A living polymerization method based on pulsed chain transfer

Abstract

The present application relates to a polymer synthesis method, in particular to a living polymerization method based on pulsed chain transfer. The polymerization method comprises chain transfer reaction stage and chain growth reaction stage alternately, and one chain growth reaction stage and one chain transfer reaction stage constitute a reaction cycle; in the chain transfer reaction stage, the whole reaction system is dominated by chain transfer reaction; in the chain growth reaction stage, the whole reaction system is dominated by the chain growth reaction of living polymerization; the living polymerization method further comprises a trigger condition, which makes the whole reaction system switch between the chain growth reaction stage and the chain transfer reaction stage; the trigger condition is a reaction condition which can be accurately controlled or a chemical condition which can be removed or changed. The present application can reduce the amount of living polymerization initiator and improve the controllability of the reaction system, and is especially suitable for preparing polymers with expected molecular weight distribution range or block polymers with expected sequence structure.

Description

Technical Field

[0001] This invention relates to a method for synthesizing polymers, and more specifically to a living polymerization method based on pulsed chain transfer. Background Technology

[0002] Living polymerization, coordination chain transfer polymerization, and chain shuttle polymerization are three different polymerization methods. Living polymerization is a chain polymerization reaction characterized by the fact that the chain growth active center does not undergo chain transfer or chain termination during the reaction. This means that the polymer chain can continue to grow until the monomer is exhausted. Living polymerization has three main characteristics: (1) During the living polymerization process, the chain growth active center does not undergo chain transfer or chain termination, so the polymer chain can continue to grow. (2) By controlling the ratio of monomer to initiator, the molecular weight of the polymer can be precisely controlled. (3) When the reaction system contains multiple molecules of initiator, since all chains start to grow at the same time and at similar rates, the resulting polymer has a narrow molecular weight distribution. These unique advantages make it an important tool for synthesizing high-performance polymer materials, especially narrow molecular weight distribution polymers and block copolymers. Common living polymerization systems include anionic living polymerization (such as the polymerization of styrene under alkyl lithium initiation), cationic living polymerization (such as the polymerization of isobutylene under specific conditions), free radical living polymerization (such as atom transfer radical polymerization (ATRP) and nitrogen oxide stable free radical polymerization (NMP), coordination living polymerization (such as the polymerization of olefins under metal catalysts), etc. However, living polymerization methods have a major bottleneck: each initiator molecule can only generate one polymer chain. This chain growth pattern necessitates a large amount of initiator to prepare low molecular weight polymers, significantly increasing costs and limiting their industrial-scale application.

[0003] Coordination chain transfer polymerization (CCTP) is a polymerization method that uses organometallic compounds (such as diethylzinc or dibutylmagnesium) as chain transfer agents to achieve the cyclic regeneration of the catalyst (or initiator) during chain growth. CCTP can be figuratively understood as a process in which the catalyst "travels back and forth" between multiple active chains. After adding several monomers to one chain, the catalyst transfers the active end of that chain to the chain transfer agent for "temporary storage" while quickly moving to another chain to add more monomers. Notably, the active chains previously "stored" at the chain transfer agent may also return to the catalyst to continue growth. This cycle repeats, allowing a small amount of catalyst to rapidly switch and coordinate between different chains under the mediation of the chain transfer agent. This enables the simultaneous and steady expansion of multiple polymer chains with only a small amount of catalyst, achieving precise control over molecular weight and distribution. For example, patent WO2016180539A1 (corresponding to Chinese patent CN107848908A) discloses a method for oligomerizing olefins via coordination chain transfer polymerization. By introducing chain substitution catalysts and chain shuttles (i.e., chain transfer agents, such as dialkylzinc or trialkylaluminum), the amount of polymerization catalyst used is reduced, making it suitable for preparing polymers such as low molecular weight polyethylene. As another example, patent CN112812211A describes a method for preparing cyclic olefin copolymers using CCTP and for controlling their molecular weight. This achieves efficient control of the molecular weight of ethylene and norbornene copolymers. Furthermore, US2014221586 discloses a method for stereoselective active coordination chain transfer polymerization. This method can produce polyolefins with highly stereoregular stereochemical microstructures.

[0004] Chain shuttle polymerization (CSP) is a special polymerization technique that combines the advantages of coordination polymerization with the use of chain shuttling agents (CSAs) to achieve chain transfer between different active sites. This allows the simultaneous use of multiple different catalysts within a single reaction system, each responsible for generating different types of polymer segments. This polymerization method was proposed by Daniel et al. (WO2005090427A2, corresponding to Chinese patent CN1976965B). CSP is developed based on CCTP technology, and its core lies in introducing two catalysts with different properties into the CCTP system to catalyze two monomers or two polymerization reactions, respectively. The unique feature of CSP technology is that it not only inherits the dynamic recycling mechanism of catalysts and chain transfer agents in CCTP, but also achieves precise copolymerization of different types of monomers through the "shuttle" effect between the two catalysts. For example, one catalyst is responsible for initiating the polymerization of nonpolar monomers (such as ethylene or propylene), while the other catalyst is suitable for the polymerization of polar monomers (such as carbonyl or hydroxyl groups), and the two work together in the same system through the chain transfer agent. This technology significantly expands the applicability of CCTP, and is particularly suitable for the efficient synthesis of multifunctional block copolymers.

[0005] Theoretically, adding a chain transfer agent to a living polymerization system allows a single initiator (catalyst) molecule to initiate the formation of multiple polymer chains, thereby reducing the amount of catalyst required. For example, in the anionic living polymerization system of butadiene, toluene can act as a chain transfer agent, reducing the molecular chain length of the product. (Kume, Shouji, et al. "Anionic telomerizations of butadiene with aromatic hydrocarbons." Die MakromolekulareChemie: Macromolecular Chemistry and Physics 84.1 (1965): 137-146.). CN107922528B discloses a catalytic system containing a vinyl aluminum transfer agent, which can efficiently produce polymers.

[0006] Although both CCTP and CSP can regulate the molecular weight distribution of the products to some extent, the polymerization methods of CCTP and CSP have the following problems:

[0007] First, both CCTP and CSP polymerization methods require the use of large amounts of organometallic compounds (such as diethylzinc, di-n-butylmagnesium, triethylaluminum, triisobutylaluminum, etc.) as chain transfer agents. These organometallic compounds are expensive, highly dangerous, and due to the large amount added in the early stage, there are more residues in the later stage, which increases the material cost.

[0008] Secondly, and more importantly, in these existing technologies, the reactive monomers, initiators, and chain transfer agents are all added to the reaction system. Although the chain transfer agent can reduce the molecular weight of the polymer product without increasing the amount of catalyst, the chain growth and chain transfer during the polymerization process are highly random. At the same time, both chain growth and chain transfer occur in the reaction system, which causes the reaction system to lose its precise "controllable" characteristics. The molecular weight distribution of the polymer product is still very wide (large PDI), and it is difficult to prepare block polymers with controllable sequence structure.

[0009] Furthermore, CCTP and CSP lack the advantage of precisely controlling polymer molecular weight found in traditional living polymerization. In traditional living polymerization, since one initiator molecule initiates the formation of a polymer chain until all monomers are consumed, the polymer molecular weight is inversely proportional to the amount of initiator when the monomer amount is fixed. This allows researchers to conveniently and precisely control the polymer molecular weight by adjusting the initiator-monomer ratio. However, for polymerization methods such as CCTP and CSP, it is difficult to precisely control the molecular weight of the polymer product by controlling the initiator / monomer ratio, resulting in poor controllability of the polymerization reaction. Therefore, it is difficult to synthesize polymers that accurately meet the expected molecular weight distribution range. Summary of the Invention

[0010] (a) Technical problems to be solved

[0011] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a living polymerization method based on pulsed chain transfer. This method can not only reduce the amount of initiator used in the living polymerization system and reduce the cost of polymer preparation, but also greatly improve the "controllability" of the reaction system. It is especially suitable for preparing polymers with expected molecular weight distribution ranges or block polymers with expected sequence structures, thus realizing precise and controllable polymer synthesis.

[0012] (II) Technical Solution

[0013] In a first aspect, the present invention provides a living polymerization method based on pulsed chain transfer, which includes alternating chain transfer reaction stages and chain growth reaction stages, wherein an adjacent chain growth reaction stage and a chain transfer reaction stage constitute a reaction cycle.

[0014] In the chain transfer reaction stage, the entire reaction system is dominated by chain transfer reaction; in the chain growth reaction stage, the entire reaction system is dominated by chain growth reaction of living polymerization; the living polymerization method also includes triggering conditions, which enable the entire reaction system to switch between the chain growth reaction stage and the chain transfer reaction stage; the triggering conditions are reaction conditions that can be precisely controlled or chemical substance conditions that can be eliminated or changed; the reaction conditions are at least one of temperature conditions, light conditions, and pressure; the chemical substance conditions are at least one of the solvent of the reaction system, the reaction atmosphere, and the auxiliary agent in contact with the reactants.

[0015] According to a preferred embodiment of the present invention, the living polymerization method is an anionic living polymerization system or a coordination polymerization system.

[0016] According to a preferred embodiment of the present invention, the anionic living polymerization system comprises a polymerization monomer, an initiator, a structure modifier, a chain transfer promoter, and a chain transfer agent; the polymerization monomer is at least one selected from butadiene, isoprene, styrene, isoprene, myrcene, and ethylene; the initiator is an alkyllithium or alkylsodium containing 1 to 20 carbon atoms; the structure modifier is a Lewis base; the chain transfer promoter is a potassium alkoxide, alkyl potassium, or amino potassium containing 1 to 20 carbon atoms; the chain transfer agent is at least one selected from benzene, alkylbenzene compounds containing 7 to 15 carbon atoms, and amine compounds containing 2 to 10 carbon atoms; the addition amounts of the structure modifier and the chain transfer promoter in the polymerization system are not simultaneously zero.

[0017] In this system, the chain transfer agent also functions as a reaction solvent. In some embodiments, the chain transfer agent in the anionic living polymerization system is a reaction solvent (without additional reaction solvent). In other embodiments, the anionic living polymerization system further includes a reaction solvent, such as an alkane organic solvent containing 4 to 12 carbon atoms. In this case, the chain transfer agent and the alkane organic solvent work together to function as a solvent.

[0018] According to a preferred embodiment of the present invention, the initiator includes at least one selected from n-butyllithium, sec-butyllithium, tert-butyllithium, and n-pentyl sodium; the chain transfer agent is at least one selected from toluene, p-xylene, m-xylene, mesitylene, and ethylbenzene; and the chain transfer agent is also the reaction solvent of the anionic living polymerization system.

[0019] According to a preferred embodiment of the present invention, the structure modifier (or polarity modifier) ​​is a tertiary amine, secondary amine, or ether compound containing 3 to 20 carbon atoms; preferably, the structure modifier is at least one of dipyrrolidinyl ethane, dipiperidine ethane, tetramethylethylenediamine, and diethylene glycol dimethyl ether; the transfer promoter is at least one selected from potassium tert-butoxide, potassium tert-pentoxide, potassium menthol, potassium ethoxide, potassium n-pentyl, potassium n-butyl, potassium isooctoxide, and potassium diisopropylamino.

[0020] According to a preferred embodiment of the present invention, the triggering condition is a temperature condition. The method of switching the entire reaction system between the chain growth reaction stage and the chain transfer reaction stage by adjusting the temperature condition is as follows: adjusting the temperature of the reaction system to -30°C to 60°C to make the reaction system enter the chain growth reaction stage; adjusting the temperature of the reaction system to 50°C to 120°C to make the reaction system enter the chain transfer reaction stage.

[0021] According to a preferred embodiment of the present invention, the amount of the structure modifier added to the polymerization system is 0 to 10 times the molar amount of the initiator, and the amount of the transfer promoter is 0 to 0.2 times the molar amount of the initiator.

[0022] According to a preferred embodiment of the present invention, preferably, the duration of the chain transfer reaction phase is 5 to 300 min and the duration of the chain growth reaction phase is 5 to 300 min within one reaction cycle.

[0023] The reaction cycle is determined based on the expected molecular weight of the polymer to be synthesized, and the number of cycles is determined based on the expected mass of the polymer and the molar amount of initiator. For example, if the reaction system contains N molecules of initiator, and the polymerization system undergoes a chain growth reaction stage and a chain transfer reaction stage for M cycles by adjusting the temperature conditions, and the duration of each chain growth reaction stage and chain transfer reaction stage is set, then theoretically, the system can produce polymers with N×M expected chain lengths.

[0024] According to a preferred embodiment of the present invention, the chain growth reaction stage lasts until the polymeric monomers are exhausted; the chain transfer reaction stage lasts for 5 to 300 minutes (the duration of the chain transfer reaction stage should ensure that all initiators are regenerated); after one reaction cycle, polymeric monomers are added to the reaction system before entering the chain growth reaction stage of the next reaction cycle. In the synthesis of block polymers, the chain growth reaction stage first consumes the initially added first monomer, and once the first monomer is exhausted, the second monomer is immediately added until the added monomers are exhausted, thus completing one chain growth reaction stage. The polymerization method of this embodiment can more precisely control the distribution range of polymer molecular weight and is particularly suitable for preparing block polymers with desired sequence structures.

[0025] When the polymer to be prepared is a homopolymer, the same type of monomer is added after one reaction cycle and before the chain growth reaction stage of the next reaction cycle. When the polymer to be prepared is a block copolymer, after the polymerization of one monomer in one reaction cycle is completed and before chain transfer occurs, another monomer is immediately added to the reaction system. After chain growth is completed, the chain transfer reaction occurs, and then the chain growth reaction stage of the next reaction cycle begins. That is, two or more reactive monomers of the block copolymer are added sequentially according to the sequence structure of the block copolymer within the same chain growth reaction stage of the same reaction cycle.

[0026] Secondly, the present invention provides an anionic living polymerization method based on pulsed chain transfer, which includes: a polymerizing monomer, an initiator, a structure regulator, a chain transfer promoter, and a reaction solvent;

[0027] The polymerization monomer is at least one selected from butadiene, isoprene, styrene, isoprene, myrcene, and ethylene; the initiator is an alkyllithium or alkylsodium containing 1 to 20 carbon atoms; the structure modifier is a Lewis base; the chain transfer promoter is a potassium alkoxide, alkyl potassium, or amino potassium containing 1 to 20 carbon atoms; wherein the addition amount of the structure modifier and the chain transfer promoter in the polymerization system is not simultaneously zero; the reaction solvent is a solvent that can act as a chain transfer agent, and the reaction solvent is at least one selected from benzene, alkylbenzene compounds containing 7 to 15 carbon atoms, and amine compounds containing 2 to 10 carbon atoms;

[0028] During the polymerization process, the temperature is controlled to switch the entire reaction system between the chain growth reaction stage and the chain transfer reaction stage, and an adjacent chain growth reaction stage and a chain transfer reaction stage constitute a reaction cycle; in the chain transfer reaction stage, the entire reaction system is dominated by the chain transfer reaction; in the chain growth reaction stage, the entire reaction system is dominated by the chain growth reaction of living polymerization.

[0029] The switching method is as follows: the temperature of the reaction system is adjusted to -30℃ to 60℃, so that the reaction system enters the chain growth reaction stage; the temperature of the reaction system is adjusted to 50℃ to 120℃, so that the reaction system enters the chain transfer reaction stage; and so on, several chain growth reaction stages are completed in a cycle until the polymer of the expected quality is obtained.

[0030] According to a preferred embodiment of the present invention, the amount of the structure modifier added to the polymerization system is 0 to 10 times the molar amount of the initiator, and the amount of the transfer promoter is 0 to 0.2 times the molar amount of the initiator.

[0031] According to a preferred embodiment of the present invention, the initiator is at least one selected from n-butyllithium, sec-butyllithium, tert-butyllithium, and n-pentyl sodium; the reaction solvent is at least one selected from toluene, p-xylene, m-xylene, mesitylene, and ethylbenzene. The reaction solvent also acts as a chain transfer agent.

[0032] According to a preferred embodiment of the present invention, the structure modifier is a tertiary amine, secondary amine, or ether compound containing 3 to 20 carbon atoms; preferably, the structure modifier is at least one of dipyrrolidinyl ethane, dipiperidine ethane, tetramethylethylenediamine, and diethylene glycol dimethyl ether; the transfer promoter is at least one selected from potassium tert-butoxide, potassium tert-pentoxide, potassium menthol, potassium ethoxide, potassium n-pentyl, potassium n-butyl, potassium isooctoxide, and potassium diisopropylamino.

[0033] According to a preferred embodiment of the present invention, the reaction cycle is determined based on the molecular weight of the polymer to be synthesized, and the number of cycles is determined based on the mass of the polymer to be prepared and the molar amount of the initiator.

[0034] (III) Beneficial Effects

[0035] This invention presents a trigger-condition controlled active polymerization method. This method artificially adjusts the trigger conditions to switch the entire reaction system between chain propagation and chain transfer reactions. Furthermore, it stops all chain transfer reactions when the chain propagation stage begins, and stops all chain propagation reactions when the chain transfer reaction stage begins. Compared to existing technologies, this invention achieves the following technical effects:

[0036] 1. Reduce the amount of initiator or chain transfer agent used to lower polymerization costs and reduce the residual amount of initiator or chain transfer agent in the product. The role of the chain transfer reaction stage is to release and regenerate the initiator from the active center of the reaction chain in living polymerization, allowing the regenerated initiator to participate in the growth reaction of another polymerization chain. Since each chain transfer will result in the regeneration of the initiator (or catalyst) to initiate the next round of chain growth reaction, theoretically, only one molecule of initiator is needed in a reaction system, and all monomers are consumed through multiple rounds of chain growth and chain transfer cycles.

[0037] 2. It facilitates more precise control of the polymer molecular weight distribution range and makes it easier to synthesize products with a lower polymer molecular weight distribution (PDI). Because each initiator molecule is regenerated after each chain transfer and subsequent chain growth, and has the same probability and speed of initiating new polymer chains, after multiple chain growth-chain transfer cycles, several polymer products (determined by the number of cycles) with the expected chain length can be obtained, and these polymer products have a narrow molecular weight distribution. Therefore, the polymerization method of this invention not only improves the utilization rate of the initiator but also allows for more precise control of the final polymer molecular weight and distribution.

[0038] 3. Suitable for preparing block polymers with controllable sequence structures. Since the entire reaction system enters the chain transfer reaction stage and simultaneously stops the molecular chain growth reaction under the control of triggering conditions, or enters the chain growth stage and simultaneously stops the chain transfer reaction stage under the control of triggering conditions, the corresponding polymerizing monomers can be added sequentially within the chain growth reaction stage of one reaction cycle according to the expected sequence structure of the block polymer (the other monomer is added after the polymerization of the previous monomer is completed), thereby obtaining a block polymer with the expected sequence structure.

[0039] 4. In the anionic living polymerization system, the triggering condition is temperature. That is, during the anionic living polymerization process, chain growth and chain transfer exhibit sensitive temperature response, making temperature changes a "switch" for chain growth and chain transfer. Controlling the living polymerization process by temperature simplifies the operation, reduces the use of additional reagents, and provides a more precise control method compared to other possible triggering conditions, such as solvent changes, alterations to the reaction atmosphere, or the use of contact additives. This makes the switching between chain growth and chain transfer faster and more efficient, thereby reducing the formation of byproducts and avoiding the problem of substance residues. It also reduces the use of unnecessary chemical reagents, which is beneficial to environmental protection. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the process of homopolymer preparation using the trigger-condition controlled living polymerization method of the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the process of preparing block polymers using the trigger-condition controlled living polymerization method of the present invention.

[0042] Figure 3 The color change of the reaction system during the chain growth reaction stage and the chain transfer reaction stage in Example 1.

[0043] Figure 4 The GPC curve of polybutadiene obtained by 20 cycles of pulsed chain transfer living polymerization in Example 1 is shown.

[0044] Figure 5 The image shows the GPC curve of the styrene-butadiene copolymer obtained after 5 cycles of pulsed chain transfer living polymerization in Example 3.

[0045] Figure 6 The image shows the 1H NMR spectrum of polybutadiene obtained after 20 cycles of pulsed chain transfer living polymerization in Example 1.

[0046] Figure 7The image shows the 1H NMR spectrum of the styrene-butadiene copolymer obtained after 5 cycles of pulsed chain transfer living polymerization in Example 3. Detailed Implementation

[0047] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The core of this invention is to introduce triggering conditions into the living polymerization system, causing the entire system to alternate between chain growth and chain transfer reaction stages. Through the chain transfer reaction, all the initiator in the polymerization system is regenerated, preparing for the initiation of a new chain growth reaction. This cycle is repeated multiple times, allowing a single initiator molecule to be reused repeatedly. Each chain growth reaction stage is a purely living polymerization process. Because chain transfer is reversible, a single initiator molecule can participate in chain growth and termination in multiple cycles, ultimately synthesizing several chains. This polymerization method significantly improves initiator utilization, reduces production costs, and enhances the controllability of polymerization. In one chain growth-chain transfer cycle, after chain growth (living polymerization) is completed, chain transfer is initiated and the chain growth reaction is stopped by changing reaction conditions (such as temperature and light conditions) or controlling the timing of adding the chain transfer agent / promoter. After chain transfer is completed, the reaction conditions are changed again or the timing of removing the chain transfer agent / promoter is controlled to initiate a new chain growth reaction. One chain growth and one chain transfer constitute one cycle. Chain transfer enables the regeneration of the initiator (or catalyst). These regenerated initiators can then initiate living polymerization again in the next cycle. By repeating this cyclic process, a large quantity of the desired polymer can be prepared using a small amount of initiator (theoretically only one molecule of initiator is needed). It can be seen that the number of cycles is the number of initiator regenerations, and is approximately equal to the number of polymer chains that each initiator molecule can initiate.

[0049] In the living polymerization system of this invention, determining controllable triggering conditions to control the switching between chain transfer and chain growth in the reaction system is key to achieving the desired outcome. A triggering condition is a reaction condition that can be precisely controlled or a chemical substance condition that can be removed or modified. The reaction condition can be at least one of temperature, light, and pressure, while the chemical substance condition can be at least one of the solvent, reaction atmosphere, and auxiliary agent in contact with the reactants. Reaction conditions are externally imposed, making them easier to precisely control and preventing the introduction of new chemical reagents into the reaction system; therefore, they are a preferred triggering condition. Chemical substances are often more difficult to control, but for reaction atmospheres or solvent systems, rapid addition / removal operations can be achieved through methods such as suction. These reaction atmospheres or solvents can act as chain transfer agents or chain transfer promoters in the reaction system. In the presence of a certain reaction atmosphere, the reaction system is in the chain growth stage, while removing or replacing the reaction atmosphere causes the reaction system to enter the chain transfer stage and stops chain growth. In summary, the triggering condition should be a means that is easy to control or modify, easy to implement, has a rapid response, and does not produce any residue. The living polymerization method of the present invention is applicable to anionic living polymerization systems or coordination polymerization systems.

[0050] For anionic living polymerization systems, this invention provides an initiator (alkyllithium / alkylsodium) - structure modifier (Lewis base, which can be a tertiary amine, secondary amine, or ether compound containing 3 to 20 carbon atoms) - chain transfer promoter (potassium alkoxide / alkylpotassium / aminopotassium) - chain transfer promoter (benzene, alkylbenzene, or an amine compound containing 2 to 10 carbon atoms) system. In this living polymerization system, the Lewis base also acts as a chain transfer promoter; therefore, the Lewis base and the chain transfer promoter can coexist or only one of them can be added. This polymerization system can catalyze the polymerization of monomers such as butadiene, isoprene, styrene, isoprene, ethylene, and myrcene. This polymerization system does not undergo chain transfer at lower temperatures, but rapidly induces chain transfer reactions with the chain transfer promoter (benzene, alkylbenzene, or an amine compound) at higher temperatures. Therefore, in this anionic living polymerization system, the occurrence of chain transfer or chain growth can be controlled by intermittent heating and cooling. When chain transfer occurs, the polymerization system is dominated by chain transfer, while chain growth is essentially halted (ideally, it stops, but individual chain growth cannot be ruled out). Conversely, when chain growth occurs, the polymerization system is dominated by chain growth, while chain transfer is essentially halted (ideally, it stops, but individual chain transfer at active sites cannot be ruled out). In this invention, this alternating chain transfer-chain growth reaction mode based on triggering conditions is termed Pulse Chain Transfer Polymerization (PTCP).

[0051] The preferred embodiment of the anionic living polymerization system of the present invention comprises a polymerizing monomer, an initiator, a structure modifier, a chain transfer promoter, and a solvent. The solvent is a solvent with chain transfer agent properties or a mixed solvent composed of a chain transfer agent and an alkane organic solvent with 4 to 12 carbon atoms. The initiator is a substance capable of initiating anionic living polymerization, including but not limited to alkyllithium or alkylsodium containing 1 to 20 carbon atoms, such as n-butyllithium, sec-butyllithium, tert-butyllithium, and n-pentylsodium. For living polymerization, the amount of initiator is related to the designed molecular weight of the polymer. Since the average molecular weight of theoretically synthesizable polymers in anionic living polymerization is unlimited, the amount of initiator is not limited, but the molar amount of initiator directly affects the rate of polymer chain formation. The structure modifier is a substance that can enhance polymerization selectivity and is a Lewis base, specifically a tertiary amine, secondary amine, or ether compound containing 3 to 20 carbon atoms, such as at least one selected from dipyrrolidinyl ethane, dipiperidine ethane, tetramethylethylenediamine, and diethylene glycol dimethyl ether. In some cases, the polymer system may not be complete without the addition of any structure modifier to obtain a polymer with a specific microstructure. Preferably, the amount of structure modifier is typically 0 to 10 times the molar amount of the initiator. The chain transfer promoter is a substance that promotes chain transfer, and is a potassium alkoxide, alkyl potassium, or amino potassium containing 1 to 20 carbon atoms, such as at least one selected from potassium tert-butoxide, potassium tert-amyloxide, potassium menthol, potassium ethoxide, potassium n-pentyl, potassium n-butyl, potassium isooctoxide, and potassium diisopropylamino. The chain transfer promoter is not always necessary, as the structure modifier also promotes chain transfer; therefore, it can sometimes be used in place of the chain transfer promoter. Preferably, the amount of chain transfer promoter is 0 to 0.2 times the molar amount of the initiator. The reaction solvent is preferably a solvent that itself has chain transfer promoting properties, such as at least one selected from benzene, alkylbenzene compounds containing 7 to 15 carbon atoms, and amine compounds containing 2 to 10 carbon atoms. Preferably, the reaction solvent is any one of toluene, p-xylene, m-xylene, mesitylene, and ethylbenzene. In some embodiments, the reaction solvent is a combination of a specialized chain transfer agent and an alkane organic solvent containing 4 to 12 carbons.

[0052] like Figure 1The schematic diagram illustrates that the active polymerization process of this invention, based on trigger condition control, consists of multiple cycles of chain growth reaction-chain transfer reaction. Each cycle (or each reaction period) includes one chain growth reaction stage and one chain transfer reaction stage. Based on the active polymerization reaction of this invention, the reaction cycle and number of cycles can be determined according to the expected polymer molecular weight, monomer molar amount, and initiator molar amount. Preferably, the reaction temperature of the chain growth reaction stage is -30 to 60°C, and the duration is 5 to 300 min. The reaction temperature of the chain transfer stage is 50°C to 120°C, and the duration is 5 to 300 min, and the reaction temperatures of the chain growth reaction stage and the chain transfer stage should not overlap. At the lower chain growth reaction temperature, butyllithium (initiator) acts as the initiator to initiate the polymerization reaction, and the active polymer chain grows rapidly. At this temperature, the monomer conversion rate is high, and the chain growth rate is fast. At the higher chain transfer reaction temperature, the effects of components such as Lewis bases (structure modifiers) and potassium alkoxides / alkyl potassiums (transfer promoters) become more significant, promoting the occurrence of the chain transfer reaction. For example, potassium alkoxides can temporarily quench active chains, forming stable alkoxides. By repeatedly lowering and raising the temperature, the polymerization system can be switched between chain growth and chain transfer, allowing each active chain to grow and terminate in multiple cycles.

[0053] In the pulsed chain transfer anionic living polymerization system of this invention, it is feasible to add a sufficient amount of monomer at once and control the polymerization system to continuously switch between chain growth and chain transfer by triggering conditions. Compared with existing technologies, this method can also more accurately control the distribution of polymer molecular weight. Furthermore, to further precisely control the molecular weight (PDI) of the product (making it closer to 1), instead of adding a sufficient amount of monomer at the beginning of the reaction, a predetermined molar amount of monomer is added before the chain growth reaction of the next reaction cycle after each chain transfer reaction. This ensures that the chain growth reaction stage of each reaction cycle is a complete living polymerization until all the monomer is exhausted, at which point the chain growth length of each chain growth reaction stage reaches the expected value. In this case, the chain growth length of each reaction cycle is precisely controlled by the molar amount of monomer just added.

[0054] Furthermore, based on the concept of this invention, in order to synthesize block polymers with a predetermined sequence structure, another monomer (such as...) is introduced during the chain growth reaction phase of each reaction cycle. Figure 2(See the schematic diagram). Monomer A is added before the chain growth reaction begins. As the chain growth reaction proceeds, monomer A is depleted. Immediately afterward, monomer B is added to continue the chain growth reaction until monomer B is depleted, completing one chain growth stage. Heating the entire reaction system then initiates the chain transfer reaction stage. Before the next chain growth stage begins, monomer A is added again, and monomer B is added immediately after monomer A is depleted. This process is repeated several times until the desired mass of block copolymer is obtained. This method not only controls the chain length and molecular weight distribution of the block copolymer but also allows for the sequential addition of different monomers according to the copolymer's sequence structure, thereby synthesizing copolymers with two or more monomers.

[0055] The polymerization method proposed in this invention not only improves the utilization rate of initiators and reduces the amount of initiator used, but also allows for more precise control of the molecular weight and distribution of the final polymer. The anionic living polymerization method of this invention is applicable to the homopolymerization or copolymerization of monomers including, but not limited to, 1,3-butadiene (butadiene), isoprene, styrene, ethylene, isoprene, and myrcene.

[0056] In summary, based on the fundamental concept of this invention, its essence lies in introducing intermittent, temperature-sensitive chain transfer reactions into the living anionic polymerization system. By artificially controlling the temperature, the reaction system alternates between chain transfer and chain propagation reactions, thereby achieving the infinite regeneration of the initiator (or catalyst) while retaining the fundamental characteristics of "living polymerization" based on chain propagation in each cycle. Therefore, the living anionic polymerization method of this invention can significantly reduce the amount of initiator used in the synthesis of polyolefins, while maintaining a narrow molecular weight distribution and preparing block polymers with the desired structure. Compared to traditional living polymerization, the polymerization method of this invention reduces the amount of initiator used by a factor directly related to the number of initiator regenerations (i.e., the number of chain transfer reaction stages). When preparing polymers of the desired quality, the amount of initiator used can be as low as one-thirtieth or even less than that used in traditional living polymerization methods. Theoretically, given enough cycles, a sufficient number of polymers can be synthesized using only one molecule of initiator.

[0057] To more clearly illustrate the technical features and effects of the present invention, the following description is provided in conjunction with specific embodiments.

[0058] Example 1

[0059] This embodiment uses butyllithium-initiated butadiene anionic living polymerization as an example to illustrate the reaction process of pulsed chain transfer polymerization (PTCP). The reaction process is as follows:

[0060] Under a dry argon atmosphere, 250 mL of toluene was added to a glass reactor equipped with a thermometer, magnetic stirrer, and high-vacuum valve. Subsequently, 12.5 g of butadiene was absorbed into the toluene by condensation. Using a syringe, 4.2 g of 1,2-dipyrrolidinyl ethane (DiPyr, a Lewis base) and 0.375 mmol of t-BuOK (t-BuOK in n-hexane solution) were sequentially introduced into the reactor. The solution was cooled to approximately 0 °C, and 12.5 mmol of n-butyllithium (a toluene solution of n-butyllithium) was rapidly injected into the reactor using a syringe. Upon addition, the solution immediately turned bright yellow. The mixture was vigorously stirred at 0 °C for 60 min to complete the first chain growth stage (e.g., ...). Figure 3 (a). Then, the reaction mixture is heated to 90°C and stirred for 30 min to complete the first chain transfer reaction stage, at which point the solution turns orange-red (as shown in the image). Figure 3 b), indicating the formation of benzyllithium.

[0061] Next, the mixture was cooled to 0°C, and 12.5g of butadiene was added back in. At this point, benzyllithium acted as an initiator to restart the butadiene polymerization. The reaction was continued at 0°C with vigorous stirring for 60 minutes to complete the second chain growth stage, causing the solution to change from orange-red to yellow (see...). Figure 3 c). Then, the reaction system is heated to 90°C and stirred for 30 min to complete the second chain transfer reaction stage, at which point the solution turns a deep orange-red (e.g., Figure 3 The d indicates that chain transfer occurred and benzyl lithium was generated.

[0062] Next, the mixture was cooled to 0°C for the third time, and 12.5g of butadiene was added to change the solution from a deep orange-red to a deep yellow (e.g., Figure 3 (e), during which a third chain growth reaction occurs. Following this method, the heating-cooling (monomer addition) reaction cycle is repeated 20 times until a sufficient amount of polymer is synthesized.

[0063] Following the above procedure, after 20 cycles of chain growth reaction, 1 mL of ethanol was added to the solution to terminate the polymerization reaction. The solution was then washed with dilute hydrochloric acid to remove impurities, and vacuum dried to obtain 386 g of polymer, with a yield >99%. GPC analysis showed (e.g.) Figure 4 The polymer (as shown) has a number-average molecular weight of 1100 and a molecular weight distribution index (PDI) of 1.12. Nuclear magnetic resonance (NMR) 1H spectroscopy analysis shows (as shown) Figure 6 (As shown) The polymer is high-1,2-polybutadiene, with a 1,2-unit content of 92%. The closer the PDI is to 1, the narrower the molecular weight distribution of the polymer, and the more uniform the individual properties of the polymer material.

[0064] In the reaction system of this embodiment, n-butyllithium is the initiator for anionic living polymerization, and DiPyr, a Lewis base, acts as a structure modifier (or polarity modifier) ​​in the reaction. DiPyr plays two roles in the polymerization process: firstly, it alters the regioselectivity of the polymerization, increasing the content of 1,2-structural units; secondly, it promotes chain transfer reactions. t-BuOK (potassium tert-butoxide) is a chain transfer promoter, accelerating the chain transfer reaction; toluene acts as both a solvent and a chain transfer agent.

[0065] Example 2

[0066] This embodiment uses the butyllithium-initiated anionic living polymerization of isoprene as an example to illustrate the reaction process of pulsed chain transfer polymerization (PTCP). The reaction process is as follows:

[0067] Under dry N2 protection, 125 mL of toluene, 2.1 g of 1,2-dipyrrolidinyl ethane (DiPyr), 0.188 mmol of potassium tert-butoxide (t-BuOK), and 15.0 g of isoprene were added to the reaction vessel. The solution was cooled to 0 °C, and 6.3 mmol of n-butyllithium was added to initiate the polymerization reaction. The solution quickly turned pale yellow. The reaction was carried out at 0 °C with vigorous stirring for 60 min to complete the first chain growth stage. The reaction mixture was then heated to 90 °C and stirred for 30 min to complete the chain transfer stage, during which the solution turned orange-red, indicating the formation of benzyllithium. At this point, the first cycle ended. The solution was then cooled to 0 °C again, and 15 g of isoprene was added again. This time, benzyllithium acted as an initiator to re-initiate the isoprene polymerization. The reaction was continued at 0 °C with vigorous stirring for 60 min to complete the second chain growth stage. The reaction mixture was then heated to 90 °C again and stirred for 30 min to complete the chain transfer stage; at this point, the second reaction cycle ended.

[0068] Following the above procedure, after 10 cycles of chain growth reaction, 1 mL of ethanol was added to the solution to terminate the polymerization reaction. The solution was then washed with dilute hydrochloric acid to remove impurities, and vacuum dried to obtain 148 g of polymer, with a yield of approximately 99%. GPC analysis showed that the polymer had a number-average molecular weight of 2420 and a molecular weight distribution index (PDI) of 1.18. 1H NMR spectroscopy showed that the polymer was high-3,4-polyisoprene, with a combined content of 90% for 3,4- and 1,2- units.

[0069] Example 3

[0070] This embodiment uses butyllithium-initiated butadiene-styrene anionic block copolymerization as an example to illustrate the reaction process of pulsed chain transfer polymerization (PTCP). The reaction process is as follows:

[0071] Under dry N2 protection, 100 mL of toluene, 1.95 g of 1,2-dipyrrolidinyl ethane (DiPyr), 0.173 mmol of potassium tert-butoxide, and 3.0 g of styrene were added to a reaction vessel. The solution was cooled to 15 °C, and 5.75 mmol of n-butyllithium was added to initiate the polymerization reaction. The solution rapidly turned pale yellow. The reaction was carried out at 15 °C with vigorous stirring for 60 min to allow complete styrene conversion; then 6.0 g of butadiene was added, and vigorous stirring was continued at 15 °C for 30 min to complete the first chain growth stage. The reaction mixture was then heated to 90 °C and stirred for 30 min to complete the chain transfer stage, during which the solution turned orange-red, indicating the formation of benzyllithium.

[0072] The solution was then cooled to 15°C again, and 3.0 g of styrene was added back. At this point, benzyllithium acted as an initiator to restart the styrene polymerization. The reaction was continued at 16°C with vigorous stirring for 60 min to ensure complete styrene conversion. Then, 6.0 g of butadiene was added again, and the mixture was stirred vigorously at 15°C for another 30 min to complete the second chain growth stage. Next, the reaction mixture was heated to 90°C and stirred for 30 min to complete the chain transfer stage.

[0073] Following the above method, after repeating the chain growth reaction stage five times, 1 mL of ethanol was added to the solution to terminate the polymerization reaction. The solution was then washed with dilute hydrochloric acid to remove impurities, and after vacuum drying, 44 g of polymer was obtained, with a yield of approximately 98%. GPC analysis showed (e.g.) Figure 5 The polymer (as shown) has a number-average molecular weight of 1637 and a molecular weight distribution index (PDI) of 1.16. Nuclear magnetic resonance (NMR) 1H spectroscopy analysis shows (as shown) Figure 7 As shown, the butadiene structural units in the polymer are mainly 1,2-structural units, accounting for 94% of the total butadiene structural units.

[0074] Examples 4-7

[0075] The polymerization systems of Examples 4-7 are basically the same as those of Example 1, except that the temperature conditions and duration of the chain growth reaction stage and the chain transfer reaction stage are different. The molecular weight distribution index (PDI) of the final synthesized products are shown in Table 1.

[0076] Table 1:

[0077]

[0078] As shown in Table 1, the temperature of the chain growth reaction stage can be set in the range of -30℃ to 60℃, while the temperature of the chain transfer reaction stage can be set in the range of 50℃ to 120℃. Relatively speaking, it is beneficial to obtain a product with a molecular weight distribution index (PDI) closer to 1 when the temperature of the chain growth reaction stage does not exceed 30℃ and the temperature of the chain transfer reaction stage does not exceed 100℃. Under the aforementioned conditions, when the temperature of the chain growth reaction stage is 0℃ and the temperature of the chain transfer reaction stage is 90℃, the PDI of the product is further brought closer to 1.

[0079] Examples 8-11

[0080] The polymerization systems of Examples 8-11 are basically the same as those of Example 1, except that the reaction solvents are different. The molecular weight distribution index (PDI) of the final synthesized products is shown in Table 2.

[0081] Table 2:

[0082]

[0083] As shown in Table 2, the anionic living polymerization system based on pulsed chain transfer of this invention can use various alkylbenzenes as reaction solvents, such as toluene, xylene, trimethylbenzene, or ethylbenzene. Specifically, when toluene, xylene, or mesitylene is used as the reaction solvent in the butadiene anionic living polymerization system initiated by butyllithium, polymerization products with a PDI close to 1 are obtained. Experiments also demonstrate that the reaction solvent can be replaced by amine compounds containing 2 to 10 carbon atoms that are liquid at room temperature.

[0084] Examples 12-14

[0085] The polymerization systems of Examples 12-14 are basically the same as those of Example 1, except that the polymerization monomers are different. The molecular weight distribution index (PDI) of the final synthesized products is shown in Table 3.

[0086] Table 3:

[0087]

[0088] As can be seen from Table 3, the anionic active polymerization method based on pulsed chain transfer of the present invention is applicable to the polymerization of various olefin monomers such as butadiene, styrene, isoprene, isoprene, ethylene, and myrcene, and can obtain polymer products with a PDI close to 1.

[0089] Examples 15-20

[0090] The polymerization systems of Examples 15-20 are basically the same as those of Example 1, except that the types and amounts of Lewis bases (structure modifiers) used are different. The molecular weight distribution index (PDI) of the final synthesized products are shown in Table 4.

[0091] Table 4:

[0092]

[0093] As shown in Table 4, in the anionic living polymerization system based on pulsed chain transfer of the present invention, in addition to DiPyr used in Example 1, at least one Lewis base such as dipiperidine ethane, tetramethylethylenediamine, and diethylene glycol dimethyl ether can also be used as a structure modifier, and all of these can yield polybutadiene products with a polymer PDI close to 1. Relatively speaking, in the butadiene anionic living polymerization system initiated by butyllithium, using DiPyr as a structure modifier and having a molar amount 1-5 times that of the initiator is beneficial for obtaining polymer products with a molecular weight distribution index (PDI) closer to 1. Experiments also show that the Lewis base that can be used as the structure modifier can be any tertiary amine, secondary amine, or ether compound containing 3-20 carbon atoms.

[0094] Examples 21-27

[0095] The polymerization systems of Examples 21-27 are basically the same as those of Example 1, except that the types and amounts of transfer promoters used are different. The molecular weight distribution index (PDI) of the final synthesized products are shown in Table 5.

[0096] Table 5:

[0097]

[0098] As shown in Table 5, in the anionic living polymerization system based on pulsed chain transfer of the present invention, in addition to potassium tert-butoxide (t-BuOK) as used in Example 1, the transfer promoter can also be at least one of potassium tert-amyloxide, potassium ethoxide, potassium menthol, potassium n-butyloxide, potassium n-pentyloxide, potassium isooctoxide, and potassium diisopropylaminooxide, all of which are potassium alkoxides, alkyl potassiums, or amino potassiums (organopotassium), and all can yield polybutadiene products with a polymer PDI close to 1. Relatively speaking, in the butadiene anionic living polymerization system initiated by butyllithium, using t-BuOK, potassium tert-amyloxide, or potassium menthol as transfer promoters, and their molar amounts being 0.03 to 0.05 times the molar amount of the initiator, is beneficial for obtaining polymer products with a molecular weight distribution index (PDI) closer to 1. Experiments also show that the transfer promoter can be any potassium alkoxide, alkyl potassium, or amino potassium containing 1 to 20 carbon atoms.

[0099] Examples 28-30

[0100] The polymerization systems of Examples 28-30 are basically the same as those of Example 1, except that the initiators used are different. The molecular weight distribution index (PDI) of the final synthesized products are shown in Table 6.

[0101] Table 6:

[0102]

[0103] As shown in Table 6, in the anionic living polymerization system based on pulsed chain transfer of the present invention, in addition to using n-butyllithium as the initiator in Example 1, at least one of tert-butyllithium, sec-butyllithium, and n-pentyl sodium can also be used, and all can yield polybutadiene products with a polymer PDI close to 1. Relatively speaking, the PDI of the polybutadiene product initiated by butyllithium is closer to 1, while the PDI of the polybutadiene product initiated by n-pentyl sodium is larger. Experiments also show that the initiator can be any alkyllithium or alkyl sodium containing 1 to 20 carbon atoms.

[0104] Examples 31-32

[0105] The polymerization systems of Examples 31-32 are basically the same as those of Example 1, except that: only a structure modifier was added to the polymerization system of Example 31 without using a transfer promoter, and only a transfer promoter was added to the polymerization system of Example 32 without adding a structure modifier. The molecular weight distribution index (PDI) of the final synthesized products are shown in Table 7.

[0106] Table 7:

[0107]

[0108] As shown in Table 7, in the anionic living polymerization system based on pulsed chain transfer of the present invention, when only one of the structure modifier and the chain transfer promoter is present, the pulsed chain transfer polymerization reaction can proceed normally, and polybutadiene products with a PDI close to 1 can be obtained in both cases. In contrast, when both the structure modifier and the chain transfer promoter are present, and the molar ratio of the structure modifier to the initiator is close to 2 and the molar ratio of the chain transfer promoter to the initiator is close to 0.03, a polymerization product with a PDI even closer to 1 can be obtained.

[0109] In summary, in the anionic living polymerization system based on pulsed chain transfer, the initiator can be selected from at least one of n-butyllithium, tert-butyllithium, sec-butyllithium, and n-pentyl sodium; DiPyr and t-BuOK can coexist in the above reaction system or only one of them can be present. The preferred amount of DiPyr is 0 to 10 times the molar amount of the initiator, and the preferred amount of t-BuOK is 0 to 0.2 times the molar amount of the initiator. Besides DiPyr, the structure modifier can also be a Lewis base such as tetramethylethylenediamine, dipiperidine ethane, or diethylene glycol dimethyl ether. Besides t-BuOK, the chain transfer promoter can also be potassium tert-butoxide, potassium tert-pentoxide, potassium menthol, potassium ethoxide, potassium n-pentyl, potassium n-butyl, potassium isooctoxide, or potassium diisopropylamino. Besides toluene, the reaction solvent can also be alkylbenzenes such as xylene, trimethylbenzene, or ethylbenzene. Different reagents can be selected adaptively according to the specific reaction system composition, such as the type of reactant monomer and the solubility of the reaction solvent.

[0110] The aforementioned specific embodiments share the following common features:

[0111] (1) Temperature acts as a switch to perform a "scissors" effect on chain polymerization, causing the polymer chains to terminate when they reach the desired degree of polymerization. These examples achieve this through simple temperature changes, simplifying the process and reducing the use and residue of additional reagents.

[0112] (2) Multiple uses of initiators: Since chain transfer is reversible, an initiator molecule can participate in chain growth and termination in multiple cycles to synthesize several chains, thereby greatly improving the utilization rate of the initiator. This is an important advantage for industrial applications, as it can significantly reduce production costs and improve efficiency.

[0113] (3) Narrow molecular weight distribution: By precisely controlling the time and magnitude of temperature changes (or other conditions), a high degree of control over the polymer chain length can be achieved, resulting in polymers with a narrow molecular weight distribution. This is highly advantageous for the preparation of high-performance materials.

[0114] (4) Temperature is used as a “switch” to trigger the process, which can reduce byproducts compared to other conditions (changing the solvent environment, using additives, etc.): Compared to traditional chain transfer methods, this method reduces the introduction of additional chemicals, reduces the generation of byproducts, and is more environmentally friendly.

[0115] (5) Reduced byproducts: Compared to traditional chain transfer methods, the polymerization methods in these embodiments reduce the introduction of additional chemicals, decrease the generation of byproducts, and are more environmentally friendly. Due to its simple and efficient operation, this method has the potential to be applied in large-scale industrial production, especially in industries that are cost-sensitive but require high-quality control.

[0116] The method of this invention is expected to bring new breakthroughs to the field of polymer synthesis.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 or all of the technical features. These modifications or substitutions, or combinations of technical features in the above embodiments that do not conflict with each other, can be made in accordance with the manner described in the embodiments. These modifications, substitutions or combinations do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An anionic living polymerization method based on pulsed chain transfer, characterized in that, This includes monomers, initiators, structure modifiers, transfer promoters, and reaction solvents; The polymerization monomer is at least one selected from butadiene, isoprene, styrene, isoprene, myrcene, and ethylene; the initiator is an alkyllithium or alkylsodium containing 1 to 20 carbon atoms; the structure modifier is a Lewis base; the chain transfer promoter is a potassium alkoxide, alkyl potassium, or amino potassium containing 1 to 20 carbon atoms; wherein the addition amount of the structure modifier and the chain transfer promoter in the polymerization system is not simultaneously zero; the reaction solvent is a solvent that can act as a chain transfer agent, and the reaction solvent is at least one selected from benzene, alkylbenzene compounds containing 7 to 15 carbon atoms, and amine compounds containing 2 to 10 carbon atoms; During the polymerization process, the temperature is controlled to switch the entire reaction system between the chain growth reaction stage and the chain transfer reaction stage, and an adjacent chain growth reaction stage and a chain transfer reaction stage constitute a reaction cycle; in the chain transfer reaction stage, the entire reaction system is dominated by the chain transfer reaction; in the chain growth reaction stage, the entire reaction system is dominated by the chain growth reaction of living polymerization. The switching method is as follows: the temperature of the reaction system is adjusted to -30℃ to 60℃, so that the reaction system enters the chain growth reaction stage; the temperature of the reaction system is adjusted to 50℃ to 120℃, so that the reaction system enters the chain transfer reaction stage; and so on, several chain growth reaction stages are completed in a cycle until the polymer of the expected quality is obtained.

2. The anionic living polymerization method according to claim 1, characterized in that, The initiator is at least one of n-butyllithium, sec-butyllithium, tert-butyllithium, and n-pentyl sodium; the reaction solvent is at least one of toluene, p-xylene, m-xylene, mesitylene, and ethylbenzene; the structure modifier is a tertiary amine, secondary amine, or ether compound containing 3 to 20 carbon atoms; the transfer promoter is at least one of potassium tert-butoxide, potassium tert-pentoxide, potassium menthol, potassium ethoxide, potassium n-pentyl, potassium n-butyl, potassium isooctoxide, and diisopropylamino potassium; the reaction cycle is determined according to the expected molecular weight of the polymer to be synthesized, and the number of cycles is determined according to the expected mass of the polymer to be prepared and the molar amount of the initiator.

3. The anionic living polymerization method according to claim 1, characterized in that, The amount of structure modifier added to the polymerization system is 0-10 times the molar amount of the initiator, and the amount of transfer promoter is 0-0.2 times the molar amount of the initiator.

4. The living polymerization method according to claim 1, characterized in that, The chain growth reaction phase lasts until the monomers are exhausted; the chain transfer reaction phase lasts for 5 to 300 minutes; monomers are added to the reaction system before the chain growth reaction phase of the next reaction cycle begins after one reaction cycle ends. In the synthesis of block polymers, the chain growth reaction stage first consumes the initially added first monomer. Once the first monomer is exhausted, the second monomer is immediately added until the added monomer is depleted, thus completing one chain growth reaction stage.

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