阅读说明：本技术 一种碳点修饰的聚合物微球的制备方法 (Preparation method of polymer microspheres modified by carbon points ) 是由 陈苏 解安全 郭佳壮 于 2020-12-31 设计创作，主要内容包括：本发明涉及一种碳点修饰的聚合物微球的制备方法,该该制备工艺主要包括以下步骤：通过乳液聚合方法,制备单分散聚合物微球；然后将合成的聚合物微球作为种子,表面接枝多官能团的水溶性碳点；经自由基引发剂引发聚合后获得碳点修饰的聚合物复合微球。本发明实现了碳点修饰的聚合物微球复合材料的化学合成,该方法简便易行,反应条件温和,碳点均匀分散在聚合物微球中,所制备的复合微球的形貌尺寸均一。(The invention relates to a preparation method of a polymer microsphere modified by carbon points, which mainly comprises the following steps: preparing monodisperse polymer microspheres by an emulsion polymerization method; then taking the synthesized polymer microspheres as seeds, and grafting water-soluble carbon dots with multiple functional groups on the surfaces; and initiating polymerization by using a free radical initiator to obtain the polymer composite microspheres modified by carbon points. The invention realizes the chemical synthesis of the polymer microsphere composite material modified by the carbon points, the method is simple and easy to implement, the reaction condition is mild, the carbon points are uniformly dispersed in the polymer microsphere, and the prepared composite microsphere has uniform appearance and size.)

1. A preparation method of a polymer microsphere modified by carbon points comprises the following specific steps:

a) weighing a proper amount of surfactant, monomer and deionized water, placing the surfactant, monomer and deionized water into a container, and mechanically stirring at a constant speed to form a uniformly dispersed oil-in-water mixed system in the container;

b) adding a free radical initiator into the container at a proper rate, and raising the temperature in the container to initiate polymerization after the initiator is added;

c) after the first-step polymerization reaction is carried out for a period of time and the color of the solution is gradually changed from transparent to light blue and milk white, adding multi-functionalized water-soluble carbon dots and a proper amount of free radical initiator to carry out the second-step reaction;

d) after the reaction is carried out for a period of time, centrifugally washing a product obtained by polymerization to obtain the polymer microsphere modified by the carbon points.

2. The method of claim 1, wherein the surfactant of step a) is one of polyvinylpyrrolidone, sodium dodecyl sulfate, or sodium dodecyl benzene sulfonate.

3. The method according to claim 1, wherein the monomer of step a) is one or more selected from styrene, methyl methacrylate, hydroxyethyl methacrylate, acrylic acid and butyl acrylate.

4. The method of claim 1 wherein the free radical initiator of step a) is one of potassium persulfate or ammonium persulfate.

5. The method according to claim 1, wherein the mass ratio of the monomers to the deionized water in the step a) is (5-12): 110; the dosage of the surfactant is 2 to 8 percent of the mass of the monomer; the total amount of the free radical initiator is 0.3-0.9% of the mass of the monomer, and the amount of the free radical initiator used in the second step of reaction is 7-20% of the amount of the free radical initiator used in the first step of reaction.

6. The method according to claim 1, wherein the mechanical stirring speed in step a) is 165-250 rpm.

7. The method according to claim 1, wherein the addition rate of the radical initiator solution in step b) is 15 to 50 mL/h; the temperature in the container is raised to 80-98 ℃.

8. The method according to claim 1, wherein the polymerization reaction time of the first step in the step c) is 2-4 h, the water-soluble carbon dots are functionalized carbon dots containing carboxyl and amino groups, and the amount of the carbon dots is 0.02-0.1% of the mass of the monomer.

9. The method according to claim 1, wherein the polymerization time in step d) is 4 to 12 hours.

Technical Field

The invention relates to synthesis of monodisperse polymer microspheres, in particular to a preparation method of polymer microspheres modified by carbon points through in-situ reaction by using an emulsion polymerization method.

Background

Carbon dots are a member of the carbon family, and have attracted extensive research interest because of their low biological toxicity, fluorescent stability, environmental friendliness, and other characteristics. The carbon dots are discovered for the first time in 2004 by walter a. scrivens et al when single-walled carbon nanotubes are purified, and the unique zero-dimensional carbon nanomaterial is defined as a new class of quantum dot materials due to the excellent fluorescence property. However, compared with the traditional semiconductor quantum dot material (such as cadmium telluride, cadmium selenide, zinc telluride and the like), the carbon dot has the characteristics of stable fluorescence performance, excitation wavelength correlation and the like; it is worth noting that the carbon dots mainly comprise elements such as C, H, O and N, and do not contain any heavy metal element, so that the carbon dots have wider application compared with the traditional semiconductor quantum dots due to the excellent biocompatibility and environmental friendliness.

At present, the construction of novel functionalized composite materials with synergistic effects of various physicochemical properties is one of the important development trends in the fields of chemistry and material science. The functionalized monodisperse polymer microsphere has wide application prospect in ordered microstructure materials, microelectronics, sensors, biological probes and other high and new technology fields. In 2017, a professor team of Rajadurai Chandrasekar of university of Hailaba, India adopts a solvothermal method to prepare a polystyrene microsphere doped with nitrogen-rich carbon dots, the microsphere doped with the carbon dots shows excellent fluorescence performance, the fluorescence intensity of the microsphere is improved by 22 times compared with that of a pure carbon dot, but only a simple physical adsorption effect exists between a polymer microsphere and the carbon dots, and the carbon dots loaded on the surface are easy to strip from the microsphere and desorb in the practical application process.

Disclosure of Invention

The invention aims to provide a method for modifying polymer microspheres with carbon points, which aims to improve the defects of the prior art, and the method comprises the following steps of taking the synthesized polymer microspheres as seeds in an emulsion polymerization mode, and grafting water-soluble carbon points with multiple functional groups on the surfaces; and initiating polymerization by using a free radical initiator to obtain the polymer composite microspheres modified by carbon points. The carbon dots in the fluorescent microspheres obtained by the method have the function of chemical bonds with the polymer microspheres, and the defect that the carbon dots in the traditional doping method are easy to fall off is overcome.

The technical scheme adopted by the invention is as follows: a method for synthesizing a polymer microsphere modified by carbon points comprises the following specific steps:

a) weighing a proper amount of surfactant, monomer and deionized water, placing the surfactant, monomer and deionized water into a container, and mechanically stirring at a constant speed to form a uniformly dispersed oil-in-water mixed system in the container;

b) adding a free radical initiator into the container at a proper rate, and raising the temperature in the container to initiate polymerization after the initiator is added;

c) after the first-step polymerization reaction is carried out for a period of time and the color of the solution is gradually changed from transparent to light blue and milk white, adding multi-functionalized water-soluble carbon dots and a proper amount of free radical initiator to carry out the second-step reaction;

d) after the reaction is carried out for a period of time, centrifugally washing a product obtained by polymerization to obtain the polymer microsphere modified by the carbon points.

Preferably, the surfactant is one of polyvinylpyrrolidone, sodium dodecyl sulfate or sodium dodecyl benzene sulfonate.

The preferable monomer is one or more of styrene, methyl methacrylate, hydroxyethyl methacrylate, acrylic acid or butyl acrylate.

Preferably, the free radical initiator is one of potassium persulfate or ammonium persulfate.

Preferably, the mass ratio of the monomer to the deionized water is (5-12): 110; the dosage of the surfactant is 2 to 8 percent of the mass of the monomer; the total amount of the free radical initiator is 0.3-0.9% of the mass of the monomer, and the amount of the free radical initiator used in the second step of reaction is 7-20% of the amount of the free radical initiator used in the first step of reaction.

Preferably, the speed of the mechanical stirring in the step a) is 165-250 rpm; the temperature for the polymerization reaction in the step b) is 80-98 ℃.

Preferably, the polymerization reaction time of the first step in the step c) is 2-4 h, the water-soluble Carbon Dots are functionalized Carbon Dots containing carboxyl and amino groups, the preparation method of the Carbon Dots is disclosed in a document published by professor of Yangbai of Guilin university (high molecular luminescence Carbon Dots for Multicolor Patterning, Sensors, and bioimaging. DOI:10.1002/ange.201300519), and the amount of the Carbon Dots is 0.02-0.1% of the mass of the monomer.

Preferably, the total polymerization time in step d) is 4 to 12 hours.

Has the advantages that:

the invention utilizes the mode of seed emulsion copolymerization to prepare the polymer microsphere modified by carbon points through the chemical action in-situ reaction between the functionalized carbon points and the polymer monomer, and compared with the prior method, the method has the following advantages: 1) all the raw materials used in the reaction are simple and easy to obtain, have no large toxicity, and can not generate byproducts harmful to the environment in the reaction process, so the method is an economic, practical, green and environment-friendly preparation route.

The reaction condition is mild, the operation is simple, and the energy consumption is low;

2) the invention realizes the in-situ assembly of the carbon dots and the polymer microspheres in an emulsion polymerization mode, and firmly fixes the carbon dots on the polymerization by utilizing the chemical reaction between the functional groups on the surface of the functionalized carbon dots and the polymer monomers

The carbon dots are not easy to peel off and fall off from the surface of the microsphere.

Drawings

FIG. 1 is a graph showing the distribution of particle sizes of the synthesized polymer microspheres modified with carbon dots according to example 1 of the present invention;

FIG. 2 is a suspension of centrifugally concentrated, carbon-modified polymeric microspheres synthesized in example 1 of the present invention;

FIG. 3 is a SEM image of synthesized carbon dot-modified polymer microspheres of example 1;

FIG. 4 is a TEM image of the synthesized carbon dot-modified polymer microspheres of example 1.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. These examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.

Example 1

110g of deionized water, 5g of styrene monomer, 0.5g of methyl methacrylate, 0.5g of acrylic acid and 0.2g of polyvinylpyrrolidone were weighed into a 250mL four-necked flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 165rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 85 ℃ after 30min, weighing 0.025g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the speed of 20mL/h through a microflow pump. After the reaction was carried out for 2 hours, 0.0015g of aminated Carbon Dots (the preparation method of Carbon Dots is described in Highly polymeric Carbon Dots for Multicolor Patterning, Sensors, and Bioimaging, which is prepared by hydrothermal reaction of 0.3g of urea, 536. mu.L of ethylenediamine and 10mL of water at 200 ℃ for 5 hours) were weighed out, 0.002g of potassium persulfate powder was dissolved in 10g of deionized water, and the solution was added to the flask by a microflow pump at a rate of 20mL/h for further reaction for 3 hours, the reaction product was cooled to room temperature, and centrifuged and washed 3 times. Thus obtaining the polystyrene-methyl methacrylate-acrylic acid microsphere modified by carbon points. As can be seen from the particle size distribution diagram of FIG. 1, the prepared composite microspheres have a particle size of 166nm, a monodispersion index (PDI) of 0.9%, and uniform size. As can be seen from the picture of the concentrated suspoemulsion in fig. 2, the composite microspheres can be stably dispersed in deionized water. FIG. 3 is a scanning electron microscope image of a carbon-modified polystyrene-methylmethacrylate-acrylic microsphere, which shows that the microsphere has a good spherical morphology. FIG. 4 is a transmission electron microscope image of a carbon dot modified polystyrene-methylmethacrylate-acrylic microsphere, and it can be seen that the carbon dots are uniformly loaded on the surface of the polymer microsphere.

Example 2

110g of deionized water, 6.5g of styrene monomer, 0.5g of butyl acrylate, 0.5g of acrylic acid and 0.25g of sodium dodecyl sulfate were weighed and placed in a 250mL four-neck flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 200rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 90 ℃ after 30min, weighing 0.03g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the speed of 25mL/h through a microflow pump. After the reaction was carried out for 2 hours, 0.003g of carboxyl-and amino-rich Carbon Dots (the preparation method of the Carbon Dots is described in Highly polymeric Carbon Dots for Multicolor Patterning, Sensors, and Bioimaging, which is prepared by hydrothermal reaction of 0.42g of citric acid, 1275. mu.L of ethylenediamine and 10mL of water at 200 ℃ for 5 hours) were weighed out, 0.004g of potassium persulfate powder was dissolved in 10g of deionized water, the solution was added to the flask by a microflow pump at a rate of 20mL/h for further reaction for 5 hours, the reaction product was cooled to room temperature, and centrifuged and washed 3 times. The polystyrene-butyl acrylate-acrylic acid microsphere modified by carbon points can be obtained. The prepared composite microspheres have the particle size of 200nm, the monodispersion index (PDI) of 0.3 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 3

110g of deionized water, 8g of styrene monomer, 0.65g of hydroxyethyl methacrylate, 0.65g of acrylic acid and 0.56g of polyvinylpyrrolidone are weighed and placed in a 250mL four-neck flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 250rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 98 ℃ after 30min, weighing 0.06g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the speed of 30mL/h through a microflow pump. After the reaction was carried out for 2 hours, 0.008g of carbon dots rich in carboxyl and amino groups (the preparation process of the carbon dots is the same as that in example 2) and 0.009g of potassium persulfate powder were weighed and dissolved in 10g of deionized water, and the solution was added into a flask by a microflow pump at a rate of 30mL/h to continue the reaction for 8 hours, and the reaction product was cooled to room temperature and washed by centrifugation for 3 times. Thus obtaining the polystyrene-hydroxyethyl methacrylate-acrylic acid microsphere modified by carbon points. The prepared composite microspheres have the particle size of 232nm, the monodispersion index (PDI) of 0.5 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 4

110g of deionized water, 9.5g of methyl methacrylate, 0.8g of acrylic acid and 0.24g of sodium dodecyl benzene sulfonate were weighed and placed in a 250mL four-necked flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 250rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 98 ℃ after 30min, weighing 0.05g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the speed of 30mL/h through a microflow pump. After the reaction is carried out for 3 hours, 0.0045g of carbon dots rich in carboxyl and amino (the preparation process of the carbon dots is the same as that of example 2) and 0.005g of potassium persulfate powder are weighed and dissolved in 10g of deionized water, the mixture is added into a flask by a microflow pump at the speed of 30mL/h for continuous reaction for 4 hours, the reaction product is cooled to room temperature, and the mixture is centrifuged and washed for 3 times. Thus obtaining the polymethyl methacrylate-acrylic acid microsphere modified by the carbon points. The prepared composite microspheres have the particle size of 250nm, the monodispersion index (PDI) of 0.6 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 5

110g of deionized water, 10g of methyl methacrylate, 0.5g of butyl acrylate, 0.5g of acrylic acid and 0.65g of polyvinylpyrrolidone were weighed into a 250mL four-necked flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 200rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 98 ℃ after 30min, weighing 0.08g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the rate of 30mL/h through a microflow pump. After 4 hours of reaction, 0.01g of carboxylated Carbon Dots (the preparation method of the Carbon Dots is described in Highly Photolutenescent Carbon Dots for Multicolor Patterning, Sensors, and Bioimaging, manufactured by hydrothermal reaction of 1.051g of citric acid with 10mL of water at 200 ℃ for 5 hours) was weighed out, 0.015g of potassium persulfate powder was dissolved in 10g of deionized water, and the solution was added to the flask by a microflow pump at a rate of 30mL/h to continue the reaction for 5 hours, cooled to room temperature, and centrifuged and washed 3 times. Thus obtaining the polymethyl methacrylate-butyl acrylate-acrylic acid microsphere modified by carbon points. The prepared composite microspheres have the particle size of 265nm, the monodispersion index (PDI) of 0.7 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 6

110g of deionized water, 8g of styrene, 0.9 g of methyl methacrylate, 0.5g of acrylic acid and 0.38g of sodium dodecyl sulfate were weighed into a 250mL four-necked flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at the rotating speed of 200rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 90 ℃ after 30min, weighing 0.0375g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the speed of 20mL/h through a microflow pump. After the reaction was carried out for 3 hours, 0.003g of carboxylated carbon dots (the preparation process of the carbon dots was the same as in example 5) and 0.004g of potassium persulfate powder were weighed and dissolved in 10g of deionized water, and the solution was added to the flask by a microflow pump at a rate of 20mL/h to continue the reaction for 2 hours, and the reaction product was cooled to room temperature and centrifuged and washed 3 times. Thus obtaining the polystyrene-methyl methacrylate-acrylic acid microsphere modified by carbon points. The prepared composite microspheres have the particle size of 235nm, the monodispersion index (PDI) of 0.09 percent and very uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 7

110g of deionized water, 7g of methyl methacrylate, 0.1g of butyl acrylate and 0.24g of sodium dodecyl benzene sulfonate are weighed and placed in a 250mL four-neck flask which is provided with a mechanical stirring device, a condenser tube and a double-row tube. Stirring at the rotating speed of 175rpm under the protection of nitrogen atmosphere to enable the mixed solution in the flask to form a uniformly dispersed oil-in-water system, heating the reaction system to 98 ℃ after 30min, weighing 0.038g of potassium persulfate powder, dissolving the potassium persulfate powder in 10g of deionized water, and adding an initiator solution at the rate of 30mL/h through a microflow pump. After the reaction was carried out for 3 hours, 0.003g of carboxylated carbon dot (the preparation process of the carbon dot was the same as in example 5) and 0.0035g of potassium persulfate powder were weighed and dissolved in 10g of deionized water, and the solution was added to the flask by a microflow pump at a rate of 30mL/h to continue the reaction for 3 hours, and the reaction product was cooled to room temperature and washed by centrifugation for 3 times. Thus obtaining the polymethyl methacrylate-butyl acrylate microsphere modified by the carbon points. The prepared composite microspheres have the particle size of 230nm, the monodispersion index (PDI) of 0.2 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.

Example 8

110g of deionized water, 6g of styrene and 0.24g of polyvinylpyrrolidone were weighed into a 250mL four-necked flask equipped with a mechanical stirring device, a condenser tube and a double row tube. Stirring at 175rpm under the protection of nitrogen atmosphere to form a uniformly dispersed oil-in-water system, heating the reaction system to 98 ℃ after 30min, weighing 0.0375g of potassium persulfate powder, dissolving in 10g of deionized water, and adding an initiator solution at a rate of 30mL/h through a microflow pump. After the reaction was carried out for 3 hours, 0.0025g of carbon dots rich in carboxyl and amino groups (the preparation process of the carbon dots was the same as that of example 2) and 0.003g of potassium persulfate powder were weighed and dissolved in 10g of deionized water, and the solution was added to the flask by a microflow pump at a rate of 30mL/h to continue the reaction for 3 hours, and the reaction product was cooled to room temperature and washed by centrifugation for 3 times. Thus obtaining the polymethyl methacrylate-butyl acrylate microsphere modified by the carbon points. The prepared composite microspheres have the particle size of 210nm, the monodispersion index (PDI) of 0.8 percent and uniform size. The microspheres have good spherical morphology as seen from a scanning electron microscope, carbon points can be uniformly loaded on the surfaces of the polymer microspheres as seen from a transmission electron microscope, and the composite microspheres can be stably dispersed in deionized water.