Green light-induced stepwise polymerized polymer and preparation and degradation method thereof

Abstract

The invention provides a green light-induced stepwise polymerized polymer and a preparation and degradation method thereof. The preparation method of the polymer comprises the following steps: step a, carrying out esterification reaction on 4-cyano-4-[(dodecyl thiocarbonyl) sulfur] valeric acid and trimethylolpropane to obtain a bifunctional chain transfer reagent DCDTPA; and b, mixing the DCDTPA and a vinyl monomer, dissolving in an organic solvent, irradiating with green light under a vacuum condition, and polymerizing to obtain the polymer. The invention solves the problems that the polymer is low in terminal group retention rate and low in molecular weight, and the synthesized polymer is easy to generate a branched structure and is difficult to retain a linear structure, and also solves the technical problem that the monomers applicable to the method are limited to high-cost and low-activity vinyl monomers.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and more specifically, to a green light-induced stepwise polymerization polymer and its preparation and degradation methods. Background Technology

[0002] In the field of polymer synthesis, reversible addition-fragmentation chain transfer (RAFT) polymerization technology has attracted much attention due to its mild polymerization conditions and effective control over polymer molecular weight and topology, becoming one of the important methods for preparing functional polymer materials. RAFT polymerization technology is mainly applied to the synthesis of all-carbon backbone polymers, but this limits the widespread application of polymers in fields such as biomedicine and biodegradable materials. To address this limitation, some progress has been made in the degradation research of all-carbon backbone polymers in recent years. However, current degradation methods struggle to achieve complete depolymerization of polymers and often require extreme conditions, which not only increases process complexity and cost but may also damage other properties of the polymer.

[0003] Stepwise polymerization, as a method for constructing polymers through reactions between functional groups, is favored because it can introduce a multifunctional backbone. However, traditional stepwise polymerization processes require harsh conditions such as high temperature and high pressure, which not only tests the tolerance of functional groups but may also trigger side reactions, such as crosslinking and branching, thereby affecting the properties of the polymer.

[0004] Yu et al. proposed the concept of RAFT-step polymerization (CN118176223A), which is a step-growth polymerization based on a single unit monomer insertion (SUMI) reaction, using a bifunctional chain transfer agent and a bifunctional vinyl monomer during the polymerization process. This polymerization method combines the advantages of RAFT polymerization (mild and easy-to-control conditions) and step-growth polymerization (multifunctional polymer backbone).

[0005] However, RAFT-step polymerization technology still faces the following challenges: the need for additional thermal initiators leads to reduced polymer end-group retention, stoichiometry, and further affects the polymer's molecular weight. Most RAFT-step polymerization technologies are limited by specific types of monomers, such as vinyl ethers or maleimides. These monomers are expensive and have low polymerization activity, making homopolymerization via a free radical mechanism difficult, and are more conducive to the formation of RAFT-SUMI adducts, thus being used in RAFT-step polymerization. Compared to monomers with low free radical polymerization activity, highly reactive monomers (such as styrene, (meth)acrylates, and (meth)acrylamide) have relatively high homopolymerization rates, making them easier to homopolymerize. This results in their lower frequency of use in RAFT-step polymerization. Compared to low-reactivity vinyl monomers, these highly reactive vinyl monomers have a wider range of applications and are cheaper. However, existing technologies limit the application of highly reactive, low-cost styrene monomers, and currently commonly used thermally initiated RAFT-step polymerization tends to produce branched or cross-linked structures, making it difficult for the polymer to maintain a linear morphology.

[0006] There are currently no good solutions to the above problems, and there is an urgent need to develop new aggregation methods to overcome them. Summary of the Invention

[0007] This application provides a green light-induced stepwise polymerization polymer and its preparation and degradation method, in order to at least solve the technical problems of existing RAFT-stepwise polymerization technology, such as low end-group retention, poor molecular weight control, narrow monomer selection range, and easy formation of nonlinear structures.

[0008] According to one aspect of the embodiments of this application, a green light-induced stepwise polymerization method is provided, comprising:

[0009] Step a: 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid is esterified with trimethylolpropane in dichloromethane under the catalysis of a catalyst to obtain the bifunctional chain transfer reagent DCDTPA;

[0010] Step b: Mix DCDTPA with vinyl monomers, dissolve in an organic solvent, and polymerize under vacuum conditions by irradiating with green light to obtain the polymer.

[0011] Furthermore, the vinyl monomer is a highly reactive vinyl monomer, preferably divinylbenzene or dithiodimethylbis(ethane-2,1-diyl) ester (DSBVB).

[0012] Furthermore, the organic solvent is selected from one or more of tetrahydrofuran, toluene, dimethyl sulfoxide, and N,N-dimethylformamide.

[0013] Furthermore, the polymerization is carried out under vacuum conditions and irradiated with green light with a wavelength of 500~550nm. Preferably, the polymerization reaction temperature is 0℃~30℃, and preferably the molecular weight of the polymer is in the range of 3000 Da to 30,000 Da.

[0014] Further, the molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valerate to trimethylolpropane is between 2:1 and 3:1, and preferably the molar ratio of DCDTPA to divinylbenzene is between 1:0.9 and 1:1.

[0015] Furthermore, the catalyst includes a Lewis base catalyst, preferably 4-dimethylaminopyridine, preferably the amount of catalyst is 10% to 50% based on the total moles of reactants, and preferably the esterification reaction is carried out at a temperature of 0°C to 30°C for 12 to 48 hours.

[0016] According to another aspect of the embodiments of this application, a green light-induced stepwise polymerization polymer is also provided, which can be prepared by the above-described green light-induced stepwise polymerization method.

[0017] According to another aspect of the embodiments of this application, a biodegradable polymer is also provided. When the vinyl monomer is selected from styrene monomers containing disulfide bonds, dithioalkyldimethylbis(ethane-2,1-dimethyl) ester (DSBVB) is preferred, and the biodegradable polymer can be prepared by the above-described green light-induced stepwise polymerization method.

[0018] According to another aspect of the embodiments of this application, a method for degrading a polymer is also provided, comprising mixing the above-mentioned degradable polymer with tributylphosphine (TBPH) to react, thereby achieving depolymerization of the polymer.

[0019] Furthermore, the molar ratio of polymer to tributylphosphine is 1:150~300, and the depolymerization time is preferably 1 to 20 minutes.

[0020] Furthermore, the depolymerization temperature is 20°C to 50°C, and depolymerization is preferably carried out in a polar solvent, more preferably tetrahydrofuran (THF), dimethyl sulfoxide (DMSO) and toluene.

[0021] In this application, the preparation method provided by the present invention is adopted, and the polymerization reaction is induced by medium wavelength green light, which reduces the occurrence of side reactions. The monomer range is also extended to styrene monomers containing highly active double bonds. By designing disulfide bonds in the monomers, the polymer can be degraded on demand, thereby solving the technical problems of low end group retention rate, poor molecular weight control, narrow monomer selection range and easy formation of nonlinear structures in the existing RAFT-step polymerization technology. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0023] Figure 1 This is a schematic diagram of green light-induced stepwise polymerization according to the present invention;

[0024] Figure 2 It is a step-polymerization product according to the embodiments of this application. 1 H NMR spectrum;

[0025] Figure 3 This is a schematic diagram of the synthesis and degradation process of the biodegradable polymer according to embodiments of this application, as well as the GPC spectrum of the polymer. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solution of the present application will be described more clearly and completely below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0028] According to an embodiment of this application, a green light-induced stepwise polymerization method is provided, comprising:

[0029] Step a: 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid is esterified with trimethylolpropane in dichloromethane under the catalysis of a catalyst to obtain the bifunctional chain transfer reagent DCDTPA;

[0030] Step b: Mix DCDTPA with vinyl monomers, dissolve in an organic solvent, and polymerize under vacuum conditions by irradiating with green light to obtain the polymer.

[0031] 4-Cyano-4-[(dodecylthiocarbonyl)thio]pentanoic acid, as the carboxylic acid component in the esterification reaction, possesses a unique and stable molecular structure, which is beneficial for controlling the molecular weight and structure of the polymer during polymerization. Trimethylolpropane, as an alcohol with three hydroxyl groups, can introduce additional functionality, enhancing the multifunctionality of the polymer. It reacts with the carboxylic acid to form ester bonds, ultimately forming the bifunctional chain transfer agent DCDTPA. DCDTPA possesses both dodecylthiocarbonyl sulfur and ester functional groups, and will be used as a chain transfer agent in photoinduced stepwise polymerization to control polymer synthesis and achieve precise control of polymer molecular weight and structure.

[0032] Esterification is preferably carried out in dichloromethane under the catalysis of a catalyst. Dichloromethane, as a good organic solvent, provides a stable environment for the esterification reaction, which is conducive to the reaction.

[0033] Optionally, DCDTPA can be purified. The purification method can be any suitable and applicable technique in the prior art, which can be selected and used as needed by those skilled in the art to ensure that no impurities interfere with the polymerization process.

[0034] In this invention, the inventors discovered that green light, as a light source, can activate the thiocarbonyl sulfur functional groups on DCDTPA, guiding the stepwise polymerization reaction. This invention achieves an environmentally friendly polymerization method while ensuring the controllability and designability of the polymer. Figure 1 A schematic diagram of the green light-induced stepwise polymerization of the present invention is shown. Figure 1 In this context, x represents the number of repeating units in the polymer chain, preferably between 20 and 55.

[0035] In a preferred embodiment, the vinyl monomer is a highly reactive vinyl monomer. The vinyl monomer is used to construct the polymer backbone. In the prior art, most RAFT-step polymerization techniques typically use monomers with lower polymerization reactivity, such as vinyl ethers or maleimides; however, these monomers are expensive. With the method of the present invention, the highly reactive vinyl monomer can be used under mild conditions, reducing side reactions and avoiding the formation of cross-linked structures, instead forming linear alternating copolymers.

[0036] The vinyl monomers of this invention are preferably divinylbenzene or dithiodi(ethane-2,1-diyl) ester. Divinylbenzene contains two vinyl groups, which can introduce cross-linking points during polymerization, enhancing the mechanical properties and thermal stability of the polymer. Dithiodi(ethane-2,1-diyl) ester has highly reactive double and disulfide bonds that can break and recombine under certain conditions (such as with tributylphosphine), thereby achieving the biodegradability and on-demand remodeling of the polymer.

[0037] The organic solvents selected in this invention are those with good solubility and no negative impact on the polymerization reaction, ensuring that the reaction mixture remains stable. In a preferred embodiment, the organic solvent is selected from one or more of tetrahydrofuran (THF), toluene, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

[0038] In a preferred embodiment, polymerization is carried out under vacuum conditions and irradiated with green light of wavelength 500-550 nm. Preferably, the polymerization reaction temperature is 0°C-30°C, and preferably the molecular weight of the polymer is in the range of 3000 Da to 30,000 Da.

[0039] Vacuum technology is used to remove oxygen or other gases that may inhibit or interfere with the polymerization reaction. Vacuum conditions help improve the purity and stability of the polymer and reduce the formation of byproducts. Furthermore, a vacuum environment helps improve the homogeneity of the reaction mixture and promotes effective contact between the monomer and the chain transfer agent DCDTPA, thereby increasing polymerization efficiency.

[0040] Green light (wavelength 500-550 nm) serves as the initiating light source for the polymerization reaction in this invention. Its mild nature avoids damage to the polymer structure caused by high temperatures or other extreme conditions, making it particularly suitable for processing monomers that are heat-sensitive or prone to side reactions at high temperatures. The inventors discovered that the medium wavelength of green light can effectively excite the thiocarbonyl sulfur functional groups on DCDTPA, promoting the stepwise polymerization reaction between the monomer and DCDTPA without causing other unnecessary side reactions. The mildness of green light also means that the reaction can be carried out at lower temperatures, such as 0°C to 30°C, reducing energy consumption and benefiting environmental protection and cost control. Typical, but not limiting, reaction temperatures are 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, or any two of these values. Illumination time can be 12 to 48 hours. Typical, but not limiting, illumination time is 12, 24, 36, 48 hours, or any two of these values.

[0041] The molecular weight of the polymer is preferably controlled within the range of 3000 Da to 30,000 Da. This range ensures good mechanical strength, thermal stability, and processability, while maintaining biocompatibility and biodegradability. Typically, but not limitingly, the molecular weight of the polymer is 3000 Da, 8000 Da, 10,000 Da, 30,000 Da, or any combination of two such values.

[0042] In a preferred embodiment, the molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valerate to trimethylolpropane is between 2:1 and 3:1, and preferably the molar ratio of DCDTPA to divinylbenzene is between 1:0.9 and 1:1.

[0043] The inventors discovered that when the molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid to trimethylolpropane is controlled between 2:1 and 3:1, the consumption of reactants can be balanced, the selectivity of the esterification reaction can be improved, and DCDTPA can achieve higher synthesis efficiency and quality. Typical, but not limiting, molar ratios of 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid to trimethylolpropane are 2:1, 2.5:1, 3:1, or any two of these values. When DCDTPA undergoes green light-induced stepwise polymerization with divinylbenzene, when the molar ratio is controlled between 1:0.9 and 1:1, the polymer has a narrower molecular weight distribution, a more linear structure, and maintains the integrity of the end-group functionalization. Typical, but not limiting, molar ratios of DCDTPA to divinylbenzene are 1:0.9, 1:1, 1:1.1, or any two of these values.

[0044] In a preferred embodiment, the catalyst comprises a Lewis base catalyst, preferably 4-dimethylaminopyridine, preferably the amount of catalyst is 10% to 50% based on the total molar amount of reactants, and preferably the esterification reaction is carried out at a temperature of 0°C to 30°C for 12 to 48 hours.

[0045] Catalysts can promote esterification reactions between carboxylic acids and alcohols, improving reaction selectivity and yield. The amount of catalyst directly affects the reaction rate and product purity. While excess catalyst can accelerate the reaction, it can also lead to side reactions, affecting product purity and yield. In this invention, based on the total molar amount of reactants, the amount of catalyst is preferably controlled between 10% and 50%, more specifically, a preferred range of 30% to 50%. Typically, but not limitingly, the amount of catalyst is 10%, 20%, 30%, 50%, or any combination of two of these values. Preferably, a co-catalyst, such as N,N'-dicyclohexylcarbodiimide, can be added. N,N'-dicyclohexylcarbodiimide is a dehydrating condensing agent that can activate carboxylic acids, converting them into intermediates that are more readily reacted with alcohols or amines, thereby promoting the formation of ester or amide bonds. More preferably, the catalyst 4-dimethylaminopyridine is used together with the co-catalyst N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine can further enhance the dehydration condensation effect of N,N'-dicyclohexylcarbodiimide.

[0046] Esterification can be carried out at low temperatures, although longer reaction times may be required to achieve complete esterification. Reaction times range from 12 to 48 hours, depending on the reaction temperature and catalyst efficiency. Typical, but not limiting, reaction times are 12, 24, 36, 48 hours, or any combination of two such values.

[0047] According to an embodiment of this application, a green light-induced stepwise polymerization polymer is also provided, which can be prepared by the above-described green light-induced stepwise polymerization method.

[0048] Figure 2 The step-polymerization products are shown 1 The 1H NMR spectrum, with data shown in the figure, is derived from the detailed characterization of the polymerization product in Example 1. 1 1H NMR spectra are important tools for analyzing the chemical structure of polymers. The information shows that the product P (DCDTPA-alt-DVB) polymerized in a 1:1 molar ratio can be determined by NMR integration to have equal content of the two components in the polymer, verifying the successful reaction.

[0049] The polymers of the present invention exhibit the characteristics of linear alternating copolymers, which means that the polymer chains are composed of alternating two different monomer units. This structure endows the polymers with unique physical and chemical properties, such as enhanced mechanical strength, improved solubility, and specific reactive sites.

[0050] According to embodiments of this application, a biodegradable polymer is also provided. When the vinyl monomer is selected from styrene monomers containing disulfide bonds, dithioalkyldimethylbis(ethane-2,1-dimethyl) ester (DSBVB) is preferred, and the biodegradable polymer can be prepared by the above-described green light-induced stepwise polymerization method.

[0051] Dithioalkyl di(ethane-2,1-diyl) ester (DSBVB) not only possesses the reactivity of vinyl monomers but also contains internal disulfide bonds. Through green light-induced stepwise polymerization, DSBVB can react efficiently with the chain transfer agent DCDTPA to form polymer chains. These polymer chains can be degraded on demand under specific conditions (such as in a mixture with tributylphosphine), enabling polymer recycling and environmental friendliness.

[0052] According to an embodiment of this application, a method for degrading a polymer is also provided, comprising mixing the above-mentioned degradable polymer with tributylphosphine to react, thereby achieving depolymerization of the polymer.

[0053] Tributylphosphine is an effective thiol reducing agent that selectively reacts with disulfide bonds in polymers, causing these bonds to break and leading to polymer chain depolymerization. This results in a significant reduction in molecular weight to a fraction of the initial value, or even less. This process not only enables polymers to degrade as designed under specific conditions but also facilitates their recycling, especially for single-use products requiring safe degradation after application. The development and application of biodegradable polymers not only solves the environmental pollution problems caused by traditional polymer waste but also reduces the cost of material recycling and processing.

[0054] In a preferred embodiment, the molar ratio of polymer to tributylphosphine is 1:150~300, and the depolymerization time is preferably 1 to 20 minutes.

[0055] When the molar ratio is controlled between 1:150 and 1:300, the disulfide bonds in the polymer can be effectively reduced and broken by tributylphosphine without causing excessive degradation of the polymer or residual tributylphosphine, which would affect subsequent utilization or degradation efficiency. Typical, but not limiting, molar ratios of polymer to tributylphosphine are 1:150, 1:200, 1:250, 1:300, or any two of these values. The depolymerization time is 1 to 20 minutes, preferably 5 to 15 minutes. This time ensures efficient depolymerization while maintaining low energy consumption and reducing resource waste caused by prolonged reactions. By controlling the depolymerization time, not only can on-demand degradation of the polymer be achieved, but the high quality of the depolymerization products can also be maintained. Typical, but not limiting, depolymerization times are 1, 5, 10, 15, 20 minutes, or any two of these values.

[0056] In a preferred embodiment, the depolymerization temperature is 20°C to 50°C, and depolymerization is preferably carried out in a polar solvent, more preferably tetrahydrofuran, dimethyl sulfoxide, or toluene.

[0057] Setting the depolymerization temperature between 20℃ and 50℃ effectively balances the depolymerization rate and the stability of the polymer structure. The depolymerization medium can be selected appropriately based on the properties of the polymer and the expected depolymerization products. Typically, but not limitingly, the depolymerization temperature is within the range of 20℃, 30℃, 40℃, 50℃, or any two of these values.

[0058] Figure 3 This is a schematic diagram of the synthesis and degradation process of the biodegradable polymer according to embodiments of this application, along with the GPC spectrum of the polymer. Figure 3In the diagram, (A) is a schematic diagram of the synthesis and degradation process of the biodegradable polymer, specifically the process mentioned in Example 3 involving the green light-induced polymerization of DSBVB monomers with biodegradable chemical bonds to obtain the biodegradable polymer, followed by RAFT polymerization to synthesize a polymer with side chains, and finally depolymerization through a mixed reaction with tributylphosphine. (B) is the GPC spectrum of the polymer, showing the molecular weight distribution of the polymer before and after degradation in the example. The synthesized polymer had a molecular weight of 116.9 kDa, and after degradation, the molecular weight was only 2.8 kDa. Figure 3 In this context, the value of x ranges from 10 to 15.

[0059] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0060] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0061] Example 1

[0062] This embodiment provides a light-induced stepwise polymerization method, specifically including the following steps:

[0063] Step 1, add 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid, trimethylolpropane, N,N' -Dicyclohexylcarbodiimide and 4-dimethylaminopyridine were reacted in a molar ratio of (2:1:3:1) in dichloromethane at 25°C for 12 h to obtain a bifunctional chain transfer reagent, denoted as DCDTPA. The volume ratio of dichloromethane to the total amount of reactants was 100:1.

[0064] Step 2: The DCDTPA obtained in Step 1 is mixed with divinylbenzene at a molar ratio of 1:1 and dissolved in tetrahydrofuran at a mass fraction of 50 wt%. The mixture is placed in a reaction tube under vacuum and then irradiated with 530 nm green light at 20 °C for 36 h to obtain the stepwise polymerization product P(DCDTPA- alt -DVB).

[0065] Example 2

[0066] This embodiment provides a light-induced stepwise polymerization method, specifically including the following steps:

[0067] Step 1, add 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid, trimethylolpropane, N,N'-Dicyclohexylcarbodiimide and 4-dimethylaminopyridine were reacted in a solution in dichloromethane at 15°C for 24 h to obtain a bifunctional chain transfer reagent, denoted as DCDTPA. The volume ratio of dichloromethane to the total amount of reactants was 100:1.

[0068] Step 2: The DCDTPA obtained in Step 1 is mixed with divinylbenzene at a molar ratio of 1:0.9, dissolved in toluene at a mass fraction of 33 wt%, placed in a reaction tube under vacuum, and then irradiated with 540 nm green light at 25 °C for 24 h to obtain the stepwise polymerization product P(DCDTPA- alt -DVB).

[0069] Example 3

[0070] This embodiment provides a light-induced stepwise polymerization method, specifically including the following steps:

[0071] Step 1, add 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid, trimethylolpropane, N,N' -Dicyclohexylcarbodiimide and 4-dimethylaminopyridine were reacted in a molar ratio of (2:1:3:1) in dichloromethane at 0°C for 48 h to obtain a bifunctional chain transfer reagent, denoted as DCDTPA. The volume ratio of dichloromethane to the total amount of reactants was 100:1.

[0072] Step 2: The DCDTPA obtained in Step 1 is mixed with divinylbenzene at a molar ratio of 1:0.8, dissolved in dimethyl sulfoxide at a mass fraction of 10 wt%, placed in a reaction tube under vacuum, and then irradiated with 550 nm green light at 30 °C for 12 h to obtain the stepwise polymerization product P(DCDTPA- alt -DVB).

[0073] Example 4

[0074] This embodiment provides a light-induced stepwise polymerization method, specifically including the following steps:

[0075] Step 1, add 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid, trimethylolpropane, N,N' -Dicyclohexylcarbodiimide and 4-dimethylaminopyridine were reacted in a molar ratio of (2:1:3:1) in dichloromethane at 10°C for 48 h to obtain a bifunctional chain transfer reagent, denoted as DCDTPA. The volume ratio of dichloromethane to the total amount of reactants was 100:1.

[0076] Step 2: The DCDTPA obtained in Step 1 is mixed with divinylbenzene at a molar ratio of 1:0.7, dissolved in DMF at a mass fraction of 5 wt%, placed in a reaction tube under vacuum, and then irradiated with 520 nm green light at 0°C for 48 h to obtain the stepwise polymerization product P(DCDTPA- alt -DVB).

[0077] Example 5

[0078] This embodiment provides a photoinduced stepwise polymerization method and a degradation method for the resulting polymer. The method is the same as steps 1 and 2 of Example 1, except that in step 2, the divinylbenzene is replaced with di(4-vinylbenzoic acid)dithiobis(ethane-2,1-diyl) ester (DSBVB) containing disulfide bonds, to obtain the degradable polymer P(DCDTPA- alt -DSBVB), and then a polymer with polymethyl acrylate (PMA) side chains was synthesized by RAFT polymerization. The polymer was then mixed with tributylphosphine and reacted for 20 min to achieve polymer depolymerization.

[0079] The molar ratio of the biodegradable polymer to tributylphosphine is approximately 1:100.

[0080] Example 6

[0081] This embodiment provides a photoinduced stepwise polymerization method and a degradation method for the resulting polymer. The method is the same as steps 1 and 2 in Example 2, except that in step 2, the divinylbenzene is replaced with di(4-vinylbenzoic acid)dithiobis(ethane-2,1-diyl) ester (DSBVB) containing disulfide bonds, to obtain the degradable polymer P(DCDTPA- alt -DSBVB), and then a polymer with polymethyl acrylate (PMA) side chains was synthesized by RAFT polymerization. The polymer was then mixed with tributylphosphine and reacted for 10 min to achieve polymer depolymerization.

[0082] The molar ratio of the biodegradable polymer to tributylphosphine is approximately 1:150.

[0083] Example 7

[0084] This embodiment provides a photoinduced stepwise polymerization method and a degradation method for the resulting polymer. The method is the same as steps 1 and 2 in Example 3, except that in step 2, the divinylbenzene is replaced with di(4-vinylbenzoic acid)dithiobis(ethane-2,1-diyl) ester (DSBVB) containing disulfide bonds, to obtain the degradable polymer P(DCDTPA- alt-DSBVB), and then a polymer with polymethyl acrylate (PMA) side chains was synthesized by RAFT polymerization. The polymer was then mixed with tributylphosphine and reacted for 5 min to achieve polymer depolymerization.

[0085] The molar ratio of the biodegradable polymer to tributylphosphine is approximately 1:200.

[0086] Example 8

[0087] This embodiment provides a photoinduced stepwise polymerization method and a degradation method for the resulting polymer. The method is the same as steps 1 and 2 in Example 4, except that in step 2, the divinylbenzene is replaced with di(4-vinylbenzoic acid)dithiobis(ethane-2,1-diyl) ester (DSBVB) containing disulfide bonds, to obtain the degradable polymer P(DCDTPA- alt -DSBVB), and then a polymer with polymethyl acrylate (PMA) side chains was synthesized by RAFT polymerization. The polymer was then mixed with tributylphosphine and reacted for 1 min to achieve polymer depolymerization.

[0088] The molar ratio of the biodegradable polymer to tributylphosphine is approximately 1:300.

[0089] The methods of Examples 1 to 8 of the present invention form alternating copolymers while maintaining a linear structure, avoiding the complexities caused by crosslinking and branching. In particular, the molecular weight of the degradation products of Examples 5 to 8 is significantly reduced.

[0090] Comparative Example 1

[0091] This comparative example provides a photoinduced stepwise polymerization method, which uses the same method as in Example 1, except that in step 2, divinylbenzene is replaced with vinyl ether, ultimately forming a RAFT-SUMI adduct instead of a homopolymer.

[0092] Comparative Example 2

[0093] This comparative example provides a photo-induced stepwise polymerization method, which uses the same method as in Example 3, except that divinylbenzene in step 2 is replaced with styrene. The end-group retention rate of the final product is significantly reduced and it is difficult to achieve structural control.

[0094] Comparative Example 3

[0095] This comparative example provides a photoinduced stepwise polymerization method, employing the same method as in Example 1, except that 530 nm green light is replaced with 490 nm blue light. The molecular weight distribution of the final product is broadened, and the end-group retention rate is significantly reduced.

[0096] The preparation method provided in this invention induces polymerization through medium-wavelength green light, reducing side reactions and expanding the monomer range to include styrene monomers containing highly reactive double bonds. By designing disulfide bonds within the monomers, on-demand polymer degradation can be achieved. This photo-induced stepwise polymerization method enables the preparation of various recyclable polymers. The polymers of this invention can be used in automotive interior and exterior materials, are easily degraded under environmental conditions, and meet the needs of carbon reduction and green development.

[0097] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A green light-induced stepwise polymerization method, characterized in that, The method includes: Step a: 4-cyano-4-[(dodecylthiocarbonyl)thio]valeric acid is esterified with trimethylolpropane in dichloromethane under the catalysis of a catalyst to obtain the bifunctional chain transfer reagent DCDTPA; Step b: Mix the DCDTPA with vinyl monomers, dissolve them in an organic solvent, and polymerize them under vacuum conditions by irradiating them with green light to obtain the polymer.

2. The method according to claim 1, characterized in that, The vinyl monomer is divinylbenzene or dithiodimethylbis(ethane-2,1-diyl) ester.

3. The method according to claim 1 or 2, characterized in that, The organic solvent is selected from one or more of tetrahydrofuran, toluene, dimethyl sulfoxide, and N,N-dimethylformamide.

4. The method according to claim 1 or 2, characterized in that, The polymerization is carried out under vacuum conditions and irradiated with green light with a wavelength of 500~550nm. Preferably, the reaction temperature of the polymerization is 0℃~30℃, and preferably the molecular weight of the polymer is in the range of 3000 Da to 30,000 Da.

5. The method according to claim 1 or 2, characterized in that, Preferably, the molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valerate to trimethylolpropane is between 2:1 and 3:1, and preferably the molar ratio of DCDTPA to divinylbenzene is between 1:0.9 and 1:

1.

6. The method according to claim 1 or 2, characterized in that, The catalyst includes a Lewis base catalyst, preferably 4-dimethylaminopyridine, preferably the amount of catalyst is 10% to 50% based on the total molar amount of reactants, and preferably the esterification reaction is carried out at a temperature of 0°C to 30°C for 12 to 48 hours.

7. A green light-induced stepwise polymer, characterized in that, The polymer is prepared by the method according to any one of claims 1 to 6.

8. The polymer according to claim 7, characterized in that, The vinyl monomer is a styrene monomer containing a disulfide bond, and preferably the vinyl monomer is a dithiodimethylbis(ethane-2,1-dimethyl) ester.

9. A method for degrading a polymer, characterized in that, The polymer is the polymer according to claim 8, and the degradation method includes reacting the polymer with tributylphosphine to achieve depolymerization of the polymer.

10. The method according to claim 9, characterized in that, The molar ratio of the polymer to the tributylphosphine is 1:150~300.

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