CN114591460A

CN114591460A - Method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization

Info

Publication number: CN114591460A
Application number: CN202210304683.4A
Authority: CN
Inventors: 汪晶; 田甜; 黄亮
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2022-03-26
Filing date: 2022-03-26
Publication date: 2022-06-07
Anticipated expiration: 2042-03-26
Also published as: CN114591460B

Abstract

The invention discloses a method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization, which comprises the following steps: adding an initiator azobisisobutyronitrile, a polymerization monomer styrene, a crosslinking agent divinylbenzene, a functional monomer acrylic acid and a reaction solvent into a reactor, heating to 80-90 ℃ under stirring, refluxing for 1-3 h at a constant temperature, and finally centrifuging, washing and vacuum drying to obtain the carboxylated crosslinked polystyrene; in the mixed liquid of azodiisobutyronitrile, styrene, divinylbenzene, acrylic acid and a reaction solvent, the mass fraction of azodiisobutyronitrile is 0.1-0.5%, the mass fraction of styrene is 1-5%, the mass fraction of divinylbenzene is 2-3%, and the mass fraction of acrylic acid is 0.5-2%. The invention regulates and controls the dosage of styrene monomer, the dosage of azodiisobutyronitrile initiator and the dosage of cross-linking agent, the microsphere prepared by the formula of the invention has good dispersibility and uniform particle size, and the prepared microsphere can be better applied according to the self requirement.

Description

Method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization

Technical Field

The invention relates to a method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization.

Background

The polymer microspheres have spherical or other geometric shapes, the diameter ranges from nano-scale to micron-scale, and researchers can select different types of polymer microspheres according to actual requirements. Meanwhile, the microsphere can be used as a micro memory, a micro reactor, a micro separator and a microstructure unit due to wide application, so that different physical and chemical properties are endowed to the microsphere material, and the application field of the polymer microsphere is expanded.

Among the various polymeric microspheres, crosslinked polystyrene microspheres have a number of significant advantages, such as: the particle size is controllable, the microspheres are not easily biodegraded, and only swell and do not dissolve in a soluble solvent, so that the subsequent application and recovery of the microspheres are facilitated. These advantages make it widely used in microelectronics, biomedicine, chemical industry and other fields, and various commercialized products are also in the endlessly.

The existing methods for preparing the crosslinked polystyrene microspheres include precipitation polymerization, emulsion polymerization, seed swelling polymerization and the like. The polymer microspheres prepared by different methods have different characteristics, the polymer particles prepared by a dispersion polymerization method have uniform particle size distribution, but the selection of a dispersing agent is dominant; the particle size of the polymer prepared by emulsion polymerization is generally less than 0.5 mu m, and the emulsifier is difficult to clean and can affect the environment; compared with emulsion polymerization, the non-soap emulsion polymerization has the advantages that the emulsifier is not added, the cost is reduced, the adverse effect of the emulsifier on the product is avoided, and the system stability is poor; the seed swelling method is also commonly used, but the steps are complicated, and the reaction time is long.

Compared with the above mentioned method, the precipitation polymerization method is one of the methods for preparing the polymeric microspheres, and has the advantages of simple instrument and reaction system, easily controlled operation conditions, short reaction time, no need of adding a stabilizer or an emulsifier in the process, simple control of the particle size of the polystyrene by changing the adding proportion of reactants in the polymerization reaction, and preparation of the microspheres by the precipitation polymerization method. However, because no stabilizer is added in the reaction, the polystyrene microspheres are easy to agglomerate in the preparation process, the surfaces of the microspheres are rough, the microspheres are mutually adhered together, and the microspheres are difficult to disperse in a medium. The invention can prepare the crosslinked polystyrene microsphere with good dispersity and uniform grain diameter by improving the adding proportion of the monomer, the initiator and the crosslinking agent.

Disclosure of Invention

In view of the above technical problems of the prior art, the present invention aims to provide a method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization. The polystyrene microsphere is synthesized by a precipitation polymerization method, a cross-linking agent divinylbenzene is added in the microsphere preparation process, and the prepared microsphere is only swelled and undissolved in a soluble solvent (such as toluene). Meanwhile, functional monomer acrylic acid is added in the preparation process, so that the prepared crosslinked polystyrene microsphere has carboxyl on the surface, and the subsequent application is facilitated. According to the preparation method, the dosage of the styrene monomer, the dosage of the azodiisobutyronitrile initiator and the dosage of the cross-linking agent are regulated and controlled in the preparation process of the polystyrene cross-linked microspheres, so that the carboxylated cross-linked polystyrene microspheres with good dispersibility and uniform particle size are prepared.

The method for preparing the carboxylated crosslinked polystyrene based on the precipitation polymerization is characterized by comprising the following steps of: adding an initiator azobisisobutyronitrile, a polymerization monomer styrene, a crosslinking agent divinylbenzene, a functional monomer acrylic acid and a reaction solvent into a reactor, heating to 80-90 ℃ under stirring, refluxing for 1-3 h at a constant temperature, and finally centrifuging, washing and vacuum drying to obtain the carboxylated crosslinked polystyrene;

in the mixed liquid of azodiisobutyronitrile, styrene, divinylbenzene, acrylic acid and a reaction solvent, the mass fraction of azodiisobutyronitrile is 0.1-0.5%, the mass fraction of styrene is 1-5%, the mass fraction of divinylbenzene is 2-3%, and the mass fraction of acrylic acid is 0.5-2%.

The method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization is characterized in that in a mixed solution of azodiisobutyronitrile, styrene, divinylbenzene, acrylic acid and a reaction solvent, the mass fraction of azodiisobutyronitrile is 0.4%, the mass fraction of styrene is 1-2%, the mass fraction of divinylbenzene is 2-3%, and the mass fraction of acrylic acid is 0.5-2%.

The method for preparing the carboxylated crosslinked polystyrene based on precipitation polymerization is characterized in that the reaction solvent is a mixed solution of acetonitrile and toluene, and the volume ratio of the acetonitrile to the toluene is 3-5: 1, preferably 4: 1.

The method for preparing the carboxylated crosslinked polystyrene based on the precipitation polymerization is characterized in that the stirring speed is 100-150 rpm, the reaction temperature is 84-85 ℃, and the constant-temperature reflux time is 2 hours.

The method for preparing the carboxylated crosslinked polystyrene based on the precipitation polymerization is characterized in that a methanol solvent is adopted for washing during washing.

The beneficial effects obtained by the invention are as follows:

the invention discloses a method for preparing carboxylated crosslinked polystyrene microspheres based on a precipitation polymerization method, which can save the synthesis time of the microspheres through the precipitation polymerization method, and the synthesized microspheres have uniform particle size and are modified with carboxyl on the surfaces. The dosage of a styrene monomer, the dosage of an azodiisobutyronitrile initiator and the dosage of a crosslinking agent are regulated and controlled in the preparation process of the polystyrene crosslinking microspheres, the microspheres prepared by the formula have good dispersibility and uniform particle size, and the prepared micron-sized carboxylated crosslinked polystyrene microsphere template can be better applied according to the requirements of the template.

Drawings

FIG. 1 is a scanning electron microscope image of crosslinked polystyrene microspheres prepared under different styrene dosages in example 1 of the present invention;

FIG. 2 is a scanning electron microscope image of crosslinked polystyrene microspheres prepared under different initiator dosages in example 2 of the present invention;

FIG. 3 is a transmission electron microscope image of the crosslinked polystyrene microsphere loaded magnetic particles prepared under the condition of 0.4 wt% of the initiator in example 2 of the present invention;

FIG. 4 is a scanning electron microscope image of crosslinked polystyrene microspheres prepared under different amounts of the crosslinking agent in example 3 of the present invention.

Detailed Description

The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.

Example 1:

synthesis of carboxylated crosslinked polystyrene template: adding raw materials into a 50 mL round-bottom flask, wherein the raw materials comprise the following components in percentage by weight: 0.078 wt% of azodiisobutyronitrile, 1 wt% -10 wt% (accounting for the mass fraction of the total substance) of styrene, 3 wt% of divinylbenzene, 1.2 wt% of acrylic acid and the balance of solvent (formed by mixing acetonitrile and toluene according to the volume ratio of 4: 1), a condenser pipe is installed, magnetic stirring is carried out (the rotating speed is set to be 120 rpm), the reaction is stopped after the temperature is increased to 84 ℃, refluxing and stirring reaction is carried out at constant temperature for 2 hours, the reaction is stopped, centrifugation is carried out at 4400 rpm, and separated precipitates are washed by methanol for three times and are dried in vacuum.

SEM images of carboxylated crosslinked polystyrene microspheres prepared under different styrene amounts in example 1 are shown in FIG. 1. From FIG. 1, it can be seen that under the conditions of different styrene dosages: the polystyrene microspheres prepared from A (1 wt%) and B (2 wt%) have basic spherical shapes, wherein the dispersibility of B is better than that of A, and compared with C (5 wt%), D (8 wt%) and E (10 wt%), a large amount of agglomeration occurs to the microspheres along with the increase of the dosage of monomer styrene.

It can be seen that when the monomer concentration is too low, the polymerization rate is slowed down, the nucleation period is prolonged, the size of the primary particle core generated is not uniform, the particle size distribution is widened, and the appropriate increase of the monomer styrene dosage is beneficial to enhancing the solubility of the medium to the generated polymer chain, so that the polymer particle size becomes relatively uniform. When the concentration of the monomer styrene is too high, a large amount of initial nuclei and polymer chains are formed in the initial stage of polymerization reaction, so that the space stabilizing effect of short chains and a gel layer on the surfaces of the microspheres is insufficient to support the microspheres to be stably dispersed in a solution, and implosion is generated. The optimum amount of styrene monomer used in example 1 was 2 wt%.

Example 2:

synthesis of carboxylated crosslinked polystyrene template: adding raw materials into a 50 mL round-bottom flask, wherein the raw materials comprise the following components in percentage by weight: 0.1-0.75 wt% (mass fraction of the total substance) of azodiisobutyronitrile, 2 wt% of styrene, 3 wt% of divinylbenzene, 1.2 wt% of acrylic acid and the balance of solvent (formed by mixing acetonitrile and toluene according to the volume ratio of 4: 1), a condensing tube is arranged, magnetic stirring is carried out (the rotating speed is set to be 120 rpm), the reaction is stopped after the temperature is increased to 84 ℃, reflux and stirring reaction is carried out for 2h at constant temperature, centrifugation is carried out at 4400 rpm, the separated precipitate is washed with methanol for three times, and vacuum drying is carried out.

SEM images of carboxylated crosslinked polystyrene microspheres prepared under different initiator amounts in example 2 are shown in FIG. 2. Wherein, the carboxylated crosslinked polystyrene microsphere added with the C (0.4 wt%) azodiisobutyronitrile has good dispersibility, the average grain diameter is about 1.7 mu m, the Zeta potential value is-32.5 mV, and the microsphere can not be dissolved in the soluble solvent (toluene). While A (0.1 wt.%), B (0.25 wt.%) produced carboxylated crosslinked polystyrene microspheres with a non-uniform particle size, D (0.5 wt.%) produced a plurality of small-particle polystyrene microspheres, and E (0.75 wt.%) produced polystyrene were copolymerized together. When the concentration of the initiator azobisisobutyronitrile is low, the concentration of the generated primary particle cores is low, and the particles are not fully aggregated, so that the particle size distribution of the microsphere is wide; with the increase of the dosage of the initiator, the concentration of the free radical active chain is increased, more primary particle cores can be generated in a shorter time, and when the coalescence and growth of the primary particle cores gradually reach balance, the particle size distribution of the generated microspheres is narrowed; when the amount of the initiator is too high, the number of free radicals of the initiator in a polymer system is increased, more monomers are initiated to be polymerized, and copolymerization is generated among primary free radicals.

Adding C (0.4 wt%) azodiisobutyronitrile to prepare carboxylated crosslinked polystyrene microspheres, and loading magnetic particles by a swelling method: 10 mg of polystyrene carboxyl microspheres were swollen in 1 mL of toluene overnight at room temperature, and 0.5 mL of oleic acid-modified Fe was sonicated₃O₄(16 mg/mL) is dipped into the swelled polystyrene carboxyl microspheres for 15min, and after the reaction is finished, the microspheres are magnetically separated and shrunk by ethanol. The obtained magnetic microspheres can be attracted by a magnet, and a transmission electron microscope of the magnetic microspheres is shown in fig. 3, so that the microspheres can be obviously loaded with magnetic substances, and in addition, the magnetic substances on the surfaces of the microspheres can be simultaneously loaded with the electrostatic adsorption effect of the carboxylated microspheres. The optimum amount of azobisisobutyronitrile initiator obtained in example 2 was 0.4 wt%.

Example 3:

synthesis of carboxylated crosslinked polystyrene template: adding raw materials into a 50 mL round-bottom flask, wherein the raw materials comprise the following components in percentage by weight: 0.4 wt% of azodiisobutyronitrile, 2 wt% of styrene, 1-5% (mass fraction of the total substance) of divinylbenzene, 1.2 wt% of acrylic acid and the balance of solvent (formed by mixing acetonitrile and toluene according to the volume ratio of 4: 1), installing a condensing tube, magnetically stirring (120 rpm), heating to 84 ℃, refluxing at constant temperature for 2 hours, stopping reaction, centrifuging at 4400 rpm, washing with methanol for three times, and drying in vacuum.

SEM images of carboxylated crosslinked polystyrene microspheres prepared under different amounts of the crosslinking agent in example 3 are shown in FIG. 4. As can be seen from fig. 4, when the divinylbenzene content is increased (from 1% to 5%), the diffusion rate of the monomer or the free radical from the medium into the particle is slowed due to the increase of the crosslinking degree, so that the particle size is slowly increased, the efficiency of capturing the free radical and the polymer chain is reduced, secondary nucleation is caused, and the particle size distribution of the microspheres is widened. When the content of the DVB is too high, the residual DVB exists on the surfaces of the microspheres, and the microspheres are crosslinked through the DVB and are bonded together. However, when the content of DVB is too low, the system is unstable, and the microspheres are agglomerated. The optimum amount of divinylbenzene crosslinking agent used in example 3 was 3 wt%.

The statements in this specification merely set forth a list of implementations of the inventive concept and the scope of the present invention should not be construed as limited to the particular forms set forth in the examples.

Claims

1. A method for preparing carboxylated cross-linked polystyrene based on precipitation polymerization is characterized by comprising the following steps: adding an initiator azobisisobutyronitrile, a polymerization monomer styrene, a crosslinking agent divinylbenzene, a functional monomer acrylic acid and a reaction solvent into a reactor, heating to 80-90 ℃ under stirring, refluxing for 1-3 h at a constant temperature, and finally centrifuging, washing and vacuum drying to obtain the carboxylated crosslinked polystyrene;

2. The method according to claim 1, wherein the mixture of azobisisobutyronitrile, styrene, divinylbenzene, acrylic acid and a reaction solvent comprises 0.4% by mass of azobisisobutyronitrile, 1-2% by mass of styrene, 2-3% by mass of divinylbenzene and 0.5-2% by mass of acrylic acid.

3. The method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization according to claim 1, wherein the reaction solvent is a mixture of acetonitrile and toluene, and the volume ratio of acetonitrile to toluene is 3-5: 1, preferably 4: 1.

4. The method for preparing carboxylated crosslinked polystyrene based on precipitation polymerization according to claim 1, wherein the stirring speed is 100-150 rpm, the reaction temperature is 84-85 ℃, and the constant temperature reflux time is 2 hours.

5. The process for preparing carboxylated crosslinked polystyrene based on precipitation polymerization according to claim 1, wherein the washing is carried out using a methanol solvent.