A controlled free radical polymerization method initiated by single electron transfer

Abstract

The present invention discloses a method for controlled free radical polymerization initiated by single electron transfer, wherein the propagating free radical of the method has a negative charge and has an "active" property, and can accurately control the molecular weight of the polymer by adjusting the polymerization time or the monomer conversion rate, and obtain a polymer product with a narrow molecular weight distribution. The method of the present invention comprises the following steps: initiating controlled free radical polymerization with a low concentration of samarium diiodide / hexamethylphosphoric triamide solution; the samarium diiodide concentration of the low concentration samarium diiodide / hexamethylphosphoric triamide solution is 0.009-0.055 mol / L. Within this low concentration range, the kinetics of polymerization initiated by samarium diiodide, ln([M]0 / [M]), increases linearly with the polymerization time, and the molecular weight of the polymer product is also linearly related to the conversion rate. The narrow molecular weight distribution of the polymer indicates that the propagating free radical has an "active" property, and the polymerization exhibits controllable characteristics.

Description

Technical Field

[0001] The invention relates to a polymerization method, and more particularly to a controllable free radical polymerization method initiated by single electron transfer. Background Art

[0002] Due to the slow initiation, fast growth and fast termination mechanism of traditional free radical polymerization, the molecular weight of the polymer is not easy to control and the molecular weight distribution is The scope of application of free radical polymerization is relatively wide, and the application field is limited. If the double radical termination of free radicals can be effectively suppressed, "active" free radicals can be obtained, and controlled free radical polymerization can be achieved. Controlled free radical polymerization can prepare polymers with controllable molecular weight and narrow molecular weight distribution. Combined with the advantages of wide applicability of monomers initiated by free radicals, controlled free radical polymerization has a wide range of applications in the preparation of block polymers, polymer brushes, carbon chain oligomers and other fields. In recent years, controlled free radical polymerization methods have received attention and have been rapidly developed. At present, controlled free radical polymerization is mostly achieved through the reversible dynamic balance of active species / dormant species, such as atom transfer mechanism, break-binding mechanism and degenerate chain transfer mechanism. Its specific implementation methods include atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), nitrogen oxide stabilized radical polymerization (NMP) and initiator chain transfer terminator method (Iniferter). However, these controlled free radical polymerization schemes still have some problems. Due to the limitation of the reversible dynamic equilibrium mechanism of active species / dormant species, the number of growing free radicals is much lower than the number of polymer chains, so the rate of controlled free radical polymerization is usually much slower than that of ordinary free radical polymerization. In addition, the ATRP method uses halides as initiators, which are highly toxic; the RAFT method requires the synthesis of toxic dithioester chain transfer agents, and such chain transfer agents are costly, unstable, and difficult to store; the NMP method is only well controllable for styrene monomers, and the polymerization temperature is high, often exceeding 120°C; the monomers of the Iniferter method are widely applicable, but the control of the polymerization products is not ideal, the actual molecular weight deviates greatly from the theoretical value, and the molecular weight distribution is wide. These problems limit the widespread application of controlled free radical polymerization.

[0003] Samarium diiodide is soluble in organic solvents, and its solution is also called Kagan reagent. It has a redox potential of -1.55V and is a typical single electron transfer reagent. Samarium diiodide is often used as a reducing agent in organic reactions. It can reduce a variety of organic compounds such as halides, aldehydes, ketones and nitro compounds. As an electron donor, it can carry out conjugate addition, free radical cyclization, Barbier reaction and nucleophilic reaction. The commercially available samarium diiodide is a 0.1 mol / L tetrahydrofuran solution with low reaction activity, but the addition of Lewis base, hexamethylphosphoric triamide and other substances with strong electron dispersibility can improve the electron transfer ability of samarium diiodide. If the single electron transfer ability of samarium diiodide can be utilized to activate and initiate the polymerization of olefin monomers with samarium diiodide / hexamethylphosphoric triamide solution, a new type of controlled free radical polymerization method can be developed for the composition and structural design of polymer materials, the preparation of block copolymers, carbon chain oligomers, polymer brushes, star polymers, etc., and the polymerization products can be used more widely in the fields of thermoplastic elastomers, material surface modification, amphiphilic dispersants, etc. Summary of the invention

[0004] The purpose of the present invention is to solve the problems and shortcomings of the prior art, such as low polymerization rate, high toxicity of the initiation system, high cost, poor controllability and high polymerization temperature, and to provide a single electron transfer initiated controlled free radical polymerization method. The single electron transfer initiated controlled free radical polymerization method has a negative charge in its propagating free radical, which has the property of "activity". The molecular weight of the polymer can be accurately controlled by adjusting the polymerization time or the monomer conversion rate, and a narrow molecular weight distribution can be obtained. The polymer product. Samarium diiodide activates the monomer through a single electron transfer reaction to obtain a negatively charged free radical growth species. Due to the repulsion of the same charge, the free radical is not easy to terminate, which not only gives the free radical the property of "activity", but also the polymerization system can maintain a high free radical concentration. Therefore, the polymerization rate is faster, which is similar to the ordinary free radical polymerization rate, and is conducive to industrial production. The polymerization can be carried out at room temperature or a temperature slightly higher than room temperature, and the reaction conditions are mild and easy to implement. The controlled free radical polymerization method of the present invention can be used for the composition and structural design of polymer materials, the preparation of block copolymers, carbon chain oligomers, polymer brushes, star polymers, etc., and realizes a wider range of uses of the polymerization product in the fields of thermoplastic elastomers, material surface modification, amphiphilic dispersants, etc.

[0005] The present invention is achieved through the following technical solutions:

[0006] The single electron transfer-initiated controlled radical polymerization method of the present invention comprises the following steps: initiating controlled radical polymerization with a low concentration of samarium diiodide / hexamethylphosphoric triamide solution; the samarium diiodide concentration of the low concentration samarium diiodide / hexamethylphosphoric triamide solution is 0.009 to 0.055 mol / L. Within this low concentration range, the kinetics of the polymerization initiated by samarium diiodide, ln ([M]0 / [M]), increases linearly with the polymerization time, the molecular weight of the polymer product is also linearly related to the conversion rate, and the molecular weight distribution of the polymer is relatively narrow. This indicates that the propagating free radical has the property of "activity" and the polymerization exhibits controllable characteristics. When the concentration of samarium diiodide is higher than 0.055 mol / L, the polymerization kinetics ln([M]0 / [M]) does not increase linearly with the polymerization time, and the polymerization product shows gelation, and the polymerization no longer exhibits controllable characteristics.

[0007] The above-mentioned single electron transfer-initiated controlled radical polymerization method of the present invention has a further technical solution in which the main steps are as follows: first, a samarium diiodide solution with a concentration of 0.1 mol / L is prepared using hexamethylphosphoric triamide as a solvent, and then hexamethylphosphoric triamide is added to dilute it to obtain a low concentration of samarium diiodide / hexamethylphosphoric triamide solution, and then an olefin monomer is added to initiate the controlled radical polymerization of the olefin monomer.

[0008] The above-mentioned single electron transfer-initiated controlled radical polymerization method of the present invention further comprises the following steps:

[0009] S1, adding sodium metal flakes to hexamethylphosphoric triamide to remove water, and then purifying by reduced pressure distillation;

[0010] S2, adding anhydrous sodium sulfate to the olefin monomer to remove water, and then purifying by reduced pressure distillation;

[0011] S3, adding measured samarium metal powder and iodine into the hexamethylphosphoric acid triamide purified in step S1, and preparing a 0.1 mol / L samarium diiodide / hexamethylphosphoric acid triamide solution by separation after the reaction is completed, and the reaction process is protected by nitrogen;

[0012] S4, diluting the 0.1 mol / L samarium diiodide / hexamethylphosphoric triamide solution prepared in step S3 with the hexamethylphosphoric triamide purified in step S1 to obtain a low concentration samarium diiodide / hexamethylphosphoric triamide solution, and then adding an olefin monomer to initiate controlled free radical polymerization of the olefin monomer, and protecting the reaction process with nitrogen.

[0013] The above-mentioned single electron transfer-initiated controlled radical polymerization method of the present invention has a further technical solution that the molar ratio of the metal samarium powder to the iodine dosage in step S3 is ≥6.5; the reaction is stirred at 85-95°C for more than 48 hours. A further technical solution is that the amount of the metal samarium powder should be greater than the amount of iodine. Taking the amount of hexamethylphosphoric triamide as 20mL, the amount of iodine is 0.51g, i.e. 0.002mol, and the amount of the metal samarium powder is 2.0g, i.e. 0.013mol. When preparing a samarium diiodide solution with a concentration of 0.1mol / L, due to heterogeneous reactions, the amount of metal samarium powder should be significantly greater than the amount of iodine.

[0014] A further technical solution of the single electron transfer-initiated controlled radical polymerization method of the present invention is that when preparing the samarium diiodide / hexamethylphosphoric triamide solution with a concentration of 0.1 mol / L, the obtained samarium diiodide solution is the supernatant liquid for separating the remaining metal samarium powder.

[0015] The above-mentioned single electron transfer initiated controlled radical polymerization method of the present invention has a further technical solution that the polymerization temperature of the controlled radical polymerization of the initiating olefin monomer is 25-60°C; within this temperature range, the higher the temperature, the faster the polymerization rate.

[0016] A further technical solution of the single electron transfer-initiated controlled radical polymerization method of the present invention is that the vinyl monomer is methyl methacrylate, styrene, methyl acrylate or acrylonitrile.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention discloses a controllable free radical polymerization method initiated by single electron transfer. The polymerization of olefin monomers is initiated by a low concentration of samarium diiodide / hexamethylphosphoric acid triamide solution of 0.009-0.055 mol / L. The polymerization kinetics ln([M]0 / [M]) increases linearly with the polymerization time. The molecular weight of the polymerization product also has a linear relationship with the conversion rate, indicating that the growing species has the property of "activity" and the polymerization has controllable characteristics. When a small amount of water is added to the polymerization system, the polymerization is not terminated but accelerated, indicating that the polymerization is not initiated by anions. The polymerization can be terminated by a free radical scavenger 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH). The free radical concentration is tested by the DPPH method, and the theoretical molecular weight is calculated accordingly. The theoretical value of the molecular weight is consistent with the GPC measured value, indicating that the polymerization belongs to a free radical process. When polymerized in a high voltage DC electric field, the polymer migrates to the anode, indicating that the active species is a negatively charged free radical. Due to the repulsive effect of the same charge, the free radical is not easy to terminate, which gives the growing free radical the property of "activity" and the controllable characteristics of the polymerization. Specifically: (1) Based on the "active" nature of the growing free radicals in the polymerization method of the present invention, the molecular weight of the polymer can be accurately adjusted and controlled according to the polymerization time and monomer conversion rate, and a polymer with a narrow molecular weight distribution can be obtained; (2) Based on the "active" free radicals in the polymerization method of the present invention, products with various structures such as block copolymers, carbon chain oligomers, polymer brushes, star polymers, etc. can be prepared; (3) Due to the repulsive effect of the same charge, the growing free radicals are not easy to terminate, the polymerization system can maintain a high free radical concentration, the polymerization rate is fast, which is equivalent to the polymerization rate of ordinary free radicals, and is conducive to industrial production; (4) The polymerization can be carried out at room temperature or slightly above room temperature, the reaction conditions are mild, and it is easy to implement; (5) It can be used for the composition and structural design of polymer materials, and the preparation of block copolymers, carbon chain oligomers, polymer brushes, star polymers, etc. can be achieved in the fields of thermoplastic elastomers, material surface modification, amphiphilic dispersants, etc. More extensive uses. DETAILED DESCRIPTION

[0019] The basic steps of the controlled free radical polymerization method initiated by single electron transfer in the embodiment are as follows:

[0020] S1, adding sodium metal flakes to hexamethylphosphoric triamide to remove water, and then purifying by reduced pressure distillation;

[0021] S2, adding anhydrous sodium sulfate to the olefin monomer to remove water, and then purifying by reduced pressure distillation;

[0022] S3, adding the measured samarium metal powder and iodine to the hexamethylphosphoric acid triamide purified in step S1, stirring and reacting at 85-95° C. for more than 48 hours, and preparing a 0.1 mol / L samarium diiodide / hexamethylphosphoric acid triamide solution by separation, and protecting the reaction process with nitrogen; the molar ratio of the samarium metal powder to the iodine is ≥6.5;

[0023] S4, diluting the 0.1 mol / L samarium diiodide / hexamethylphosphoric triamide solution prepared in step S3 with the hexamethylphosphoric triamide purified in step S1 to obtain a low concentration samarium diiodide / hexamethylphosphoric triamide solution, and then adding an olefin monomer to initiate controlled free radical polymerization of the olefin monomer, and protecting the reaction process with nitrogen.

[0024] Example 1

[0025] 2.0g of metal samarium powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, stirred and reacted at 90°C for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was prepared by separation. Take 5.5mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 4.5mL of hexamethylphosphoric acid triamide to dilute, mix evenly to obtain a samarium diiodide solution with a concentration of 0.055mol / L, and then add 10mL of methyl methacrylate and polymerize at 35°C. The polymerization kinetics ln([M]0 / [M]) increases linearly with the increase of polymerization time, the molecular weight of the polymerization product is controllable, and the molecular weight distribution is The value is less than 1.4 and can reach a minimum of 1.16. The results are shown in Table 1.

[0026] Table 1 ln([M]0 / [M]), molecular weight, Relationship between value and aggregation time

[0027]

[0028] Example 2

[0029] 2.0g of samarium metal powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, stirred and reacted at 85°C for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was prepared by separation. Take 5mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 5mL of hexamethylphosphoric acid triamide to dilute, mix evenly to obtain a 0.05mol / L samarium diiodide solution, and then add 8mL of methyl methacrylate and polymerize at 60°C. The polymerization kinetics ln([M]0 / [M]) increases linearly with the increase of polymerization time, the molecular weight of the polymerization product is controllable, and the molecular weight distribution is The value is less than 1.4. The results are shown in Table 2.

[0030] Table 2 ln([M]0 / [M]), molecular weight, Relationship between value and aggregation time

[0031]

[0032]

[0033] Example 3

[0034] 2.0g of metal samarium powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, stirred and reacted at 95°C for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was prepared by separation. 4mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was taken, 6mL of hexamethylphosphoric acid triamide was added to dilute, and mixed evenly to obtain a samarium diiodide solution with a concentration of 0.04mol / L, and then 10mL of methyl acrylate was added to polymerize at 45°C. The polymerization kinetics ln([M]0 / [M]) increased linearly with the increase of polymerization time, the molecular weight of the polymer product was controllable, and the molecular weight distribution D value was less than 1.4. The results are shown in Table 3.

[0035] Table 3 ln([M]0 / [M]), molecular weight, Relationship between value and aggregation time

[0036]

[0037] Example 4

[0038] 2.0g of samarium metal powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, stirred and reacted at 88°C for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was prepared by separation. Take 0.9mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 9.1mL of hexamethylphosphoric acid triamide to dilute, mix evenly to obtain a samarium diiodide solution with a concentration of 0.009mol / L, and then add 3mL of acrylonitrile and polymerize at 50°C. The polymerization kinetics ln([M]0 / [M]) increases linearly with the increase of polymerization time, the molecular weight of the polymerization product is controllable, and the molecular weight distribution is The value is less than 1.4. The results are shown in Table 4.

[0039] Table 4 ln([M]0 / [M]), molecular weight, and Relationship between value and aggregation time

[0040]

[0041] Example 5

[0042] 2.0g of metal samarium powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, and the mixture was stirred at 93°C for 48 hours to prepare a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution. Take 3.5mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 6.5mL of hexamethylphosphoric acid triamide to dilute, mix well to obtain a 0.035mol / L samarium diiodide solution, and then add 10mL of acrylonitrile to polymerize at 25°C. The polymerization kinetics ln([M]0 / [M]) increases linearly with the increase of polymerization time, and the molecular weight of the polymer product is controllable, and the molecular weight distribution is The value is less than 1.4. The results are shown in Table 5.

[0043] Table 5 ln([M]0 / [M]), molecular weight, Relationship between value and aggregation time

[0044]

[0045] Example 6

[0046] 2.0g of samarium metal powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, and the mixture was stirred at 90°C for 48 hours to prepare a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution. Take 5.5mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 4.5mL of hexamethylphosphoric acid triamide to dilute, mix well to obtain a 0.055mol / L samarium diiodide solution, and then add 10mL of styrene to polymerize at 60°C. The polymerization kinetics ln([M]0 / [M]) increases linearly with the increase of polymerization time, and the molecular weight of the polymer product is controllable, and the molecular weight distribution is The value is less than 1.4. The results are shown in Table 6.

[0047] Table 6 ln([M]0 / [M]), molecular weight, Relationship between value and aggregation time

[0048]

[0049] Comparative Example 1

[0050] 2.0g of samarium metal powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, and the mixture was stirred at 90°C for 48 hours to prepare a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution by separation. Take 6.5mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution, add 3.5mL of hexamethylphosphoric acid triamide to dilute, mix well to obtain a 0.065mol / L samarium diiodide solution, and then add 10mL of methyl methacrylate and polymerize at 35°C. The polymerization kinetics ln([M]0 / [M]) does not increase linearly with the increase of polymerization time. The polymerization products with polymerization time of 16 and 24h are in a gel state, and the molecular weight and The value is unmeasurable, and the results are shown in Table 7.

[0051] Table 7 Relationship between ln([M]0 / [M]), molecular weight, molecular weight distribution and polymerization time of polymethyl methacrylate

[0052]

[0053] Comparative Example 2

[0054] 2.0g of samarium metal powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric acid triamide, stirred and reacted at 90℃ for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was prepared by separation. 10mL of 0.1mol / L samarium diiodide / hexamethylphosphoric acid triamide solution was added to 10mL of methyl methacrylate and polymerized at 35℃. The polymerization rate was significantly accelerated, and the polymer product was in a gel state. The molecular weight and The value is unpredictable.

[0055] Comparative Example 3

[0056] 2.0g of metal samarium powder and 0.51g of iodine were added to 20mL of hexamethylphosphoric triamide, stirred and reacted at 90°C for 48 hours, and a 0.1mol / L samarium diiodide / hexamethylphosphoric triamide solution was prepared by separation. 0.4mL of 0.1mol / L samarium diiodide / hexamethylphosphoric triamide solution was taken, 9.6mL of hexamethylphosphoric triamide was added to dilute, and mixed evenly to obtain a samarium diiodide solution with a concentration of 0.004mol / L, and then 10mL of methyl methacrylate was added, and polymerization was carried out at 35°C, and no polymerization product was obtained.

[0057] From the above results, it can be seen that according to the single electron transfer initiated controlled radical polymerization method of the present invention, the polymerization of olefin monomers is initiated by using a low concentration of 0.009-0.055 mol / L samarium diiodide / hexamethylphosphoric acid triamide solution. The polymerization kinetics ln([M]0 / [M]) of Examples 1-6 increases linearly with the increase of polymerization time, the molecular weight of the polymer is controllable, and the molecular weight distribution is The value is lower than 1.4, and the lowest value can reach 1.16, indicating that the growth species of the polymerization has the property of "activity" and exhibits the characteristics of controlled polymerization. The polymerization of Examples 1 to 6 can be terminated by DPPH, but not by water, indicating that the growth species is a free radical and the polymerization belongs to controlled free radical polymerization. The concentration of the growth free radical in Examples 1 to 6 is between 10 -4 mol / L, which is much higher than the steady-state free radical concentration of ordinary free radical polymerization ~10 -8 mol / L, so its polymerization rate is fast, comparable to that of ordinary free radical polymerization.

[0058] Compared with Example 1, Comparative Examples 1 and 2 use samarium diiodide / hexamethylphosphoric acid triamide solution with a concentration higher than 0.055 mol / L to initiate the polymerization of methyl methacrylate. The polymerization kinetics ln([M]0 / [M]) does not increase linearly with the increase of polymerization time, and the polymerization product shows gel and cross-linking phenomena, and the polymerization is uncontrollable. The polymerization system of Comparative Examples 1 and 2 is not terminated by DPPH, but can be terminated by water, indicating that the growing active species are not free radicals. The samarium diiodide / hexamethylphosphoric acid triamide solution with a concentration higher than 0.055 mol / L in Comparative Examples 1 and 2 can initiate the polymerization of non-olefin monomer ε-caprolactone. In view of the single electron transfer property of samarium diiodide, the active species initiating the polymerization in Comparative Examples 1 and 2 should be anions, indicating that as the concentration of samarium diiodide / hexamethylphosphoric acid triamide solution increases, its initiation of polymerization changes from a free radical process to an anionic process. In the anionic polymerization of methyl methacrylate, the anionic active species easily undergoes nucleophilic reaction to the carbonyl group within or between molecules, resulting in side reactions such as cyclization, grafting, crosslinking and chain termination. Therefore, the polymerization kinetics of Comparative Examples 1 and 2 no longer show linear growth, and the polymerization products show gelation. Comparative Example 3 uses a samarium diiodide / hexamethylphosphoric triamide solution with a concentration lower than 0.009 mol / L to initiate polymerization, and no polymerization product is produced, indicating that the initiation is invalid. This ineffective initiation may be caused by a small amount of impurities remaining in the polymerization container or the polymerization system, and the samarium diiodide / hexamethylphosphoric triamide with a concentration lower than 0.009 mol / L is not enough to consume these impurities and then initiate polymerization.

[0059] The above results show that the single electron transfer initiated controlled radical polymerization method of the present invention uses a 0.009-0.055 mol / L low concentration of samarium diiodide / hexamethylphosphoric acid triamide solution to initiate the polymerization of olefin monomers, and the polymerization has the properties of controlled free radical polymerization, and can prepare a olefin monomer with a precisely controlled molecular weight and a narrow molecular weight distribution. of polymers.

Claims

1. A method for controlled free radical polymerization initiated by single electron transfer, characterized in that: The following steps are involved: A low concentration of samarium diiodide / hexamethylphosphoric acid triamide solution is used to initiate controlled free radical polymerization of olefin monomers, and the propagating free radicals have a negative charge and have an "active" property; the concentration of samarium diiodide in the low concentration of samarium diiodide / hexamethylphosphoric acid triamide solution is 0.009-0.055 mol / L.

2. The method for controlled free radical polymerization initiated by single electron transfer according to claim 1, characterized in that: The main steps are as follows: first, a samarium diiodide solution with a concentration of 0.1 mol / L is prepared using hexamethylphosphoric triamide as a solvent, and then hexamethylphosphoric triamide is added to dilute it to obtain a low concentration of samarium diiodide / hexamethylphosphoric triamide solution, and then an olefin monomer is added to initiate controlled free radical polymerization of the olefin monomer.

3. The method for controlled free radical polymerization initiated by single electron transfer according to claim 2, characterized in that: The following steps are involved: S1, adding sodium metal flakes to hexamethylphosphoric triamide to remove water, and then purifying by reduced pressure distillation; S2, adding anhydrous sodium sulfate to the olefin monomer to remove water, and then purifying by reduced pressure distillation; S3, adding measured samarium metal powder and iodine into the hexamethylphosphoric acid triamide purified in step S1, and preparing a 0.1 mol / L samarium diiodide / hexamethylphosphoric acid triamide solution by separation after the reaction is completed, and the reaction process is protected by nitrogen; S4, diluting the 0.1 mol / L samarium diiodide / hexamethylphosphoric triamide solution prepared in step S3 with the hexamethylphosphoric triamide purified in step S1 to obtain a low concentration samarium diiodide / hexamethylphosphoric triamide solution, and then adding an olefin monomer to initiate controlled free radical polymerization of the olefin monomer, and protecting the reaction process with nitrogen.

4. The method for controlled free radical polymerization initiated by single electron transfer according to claim 3, characterized in that: The molar ratio of the samarium metal powder to the iodine in step S3 is ≥ 6.5; the reaction is carried out by stirring at 85-95° C. for more than 48 hours.

5. The method for controlled free radical polymerization initiated by single electron transfer according to claim 4, characterized in that: The amount of the samarium metal powder used should be greater than the amount of iodine used. Based on 20 mL of hexamethylphosphoric triamide, the amount of iodine used is 0.51 g, i.e., 0.002 mol, and the amount of the samarium metal powder used is 2.0 g, i.e., 0.013 mol.

6. The single electron transfer-initiated controlled radical polymerization method according to claim 3, characterized in that: When preparing the samarium diiodide / hexamethylphosphoric acid triamide solution with a concentration of 0.1 mol / L, the obtained samarium diiodide solution is the supernatant liquid for separating the remaining metal samarium powder.

7. The single electron transfer-initiated controlled radical polymerization method according to claim 3, characterized in that: The polymerization temperature of the controlled free radical polymerization of the olefin monomer is 25-60°C.

8. The single electron transfer-initiated controlled radical polymerization method according to claim 3, characterized in that: The vinyl monomer is methyl methacrylate, styrene, methyl acrylate or acrylonitrile.

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