Active polymerization method based on pulse type chain transfer

Abstract

The invention relates to a synthesis method of a polymer, in particular to a living polymerization method based on pulse type chain transfer. The polymerization method comprises chain transfer reaction stages and chain propagation reaction stages which are alternately carried out, and one chain propagation reaction stage and one chain transfer reaction stage which are adjacent form a reaction period; in the chain transfer reaction stage, the whole reaction system is dominated by the 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 triggering condition which enables the whole reaction system to be switched between a chain propagation reaction stage and a chain transfer reaction stage. The triggering condition is a reaction condition capable of being accurately regulated and controlled or a chemical substance condition capable of being cleared or changed. The method provided by the invention can reduce the dosage of the active 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 structures.

Description

Technical Field

[0001] The invention relates to a method for synthesizing a polymer, in particular to a living polymerization method based on pulse chain transfer. Background Art

[0002] Living polymerization, coordination chain transfer polymerization and chain shuttling polymerization are three different polymerization methods. Living polymerization is a chain polymerization reaction characterized by the fact that chain transfer or chain termination does not occur at the active center of chain growth 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, chain transfer or chain termination does not occur at the active center of chain growth, 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 initiator molecules, since all chains start to grow at the same time and at similar rates, the molecular weight distribution of the generated polymer is narrow. These unique advantages make it an important tool for the synthesis of 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 initiated by alkyl lithium), cationic living polymerization (such as the polymerization of isobutylene under specific conditions), free radical living polymerization (such as atom transfer radical polymerization ATRP and nitroxide stabilized radical polymerization NMP), coordination living polymerization (such as the polymerization of olefins under metal catalysts), etc. However, the living polymerization method has a major bottleneck: each initiator molecule can only produce one polymer chain. This chain growth mode requires a large amount of initiator to prepare low molecular weight polymers, which significantly increases the cost and limits its application on an industrial scale.

[0003] Coordination chain transfer polymerization (CCTP) is a polymerization method that achieves the recycling of catalysts (or initiators) during chain growth by introducing metal organic compounds (such as diethyl zinc or dibutyl magnesium) as chain transfer agents. CCTP can be figuratively understood as the process of the catalyst "traveling back and forth" between multiple active chains. After the catalyst adds a number of monomers to a chain, it transfers the active end of the chain to the chain transfer agent for "temporary custody or deposit", and quickly goes to another chain to continue adding monomers. It is worth noting that the active chain that was previously "deposited" at the chain transfer agent also has the opportunity to return to the catalyst to continue growing. In this way, a small amount of catalyst can switch and coordinate between different chains at high speed under the mediation of the chain transfer agent, so that only a small amount of catalyst can steadily expand multiple polymer chains at the same time and achieve precise molecular weight and distribution control. For example, patent WO2016180539A1 (corresponding to Chinese patent CN107848908A) discloses a method for olefin oligomerization by coordination chain transfer polymerization, which reduces the amount of polymerization catalyst by introducing chain displacement catalysts and chain shuttling agents (i.e., chain transfer agents, such as dialkyl zinc or trialkyl aluminum, etc.), and is suitable for preparing polymers such as low molecular weight polyethylene. For another example, patent CN112812211A describes a method for preparing cycloolefin copolymers and regulating their molecular weight using the CCTP method. Efficient regulation of the molecular weight of ethylene and norbornene copolymers is achieved. For another example, US2014221586 discloses a method for stereoselective active coordination chain transfer polymerization. This method can produce polyolefins with a highly stereoregular stereochemical microstructure.

[0004] Chain shuttling polymerization (CSP) is a special polymerization technology that combines the advantages of coordination polymerization and uses chain shuttling agents (CSA) to achieve chain transfer between different active centers. This makes it possible to use multiple different catalysts in a reaction system at the same time, each responsible for producing different types of polymer segments. This polymerization method was proposed by Daniel et al. (WO2005090427A2, corresponding to Chinese patent CN1976965B). CSP is developed on the basis of CCTP technology. Its core lies in the introduction of two catalysts with different properties in the CCTP system, which are used to catalyze two monomers or two polymerization reactions respectively. The uniqueness of CSP technology lies in that it not only inherits the mechanism of dynamic recycling regeneration of catalysts and chain transfer agents in CCTP, but also realizes the precise copolymerization of different types of monomers through the "shuttling" effect between the two catalysts. For example, one catalyst is responsible for initiating the polymerization of non-polar monomers (such as ethylene or propylene), while the other catalyst is suitable for the polymerization of polar monomers (such as carbonyl or hydroxyl groups). The two work together in the same system through chain transfer agents. This technology significantly expands the application scope of CCTP and is particularly suitable for the efficient synthesis of multifunctional block copolymers.

[0005] Theoretically, adding a chain transfer agent to an active polymerization system can allow one initiator (catalyst) molecule to initiate the generation of multiple polymer chains, thereby reducing the amount of catalyst used. For example, in a butadiene anion active polymerization system, toluene can act as a chain transfer agent, reducing the molecular chain of the product. (Kume, Shouji, et al. "Anionictelomerizations of butadiene with aromatic hydrocarbons." Die Makromolekulare Chemie: Macromolecular Chemistry and Physics 84.1 (1965): 137-146.). For example, CN107922528B discloses a catalytic system containing a vinyl aluminum transfer agent, which can efficiently produce polymers.

[0006] Although CCTP and CSP can regulate the molecular weight distribution of the product to a certain extent, the polymerization methods of CCTP and CSP have the following problems:

[0007] First, the polymerization methods of CCTP and CSP both require the use of a large amount of metal organic compounds (such as diethyl zinc, di-n-butyl magnesium, triethyl aluminum, triisobutyl aluminum, etc.) as chain transfer agents. These metal organic compounds are relatively expensive and dangerous. In addition, due to the large amount added in the early stage, there are more residues in the later stage, which increases the material cost.

[0008] Second, more noteworthy is that in these prior arts, the reaction monomers, initiators and chain transfer agents are added to the reaction system together. Although the chain transfer agent can reduce the molecular weight of the polymerization product without increasing the amount of catalyst, the occurrence of chain growth and chain transfer in the polymerization process is highly random. At the same time, there are both chain growth and chain transfer in the reaction system, which also makes the reaction system lose its more precise "controllable" characteristics. The molecular weight distribution of the polymerization product is still very wide (PDI is large), and it is difficult to prepare block polymers with controllable sequence structure.

[0009] In addition, CCTP and CSP do not have the advantage of precisely controlling the molecular weight of polymers in traditional living polymerization. In traditional living polymerization, since one molecule of initiator triggers the generation of a polymer chain until all monomers are consumed, when the amount of monomers is determined, the molecular weight of the polymer is inversely proportional to the amount of initiator, so researchers can conveniently and accurately control the molecular weight of the polymer by adjusting the ratio of initiator to monomer. However, it is difficult to precisely control the molecular weight of the polymer product by controlling the ratio of initiator to monomer for the aforementioned polymerization methods such as CCTP and CSP, which makes the controllability of the polymerization reaction very poor, so it is difficult to accurately synthesize polymers that meet the expected molecular weight distribution range. Summary of the invention

[0010] 1. Technical issues to be resolved

[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, which 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 "controllable" characteristics of the reaction system. It is particularly suitable for preparing polymers with an expected molecular weight distribution range or block polymers with an expected sequence structure, thereby achieving precise 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 comprises a chain transfer reaction stage and a chain growth reaction stage performed alternately, and an adjacent chain growth reaction stage and a chain transfer reaction stage constitute a reaction cycle;

[0014] Among them, 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 active polymerization; the active polymerization method also includes a trigger condition, and the trigger condition causes the entire reaction system to switch between the chain growth reaction stage and the chain transfer reaction stage; the trigger condition is a reaction condition that can be precisely controlled or a chemical condition that can be removed or changed; the reaction condition is at least one of temperature conditions, light conditions and pressure; the chemical condition is 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 regulator, a transfer accelerator and a chain transfer agent; the polymerization monomer is at least one of butadiene, isoprene, styrene, isoprene, myrcene and ethylene; the initiator is an alkyl lithium or an alkyl sodium containing 1 to 20 carbon atoms; the structure regulator is a Lewis base, and the transfer accelerator is an alcohol potassium, an alkyl potassium or an amine potassium containing 1 to 20 carbon atoms; the chain transfer agent is at least one of benzene, an alkyl benzene compound containing 7 to 15 carbon atoms and an amine compound containing 2 to 10 carbon atoms; the addition amounts of the structure regulator and the transfer accelerator in the polymerization system are not zero at the same time.

[0017] The chain transfer agent also serves as a reaction solvent. In some embodiments, the chain transfer agent of the anionic living polymerization system is a reaction solvent (without adding a separate reaction solvent). In other embodiments, the anionic living polymerization system further comprises 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 are combined to serve as a solvent.

[0018] According to a preferred embodiment of the present invention, the initiator includes at least one of n-butyl lithium, sec-butyl lithium, tert-butyl lithium and n-pentyl sodium; the chain transfer agent is at least one of 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 regulator (or polarity regulator) is a tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms; preferably, the structure regulator is at least one of dipyrrolidinoethane, dipiperidineethane, tetramethylethylenediamine and diethylene glycol dimethyl ether; the transfer promoter is at least one selected from potassium tert-butoxide, potassium tert-amyl alcohol, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctanoate and potassium diisopropylamine.

[0020] According to a preferred embodiment of the present invention, the trigger condition is a temperature condition, and 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: adjusting the temperature of the reaction system to -30°C to 60°C, so that the reaction system enters the chain growth reaction stage; adjusting the temperature of the reaction system to 50°C to 120°C, so that the reaction system enters the chain transfer reaction stage.

[0021] According to a preferred embodiment of the present invention, the amount of the structure regulator 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, within one reaction cycle, the duration of the chain transfer reaction stage is 5 to 300 minutes, and the duration of the chain extension reaction stage is 5 to 300 minutes.

[0023] The reaction cycle is determined according to the expected molecular weight of the synthesized polymer, and the number of cycles is determined according to the expected mass of the prepared polymer and the molar amount of the initiator. For example, if there are N molecules of initiator in the reaction system, the polymerization system undergoes M cycles of chain growth reaction stage-chain transfer reaction stage by adjusting the temperature conditions, and the duration of each chain growth reaction stage and chain transfer reaction stage is set, then the system can theoretically produce N×M polymers of the expected chain length.

[0024] According to a preferred embodiment of the present invention, the duration of the chain growth reaction stage is until the polymerization monomer is exhausted; the duration of the chain transfer reaction stage is 5 to 300 minutes (the duration of the chain transfer reaction stage needs to ensure that all initiators are regenerated); after a reaction cycle, the polymerization monomer is added to the reaction system before entering the chain growth reaction stage of the next reaction cycle. When synthesizing block polymers, the chain growth reaction stage first consumes the first monomer initially added, and when the first monomer is consumed, the second monomer is immediately added until the added monomer is exhausted, that is, a chain growth reaction stage is completed. The polymerization method of this embodiment can more accurately control the distribution range of polymer molecular weight, and is particularly suitable for preparing block polymers with expected sequence structures.

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

[0026] In a second aspect, the present invention provides an anionic living polymerization method based on pulse chain transfer, which comprises: a polymerization monomer, an initiator, a structure regulator, a transfer promoter and a reaction solvent;

[0027] The polymerization monomer is at least one of butadiene, isoprene, styrene, isoprene, myrcene and ethylene; the initiator is an alkyl lithium or an alkyl sodium containing 1 to 20 carbon atoms; the structure regulator is a Lewis base; the transfer promoter is an alcohol potassium, an alkyl potassium or an amine potassium containing 1 to 20 carbon atoms; wherein the addition amount of the structure regulator and the transfer promoter in the polymerization system is not zero at the same time; the reaction solvent is a solvent that can act as a chain transfer agent, and the reaction solvent is at least one of benzene, an alkyl benzene compound containing 7 to 15 carbon atoms and an amine compound containing 2 to 10 carbon atoms;

[0028] During the polymerization process, the temperature is adjusted 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 active polymerization;

[0029] The switching method is: adjusting the temperature of the reaction system to -30°C to 60°C, so that the reaction system enters the chain growth reaction stage; adjusting the temperature of the reaction system to 50°C to 120°C, so that the reaction system enters the chain transfer reaction stage; according to this method, several chain growth reaction stages are cycled until a polymer of expected quality is obtained.

[0030] According to a preferred embodiment of the present invention, the amount of the structure regulator 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 of n-butyl lithium, sec-butyl lithium, tert-butyl lithium and n-pentyl sodium; the reaction solvent is at least one of 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 regulator is a tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms; preferably, the structure regulator is at least one of dipyrrolidinoethane, dipiperidineethane, tetramethylethylenediamine and diethylene glycol dimethyl ether; the transfer promoter is at least one selected from potassium tert-butoxide, potassium tert-amyloxide, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctanoate and potassium diisopropylamine.

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

[0034] (III) Beneficial effects

[0035] The present invention designs a method of active polymerization based on trigger condition control, which switches the entire reaction system between chain growth reaction and chain transfer reaction by artificially regulating the trigger condition, and stops all chain transfer reaction stages when the chain growth reaction stage is started, and stops all chain growth reactions when the chain transfer reaction stage is started. Compared with the prior art, the present invention can achieve the following technical effects:

[0036] 1. Reduce the amount of initiator or chain transfer agent, reduce the polymerization cost and 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 active polymerization initiator from the active center of the reaction chain, so that the regenerated initiator participates in the growth reaction of another polymerization chain. Since each chain transfer will cause the initiator (or catalyst) to be regenerated in order to trigger the next round of chain growth reaction, theoretically only one molecule of initiator is required in a reaction system, and all monomers will be consumed through multiple rounds of chain growth ~ chain transfer cycles.

[0037] 2. It is conducive to more accurately controlling the molecular weight distribution range of the polymer, and it is easier to synthesize products with a smaller molecular weight PDI. Since each chain transfer occurs, when the chain growth is performed again, each molecule of the initiator is regenerated, and has the same probability and speed to initiate the generation of new polymer chains, so after multiple rounds of chain growth-chain transfer cycles, several (determined by the number of cycles) polymer products with expected chain lengths can be obtained, and these polymer products have a narrower molecular weight distribution. Therefore, the polymerization method of the present invention not only improves the utilization rate of the initiator, but also can more accurately control the molecular weight and distribution of the final polymer.

[0038] 3. Suitable for preparing block polymers with controllable sequence structures. Since the entire reaction system enters the chain transfer reaction stage under the control of trigger conditions and stops the molecular chain growth reaction at the same time, or enters the chain growth stage under the control of trigger conditions and stops the chain transfer reaction stage at the same time, the corresponding polymerization monomers can be added sequentially in the chain growth reaction stage of a reaction cycle according to the expected sequence structure of the block polymer (adding another monomer after the polymerization of the previous monomer is completed), thereby preparing a block polymer with an expected sequence structure.

[0039] 4. In the anionic living polymerization system, the trigger condition is the temperature condition, that is, in the anionic living polymerization process, chain growth and chain transfer have sensitive temperature responsiveness, so that temperature changes constitute the "switch" of chain growth and chain transfer. By "switching" the living polymerization process through temperature regulation, the operation process is simplified and the use of additional reagents is reduced. Compared with other possible trigger conditions, such as solvent changes, changes in reaction atmosphere or the use of contact additives, temperature regulation provides a more precise control method. This makes the switch between chain growth and chain transfer faster and more effective, thereby reducing the formation of by-products and avoiding the problem of material residues. It reduces the use of unnecessary chemical reagents and is beneficial to environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention is a schematic diagram of the process of preparing a homopolymer by the living polymerization method based on trigger condition control.

[0041] Figure 2 The present invention is a schematic diagram of the process of preparing block polymers by the living polymerization method based on trigger condition control.

[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 is shown.

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

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

[0045] Figure 6 This is a hydrogen nuclear magnetic resonance spectrum of the polybutadiene obtained after 20 cycles of living polymerization by pulsed chain transfer in Example 1.

[0046] Figure 7This is a hydrogen nuclear magnetic resonance spectrum of the styrene-butadiene copolymer obtained after 5 cycles of living polymerization by pulsed chain transfer in Example 3. DETAILED DESCRIPTION

[0047] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0048] The core of the present invention is to introduce trigger conditions into the active polymerization system, so that the entire active polymerization system alternately performs chain growth reaction and chain transfer reaction stages, and the initiator of the polymerization system is completely regenerated through the chain transfer reaction, so as to prepare for the re-initiation of a new chain growth reaction, and so on. The cycle is repeated for multiple rounds, so that one molecule of initiator is repeatedly used. Among them, each chain growth reaction stage is a pure active polymerization process. Since the chain transfer is reversible, an initiator molecule can participate in the growth and termination of the chain in multiple cycles, and finally synthesize several chains. By using this polymerization method, the utilization rate of the initiator is greatly improved, the production cost is reduced, and the controllability of the polymerization is improved. In a round of chain growth-chain transfer cycle, after the chain growth (active polymerization) is completed, the chain transfer is started and the chain growth reaction is stopped by changing the reaction conditions (such as temperature conditions, light conditions) or controlling the timing of adding chain transfer agent / promoting transfer agent; when the chain transfer is completed, the reaction conditions are changed again or the timing of removing the chain transfer agent / promoting transfer agent is controlled to start a new round of chain growth reaction. One chain growth and one chain transfer constitute a cycle. Among them, chain transfer realizes the regeneration of initiators (or catalysts). These regenerated initiators can initiate active polymerization again in the next cycle. By repeating the above cycle process, a large amount of desired polymers 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 times the initiator is regenerated, which is also approximately equal to the number of polymer chains that can be generated by each molecule of initiator.

[0049] In the active polymerization system of the present invention, determining a controllable trigger condition to control the reaction system to switch between chain transfer and chain growth is the key to the implementation scheme. The trigger condition is a reaction condition that can be precisely controlled or a chemical condition that can be removed or changed. Among them, the reaction condition can be at least one of temperature conditions, light conditions and pressure, and the chemical condition is at least one of the solvent of the reaction system, the reaction atmosphere and the auxiliary agent in contact with the reactant. The reaction condition is given by the outside world, so it is easier to precisely control and no new chemical reagents are introduced into the reaction system. It is a preferred trigger condition; while the chemical condition is often difficult to control, but for the reaction atmosphere or solvent system, etc., rapid addition / removal operations can also be achieved by suction and other methods. These reaction atmospheres or solvents can act as chain transfer agents or transfer promoters in the reaction system, etc., and the reaction system is in the chain growth reaction stage in the presence of a certain reaction atmosphere. After the reaction atmosphere is pumped out or replaced, the reaction system is prompted to enter the chain transfer reaction stage and stop chain growth. In short, the trigger condition should be a means that is easy to control or change, easy to implement, quick to respond, and does not produce material residues. The living polymerization method of the present invention is applicable to an anionic living polymerization system or a coordination polymerization system.

[0050] For anionic living polymerization system, the present invention provides an initiator (alkyl lithium / alkyl sodium)-structure regulator (Lewis base, which can be a tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms)-transfer promoter (potassium alcohol / alkyl potassium / amine potassium)-chain transfer agent (benzene, alkylbenzene or amine compound containing 2 to 10 carbon atoms) system. In this living polymerization system, the Lewis base also has the function of a transfer promoter, so the Lewis base and the transfer promoter can exist at the same time, 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 a relatively low temperature, but rapidly undergoes a chain transfer reaction of the chain transfer agent (benzene, alkylbenzene or amine compound) at a high temperature. Therefore, in this anionic living polymerization system, the occurrence of chain transfer or chain growth can be controlled by intermittent heating and cooling. When the chain transfer reaction occurs, the polymerization system is dominated by the chain transfer reaction, and the chain growth reaction basically stops (ideally it stops, but chain growth does not exclude individual active centers from occurring); when the chain growth reaction occurs, the polymerization system is dominated by the chain growth reaction, and the chain transfer reaction basically stops (ideally it stops, but chain transfer does not exclude individual active centers from occurring). In the present invention, this chain transfer-chain growth reaction mode that is alternately carried out based on trigger conditions is referred to as pulse chain transfer polymerization PTCP (Pulse Chain Transfer Polymerization).

[0051] The anionic living polymerization system of the preferred embodiment of the present invention comprises a polymerization monomer, an initiator, a structure regulator, a transfer promoter and a solvent, wherein the solvent is a solvent having a chain transfer agent effect or a mixed solvent composed of a chain transfer agent and an alkane organic solvent of 4 to 12 carbon atoms. The initiator is a substance that can initiate anionic living polymerization, including but not limited to alkyl lithium or alkyl sodium containing 1 to 20 carbon atoms, such as n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-pentyl sodium, etc. For living polymerization, the amount of initiator used is related to the designed molecular weight of the polymer. Since the average molecular weight of the synthesizable polymer in anionic living polymerization is theoretically unlimited, the amount of initiator used is not limited, but the molar amount of the initiator directly affects the speed of the polymerization chain generation. The structure regulator is a substance that can enhance the polymerization selectivity, which is a Lewis base, specifically a tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms, for example, at least one selected from dipyrrolidyl ethane, dipiperidinyl ethane, tetramethylethylenediamine and diethylene glycol dimethyl ether. In some cases, the polymer system may not be without any structure regulator to obtain a polymer with a special microstructure. Preferably, the amount of the structure regulator is usually 0 to 10 times the molar amount of the initiator. The transfer promoter is a substance that promotes chain transfer. The transfer promoter is a potassium alcoholate, an alkyl potassium or an amine potassium containing 1 to 20 carbon atoms, for example, at least one selected from potassium tert-butoxide, potassium tert-amyl alcoholate, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctyl and potassium diisopropylamine. The transfer promoter is not necessary in some cases, because the structure regulator also has the effect of promoting chain transfer, so the structure regulator can sometimes replace the transfer promoter. Preferably, the amount of the transfer promoter can be 0 to 0.2 times the molar amount of the initiator. The reaction solvent is preferably a solvent that has a chain transfer agent function itself, such as at least one of 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 special chain transfer agent and an alkane organic solvent containing 4 to 12 carbon atoms.

[0052] like Figure 1As shown in the schematic diagram, the active polymerization process based on the trigger condition control of the present invention consists of multiple rounds of chain growth reaction-chain transfer reaction cycles, and each cycle (or each reaction cycle) includes a chain growth reaction stage and a chain transfer reaction stage. Based on the active polymerization reaction of the present invention, the reaction cycle and the number of cycles can be determined according to the expected molecular weight of the synthesized polymer, the molar amount of the monomer and the molar amount of the initiator. Preferably, the reaction temperature of the chain growth reaction stage is -30 to 60°C, and the duration is 5 to 300min. The reaction temperature of the chain transfer stage is 50°C to 120°C, and the duration is 5 to 300min, and the reaction temperature of the chain growth reaction stage should not overlap with the reaction temperature of the chain transfer stage. Among them, the chain growth reaction temperature is low, and at this low temperature, butyl lithium (initiator) is used as an initiator to start the polymerization reaction, and the active polymer chain grows rapidly. At this time, the conversion rate of the monomer is high and the chain growth rate is fast. The chain transfer reaction temperature is high, and at this high temperature, the effects of components such as Lewis base (structure regulator), potassium alkoxide / alkyl potassium (promoter transfer agent) become more significant, which promotes the occurrence of chain transfer reaction. For example, potassium alcoholate can temporarily quench the active chain to form a stable alcoholate. By repeatedly adjusting the temperature by cooling and heating, the polymerization system can switch between chain growth and chain transfer, so that each active chain can grow and terminate in multiple cycles.

[0053] In the pulsed chain transfer anion active polymerization system of the present invention, a sufficient amount of polymerization monomer can be added at one time, and at the same time, the method of controlling the polymerization system to continuously switch between chain growth and chain transfer through trigger conditions is feasible, and the distribution of polymer molecular weight can be more accurately controlled compared with the prior art. On this basis, in order to further accurately control the molecular weight PDI value of the product (to make it closer to 1), do not add a sufficient amount of polymerization monomer at the beginning of the reaction, but instead add a predetermined molar amount of polymerization monomer before entering the chain growth reaction of the next round of reaction cycle after each chain transfer reaction, so that the chain growth reaction stage of each reaction cycle is a complete active polymerization until the monomer is completely exhausted, and the length of the chain growth in each chain growth reaction stage reaches the expected length. In this case, the chain growth length of each reaction cycle is accurately controlled by the molar amount of the monomer just added.

[0054] Further, based on the concept of the present invention, in order to synthesize a block polymer with a predetermined sequence structure, another monomer (such as Figure 2Schematic diagram shown). That is, monomer A is added before the chain growth reaction starts. As the chain growth reaction proceeds, monomer A is consumed. At this time, monomer B is immediately added to allow the chain growth reaction to continue until monomer B is consumed. At this time, a chain growth reaction stage is completed; the entire reaction system enters the chain transfer reaction stage by heating. Before the next round of chain growth reaction stage begins, monomer A is added again, and monomer B is immediately added after monomer A is consumed. The chain growth reaction is repeated several times according to the above method until a block copolymer of the desired quality is obtained. This method can not only control the chain length and molecular weight distribution of the block copolymer, but also add different monomers in sequence according to the sequence structure of the copolymer, thereby synthesizing a copolymer of two or more monomers.

[0055] The polymerization method proposed by the present invention not only improves the utilization rate of the initiator and reduces the amount of the initiator, but also can more accurately control the molecular weight and distribution of the final polymer. The anionic living polymerization method of the present invention can be applied to the homopolymerization or copolymerization of monomers including but not limited to 1,3-butadiene (referred to as butadiene), isoprene, styrene, ethylene, isoprene and myrcene.

[0056] In summary, based on the basic concept of the present invention, its essence is to introduce an intermittent, temperature-sensitive chain transfer reaction into the living anionic polymerization system, and to cause the reaction system to alternately undergo chain transfer reaction and chain growth reaction by artificially regulating the temperature, thereby realizing the infinite regeneration of the initiator (or catalyst) under the premise of retaining the basic characteristics of "living polymerization" based on chain growth in each cycle. Therefore, the living anionic polymerization method of the present invention can greatly reduce the amount of initiator used when synthesizing polyolefins, and can maintain the narrow molecular weight distribution of living polymerization and prepare block polymers of expected structure. Compared with traditional living polymerization, the polymerization method of the present invention reduces the amount of initiator by a multiple that is directly related to the number of times the initiator is regenerated (i.e., the number of times the chain transfer reaction stage occurs). When preparing a polymer of expected quality, the amount of initiator used can be as low as one-thirtieth of the amount used in the traditional living polymerization method or even lower. Theoretically, as long as the number of cycles is large enough, enough polymers can be synthesized with one molecule of initiator.

[0057] In order to more clearly illustrate the technical features and effects of the solution of the present invention, a description is given below in conjunction with specific embodiments.

[0058] Example 1

[0059] This embodiment takes the anionic living polymerization of butadiene initiated by butyl lithium as an example to illustrate the reaction process of pulsed chain transfer polymerization of PTCP, and the reaction process is as follows:

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

[0061] Next, the mixed system was cooled to 0°C and 12.5 g of butadiene was added again. At this time, benzyl lithium was used as an initiator to reinitiate the polymerization of butadiene; the reaction was continued at 0°C with vigorous stirring for 60 min to complete the second chain growth reaction stage, causing the solution to change from orange-red to yellow (see Figure 2 Then, the reaction system was heated to 90°C and stirred for 30 min to complete the second chain transfer reaction stage, at which time the solution turned into a darker orange-red color (such as Figure 2 d), indicating that chain transfer occurred and benzyl lithium was generated.

[0062] Next, the mixed system was cooled to 0°C for the third time, and 12.5 g of butadiene was added to make the solution return from a dark orange-red color to a dark yellow color (eg Figure 2 e), during which the third chain extension reaction occurs. According to this method, the heating-cooling (monomer addition) reaction cycle is repeated 20 times until a sufficient amount of polymer is synthesized.

[0063] 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 the solution was vacuum dried to obtain 386 g of polymer with a yield of >99%. GPC analysis showed (as shown in Figure 4 The number average molecular weight of the polymer is 1100, and the molecular weight distribution index PDI is 1.12. The H NMR spectrum analysis shows that (as shown) Figure 6 The polymer shown in the figure 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-butyl lithium is the initiator of anionic living polymerization, and DiPyr is a Lewis base that acts as a structural regulator (or polarity regulator) in the reaction. DiPyr has two functions in the polymerization process: one is to change the regioselectivity of the polymerization and increase the content of 1,2-structural units, and the other is to promote chain transfer reactions. t-BuOK (potassium tert-butoxide) is a transfer promoter that promotes chain transfer reactions; toluene acts as a solvent and a chain transfer agent.

[0065] Example 2

[0066] This example takes the isoprene anion living polymerization initiated by butyl lithium as an example to illustrate the reaction process of pulse chain transfer polymerization of PTCP. The reaction process is as follows:

[0067] Under the protection of dry N2, 125mL toluene, 2.1g of 1,2-dipyrrolidinoethane (DiPyr), 0.188mmol potassium tert-butoxide (t-BuOK) and 15.0g of isoprene were added to the reaction vessel. The solution was cooled to 0°C and 6.3mmol of n-butyl lithium was added to initiate the polymerization reaction. The solution quickly turned light yellow. The reaction was carried out at 0°C and under vigorous stirring for 60min to complete the first chain extension reaction stage. The reaction mixture was then heated to 90°C and stirred for 30min to complete the chain transfer reaction stage, during which the solution turned orange-red, indicating that benzyl lithium was formed. At this point, the first cycle ended. Then, the solution was cooled to 0°C again, and 15g of isoprene was added again. At this time, benzyl lithium was used as an initiator to reinitiate the polymerization of isoprene, and the reaction was continued at 0°C and under vigorous stirring for 60min to complete the second chain extension reaction stage. Then, the reaction mixture was heated to 90°C and stirred for 30min to complete the chain transfer reaction; at this time, the second reaction cycle ended.

[0068] According to the above method, after 10 cycles of chain growth reaction stages, 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 the solution was vacuum dried to obtain 148 g of polymer with a yield of about 99%. GPC analysis showed that the number average molecular weight of the polymer was 2420, and the molecular weight distribution index PDI = 1.18. Nuclear magnetic resonance hydrogen spectrum analysis showed that the polymer was high 3,4-polyisoprene, and the sum of 3,4- and 1,2-unit contents was 90%.

[0069] Example 3

[0070] This embodiment takes the anionic block copolymerization of butadiene and styrene initiated by butyl lithium as an example to illustrate the reaction process of pulse chain transfer polymerization PTCP, and the reaction process is as follows:

[0071] Under the protection of dry N2, 100mL toluene, 1.95g 1,2-dipyrrolidinoethane (DiPyr), 0.173mmol potassium tert-butoxide and 3.0g styrene were added to the reaction vessel. The solution was cooled to 15°C and 5.75mmol n-butyl lithium was added to initiate the polymerization reaction. The solution quickly turned light yellow. The reaction was carried out at 15°C and under vigorous stirring for 60min to completely convert styrene; then 6.0g butadiene was added and continued to be vigorously stirred at 15°C for 30min to complete the first chain extension reaction stage. The reaction mixture was then heated to 90°C and stirred for 30min to complete the chain transfer reaction stage, during which the solution turned orange-red, indicating the formation of benzyl lithium.

[0072] Then, the solution was cooled to 15°C again, and 3.0 g of styrene was added again. At this time, benzyl lithium was used as an initiator to reinitiate the polymerization of styrene, and the reaction was continued at 16°C and under vigorous stirring for 60 minutes to completely convert styrene; then 6.0 g of butadiene was added again, and vigorous stirring was continued at 15°C for 30 minutes to complete the second chain growth reaction stage. Then, the reaction mixture was heated to 90°C again and stirred for 30 minutes to complete the chain transfer reaction stage.

[0073] After repeating the chain growth reaction stage for 5 times in the above manner, 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 the solution was vacuum dried to obtain 44 g of polymer with a yield of about 98%. GPC analysis showed (as shown in Figure 5 The number average molecular weight of the polymer is 1637, and the molecular weight distribution index PDI is 1.16. The H NMR spectrum analysis shows that (as shown) Figure 7 The butadiene structural units in the polymer (shown) are mainly 1,2-structural units, accounting for 94% of the total butadiene structural units.

[0074] Embodiment 4-7

[0075] The polymerization system of Examples 4-7 is basically the same as that 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 product is shown in Table 1.

[0076] Table 1:

[0077]

[0078] It can be seen from Table 1 that the temperature of the chain growth reaction stage can be set in the range of -30°C to 60°C, and the temperature of the chain transfer reaction stage can be set in the range of 50 to 120°C. Relatively speaking, when the temperature of the chain growth reaction stage does not exceed 30°C and the temperature of the chain transfer reaction stage does not exceed 100°C, it is beneficial to obtain a product with a molecular weight distribution index PDI closer to 1; and when the above conditions are met, when the temperature of the chain growth reaction stage is 0°C and the temperature of the chain transfer reaction stage is 90°C, the PDI of the product is further made close to 1.

[0079] Embodiment 8-11

[0080] The polymerization system of Examples 8-11 is basically the same as that of Example 1, except that the type of reaction solvent is different. The molecular weight distribution index PDI of the final synthesized product is shown in Table 2.

[0081] Table 2:

[0082]

[0083]

[0084] As can be seen from Table 2, the reaction solvent of the anionic living polymerization system based on pulse chain transfer of the present invention can be a variety of different alkylbenzenes, such as toluene, xylene, trimethylbenzene or ethylbenzene. Among them, when toluene, xylene and trimethylbenzene are used as the reaction solvent of the anionic living polymerization system of butadiene initiated by butyl lithium, a polymer product with a molecular weight PDI close to 1 can be obtained. Experiments also show that the reaction solvent can also be replaced by an amine compound containing 2 to 10 carbon atoms that is liquid at room temperature.

[0085] Examples 12-14

[0086] The polymerization system of Examples 12-14 is basically the same as that of Example 1, except that the polymerization monomers are different. The molecular weight distribution index PDI of the final synthesized product is shown in Table 3.

[0087] Table 3:

[0088]

[0089] As can be seen from Table 3, the anionic living polymerization method based on pulse chain transfer of the present invention can be applied to the polymerization of various olefin monomers such as butadiene, styrene, isoprene, piperylene, ethylene, myrcene, etc., and a polymerization product with a polymer PDI close to 1 can be obtained.

[0090] Examples 15-20

[0091] The polymerization system of Examples 15-20 is basically the same as that of Example 1, except that the type of Lewis base (structure regulator) used or the amount added is different. The molecular weight distribution index PDI of the final synthesized product is shown in Table 4.

[0092] Table 4:

[0093]

[0094]

[0095] It can be seen from Table 4 that in the anionic living polymerization system based on pulse chain transfer of the present invention, in addition to DiPyr in Example 1, the structure regulator can also use at least one Lewis base such as dipiperidine ethane, tetramethylethylenediamine and diethylene glycol dimethyl ether, and all of them can obtain polybutadiene products with a polymer PDI close to 1; relatively speaking, in the anionic living polymerization system of butadiene initiated by butyl lithium, when DiPyr is used as the structure regulator and its molar amount is 1-5 times the molar amount of the initiator, it is beneficial to obtain a polymerization product with a molecular weight distribution index PDI closer to 1. Experiments also show that the Lewis base that can be used as the structure regulator can be any tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms.

[0096] Examples 21-27

[0097] The polymerization systems of Examples 21-27 are basically the same as those of Example 1, except that the types of transfer promoters used or the amounts added are different. The molecular weight distribution index (PDI) of the final synthesized products is shown in Table 5.

[0098] Table 5:

[0099]

[0100]

[0101] As can be seen from Table 5, in the anionic living polymerization system based on pulse chain transfer of the present invention, in addition to the potassium tert-butoxide (t-BuOK) in Example 1, the transfer promoter can also use potassium tert-amyl alcoholate, potassium ethoxide, potassium menthol, n-butyl potassium, n-pentyl potassium, potassium isooctoxide and potassium diisopropylamine, etc., and at least one potassium alkoxide, alkyl potassium or amine potassium (organic potassium), and all can obtain polybutadiene products with a polymer PDI close to 1; relatively speaking, in the anionic living polymerization system of butadiene initiated by butyl lithium, when t-BuOK, potassium tert-amyl alcoholate, potassium menthol is used as the transfer promoter and its molar amount is 0.03 to 0.05 times the molar amount of the initiator, it is conducive to obtaining a polymer product with a molecular weight distribution index PDI closer to 1. Experiments also show that the transfer promoter can use any potassium alkoxide, alkyl potassium or amine potassium containing 1 to 20 carbon atoms.

[0102] Examples 28-30

[0103] The polymerization system of Examples 28-30 is basically the same as that of Example 1, except that different initiators are used. The molecular weight distribution index PDI of the final synthesized product is shown in Table 6.

[0104] Table 6:

[0105]

[0106] As can be seen from Table 6, in the anionic living polymerization system based on pulse chain transfer of the present invention, in addition to n-butyl lithium in Example 1, at least one of tert-butyl lithium, sec-butyl lithium and n-pentyl sodium can be used as the initiator, and a polybutadiene product with a polymer PDI close to 1 can be obtained; relatively speaking, the PDI of the polybutadiene product initiated by butyl lithium is closer to 1, while the PDI of the polybutadiene product initiated by n-pentyl sodium is relatively large. Experiments also show that the initiator can use any alkyl lithium or alkyl sodium containing 1 to 20 carbon atoms.

[0107] Examples 31-32

[0108] The polymerization system of Examples 31-32 is basically the same as that of Example 1, except that only a structure regulator is added to the polymerization system of Example 31 without using a transfer accelerator, and only a transfer accelerator is added to the polymerization system of Example 32 without adding a structure regulator. The molecular weight distribution index PDI of the final synthesized product is shown in Table 7.

[0109] Table 7:

[0110]

[0111] It can be seen from Table 7 that in the anionic living polymerization system based on pulse chain transfer of the present invention, when only one of the structure regulator and the transfer promoter is present, the pulse chain transfer polymerization reaction can proceed normally, and a polybutadiene product with a PDI close to 1 can be obtained; relatively speaking, when the structure regulator and the transfer promoter are present at the same time, and the molar ratio of the structure regulator to the initiator is close to 2, and the molar ratio of the transfer promoter to the initiator is close to 0.03, a polymerization product with a PDI closer to 1 can be obtained.

[0112] In summary, in the anionic living polymerization system based on pulse chain transfer, the initiator can be selected from at least one of n-butyl lithium, tert-butyl lithium, sec-butyl lithium and n-pentyl sodium; DiPyr and t-BuOK can be present in the above reaction system at the same time or only one of them exists, and 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. Among them, in addition to DiPyr, the structure regulator can also be selected from Lewis bases such as tetramethylethylenediamine, dipiperidylethane or diethylene glycol dimethyl ether. In addition to t-BuOK, the transfer promoter can also be selected from potassium tert-butoxide, potassium tert-amyl alcohol, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctoxide or potassium diisopropylamide. In addition to toluene, the reaction solvent can also use alkylbenzenes such as xylene, trimethylbenzene or ethylbenzene. Different reagents can be adaptively selected according to the specific composition of the reaction system, such as the type of reaction monomers, the solubility of the reaction solvent, etc.

[0113] The above specific embodiments have the following common features:

[0114] (1) Using temperature as a switch to exert a "scissor" effect on chain polymerization, so that the polymerization chain is terminated when it grows to a desired degree of polymerization. These embodiments achieve this goal through simple temperature changes, simplifying the operation process and reducing the use and residue of additional reagents.

[0115] (2) Multiple utilization of initiators: Since chain transfer is reversible, one initiator molecule can participate in chain growth and termination in multiple cycles and synthesize several chains, thus greatly improving the utilization rate of the initiator. This is an important advantage for industrial applications because it can significantly reduce production costs and improve efficiency.

[0116] (3) Narrow molecular weight distribution: By precisely controlling the time and amplitude of temperature change (or other conditions), a high degree of control over polymer chain length can be achieved, resulting in polymers with narrow molecular weight distribution. This is very beneficial for the preparation of high-performance materials.

[0117] (4) Using temperature as a "switch" to trigger the reaction can reduce by-products compared to other conditions (changing the solvent environment, using additives, etc.): Compared with traditional chain transfer methods, this method reduces the introduction of additional chemicals, reduces the generation of by-products, and is more environmentally friendly.

[0118] (5) Reduction of by-products: Compared with the conventional chain transfer method, the polymerization method of these embodiments reduces the introduction of additional chemicals, reduces the generation of by-products, and is more environmentally friendly. Due to its simple operation and high efficiency, this method has the potential to be applied to large-scale industrial production, especially in industries that are cost-sensitive but require high quality control.

[0119] The method of the present invention is expected to bring new breakthroughs in the field of polymer synthesis.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. These modifications or replacements, or the technical features in the above embodiments may be combined in the manner described in the embodiments if they do not conflict with each other, and these modifications, replacements 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. A living polymerization method based on pulsed chain transfer, characterized in that: It includes chain transfer reaction stages and chain growth reaction stages that are performed alternately, and an adjacent chain growth reaction stage and a chain transfer reaction stage constitute a reaction cycle; Among them, 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 active polymerization; the active polymerization method also includes a trigger condition, and the trigger condition causes the entire reaction system to switch between the chain growth reaction stage and the chain transfer reaction stage; the trigger condition is a reaction condition that can be precisely controlled or a chemical condition that can be removed or changed; the reaction condition is at least one of temperature conditions, light conditions and pressure; the chemical condition is at least one of the solvent of the reaction system, the reaction atmosphere and the auxiliary agent in contact with the reactants.

2. The living polymerization method according to claim 1, characterized in that: The living polymerization method is an anionic living polymerization method or a coordination polymerization method.

3. The living polymerization method according to claim 2, characterized in that: The anionic living polymerization system comprises a polymerization monomer, an initiator, a structure regulator, a transfer promoter and a chain transfer agent; the polymerization monomer is at least one of butadiene, isoprene, styrene, isoprene, myrcene and ethylene; the initiator is an alkyl lithium or an alkyl sodium containing 1 to 20 carbon atoms; the structure regulator is a Lewis base, and the transfer promoter is an alcohol potassium, an alkyl potassium or an amine potassium containing 1 to 20 carbon atoms; the chain transfer agent is at least one of benzene, an alkyl benzene compound containing 7 to 15 carbon atoms and an amine compound containing 2 to 10 carbon atoms; the addition amounts of the structure regulator and the transfer promoter in the polymerization system are not zero at the same time.

4. The living polymerization method according to claim 3, characterized in that: The initiator includes at least one of n-butyl lithium, sec-butyl lithium, tert-butyl lithium and n-pentyl sodium; the chain transfer agent is at least one of toluene, p-xylene, m-xylene, mesitylene and ethylbenzene.

5. The living polymerization method according to claim 3, characterized in that: The structure regulator is a tertiary amine, secondary amine or ether compound containing 3 to 20 carbon atoms; the transfer promoter is at least one selected from potassium tert-butoxide, potassium tert-amyloxide, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctoxide and potassium diisopropylamine.

6. The living polymerization method according to claim 3, characterized in that: The trigger 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: adjusting the temperature of the reaction system to -30°C to 60°C, so that the reaction system enters the chain growth reaction stage; adjusting the temperature of the reaction system to 50°C to 120°C, so that the reaction system enters the chain transfer reaction stage.

7. The living polymerization method according to claim 3, characterized in that: The amount of the structure regulator added in 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.

8. The living polymerization method according to claim 1, characterized in that: The duration of the chain growth reaction stage is until the polymerization monomer is exhausted; the duration of the chain transfer reaction stage is 5 to 300 minutes; after a reaction cycle ends, the polymerization monomer is added to the reaction system before entering the chain growth reaction stage of the next reaction cycle; When synthesizing block polymers, the chain growth reaction stage consumes the first monomer initially added, and when the first monomer is consumed, the second monomer is immediately added until the added monomer is consumed, that is, one chain growth reaction stage is completed.

9. An anionic living polymerization method based on pulsed chain transfer, characterized in that: It includes polymerization monomers, initiators, structure regulators, transfer promoters and reaction solvents; The polymerization monomer is at least one of butadiene, isoprene, styrene, isoprene, myrcene and ethylene; the initiator is an alkyl lithium or an alkyl sodium containing 1 to 20 carbon atoms; the structure regulator is a Lewis base; the transfer promoter is an alcohol potassium, an alkyl potassium or an amine potassium containing 1 to 20 carbon atoms; wherein the addition amount of the structure regulator and the transfer promoter in the polymerization system is not zero at the same time; the reaction solvent is a solvent that can act as a chain transfer agent, and the reaction solvent is at least one of benzene, an alkyl benzene compound containing 7 to 15 carbon atoms and an amine compound containing 2 to 10 carbon atoms; During the polymerization process, the temperature is adjusted 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 active polymerization; The switching method is: adjusting the temperature of the reaction system to -30°C to 60°C, so that the reaction system enters the chain growth reaction stage; adjusting the temperature of the reaction system to 50°C to 120°C, so that the reaction system enters the chain transfer reaction stage; according to this method, several chain growth reaction stages are cycled until a polymer of expected quality is obtained.

10. The anionic living polymerization method according to claim 9, characterized in that: The initiator is at least one of n-butyl lithium, sec-butyl lithium, tert-butyl lithium and n-pentyl sodium; the reaction solvent is at least one of toluene, p-xylene, m-xylene, mesitylene and ethylbenzene; the structure regulator 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-amyl alcohol, potassium menthol, potassium ethoxide, n-pentyl potassium, n-butyl potassium, potassium isooctoxide and diisopropylamine potassium; the reaction cycle is determined according to the molecular weight of the expected synthesized polymer, and the number of cycles is determined according to the expected mass of the prepared polymer and the molar amount of the initiator.

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