has a spherical shell composited with temperature-sensitive bidirectional shape memory polymer nanoparticles. The nanoparticles act as a "microswitch" in the spherical shell, and the shrinkage / recovery effect produced by the nanoparticles in response to temperature rise / fall can be utilized to increase / decrease the pore size in the spherical shell, thereby intelligently regulating the permeability of the spherical shell.

[0008] The present invention also provides a method for preparing temperature-sensitive polymer microspheres with self-regulated spherical shell permeability, which is characterized by comprising:

[0009] Preparation of polyurethane films using diisocyanates and polyester diols;

[0010] The prepared polyurethane film is subjected to bidirectional shape memory performance training to obtain a temperature-sensitive bidirectional shape memory polyurethane film, and then the temperature-sensitive bidirectional shape memory polyurethane film is made into nanoparticles;

[0011] The prepared nanoparticles are suspended in an oil phase solution and continuously stirred to form an oil phase working medium, wherein the mass concentration of the nanoparticles in the oil phase working medium is in a range of 5% to 10%;

[0012] The oil phase working fluid is prepared into a water-oil-water double emulsion by using microfluidic technology, and the temperature-sensitive polymer microspheres with self-regulated spherical shell permeability are obtained through solidification and drying.

[0013] The invention discloses a method for preparing a temperature-sensitive polymer microsphere with self-regulating spherical shell permeability. First, a diisocyanate, a polyester diol and a chain extender undergo a polymerization reaction under a catalytic action, and a polyurethane polymer blank is prepared through extraction and drying, and the blank is hot-pressed into a polyurethane film, and a bidirectional shape memory performance training is performed to give it a "switch" effect, and then the blank is ground into nanoparticles; then, the nanoparticles with the "switch" effect are suspended in an oil phase solution, and continuously stirred to become an oil phase working fluid; finally, the oil phase working fluid is prepared into a water / oil / water double emulsion by using microfluidic technology, and the intelligent temperature-sensitive polymer microsphere with self-regulating spherical shell permeability is obtained through curing and drying.

[0014] The specific steps include:

[0015] S1: Preparation of polyurethane polymer blank: adding a certain ratio of diisocyanate and polyester diol into a round-bottom flask, heating at a constant temperature under a protective atmosphere to carry out a first polymerization reaction; then, adding a chain extender and a catalyst and carrying out a second polymerization reaction under a constant temperature condition; continuously stirring during the two-step polymerization reaction to form a polyurethane polymer blank; finally, extracting the polymer blank and drying it in a vacuum thermostat to obtain the polyurethane polymer blank.

[0016] S2: Preparation of materials with bidirectional shape memory properties: The polyurethane polymer blank is hot-pressed into a uniform polyurethane film under vacuum conditions, and bidirectional shape memory performance training is performed between a preset drying temperature (i.e., the shaping temperature Td) and room temperature Tr, so that the uniform polyurethane film has a "switch" effect.

[0017] S3: preparing oil phase working fluid: the polyurethane film having the "switch" effect is ball-milled at high speed into nanoparticles, the nanoparticles are suspended in an oil phase solution, and the mixture is continuously stirred to be uniform, so as to prepare an oil phase working fluid containing temperature-sensitive bidirectional shape memory polymer nanoparticles.

[0018] S4: preparing a water / oil / water double emulsion: using microfluidics technology to prepare the oil phase working fluid into a water / oil / water double emulsion containing a water phase core.

[0019] S5: Preparation of core-shell polymer microspheres: The water / oil / water double emulsion is solidified, cleaned and dried to obtain thermosensitive polymer microspheres with self-regulated shell permeability and embedded with trace amounts of polyurethane nanoparticles.

[0020] The diisocyanate described in S1 is one of 2,4-toluene dicyanate (TPI), 4,4′-diphenylmethane diisocyanate (MDI), and polyphenylmethane polyisocyanate (PAPI).

[0021] The polyester diol described in S1 is one of polycaprolactone diol (PCL-diol), terminal hydroxy polyethylene glycol (PEG), polybutylene glycol (PTMEG), polyethylene glycol (PHG), polybutylene adipate (PHBA), polyhexane adipate (PHDEG), and polytetramethylene ether glycol (PTMEG).

[0022] The chain extender described in S1 is a small molecule diol chain extender, specifically one of 1,4-butanediol (BDO), ethylene glycol (EG), and propylene glycol (PG).

[0023] The catalyst described in S1 is one of toluene, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) or methyl isobutyl ketone (MIBK).

[0024] The protective atmosphere and constant temperature heating in the two-step polymerization reaction described in S1 specifically refer to a nitrogen atmosphere and a heating temperature of 70°C to 90°C; the stirring conditions are mechanical stirring or magnetic stirring, and the stirring rate is 300rpm to 600rpm; the extraction solvent is distilled water or deionized water, and the constant temperature drying refers to drying in a vacuum thermostat for 24 hours, and the set temperature range is between 60°C and 80°C.

[0025] The hot pressing process described in S2 refers to the process of pressing at a temperature higher than the setting temperature T d The polyurethane film is stretched under vacuum conditions to melt and extend all its components; then the stretched state of the polyurethane film is maintained and the ambient temperature is lowered to T r , so that the molecular chains of each component of the polyurethane film produce oriented crystals along the stretching direction. The ambient temperature is raised to T d When the temperature drops to T, the components with higher melting temperatures in the polyurethane film still maintain an oriented crystal state, while the components with lower melting temperatures melt, and the polyurethane film exhibits shrinkage behavior. r When T is , the oriented crystallization provides an anisotropic skeleton structure for the molten phase, so that the molten phase recrystallizes along the skeleton direction, and the polyurethane film exhibits elongation behavior. d With T r The multiple cooling and heating processes can cause the components with lower melting temperatures to repeatedly undergo oriented crystallization and melting, which is macroscopically manifested as reversible elongation and contraction behavior of the polyurethane film, that is, the polyurethane film has acquired a two-way shape memory property, that is, it has a "switch" effect.

[0026] The diameter range of the nanoparticles described in S3 is between 100 and 250 nm; the oil phase solution is one of polystyrene (PS), polyvinyl chloride (PVC), polymethyl styrene (PAMS), polyethylene (PE), and polypropylene (PP); the mass concentration range of the nanoparticles in the oil phase working fluid is between 5 and 10%; the stirring adopts a mechanical stirring method, and the stirring rate is 900rpm to 1500rpm.

[0027] The microfluidic technology described in S4 adopts one of T-type microchannel, co-flow capillary, and focusing microchannel; the inner water phase of the water / oil / water double emulsion is ultrapure water or deionized water.

[0028] The water / oil / water double emulsion curing process described in S5 is carried out in a rotary evaporator, the curing temperature range is 25°C to 45°C, the curing time is not less than 48 hours, and the rotation speed range of the rotary evaporator is 20rpm to 50rpm; the cleaning process is specifically to first clean with distilled water or deionized water 4-5 times, and then clean with anhydrous ethanol 2-3 times; the drying process is carried out in a constant temperature drying oven, the drying temperature range is 25°C to 60°C, and the drying time is not less than 48 hours.

[0029] Beneficial Effects

[0030] Based on the drying process of water-containing core-shell polymer microspheres, the thermosensitive spherical shell permeability self-regulating polymer microspheres of the present invention are based on the premise of not destroying the physical structure of the microspheres, and utilize the shrinkage / recovery effect of thermosensitive bidirectional shape memory nanoparticles in response to temperature rise / fall to achieve the increase / decrease of the pore size in the spherical shell, thereby intelligently regulating the spherical shell permeability. During the heating and drying process, the thermosensitive nanoparticles embedded in the spherical shell shrink, which increases the pore size in the spherical shell, thereby improving the water vapor permeability and accelerating the escape rate of water in the microsphere core; at room temperature after the drying is completed, the thermosensitive nanoparticles embedded in the spherical shell return to their original shape, and the pore size in the spherical shell is reduced, ensuring the mechanical properties and optical properties required for the application of polymer hollow microspheres. Therefore, the application of the present invention can significantly improve the drying efficiency of the water-containing microsphere preform and help the high-throughput manufacturing of polymer hollow microspheres. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Working principle of thermosensitive polymer microspheres with self-regulating shell permeability;

[0032] Figure 2 Flow chart for preparation of temperature-sensitive permeability self-regulating polymer materials;

[0033] Figure 3 Schematic diagram of the preparation process of thermosensitive polymer microspheres with self-regulated spherical shell permeability;

[0034] Figure 4 Schematic diagram of the molecular mechanism of bidirectional shape memory performance training;

[0035] Figure 5 The permeation time of the temperature-sensitive permeability self-regulating polymer material at different temperatures in Example 1;

[0036] Figure 6 The permeation time of the temperature-sensitive permeability self-regulating polymer material at different temperatures in Example 2;

[0037] Figure 7 The permeation time of the temperature-sensitive permeability self-regulating polymer material at different temperatures in Example 3;

[0038] Figure 8 The temperature-sensitive spherical shell permeability self-regulating polymer microsphere and spherical shell cross-section diagram in Example 4;

[0039] Fig. 9 The temperature-sensitive spherical shell permeability self-regulating polymer microsphere and spherical shell cross-section diagram in Example 5;

[0040] Fig.10 The temperature-sensitive spherical shell permeability self-regulating polymer microsphere and spherical shell cross-section diagram in Example 6. DETAILED DESCRIPTION

[0041] The present invention will be described in more detail below in conjunction with the accompanying drawings. In the following detailed description, only certain exemplary embodiments of the present invention are described by way of illustration. It is undoubted that those skilled in the art will recognize that the described embodiments may be modified in various ways without departing from the claims of the present invention.

[0042] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, "including but not limited to". Therefore, the drawings and descriptions are illustrative in nature and are not intended to limit the scope of protection of the claims.

[0043] The intelligent temperature-sensitive polymer microsphere with self-regulating spherical shell permeability proposed in the present invention comprises temperature-sensitive bidirectional shape memory polymer nanoparticles 1 and polymer microsphere shells 2. The working principle of the temperature-sensitive polymer microsphere with self-regulating spherical shell permeability proposed in the present invention is as follows: Figure 1 As shown. The oil phase solution containing the temperature-sensitive bidirectional shape memory polymer nanoparticles 1 of the present invention is used as the intermediate oil phase working fluid, and a water / oil / water double emulsion containing the water phase core 3 is prepared by using microfluidic technology, and then solidified to form a polymer microsphere preform containing the water phase core 3, and then dried to obtain the intelligent temperature-sensitive polymer microsphere with self-regulating spherical shell permeability.

[0044] When the environment is heated up for drying, some components in the thermosensitive nanoparticles 1 embedded in the spherical shell 2 begin to melt and shrink, the pores of the spherical shell 2 become larger, the permeability is increased, and the water phase core 3 of the microsphere is vaporized into water molecules 4 and the speed of escaping outward is accelerated, thereby accelerating the drying process of the polymer microsphere preform. When the drying is completed, the ambient temperature drops to room temperature, the components in the thermosensitive nanoparticles 1 embedded in the spherical shell 2 recrystallize and expand, the pores of the spherical shell 2 begin to shrink, and finally return to the initial state, ensuring the mechanical properties and optical properties required for the application of the polymer hollow microspheres.

[0045] The preparation process of temperature-sensitive permeability self-regulating polymer material is as follows Figure 2 shown.

[0046] First, add diisocyanate and polyester diol in a ratio of 1:1 to 3:1 into a round-bottom flask, and heat at a constant temperature under a protective atmosphere to carry out the first step of polymerization reaction;

[0047] Then, a chain extender and a catalyst are added thereto and a second polymerization reaction is carried out under constant temperature conditions; stirring is continued during the two-step polymerization reaction to form a polyurethane polymer blank; the polymer blank is extracted by a precipitation process using distilled water or deionized water, and dried in a vacuum thermostat at 60° C. for 24 hours;

[0048] Secondly, the polyurethane polymer blank is hot pressed into a uniform polyurethane film under vacuum conditions and dried at a preset drying temperature (i.e., the setting temperature T d , setting temperature T d In the range of 70℃~90℃, the specific temperature varies according to the material) and room temperature T r Performing bidirectional shape memory performance training between the two layers, so that the uniform polyurethane film has a "switch" effect;

[0049] Finally, the polyurethane film with the "switch" effect is ball-milled at high speed into nanoparticles 1, which are slightly suspended in an oil phase solution and continuously stirred to prepare an oil phase working fluid containing temperature-sensitive bidirectional shape memory polymer nanoparticles 1.

[0050] After the above oil phase working fluid is prepared, a water / oil / water double emulsion is constructed using microfluidic technology, such as Figure 3As shown in step 1. Then, the solvent is removed by mass transfer, and a polymer microsphere preform containing a core water phase 3 is solidified in a rotary evaporator. The obtained microsphere preform is first washed with distilled water for 4-5 times, and then washed with anhydrous ethanol for 2-3 times; finally, the microsphere preform is dried by heating. During the heating and drying process, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 shrink, so that the pore size of the spherical shell 2 increases, thereby increasing the water vapor permeability and accelerating the water dissipation rate of the polymer microsphere core; at room temperature after the drying is completed, the thermosensitive nanoparticles 1 embedded in the polymer microsphere shell 2 return to their original shape, and the pore size in the polymer microsphere shell 2 is reduced, and finally qualified polymer hollow microspheres are obtained.

[0051] Molecular mechanism of bidirectional shape memory performance training Figure 4 As shown. In the initial state, both components of the polymer material are in a state of irregular orientation, and the melting and crystallization process cannot change the shape of the sample (shape D). First, by applying external force to stretch the sample at high temperature for deformation (shape C), keep the stretched state and cool it to low temperature, so that both components undergo oriented crystallization along the stretching direction (shape C); after removing the applied external force, shape B can be obtained. Then, it is raised to a certain temperature again, so that the component with a lower melting temperature melts, and the component with a higher melting temperature still maintains an oriented crystallization state, which is equivalent to providing an anisotropic skeleton structure (or internal stress) for the melt phase. At this time, the melted molecular chain maintains a partial oriented state (shape A). In this way, the component with a lower melting temperature can be repeatedly oriented, crystallized and melted through the cooling and heating process without external force, which is manifested as reversible elongation and contraction behavior of the material, that is, the material obtains two-way shape memory properties.

[0052] Example 1

[0053] The present embodiment provides a method for preparing a temperature-sensitive bidirectional shape memory polyurethane film for preparing temperature-sensitive polymer microspheres with self-regulated spherical shell permeability, comprising the following steps:

[0054] (1) First, diisocyanate HMDI and polycaprolactone diol PCL-diol in a molar ratio of 3:1 were added to a round-bottom flask, and the mixture was placed at 70°C for 3 hours under a nitrogen atmosphere for the first polymerization. Then, 3-5 g of a chain extender BD and 20 g of a catalyst toluene solution DBTDL were added thereto, and the mixture was kept at a constant temperature of 70°C for 24 hours to ensure the completion of the second polymerization process. Mechanical stirring was continuously performed during the two-step polycondensation reaction to form a polyurethane polymer blank. Finally, the polymer blank was extracted using distilled water through a precipitation process and dried in a vacuum thermostat at 60°C for 24 hours.

[0055] (2) The obtained polyurethane polymer was prepared into a 0.2 mm uniform film by a vacuum hot press, cut into 2 cm×6 cm, and then stretched along the long axis at 90° C. using a stretching machine, maintained for 5 minutes, and then gradually cooled to 5° C.

[0056] (3) The obtained polyurethane film is ball-milled at high speed into nanoparticles 1, which are slightly suspended in a PS oil phase solution and continuously stirred to be uniform, thereby preparing an oil phase working fluid containing temperature-sensitive bidirectional shape memory polymer nanoparticles 1.

[0057] (4) The polyurethane microparticle-polystyrene emulsion prepared above was cast on a polytetrafluoroethylene sheet membrane to prepare a 5 cm×5 cm×0.2 mm membrane. After standing at 60°C for 10 hours, the membrane was further dried at 100°C under vacuum for 10 hours and then taken out and cooled to room temperature, thereby obtaining a smart temperature-sensitive permeability self-regulating membrane sample.

[0058] The air permeability tester was used to test the permeability change of the sample membrane during the process of heating from 5℃ to 85℃ and then cooling back to 5℃, and a sample point was taken every 10℃. The test results are as follows Figure 5 As shown in the figure, the time for 100 mL of air to pass through the sample membrane decreases as the temperature increases, and the permeation time at 85°C is about half of that at 5°C. That is, the permeability of the sample membrane increases as the temperature increases, and the increase rate can reach 100%.

[0059] Example 2

[0060] The present embodiment provides a method for preparing a temperature-sensitive bidirectional shape memory polyurethane film for preparing temperature-sensitive polymer microspheres with self-regulated spherical shell permeability, the steps comprising:

[0061] (1) First, diisocyanate HMDI and polycaprolactone diol PCL-diol in a molar ratio of 2:1 were added into a round-bottom flask, and placed at 70°C for 3 hours under a nitrogen atmosphere for the first polymerization; then, 3-5 g of chain extender BD and 20 g of catalyst toluene solution DBTDL were added thereto, and the mixture was kept at a constant temperature of 70°C for 24 hours to ensure the completion of the second polymerization process; mechanical stirring was continuously performed during the two-step polycondensation reaction to form a polyurethane polymer blank; finally, the polymer blank was extracted using distilled water through a precipitation process and dried in a vacuum thermostat at 60°C for 24 hours.

[0062] (2) The obtained polyurethane polymer was prepared into a 0.2 mm uniform film by a vacuum hot press, cut into 2 cm×6 cm, and then stretched along the long axis at 90° C. using a stretching machine, maintained for 5 minutes, and then gradually cooled to 5° C.

[0063] (3) The obtained polyurethane film is ball-milled at high speed into nanoparticles 1, which are slightly suspended in a PS oil phase solution and continuously stirred to be uniform, thereby preparing an oil phase working fluid containing temperature-sensitive bidirectional shape memory polymer nanoparticles 1.

[0064] (4) The polyurethane microparticle-polystyrene emulsion prepared above was cast on a polytetrafluoroethylene sheet membrane to prepare a 5 cm×5 cm×0.2 mm membrane. After standing at 60°C for 10 hours, the membrane was further dried at 100°C under vacuum for 10 hours and then taken out and cooled to room temperature, thereby obtaining a smart temperature-sensitive permeability self-regulating membrane sample.

[0065] The air permeability tester was used to test the permeability change of the sample membrane during the process of heating from 5℃ to 85℃ and then cooling back to 5℃, and a sample point was taken every 10℃. The test results are as follows Figure 6 As shown in the figure, the time for 100 mL of air to pass through the sample membrane decreases as the temperature increases, and the permeation time at 85°C is about half of that at 5°C. That is, the permeability of the sample membrane increases as the temperature increases, and the increase rate can reach 100%.

[0066] Example 3

[0067] This embodiment provides a temperature-sensitive polymer microsphere with self-regulated spherical shell permeability and a preparation method, the preparation method comprising the following steps:

[0068] (1) First, diisocyanate HMDI and polycaprolactone diol PCL-diol in a molar ratio of 1:1 were added into a round-bottom flask, and placed in a nitrogen atmosphere at 70°C for 3 hours for the first polymerization; then, 3-5 g of chain extender BD and 20 g of catalyst toluene solution DBTDL were added thereto, and the mixture was kept at a constant temperature of 70°C for 24 hours to ensure the completion of the second polymerization process; mechanical stirring was continuously performed during the two-step polycondensation reaction to form a polyurethane polymer blank; finally, the polymer blank was extracted using distilled water through a precipitation process and dried in a vacuum thermostat at 60°C for 24 hours.

[0069] (2) The obtained polyurethane polymer was prepared into a 0.2 mm uniform film by a vacuum hot press, cut into 2 cm×6 cm, and then stretched along the long axis at 90° C. using a stretching machine, maintained for 5 minutes, and then gradually cooled to 5° C.

[0070] (3) The obtained polyurethane film is ball-milled at high speed into nanoparticles 1, which are slightly suspended in a PS oil phase solution and continuously stirred to be uniform, thereby preparing an oil phase working fluid containing temperature-sensitive bidirectional shape memory polymer nanoparticles 1.

[0071] (4) The polyurethane microparticle-polystyrene emulsion prepared above was cast on a polytetrafluoroethylene sheet membrane to prepare a 5 cm×5 cm×0.2 mm membrane. After standing at 60°C for 10 hours, the membrane was further dried at 100°C under vacuum for 10 hours and then taken out and cooled to room temperature, thereby obtaining a smart temperature-sensitive permeability self-regulating membrane sample.

[0072] The air permeability tester was used to test the permeability change of the sample membrane during the process of heating from 5℃ to 85℃ and then cooling back to 5℃, and a sample point was taken every 10℃. The test results are as follows Figure 7 As shown in the figure, the time for 100 mL of air to pass through the sample membrane decreases as the temperature increases, and the permeation time at 85°C is about half of that at 5°C. That is, the permeability of the sample membrane increases as the temperature increases, and the increase rate can reach 100%.

[0073] Example 4

[0074] This embodiment provides a method for preparing a temperature-sensitive polymer microsphere with self-regulated spherical shell permeability, the steps comprising:

[0075] (1) The polyurethane film of Example 1 was ball-milled at high speed into nanoparticles 1, which were slightly suspended in 10 ml of a 12 wt % polystyrene-fluorobenzene solution, and stirred for 30 min to mix the nanoparticles 1 and the oil phase solution evenly, thereby obtaining an oil phase working fluid containing 10 wt % nanoparticles.

[0076] (2) The oil phase working fluid is prepared into a water / oil / water double emulsion containing a water phase inner core by a coaxial co-flow "one-step method", wherein the outer water phase is a polyvinyl alcohol aqueous solution with a mass concentration of 2%, and the inner water phase is ultrapure water; the diameter and wall thickness of the water / oil / water double emulsion are set to 1500 μm and 20 μm, respectively.

[0077] (3) After the composite emulsion is generated, it is collected in a rotary evaporation bottle, then placed in a water bath at 45° C. for heating, and horizontally rotated at a speed of 35 r / min for 48 h to obtain a PS hard microsphere preform containing internal phase water.

[0078] (4) The cured PS-based microsphere preform is taken out and first washed with distilled water for 4-5 times, and then washed with anhydrous ethanol for 2-3 times; finally, the washed PS-based microsphere preform is placed in a vacuum thermostat at 55° C. and dried for 24 hours.

[0079] The core-shell polymer hollow microspheres and the electron microscopy images of the shell cross section obtained by drying at 55°C. Figure 8As shown, during the heating and drying process, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 shrink, increasing the pore size of the spherical shell 2, thereby increasing the water vapor permeability and accelerating the water dissipation rate of the polymer microsphere core; at room temperature after the drying is completed, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 return to their original shape, and the pore size in the spherical shell 2 is reduced, and finally qualified core-shell polymer hollow microspheres are obtained. The drying time of the water-containing core-shell polymer microspheres of the present invention is reduced to 24 hours, and the drying promotion rate reaches 100%, which significantly reduces the time required for drying the water-containing core-shell polymer microspheres, and can achieve a large number of high-quality hollow microspheres, which helps the high-throughput manufacturing of microspheres.

[0080] Example 5

[0081] This embodiment provides a method for preparing a temperature-sensitive polymer microsphere with self-regulated spherical shell permeability, the steps comprising:

[0082] (1) The polyurethane film of Example 2 was ball-milled at high speed into nanoparticles 1, which were slightly suspended in 10 ml of a 12 wt % polystyrene-fluorobenzene solution and stirred for 30 min to mix the nanoparticles 1 and the oil phase solution evenly, thereby obtaining an oil phase working fluid containing 10 wt % nanoparticles.

[0083] (2) The oil phase working fluid is prepared into a water / oil / water double emulsion containing a water phase inner core by a coaxial co-flow "one-step method", wherein the outer water phase is a polyvinyl alcohol aqueous solution with a mass concentration of 2%, and the inner water phase is ultrapure water; the diameter and wall thickness of the water / oil / water double emulsion are set to 1500 μm and 20 μm, respectively.

[0084] (3) After the composite emulsion is generated, it is collected in a rotary evaporation bottle, then placed in a water bath at 45° C. for heating, and horizontally rotated at a speed of 35 r / min for 48 h to obtain a PS hard microsphere preform containing internal phase water.

[0085] (4) The cured PS-based microsphere preform is taken out and first washed with distilled water for 4-5 times, and then washed with anhydrous ethanol for 2-3 times; finally, the washed PS-based microsphere preform is placed in a vacuum thermostat at 55° C. and dried for 24 hours.

[0086] The core-shell polymer hollow microspheres and the electron microscopy images of the shell cross section obtained by drying at 55°C. Fig. 9As shown, during the heating and drying process, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 shrink, increasing the pore size of the spherical shell 2, thereby increasing the water vapor permeability and accelerating the water dissipation rate of the polymer microsphere core; at room temperature after the drying is completed, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 return to their original shape, and the pore size in the spherical shell 2 is reduced, and finally qualified core-shell polymer hollow microspheres are obtained. The drying time of the water-containing core-shell polymer microspheres of the present invention is reduced to 24 hours, and the drying rate reaches 100%, which significantly reduces the time required for drying the water-containing core-shell polymer microspheres, and can achieve a large number of high-quality hollow microspheres, which helps the high-throughput manufacturing of microspheres.

[0087] Example 6

[0088] This embodiment provides a method for preparing a temperature-sensitive polymer microsphere with self-regulated spherical shell permeability, the steps comprising:

[0089] (1) The polyurethane film of Example 3 was ball-milled at high speed into nanoparticles 1, which were slightly suspended in 10 ml of a polystyrene-fluorobenzene solution with a mass concentration of 12 wt%, and stirred for 30 min to mix the nanoparticles 1 and the oil phase solution evenly, thereby preparing an oil phase working fluid containing 10 wt% of nanoparticles.

[0090] (2) The oil phase working fluid is prepared into a water / oil / water double emulsion containing a water phase inner core by a coaxial co-flow "one-step method", wherein the outer water phase is a polyvinyl alcohol aqueous solution with a mass concentration of 2%, and the inner water phase is ultrapure water; the diameter and wall thickness of the water / oil / water double emulsion are set to 1500 μm and 20 μm, respectively.

[0091] (3) After the composite emulsion is generated, it is collected in a rotary evaporation bottle, then placed in a water bath at 45° C. for heating, and horizontally rotated at a speed of 35 r / min for 48 h to obtain a PS hard microsphere preform containing internal phase water.

[0092] (4) The cured PS-based microsphere preform is taken out and first washed with distilled water for 4-5 times, and then washed with anhydrous ethanol for 2-3 times; finally, the washed PS-based microsphere preform is placed in a vacuum thermostat at 55° C. and dried for 24 hours.

[0093] The core-shell polymer hollow microspheres and the electron microscopy images of the shell cross section obtained by drying at 55°C. Fig.10As shown, during the heating and drying process, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 shrink, increasing the pore size of the spherical shell 2, thereby increasing the water vapor permeability and accelerating the water dissipation rate of the polymer microsphere core; at room temperature after the drying is completed, the thermosensitive nanoparticles 1 embedded in the spherical shell 2 return to their original shape, and the pore size in the spherical shell 2 is reduced, and finally qualified core-shell polymer hollow microspheres are obtained. The drying time of the water-containing core-shell polymer microspheres of the present invention is reduced to 24 hours, and the drying rate reaches 100%, which significantly reduces the time required for drying the water-containing core-shell polymer microspheres, and can achieve a large number of high-quality hollow microspheres, which helps the high-throughput manufacturing of microspheres.

Claims

1. A temperature-sensitive polymer microsphere with self-regulating shell permeability, comprising a core and a shell encapsulating the core, characterized in that: The shell is compounded with thermosensitive bidirectional shape memory polymer nanoparticles; the thermosensitive bidirectional shape memory polymer nanoparticles produce a contraction effect when the temperature rises so that the pore size in the shell increases, and the thermosensitive bidirectional shape memory polymer nanoparticles produce a recovery effect in response to a decrease in temperature so that the pore size in the shell decreases, thereby intelligently regulating the permeability of the shell; the thermosensitive bidirectional shape memory polymer nanoparticles are thermosensitive bidirectional shape memory polymer polyurethane nanoparticles; A method for preparing temperature-sensitive bidirectional shape memory polymer polyurethane nanoparticles comprises: Preparation of polyurethane polymer blanks using diisocyanates and polyester diols; The prepared polyurethane polymer blank is hot-pressed into a polyurethane film, and the polyurethane film is subjected to two-way shape memory performance training to obtain a temperature-sensitive two-way shape memory polyurethane film; Grinding a thermosensitive bidirectional shape memory polyurethane film into nanoparticles; The method of hot-pressing the prepared polyurethane polymer blank into a polyurethane film and training the polyurethane film to have a two-way shape memory performance to obtain a temperature-sensitive two-way shape memory polyurethane film comprises: Hot pressing of polyurethane polymer blanks: above the setting temperature T d stretching the polyurethane film under vacuum conditions to melt and extend all components of the polyurethane film; Perform bidirectional shape memory performance training on polyurethane film: keep the polyurethane film in a stretched state after hot pressing and lower the ambient temperature to room temperature T r , so that the molecular chains of each component of the polyurethane film produce oriented crystals along the stretching direction; T d and T r The temperature is lowered and raised 8 to 12 times to make the polyester diol with a lower melting temperature repeatedly undergo oriented crystallization and melting.

2. The temperature-sensitive polymer microsphere with self-regulated shell permeability according to claim 1, characterized in that: The diameter of the thermoresponsive bidirectional shape memory polymer polyurethane nanoparticles ranges from 100 to 250 nm.

3. The temperature-sensitive polymer microsphere with self-regulated shell permeability according to claim 1, characterized in that: The steps for preparing a polyurethane polymer blank using diisocyanate and polyester diol are: Diisocyanate and polyester diol in a ratio of 1:1 to 3:1 are heated at a constant temperature under a protective atmosphere to carry out the first step of polymerization reaction; After the first polymerization, a chain extender and a catalyst are added and a second polymerization reaction is carried out under constant temperature conditions; The polymerization product is extracted and dried to obtain a polyurethane polymer blank.

4. The temperature-sensitive polymer microsphere with self-regulated spherical shell permeability according to claim 3, characterized in that: The diisocyanate is one of 2,4-toluene dicyanate, 4,4′-diphenylmethane diisocyanate or polyphenylmethane polyisocyanate; the chain extender is one of 1,4-butanediol, ethylene glycol or propylene glycol; the catalyst is one of toluene, dimethyl sulfoxide, N,N-dimethylformamide or methyl isobutyl ketone.

5. The temperature-sensitive polymer microsphere with self-regulated shell permeability according to claim 3, characterized in that: The protective atmosphere in the two polymerization reactions is nitrogen, the heating temperature of the constant temperature heating is 70°C~90°C; the stirring condition is mechanical stirring or magnetic stirring, and the stirring rate is 300rpm~600rpm; the extraction solvent is distilled water or deionized water; the constant temperature drying is drying in a vacuum constant temperature box, and the drying temperature is set between 60°C~80°C.

6. The method for preparing the temperature-sensitive polymer microspheres with self-regulated spherical shell permeability according to any one of claims 1 to 5, characterized in that: include: Preparation of polyurethane films using diisocyanates and polyester diols; The prepared polyurethane film is subjected to bidirectional shape memory performance training to obtain a temperature-sensitive bidirectional shape memory polyurethane film, and then the temperature-sensitive bidirectional shape memory polyurethane film is made into nanoparticles; The prepared nanoparticles are suspended in an oil phase solution and continuously stirred to form an oil phase working medium, wherein the mass concentration of the nanoparticles in the oil phase working medium ranges from 5% to 10%; The oil phase working fluid is prepared into a water-oil-water double emulsion by using microfluidic technology, and the temperature-sensitive polymer microspheres with self-regulated spherical shell permeability are obtained through solidification and drying.

7. The preparation method according to claim 6, characterized in that: The stirring is carried out by mechanical stirring, and the stirring rate is 900rpm~1500rpm.

8. The preparation method according to claim 6, characterized in that: The microfluidic technology adopts one of a T-shaped microchannel, a co-flow capillary or a focusing microchannel; the inner water phase of the water-oil-water double emulsion is ultrapure water or deionized water; the water / oil / water double emulsion curing process is carried out in a rotary evaporator to obtain a polymer microsphere preform, the curing temperature range is 25°C to 45°C, the curing time is not less than 48 hours, and the rotary evaporator speed range is 20 rpm to 50 rpm; The cured polymer microsphere preform is cleaned by first cleaning it with distilled water or deionized water for 4-5 times, and then cleaning it with anhydrous ethanol for 2-3 times.

Images