A dual-responsive cabc type asymmetric block copolymer and a synthesis method thereof
A CO2/photoresponsive CABC-type asymmetric block copolymer was synthesized by reversible complexation-mediated free radical polymerization, which solved the problems of cumbersome and unstable traditional methods and realized the macroscopic fluorescence performance and photoresponsive crosslinking ability of CO2-responsive nanovesicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FUZHOU UNIV
- Filing Date
- 2023-05-26
- Publication Date
- 2026-05-05
AI Technical Summary
Existing CO2-responsive nanodevices cannot demonstrate responsiveness on a macroscopic scale, and the traditional synthesis process of block copolymers is cumbersome and unstable.
A CO2/photoresponsive CABC-type asymmetric block copolymer was synthesized using reversible complexation-mediated free radical polymerization. CO2/photoresponsive polymer vesicles were prepared by a three-step method, and the CO2 response behavior was reflected by fluorescent monomers.
The synthesis process of block copolymers was simplified, efficiency was improved, and block copolymers with precise molecular weight and low polydispersity were obtained, realizing the macroscopic fluorescence performance and photoresponsive crosslinking ability of CO2-responsive nanovesicles.
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Figure CN116554420B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanomaterial preparation, specifically relating to a CO2 / photoresponsive CABC-type asymmetric block copolymer and its preparation method, and CO2 / photoresponsive polymer vesicles formed by its self-assembly. Background Technology
[0002] Stimulus-responsive block copolymers, also known as environmentally responsive block copolymers, are a class of polymers that undergo corresponding changes in response to certain external stimuli. These stimulus-response changes are non-linear and generally involve alterations in molecular configuration, molecular solubility, and the formation or breaking of chemical bonds. External stimuli include physical, chemical, and biochemical stimuli, such as CO2, light, and pH. Based on the specific external stimulus, stimulus-responsive block copolymers are classified into CO2-responsive block copolymers, light-responsive block copolymers, pH-responsive block copolymers, etc. However, previous studies have shown that single CO2-responsive nanodevices are often limited to microscopic responses, failing to demonstrate macroscopic response effects.
[0003] CABC-type asymmetric block copolymers are an interesting class of block copolymers that can self-assemble into non-centrosymmetric nanostructures, exhibiting properties different from ordinary block copolymers. Currently, almost all block copolymers are synthesized using controlled polymerization methods, primarily including anionic polymerization, controlled radical polymerization, and group transfer polymerization. Among these controlled polymerization technologies, controlled radical polymerization is the most promising industrial production technology due to its wide monomer range and mild conditions, possessing greater practical significance.
[0004] Taking advantage of the simple operation, energy saving, spatiotemporal controllable polymer polydispersity (Mw / Mn), and strong tolerance to functional groups of reversible complex-mediated free radical polymerization (RCMP), CO2-stimulated responsive monomers and photo-stimulated responsive monomers can be simultaneously introduced into CABC-type asymmetric block copolymers to obtain a polymer with CO2-responsive and photo-responsive functions, which can then be self-assembled to obtain CO2 / photo-responsive nanovesicles. Summary of the Invention
[0005] The purpose of this invention is to provide a CO2 / photoresponsive CABC-type asymmetric block copolymer and its preparation method, as well as CO2 / photoresponsive polymer vesicles assembled therefrom.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A CO2 / light-responsive CABC-type asymmetric block copolymer, wherein the block monomers include:
[0008] (1) Hydrophobic monomer A;
[0009] (2) Photoresponsive monomer B with hydrophobic and fluorescent properties;
[0010] (3) CO2-responsive monomer C with hydrophilic properties.
[0011] Wherein, monomer A is methyl methacrylate (MMA), and CO2-responsive monomer C is dimethylaminoethyl methacrylate (DMAEMA).
[0012] The photoresponsive monomer B is specifically a coumarin-based photoresponsive monomer (CMMA), and its synthetic route is as follows: Its synthesis steps include:
[0013] a) Mix 0.529 g of 7-hydroxy-4-methylcoumarin, 10 mL of 16.8 g / L potassium hydroxide solution, 0.05 g of polyethylene glycol and 40 mL of tetrahydrofuran (THF), sonicate for 20 min, and then deoxygenate with high-purity nitrogen in an ice-water bath for 20 min.
[0014] b) Add 1.41 mL of methacryloyl chloride to the mixture obtained in step a), stir at 0°C for 2.5 h, then add it to deionized water for precipitation, and filter to remove excess impurities;
[0015] c) Subsequently, the sample was washed successively with a 40 g / L sodium hydroxide solution and a saturated sodium chloride solution, and then dried under vacuum to obtain the coumarin-based photoresponsive monomer.
[0016] Coumarin-based photoresponsive monomers exhibit changes in fluorescence intensity with microscale variations in nanodevices due to their polymerization-induced mechanisms. This characteristic may contribute to the visualization of CO2 responsiveness in nanodevices.
[0017] The preparation of the CO2 / photoresponsive CABC-type asymmetric block copolymer involves first synthesizing a bromine initiator containing two initiation sites, then converting the bromine initiator with two initiation sites into a macromolecular initiator with carbon-iodine bond active sites at both ends. The macromolecular initiator is then photoinitiated to polymerize monomer MMA via the carbon-iodine bonds on the macromolecular initiator. The resulting polymer is then photoinitiated to polymerize the photoresponsive monomer CMMA via the carbon-iodine bonds at both ends. Finally, the resulting polymer is thermally polymerized using the carbon-iodine bonds at both ends and the intermediate azo group. The preparation method includes the following steps:
[0018] (1) 4,4'-azobis(4-cyanopentanol), α-bromophenylacetic acid and 4-dimethylaminopyridine were mixed evenly in dichloromethane, and N,N'-dicyclohexylcarboimide dissolved in dichloromethane was added at 0°C. After stirring for 1 h, the reaction system was transferred to room temperature and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered, and the filtrate was concentrated by rotary evaporation and purified by silica gel column chromatography to obtain the bromine initiator Br-EPhAzo-Br containing dual initiation sites.
[0019] (2) MMA, the bromine initiator Br-EPhAzo-Br with dual initiation sites obtained in step (1), sodium iodide and pentamethyldiethylenetriamine were added to a glass bottle in sequence, the bottle mouth was sealed with a rubber stopper and excess air was removed, and then the reaction was carried out under stirring and irradiated with a white LED light. After the reaction, the sample was precipitated in n-hexane and then dried under vacuum to obtain the macromolecular initiator I-PMMA-N=N-PMMA-I;
[0020] (3) CMMA, the macromolecular initiator I-PMMA-N=N-PMMA-I obtained in step (2), iodine, pentamethyldiethylenetriamine, and toluene were added sequentially to a glass bottle. The bottle opening was sealed with a rubber stopper to remove excess air. The reaction was then carried out under stirring and irradiated with a white LED light. After the reaction, the sample was precipitated in petroleum ether, washed with diethyl ether, and then dried under vacuum to obtain the macromolecular initiator I-PCMMA- b -PMMA-N=N-PMMA- b -PCMMA-I;
[0021] (4) Add DMAEMA and the macromolecular initiator I-PCMMA obtained in step (3) b -PMMA-N=N-PMMA- b -PCMMA-I was added sequentially to a Schlenk tube with elemental iodine, tetrabutylammonium iodide, and toluene. After three cycles of liquid nitrogen freezing-vacuuming-thawing for deoxygenation, polymerization was carried out at a specific temperature. The resulting sample was precipitated in petroleum ether, washed with diethyl ether, and then vacuum dried to obtain the target product I-PDMAEMA-. b -PMMA- b -PCMMA- b -PDMAEMA-I.
[0022] Furthermore, the molar ratio of 4,4'-azobis(4-cyanopentanol), α-bromophenylacetic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarboimide used in step (1) is 1:2.2:0.19:2.4.
[0023] Furthermore, the silica gel column chromatography purification in step (1) uses a 4:1 volume ratio of dichloromethane / n-hexane mixed solution as the eluent.
[0024] Furthermore, the molar ratio of MMA, bromine initiator Br-EPhAzo-Br containing dual initiation sites, sodium iodide and pentamethyldiethylenetriamine used in step (2) is 100:1:2.4:0.5.
[0025] Furthermore, the irradiation power in step (2) is 13 Wm. -1 Strength is 15 mW·cm -2 The reaction time is 120 min.
[0026] Furthermore, the molar ratio of CMMA, macromolecular initiator I-PMMA-N=N-PMMA-I, elemental iodine and pentamethyldiethylenetriamine used in step (3) is 60:1:1:0.5.
[0027] Furthermore, the irradiation power in step (3) is 13 Wm. -1 Strength is 15 mW·cm -2 The reaction time is 180 min.
[0028] Furthermore, the DMAEMA and macromolecular initiator I-PBzMA- used in step (4) b -PMMA-N=N-PMMA- b The molar ratio of PBzMA-I, elemental iodine, and tetrabutylammonium iodide is 800:1:1:4.
[0029] Furthermore, the polymerization reaction in step (4) is carried out at a temperature of 90 °C for 60 min.
[0030] The CO2 / photoresponsive CABC-type asymmetric block copolymer can be further prepared into CO2 / photoresponsive polymer vesicles, the vesicle wall of which is composed of hydrophobic PMMA and PCMMA blocks, and the outer coronal structure and the inner core region are composed of hydrophilic PDMAEMA blocks.
[0031] Furthermore, the specific method for preparing this polymer vesicle involves applying 1 mg of polymer I-PDMAEMA- b -PMMA- b -PCMMA- b -PDMAEMA-I was fully dissolved in 0.5 mL of tetrahydrofuran, and 1 mL of ultrapure water was slowly added dropwise while stirring for 1 h. Then, 9 mL of ultrapure water was added, and the mixture was stirred for another 1 h before being allowed to stand for 24 h to obtain the CO2 / photoresponsive polymer vesicles.
[0032] This invention utilizes reversible complexation-mediated polymerization technology to construct a three-step method of photopolymerization-photopolymerization-thermal polymerization for the synthesis of CO2 / photoresponsive CABC-type asymmetric block copolymers. This method overcomes the problems of cumbersome and unstable controllability inherent in traditional sequential polymerization processes, and solves the difficulties in preparing and storing iodine catalysts and the susceptibility of end groups to thermal decomposition in reversible complexation-mediated polymerization systems. Furthermore, the CO2 / photoresponsive nanovesicles prepared using the obtained asymmetric block copolymers can macroscopically exhibit CO2 responsiveness through varying fluorescence intensity, providing insights and support for the research of CO2-sensing nanodevices.
[0033] The key features of this invention are:
[0034] 1. The synthesis method of CO2 / photoresponsive CABC type asymmetric block copolymer established in this invention is simpler and more efficient than conventional sequential polymerization.
[0035] 2. The synthesis method of CO2 / photoresponsive CABC type asymmetric block copolymer established in this invention is controllable, and a CO2 / photoresponsive CABC type asymmetric block copolymer with accurate molecular weight and low polydispersity is obtained.
[0036] 3. The CO2 / photoresponsive polymer vesicles synthesized using the asymmetric block copolymer obtained in this invention can reflect the CO2 response behavior by observing changes in fluorescence intensity with the naked eye, and also have photoresponsive crosslinking ability. Attached Figure Description
[0037] Figure 1 This is a synthetic route diagram for the CO2 / photoresponsive CABC-type asymmetric block copolymer of the present invention.
[0038] Figure 2 The image shows the proton NMR spectrum of the photoresponsive monomer CMMA obtained in Example 1.
[0039] Figure 3 The image shows the 1H NMR spectrum of the initiator Br-EPhAzo-Br obtained in Example 2.
[0040] Figure 4 The I-PMMA-N=N-PMMA-I and I-PCMMA- obtained in Examples 3-5 b -PMMA-N=N-PMMA- b -PCMMA-I, I-PDMAEMA- b -PMMA- b -PCMMA- b -PDMAEMA-I 1H NMR spectrum.
[0041] Figure 5The I-PMMA-N=N-PMMA-I and I-PCMMA- obtained in Examples 3-5 b -PMMA-N=N-PMMA- b -PCMMA-I, I-PDMAEMA- b -PMMA- b -PCMMA- b -PDMAEMA-I GPC effluent time curve.
[0042] Figure 6 This is a transmission electron microscope (TEM) image of the polymer vesicles obtained in Example 6.
[0043] Figure 7 The graph shows the hydrodynamic diameter changes of the polymer vesicles in Example 7 under CO2 and N2 stimulation.
[0044] Figure 8 The graph shows the fluorescence intensity changes of the polymer vesicles in Example 7 under CO2 and N2 stimulation.
[0045] Figure 9 This is a graph showing the fluorescence intensity changes of the polymer vesicles in Example 8 under ultraviolet light stimulation. Detailed Implementation
[0046] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.
[0047] Example 1
[0048] 0.529 g of 7-hydroxy-4-methylcoumarin, 10 mL of potassium hydroxide solution (16.8 g / L), 0.05 g of polyethylene glycol, and 40 mL of THF were added to a round-bottom flask. After ultrasonic dispersion for 20 min, the mixture was deoxygenated with high-purity nitrogen in an ice-water bath for 20 min. Then, 1.4 mL of methacryloyl chloride was added to the round-bottom flask, and the mixture was stirred at 0 °C for 2.5 h. The resulting mixture was added to deionized water for precipitation, and then filtered to remove excess impurities. Subsequently, the crude product was washed successively with 40 g / L sodium hydroxide solution and saturated sodium chloride solution, and dried in a vacuum drying oven to obtain the coumarin-based photoresponsive monomer CMMA as a dry white flocculent with a yield of 94%.
[0049] The product obtained in Example 1 was analyzed by proton nuclear magnetic resonance spectroscopy (deuterated acetone was used as the deuteration reagent), and the results are shown in the figure. Figure 2 . Figure 2 The results indicate the successful synthesis of CMMA.
[0050] Example 2
[0051] In a 100 mL round-bottom flask, 2.0 g of 4,4'-azobis(4-cyanopentanol), 3.784 g of α-bromophenylacetic acid, and 0.185 g of 4-dimethylaminopyridine were added to 50 mL of dichloromethane and mixed thoroughly. Then, N,N'-dicyclohexylcarboimide (3.955 g) dissolved in 15 mL of dichloromethane was slowly added dropwise at 0 °C. After stirring for 1 h, the reaction system was transferred to room temperature and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered, and the filtrate was concentrated by rotary evaporation and purified by silica gel column chromatography (eluent: dichloromethane:n-hexane = 4:1, v / v). The target product Br-EPhAzo-Br was finally obtained in 63% yield.
[0052] The product obtained in Example 2 was analyzed by proton nuclear magnetic resonance spectroscopy (deuterated chloroform was used as the deuteration reagent), and the results are shown in the figure. Figure 3 . Figure 3 The results indicate the successful synthesis of Br-EPhAzo-Br.
[0053] Example 3
[0054] 2 mL of MMA, 122.0 mg of Br-EPhAzo-Br, 68.0 mg of NaI, and 4.08 mg of PMDETA were sequentially added to a 3 mL glass bottle. The bottle was sealed with a rubber stopper, and excess air was removed by purging with nitrogen. The bottle containing the reaction mixture was then placed on a stirring table, and an LED lamp (13 Wm) was used for stirring. -1 Strength is 15 mW·cm -2 After irradiation for 120 minutes, the mixture was redeposited in n-hexane and dried under vacuum to obtain the macromolecular initiator I-PMMA-N=N-PMMA-I. M n =6600, M w / M n =1.20.
[0055] Example 4
[0056] 276.40 mg CMMA, 109.5 mg I-PMMA-N=N-PMMA-I, 4.80 mg iodine, 1.63 mg PMDETA, and 4 mL toluene were added sequentially to a 10 mL glass bottle. The bottle was sealed directly with a rubber stopper. Excess air was then removed from the bottle by purging with nitrogen. The glass bottle containing the reaction mixture was then placed on a stirring table, and an LED lamp (13 Wm) was used for stirring. -1 Strength is 15 mW·cm -2After irradiation for 180 min, the reacted sample was precipitated in petroleum ether, washed with diethyl ether, and then vacuum dried to obtain the macromolecular initiator I-PCMMA-. b -PMMA-N=N-PMMA- b -PCMMA-I, its M n =7800, M w / M n =1.18.
[0057] Example 5
[0058] Combine 3.18mL DMAEMA, 193.52mg I-PBzMA- b -PMMA-N=N-PMMA- b 6.00 mg I2, 34.83 mg BNI, and 4 mL toluene were sequentially added to a 25 mL Schlenk tube, and the tube was sealed directly with a rubber stopper. The Schlenk tube containing the reaction mixture was then subjected to three cycles of liquid nitrogen freezing-evacuation-thawing for deoxygenation. The reaction mixture was then reacted at 90 °C for 60 min. The resulting sample was precipitated in petroleum ether, washed with diethyl ether, and then vacuum dried to obtain the CABC-type asymmetric block copolymer I-PDMAEMA- b -PMMA- b -PCMMA- b -PDMAEMA-I, its M n =9100, M w / M n =1.35.
[0059] The products obtained in Examples 3-5 were analyzed using 1H NMR spectroscopy (deuterated acetone and deuterated chloroform were used as the deuteration reagents), and the results are shown in the figure. Figure 4 . Figure 4 The results show that I-PDMAEMA- b -PMMA- b -PCMMA- b The presence of characteristic peaks for each block monomer of -PDMAEMA-I indicates that the CABC-type asymmetric block copolymer I-PDMAEMA- b -PMMA- b -PCMMA- b Successful synthesis of PDMAEMA-I.
[0060] The molecular weights of the products obtained in Examples 3-5 were determined using gel permeation chromatography, and the results are shown in the figure. Figure 5 . Figure 5 The results demonstrate the chain extension process of each block monomer during polymer synthesis, proving the smooth progress of the polymerization process.
[0061] Example 6
[0062] 1 mg of polymer I-PDMAEMA- b -PMMA- b -PCMMA- b - PDMAEMA-I was fully dissolved in 0.5 mL of tetrahydrofuran, and 1 mL of ultrapure water was slowly added dropwise. The mixture was stirred continuously for 1 h, and then 9 mL of ultrapure water was added. The mixture was stirred continuously for another 1 h and then allowed to stand for 24 h to obtain CO2 / photoresponsive polymer vesicles.
[0063] The product obtained in Example 6 was tested using transmission electron microscopy (TEM), and the results are shown in the figure. Figure 6 . Figure 6 The results revealed the specific configuration of the polymer vesicles, namely, the vesicle walls are composed of hydrophobic PMMA and PCMMA blocks, which serve to block the water medium inside and outside the vesicles and also stabilize the vesicle structure; the outer coronal structure and the inner core region of the vesicles are composed of hydrophilic PDMAEMA blocks.
[0064] Example 7
[0065] Carbon dioxide was bubbled into a 10 mL solution of polymer vesicles at a rate of 1 mL / s using a float flowmeter for 20 min. The resulting gas was then analyzed using a nanoparticle size analyzer and a fluorescence spectrophotometer. Subsequently, nitrogen gas was bubbled into the polymer vesicle solution at a rate of 4 mL / s using a float flowmeter for 20 min. This gas was then again characterized using a nanoparticle size analyzer and a fluorescence spectrophotometer.
[0066] Figure 7 The graph shows the hydrodynamic diameter changes of polymer vesicles under CO2 and N2 stimulation. Figure 7 The results confirmed that polymer vesicles have the ability to undergo microscopic volume changes in response to carbon dioxide stimulation.
[0067] Figure 8 The fluorescence intensity changes of polymer vesicles under CO2 and N2 stimulation. Figure 8 The results confirmed that polymer vesicles can express microscopic responsive behavior as macroscopic changes in fluorescence intensity.
[0068] Example 8
[0069] A solution of 1.2 mL of polymer vesicles was placed in a cuvette and continuously irradiated with a 365 nm UV lamp for 30 min, 60 min, 120 min, 240 min, 360 min and 480 min, and then tested and analyzed by a fluorescence spectrophotometer.
[0070] Figure 9 The fluorescence intensity change of polymer vesicles under ultraviolet light stimulation. Figure 9 The results confirmed that the polymer vesicles have the ability to change fluorescence intensity in response to ultraviolet light stimulation.
[0071] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for synthesizing a CO2 / light-responsive CABC-type asymmetric block copolymer, characterized in that: First, a bromine initiator containing two initiation sites is synthesized. Then, the bromine initiator with two initiation sites is converted in situ via bromine-iodine conversion to generate a macromolecular initiator with carbon-iodine bond active sites at both ends. Monomer A is then photoinitiated using the carbon-iodine bonds on the macromolecular initiator. Next, the carbon-iodine bonds at both ends of the resulting polymer are used to photoinitiate chain extension polymerization of photoresponsive monomer B. Finally, the carbon-iodine bonds at both ends and the intermediate azo group of the resulting polymer are used to simultaneously thermally initiate the polymerization of CO2-responsive monomer C, thereby obtaining the CO2 / photo-responsive CABC type asymmetric block copolymer. The specific steps include the following: (1) 4,4'-azobis(4-cyanopentanol), α-bromophenylacetic acid and 4-dimethylaminopyridine were mixed evenly in dichloromethane, and N,N'-dicyclohexylcarboimide dissolved in dichloromethane was added at 0°C. After stirring for 1 h, the reaction system was transferred to room temperature and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered, and the filtrate was concentrated by rotary evaporation and purified by silica gel column chromatography to obtain the bromine initiator Br-EPhAzo-Br containing dual initiation sites. (2) Add monomer A, the bromine initiator Br-EPhAzo-Br with dual initiation sites obtained in step (1), sodium iodide and pentamethyldiethylenetriamine to a glass bottle in sequence, seal the bottle mouth with a rubber stopper and remove excess air, and then react under stirring conditions with white LED light. After the reaction, the sample is precipitated in n-hexane and then dried under vacuum to obtain the macromolecular initiator I-PMMA-N=N-PMMA-I; (3) The photoresponsive monomer B, the macromolecular initiator I-PMMA-N=N-PMMA-I obtained in step (2), iodine, pentamethyldiethylenetriamine, and toluene were sequentially added to a glass bottle. The bottle mouth was sealed with a rubber stopper to remove excess air. The reaction was then carried out under stirring and irradiated with a white LED lamp. After the reaction, the sample was precipitated in petroleum ether, washed with diethyl ether, and then dried under vacuum to obtain the macromolecular initiator I-PCMMA- b -PMMA-N=N-PMMA- b -PCMMA-I; (4) Combine the CO2-responsive monomer C and the macromolecular initiator I-PCMMA obtained in step (3). b -PMMA-N=N-PMMA- b -PCMMA-I was added sequentially to a Schlenk tube with elemental iodine, tetrabutylammonium iodide, and toluene. After three cycles of liquid nitrogen freezing-vacuuming-thawing for deoxygenation, polymerization was carried out at a specific temperature. The resulting sample was precipitated in petroleum ether, washed with diethyl ether, and then vacuum dried to obtain the target product I-PDMAEMA-. b -PMMA- b -PCMMA- b -PDMAEMA-I; Wherein, monomer A is methyl methacrylate, CO2-responsive monomer C is dimethylaminoethyl methacrylate, and photoresponsive monomer B is specifically a coumarin-based photoresponsive monomer with the following structural formula: .
2. The method for synthesizing a CO2 / photoresponsive CABC-type asymmetric block copolymer according to claim 1, characterized in that: The molar ratio of 4,4'-azobis(4-cyanopentanol), α-bromophenylacetic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarboimide used in step (1) is 1:2.2:0.19:2.4; The silica gel column chromatography purification uses a 4:1 volume ratio of dichloromethane / n-hexane mixed solution as the eluent.
3. The method for synthesizing a CO2 / photoresponsive CABC-type asymmetric block copolymer according to claim 1, characterized in that: The molar ratio of monomer A, bromine initiator Br-EPhAzo-Br containing two initiation sites, sodium iodide and pentamethyldiethylenetriamine used in step (2) is 100:1:2.4:0.5; The irradiation power was 13 Wm. -1 Strength is 15 mW·cm -2 The reaction time is 120 min.
4. The method for synthesizing a CO2 / photoresponsive CABC-type asymmetric block copolymer according to claim 1, characterized in that: The molar ratio of photoresponsive monomer B, macromolecular initiator I-PMMA-N=N-PMMA-I, elemental iodine and pentamethyldiethylenetriamine used in step (3) is 60:1:1:0.5; The irradiation power was 13 Wm. -1 Strength is 15 mW·cm -2 The reaction time is 180 min.
5. The method for synthesizing a CO2 / photoresponsive CABC-type asymmetric block copolymer according to claim 1, characterized in that: The CO2-responsive monomer C and the macromolecular initiator I-PBzMA- used in step (4) b -PMMA-N=N-PMMA- b -PBzMA-I, the molar ratio of elemental iodine to tetrabutylammonium iodide is 800:1:1:4; The polymerization reaction was carried out at a temperature of 90 °C for 60 min.
6. The method for synthesizing a CO2 / photoresponsive CABC-type asymmetric block copolymer according to claim 1, characterized in that: The synthesis steps of the photoresponsive monomer B include: a) Mix 0.529 g of 7-hydroxy-4-methylcoumarin, 10 mL of 16.8 g / L potassium hydroxide solution, 0.05 g of polyethylene glycol and 40 mL of THF, sonicate for 20 min, and then deoxygenate with high-purity nitrogen in an ice-water bath for 20 min. b) Add 1.41 mL of methacryloyl chloride to the mixture obtained in step a), stir at 0°C for 2.5 h, then add it to deionized water for precipitation, and filter to remove excess impurities; c) Subsequently, the sample was washed successively with a 40 g / L sodium hydroxide solution and a saturated sodium chloride solution, and then dried under vacuum to obtain the coumarin-based photoresponsive monomer.