A method for preparing a polystyrene with a controlled molecular weight

Abstract

This invention provides a method for preparing polystyrene with controllable molecular weight, comprising the following steps: under an inert atmosphere, a reducing agent is added to an anhydrous and oxygen-free organic solvent, followed by the addition of styrene monomer, a catalyst, and a dormant initiator, and the polymerization reaction is carried out under controlled temperature; after the reaction is completed, the reaction is terminated, and after post-treatment, polystyrene is obtained; wherein, the catalyst is a copper bromide / pentamethyldiethylenetriamine complex; the dormant initiator includes any one or a combination of at least two of alkyl chloride, alkyl bromide, or alkyl iodide; the reducing agent is graphene oxide grafted with phenolic hydroxyl groups, with the active component phenolic hydroxyl groups grafted onto the support graphene oxide. This invention uses a supported reducing agent, fundamentally changing the kinetic environment of the polymerization reaction, controlling the concentration of free radicals in the system to an extremely low level, thereby greatly reducing the rate of side reactions from the root cause and achieving controllable molecular weight; it belongs to the field of organic synthesis technology.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing polystyrene with controllable molecular weight. Background Technology

[0002] Polystyrene is a widely used thermoplastic that is widely used in packaging, construction, electronics, medical and other industries due to its good transparency, processability and insulation properties.

[0003] Free radical polymerization is one of the most important synthetic methods for preparing polystyrene, widely used in industrial production due to its wide range of applicable monomers, mild reaction conditions, and simple process. However, traditional free radical polymerization (such as using azobisisobutyronitrile or benzoyl peroxide as initiators) inherently involves randomness and uncontrollability in chain initiation and termination reactions. This makes it difficult to precisely control the molecular weight and molecular weight distribution (PDI) of the prepared polymer, resulting in inconsistent product performance. Furthermore, due to the uncontrollability of free radical polymerization, numerous side reactions may occur, generating a large number of byproducts, affecting the quality and environmental friendliness of the final product. Therefore, developing a method for preparing polystyrene that can precisely control its molecular weight is of significant practical importance. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the technical solution adopted in this application is to provide a method for preparing polystyrene with controllable molecular weight, so as to solve the technical problems of uncontrollable molecular weight and molecular weight distribution and numerous side reactions in the existing polystyrene free radical polymerization method.

[0005] This application provides a method for preparing polystyrene with controllable molecular weight, comprising the following steps:

[0006] Under an inert atmosphere, a reducing agent is added to an anhydrous and oxygen-free organic solvent, followed by styrene monomer, a catalyst, and a dormant initiator. The polymerization reaction is carried out under controlled temperature. After the reaction is completed, the reaction is terminated, and polystyrene is obtained after post-treatment.

[0007] The catalyst is a copper bromide / pentamethyldiethylenetriamine complex;

[0008] The dormancy initiator is n-butyl chloride;

[0009] The reducing agent is graphene oxide grafted with phenolic hydroxyl groups, and the active component phenolic hydroxyl groups are grafted onto the support graphene oxide.

[0010] Preferably, the method for preparing the reducing agent includes the following steps:

[0011] Under an inert atmosphere, graphene oxide was dispersed in anhydrous N,N-dimethylformamide and ultrasonically dispersed. 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added and stirred for activation. Then, 4-aminophenol and triethylamine were added and stirred for condensation reaction. After the reaction was completed, the graphene oxide grafted with phenolic hydroxyl groups was separated, washed, and dried to obtain the reducing agent.

[0012] Preferably, during activation, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide are added in an ice-water bath, with the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to graphene oxide being 0.3 to 1:1 and the molar ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide being 1:1; and the mixture is stirred and activated at room temperature for 2 to 4 hours.

[0013] Preferably, during the condensation reaction, the mass ratio of 4-aminophenol to graphene oxide is 0.2–0.7:1, and the molar ratio of triethylamine to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 2:1; the condensation reaction is carried out by stirring at room temperature for 12–16 h; during washing, anhydrous N,N-dimethylformamide, ethanol, and deionized water are used alternately; during drying, the mixture is vacuum dried overnight at 50–80 °C.

[0014] Preferably, the organic solvent includes any one or a combination of at least two of dichloromethane, dichloroethane, bromochloromethane, benzene, toluene, xylene, tetrahydrofuran, chloroform, and cyclohexane, and the water content in the anhydrous and oxygen-free organic solvent is less than 200 ppm; the amount of styrene monomer and organic solvent used is 100 g / 200-300 mL.

[0015] Preferably, the mass ratio of catalyst to styrene monomer is 0.0001 to 0.001:1, the mass ratio of reducing agent to catalyst is 10 to 50:1, and the mass ratio of dormant initiator to reducing agent is 0.5 to 2:1.

[0016] Preferably, the polymerization reaction is carried out at a temperature of 80–100°C for 6–12 hours.

[0017] Preferably, the specific steps of the post-processing include:

[0018] After the reaction was terminated, a large amount of methanol was added to the reaction system, and the mixture was separated to obtain a precipitate. Then, tetrahydrofuran was added to the precipitate, and the mixture was separated to obtain a solid and a supernatant. The solid was dried under vacuum to obtain a reducing agent, which was reused. A large amount of methanol was added to the supernatant again, and the mixture was separated and washed. The organic phase was dried under vacuum to obtain polystyrene.

[0019] Preferably, the reducing agent is obtained by vacuum drying the solid at 50–70°C for 12–24 hours; the polystyrene is obtained by vacuum drying the organic phase at 70–90°C for 24–48 hours.

[0020] This invention provides a method for preparing polystyrene with controllable molecular weight. Compared with the prior art, the advantages of this invention are:

[0021] (1) In this invention, graphene oxide (GO) rich in carboxyl groups is used as a carrier. By grafting phenolic hydroxyl groups (-OH), a supported reducing agent GO-OH is obtained. Its active component (-OH) can reduce the initial Cu(II) to Cu(I), thereby initiating the polymerization reaction. In addition, during the polymerization reaction, all Cu(I) lost due to side reactions will be re-oxidized to Cu(II), and GO-OH will continuously reduce these Cu(I) lost due to side reactions (which have been converted to Cu(II)) back to Cu(I), thereby maintaining the concentration of Cu(I) in the reaction system at a stable level. Moreover, since Cu(I) can be continuously regenerated, the reaction can be carried out at extremely low catalyst concentrations, which greatly reduces the amount of catalyst used and significantly reduces costs.

[0022] (2) This invention uses oxidized Cu(II) as a catalyst precursor and combines it with a highly efficient supported reducing agent to continuously regenerate activated Cu(I), making the entire reaction system more tolerant to trace oxygen (oxygen will oxidize Cu(I) to Cu(II), while GO-OH can reduce it back), which is superior to conventional atom transfer radical polymerization (ATRP). This allows the polymerization reaction to "resist" a certain degree of oxygen interference and continue until the monomer is almost completely consumed, achieving extremely high conversion rate, more stable reaction process, better reproducibility, and easier quality control for large-scale production.

[0023] (3) The present invention uses a supported reducing agent. By precisely controlling the amount of monomer and dormant initiator, the molecular weight and molecular weight distribution of polystyrene can be precisely controlled. In addition, since new catalysts are constantly regenerated, the concentration of the catalyst remains basically constant throughout the reaction process. The consumption rate of monomer is uniform, and all polymer chains grow at almost the same rate, thereby obtaining a polymer with a very narrow molecular weight distribution. This avoids the reaction runaway caused by drastic changes in initiator concentration, greatly reduces the probability of uncontrollable chain transfer, and helps to obtain a polymer with a regular structure and a very narrow molecular weight distribution.

[0024] (4) This invention employs a supported reducing agent to establish a rapid dynamic equilibrium between growing free radicals (Pn•) and dormant polymer chains (Pn-Cl). In this equilibrium, the vast majority (>99%) of the polymer chains exist in the form of "dormant species" (Pn-Cl), which have no free radical activity and do not collide with each other, thus preventing side reactions. Only a very small number of polymer chains are "activated" into growing free radicals (Pn•) at any given time. This mechanism fundamentally changes the kinetic environment of the polymerization reaction, controlling the concentration of free radicals in the system at an extremely low level, thereby greatly reducing the rate of side reactions from the root. This is the intrinsic reason why it can achieve the core advantage of "controllable molecular weight".

[0025] (5) The supported reducing agent of the present invention exists in solid form. As a heterogeneous reducing agent, it can be separated from the product by simple centrifugation or filtration. The recovered reducing agent can be recycled after washing and drying, which conforms to the principle of green chemistry and significantly reduces costs. It has the characteristics of atom economy and green environmental protection. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The elution curve of the product prepared in Example 1 of this application is shown.

[0028] Figure 2 This is a GPC molecular weight distribution diagram of the product prepared in Example 1 of this application. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application. Unless otherwise specified, the raw materials and apparatus used in this invention are all conventional commercially available products; the methods used, unless otherwise specified, are all conventional methods.

[0030] Example 1

[0031] This embodiment provides a method for preparing polystyrene, including the following steps:

[0032] (1) Preparation of reducing agent

[0033] Under argon protection, 10 g of graphene oxide (GO) was dispersed in 2000 mL of anhydrous N,N-dimethylformamide (DMF). 6 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and 3.6 g of N-hydroxysuccinimide (NHS) were added in an ice-water bath. The ice-water bath was removed, and the reaction system was brought to room temperature and activated by stirring at room temperature for 3 h. During this process, the carboxyl groups on the GO surface were converted into NHS active esters.

[0034] Under argon protection, 4g of 4-aminophenol and 6.33g of triethylamine were added, and the mixture was stirred at room temperature for 14 hours to carry out the condensation reaction. After the reaction was completed, the solid and liquid were separated by centrifugation. The solid was washed three times alternately with DMF, ethanol and deionized water, and then dried under vacuum at 60°C overnight to obtain GO grafted with phenolic hydroxyl groups, which was the reducing agent and named GO-OH.

[0035] (2) Preparation of polystyrene

[0036] Under argon protection, 2.46 g of GO-OH reducing agent was added to a dry three-necked flask, followed by 300 mL of anhydrous and oxygen-free toluene. The mixture was sonicated for 30 min to ensure uniform dispersion of GO-OH.

[0037] Add 0.0501g of copper bromide (CuBr2) and 10μL of pentamethyldiethylenetriamine (PMDETA), then add 100g of purified styrene monomer, 2.42g of n-butyl chloride (n-BuCl) and 14μL of triethylamine using a syringe. Place the reaction apparatus in a -78℃ dry ice-acetone bath and perform three "freeze-evacuate-thaw" cycles to completely remove oxygen from the system.

[0038] The flask was quickly transferred to an oil bath preheated to 90°C and the polymerization reaction was carried out at 90°C. When the solution color changed from yellow-green to brown or dark brown, it indicated that GO-OH had started to reduce Cu(II) and the polymerization reaction was initiated. At this time, the timer was started and the reaction was carried out for 10 hours.

[0039] After the reaction was complete, the flask was removed, the oil bath was removed, and the mixture was left open to cool and stir in the air. Oxygen quenched all active species. A large amount of methanol was added to the reaction system, and the mixture was centrifuged to obtain a precipitate. Tetrahydrofuran was added to the precipitate, and the mixture was centrifuged to obtain a solid and a supernatant. The solid was dried under vacuum at 60°C overnight to obtain a reducing agent, which could be reused. A large amount of methanol was added to the supernatant again, and the mixture was centrifuged. The organic phase was washed three times with methanol and then dried under vacuum at 80°C for 24 hours to obtain 98.5 g of polystyrene, with a yield of 98.5%. The molecular weight Mn was measured to be 4990, and the PDI was 1.05.

[0040] The reaction equation is as follows:

[0041] GO-OH + Cu(II)Br2 / L → GO-O•(phenoxy radical) + Cu(I)Br / L + HBr

[0042] n-BuCl + Cu(I)Br / L → n-Bu• + Cu(II)BrCl / L

[0043] n-Bu• + M (styrene monomer) → n-Bu-M• (P1•)

[0044] P1• + nM (styrene monomer) → P n+1 •

[0045] P n+1 • + Cu(II)BrCl / L → P n+1 -Cl (dormant species) + Cu(I)Br / L

[0046] Example 2

[0047] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of the catalyst to the styrene monomer is 0.0001:1, and the rest of the operation is the same, and polystyrene is finally obtained.

[0048] Example 3

[0049] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of the catalyst to the styrene monomer is 0.001:1, and the rest of the operation is the same, and polystyrene is finally obtained.

[0050] Example 4

[0051] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of reducing agent to catalyst is 25:1, and the rest of the operation is the same, and polystyrene is finally obtained.

[0052] Example 5

[0053] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of reducing agent to catalyst is 10:1, and the rest of the operation is the same, and polystyrene is finally obtained.

[0054] Example 6

[0055] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of the dormant initiator to the reducing agent is 0.5:1, and the rest of the operation is the same, and polystyrene is finally obtained.

[0056] Example 7

[0057] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of the dormant initiator to the reducing agent is 2:1; the rest of the operations are the same, and polystyrene is finally obtained.

[0058] Example 8

[0059] The difference between this embodiment and embodiment 1 is that in step (2), the polymerization reaction temperature is 100°C, while the rest of the operations are the same, and polystyrene is finally obtained.

[0060] Example 9

[0061] The difference between this embodiment and Embodiment 1 is that in step (2), the polymerization reaction temperature is 80°C, while the rest of the operations are the same, and polystyrene is finally obtained.

[0062] Example 10

[0063] The difference between this embodiment and embodiment 1 is that in step (2), the polymerization reaction time is 12 hours, while the rest of the operation is the same, and polystyrene is finally obtained.

[0064] Example 11

[0065] The difference between this embodiment and embodiment 1 is that in step (2), the polymerization reaction time is 8 hours, while the rest of the operation is the same, and polystyrene is finally obtained.

[0066] Example 12

[0067] The difference between this embodiment and embodiment 1 is that in step (2), the polymerization reaction time is 6 hours, while the rest of the operation is the same, and polystyrene is finally obtained.

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 is that step (1) is deleted, and a reducing agent is not used in step (2). 0.0501g of copper bromide (CuBr2) is replaced with 0.0322g of cuprous bromide (CuBr). The rest of the operation is the same, and polystyrene is finally obtained.

[0070] It should be noted that in Examples 1-12 above, during the preparation of the reducing agent, the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to graphene oxide during activation was 0.3-1:1, and the activation was carried out by stirring at room temperature for 2-4 hours. During the condensation reaction, the mass ratio of 4-aminophenol to graphene oxide was 0.2-0.7:1, and the condensation reaction was carried out by stirring at room temperature for 12-16 hours. During drying, the product was vacuum dried overnight at 50-80°C. These parameters only need to be within the specified range; adjustments can be made according to specific circumstances during actual operation.

[0071] In Examples 1-12 above, during the preparation of polystyrene, the organic solvent includes any one or a combination of at least two of dichloromethane, dichloroethane, bromochloromethane, benzene, toluene, xylene, tetrahydrofuran, chloroform, and cyclohexane. The water content in the anhydrous and oxygen-free organic solvent is below 200 ppm. The amount of styrene monomer and organic solvent used is 100 g / 200-300 mL. The dormant initiator includes any one or a combination of at least two of sec-butyl chloride, n-butyl chloride, isopropyl chloride, sec-butyl bromide, n-butyl bromide, isopropyl bromide, sec-butyl iodine, n-butyl iodine, and isopropyl iodine. During post-treatment, the solid is vacuum dried at 50-70°C for 12-24 h to obtain the reducing agent; the organic phase is vacuum dried at 70-90°C for 24-48 h to obtain polystyrene. The above parameters only need to be within the specified range; adjustments can be made according to specific circumstances during actual operation.

[0072] To more intuitively compare the reaction parameters and results of Examples 1-12 and Comparative Example 1, the following table 1 is presented.

[0073] Table 1. Reaction parameters and results of Examples 1-12 and Comparative Example 1

[0074]

[0075] As shown in Table 1:

[0076] Comparing Examples 1-12 and Comparative Example 1, it can be seen that the polystyrene prepared by the method of the present invention has a high yield and a narrow molecular weight distribution, all below 1.20. This indicates that the preparation method of the present invention can obtain polymers with extremely narrow molecular weight distributions. This is because the present invention uses a supported reducing agent, which continuously regenerates new catalysts, keeping the catalyst concentration essentially constant throughout the reaction process. The monomer consumption rate is uniform, and all polymer chains grow at nearly the same rate, thus obtaining polymers with extremely narrow molecular weight distributions. This avoids reaction runaway caused by drastic changes in initiator concentration, greatly reduces the probability of uncontrollable chain transfer, and helps to obtain polymers with regular structures and extremely narrow molecular weight distributions.

[0077] Comparing Examples 1 to 12, it can be seen that the present invention uses a supported reducing agent. By precisely controlling the amount of monomer and dormant initiator, the molecular weight and molecular weight distribution of polystyrene can be precisely controlled, and the molecular weight can be controlled between 1800 and 80000 Daltons.

[0078] The product prepared in Example 1 was tested, and its elution curve was obtained as shown in the figure. Figure 1 As shown in the figure, the molecular weight distribution of GPC is as follows: Figure 2 As shown. From Figure 1As can be seen from the spectrum, there is only one peak, with no byproducts generated. By comparing the peak times, the product can be identified as polystyrene. Figure 2 As can be seen, the molecular weight of the product is 4990 Daltons, which meets the design expectation. Therefore, it can be concluded that the product prepared in Example 1 is polystyrene.

[0079] This invention provides a method for preparing polystyrene with controllable molecular weight, which, compared with the prior art:

[0080] (1) In this invention, graphene oxide (GO) rich in carboxyl groups is used as a carrier. By grafting phenolic hydroxyl groups (-OH), a supported reducing agent GO-OH is obtained. Its active component (-OH) can reduce the initial Cu(II) to Cu(I), thereby initiating the polymerization reaction. In addition, during the polymerization reaction, all Cu(I) lost due to side reactions will be re-oxidized to Cu(II), and GO-OH will continuously reduce these Cu(I) lost due to side reactions (which have been converted to Cu(II)) back to Cu(I), thereby maintaining the concentration of Cu(I) in the reaction system at a stable level. Moreover, since Cu(I) can be continuously regenerated, the reaction can be carried out at extremely low catalyst concentrations, which greatly reduces the amount of catalyst used and significantly reduces costs.

[0081] (2) This invention uses oxidized Cu(II) as a catalyst precursor and combines it with a highly efficient supported reducing agent to continuously regenerate activated Cu(I), making the entire reaction system more tolerant to trace oxygen (oxygen will oxidize Cu(I) to Cu(II), while GO-OH can reduce it back), which is superior to conventional atom transfer radical polymerization (ATRP). This allows the polymerization reaction to "resist" a certain degree of oxygen interference and continue until the monomer is almost completely consumed, achieving extremely high conversion rate, more stable reaction process, better reproducibility, and easier quality control for large-scale production.

[0082] (3) The present invention uses a supported reducing agent. By precisely controlling the amount of monomer and dormant initiator, the molecular weight and molecular weight distribution of polystyrene can be precisely controlled. In addition, since new catalysts are constantly regenerated, the concentration of the catalyst remains basically constant throughout the reaction process. The consumption rate of monomer is uniform, and all polymer chains grow at almost the same rate, thereby obtaining a polymer with a very narrow molecular weight distribution. This avoids the reaction runaway caused by drastic changes in initiator concentration, greatly reduces the probability of uncontrollable chain transfer, and helps to obtain a polymer with a regular structure and a very narrow molecular weight distribution.

[0083] (4) This invention employs a supported reducing agent to establish a rapid dynamic equilibrium between growing free radicals (Pn•) and dormant polymer chains (Pn-Cl). In this equilibrium, the vast majority (>99%) of the polymer chains exist in the form of "dormant species" (Pn-Cl), which have no free radical activity and do not collide with each other, thus preventing side reactions. Only a very small number of polymer chains are "activated" into growing free radicals (Pn•) at any given time. This mechanism fundamentally changes the kinetic environment of the polymerization reaction, controlling the concentration of free radicals in the system at an extremely low level, thereby greatly reducing the rate of side reactions from the root. This is the intrinsic reason why it can achieve the core advantage of "controllable molecular weight".

[0084] (5) The supported reducing agent of the present invention exists in solid form. As a heterogeneous reducing agent, it can be separated from the product by simple centrifugation or filtration. The recovered reducing agent can be recycled after washing and drying, which conforms to the principle of green chemistry and significantly reduces costs. It has the characteristics of atom economy and green environmental protection.

[0085] This invention can be widely applied in the field of organic synthesis technology.

[0086] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing polystyrene with controllable molecular weight, characterized in that, Includes the following steps: Under an inert atmosphere, a reducing agent is added to an anhydrous and oxygen-free organic solvent, followed by styrene monomer, a catalyst, and a dormant initiator. The polymerization reaction is carried out under controlled temperature. After the reaction is completed, the reaction is terminated, and polystyrene is obtained after post-treatment. The catalyst is a copper bromide / pentamethyldiethylenetriamine complex; The dormancy initiator is n-butyl chloride; The reducing agent is graphene oxide grafted with phenolic hydroxyl groups, and the active component phenolic hydroxyl groups are grafted onto the support graphene oxide.

2. The method for preparing molecular weight controllable polystyrene according to claim 1, characterized in that, The method for preparing the reducing agent includes the following steps: Under an inert atmosphere, graphene oxide was dispersed in anhydrous N,N-dimethylformamide and ultrasonically dispersed. 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added and stirred for activation. Then, 4-aminophenol and triethylamine were added and stirred for condensation reaction. After the reaction was completed, the graphene oxide grafted with phenolic hydroxyl groups was separated, washed, and dried to obtain the reducing agent.

3. The method for preparing molecular weight controllable polystyrene according to claim 2, characterized in that, During activation, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added in an ice-water bath. The mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to graphene oxide was 0.3 to 1:1, and the molar ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide was 1:

1. The mixture was stirred and activated at room temperature for 2 to 4 hours.

4. The method for preparing molecular weight controllable polystyrene according to claim 2, characterized in that, During the condensation reaction, the mass ratio of 4-aminophenol to graphene oxide was 0.2–0.7:1, and the molar ratio of triethylamine to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 2:

1. The condensation reaction was carried out at room temperature with stirring for 12–16 h. During washing, anhydrous N,N-dimethylformamide, ethanol, and deionized water were used alternately. During drying, the mixture was vacuum dried overnight at 50–80 °C.

5. The method for preparing molecular weight controllable polystyrene according to claim 1, characterized in that, The organic solvent includes any one or a combination of at least two of the following: dichloromethane, dichloroethane, bromochloromethane, benzene, toluene, xylene, tetrahydrofuran, chloroform, and cyclohexane. The water content in the anhydrous and oxygen-free organic solvent is less than 200 ppm. The amount of styrene monomer and organic solvent used is 100 g / 200-300 mL.

6. The method for preparing molecular weight controllable polystyrene according to claim 1, characterized in that, The mass ratio of catalyst to styrene monomer is 0.0001 to 0.001:1, the mass ratio of reducing agent to catalyst is 10 to 50:1, and the mass ratio of dormant initiator to reducing agent is 0.5 to 2:

1.

7. The method for preparing molecular weight controllable polystyrene according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 80–100℃ for 6–12 hours.

8. The method for preparing molecular weight controllable polystyrene according to claim 1, characterized in that, The specific steps of the post-processing include: After the reaction was terminated, a large amount of methanol was added to the reaction system, and the mixture was separated to obtain a precipitate. Then, tetrahydrofuran was added to the precipitate, and the mixture was separated to obtain a solid and a supernatant. The solid was dried under vacuum to obtain a reducing agent, which was reused. A large amount of methanol was added to the supernatant again, and the mixture was separated and washed. The organic phase was dried under vacuum to obtain polystyrene.

9. The method for preparing molecular weight controllable polystyrene according to claim 8, characterized in that, The reducing agent is obtained by vacuum drying the solid at 50–70°C for 12–24 hours; the polystyrene is obtained by vacuum drying the organic phase at 70–90°C for 24–48 hours.

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