A photo-controlled reversible crosslinking agent and its preparation method and application in amide polymer

Abstract

The present application discloses a photo-controlled reversible cross-linking agent, a preparation method thereof, and an application in amide polymers, and belongs to the field of new material technology. The photo-controlled reversible cross-linking agent of the present application is a multifunctional cross-linking agent based on the coupling of diarylethene photoswitch and maleic anhydride, which can realize the regulation of partial electronic effect and ring tension of the anhydride by bidirectional visible light, and then control its reactivity with secondary amines, and is used for variable cross-linking density of amide polymers and photo-activated recycling and reuse. Furthermore, the photo-controlled activation and closure of the above-mentioned amide bond can be used to realize controllable degradation and recovery of polymers and selective switching of high stability, thereby realizing selective customization of material properties. The photo-controlled reversible cross-linking agent provided by the present application has a good application prospect in the selective in-situ customization of polymer material properties.

Description

Technical Field

[0001] The present application relates to a light-controlled reversible crosslinking agent, a preparation method thereof and application in amide polymers, and belongs to the technical field of new materials. Background Art

[0002] Global issues such as environmental pollution, energy shortages, and climate change have put forward urgent requirements for the development of sustainable chemistry. As a typical example, high-performance polymer materials (such as rubber, plastic, and resin) play a very important role in human production and life, but the problem of recycling and reuse has caused resource waste and seriously affected the environment. A strategy in chemical recycling that can achieve polymer degradation and recycling is expected to contribute to this solution and is one of the frontiers of chemical and material research. Decomposing covalent materials into starting building blocks (such as polymer monomers) and then reassembling them to complete closed-loop recycling will achieve a circular economy, and precise control of the breaking and formation of covalent bonds will be the key.

[0003] Dynamic covalent bond chemistry is a powerful tool for the development of recyclable chemistry due to the reversible formation, breaking and exchange of covalent bonds. It also creates rich opportunities for the research of responsive, adaptive and repairable materials. In particular, by manipulating the reversible exchange properties of covalent bonds in dynamic covalent polymer networks, the robustness of thermosetting materials and the processability of thermoplastic materials can be taken into account. Although dynamic covalent bonds are easily broken under external stimuli (such as temperature, acid and alkali), they are usually at the expense of inherent stability. For example, dynamic carbon-nitrogen bonds are generally not acid-resistant. How to balance the contradiction between the kinetic dynamics and stability of dynamic covalent bonds to achieve the control of the recyclability and stability of covalent materials is a challenge.

[0004] As an important functional group, amide bonds are widely present in the structures of polymers (nylon, Kevlar), biomolecules (proteins) or drugs (accounting for 54% of marketed drugs). Compared with other types of dynamic covalent bonds, due to the p-π conjugation between the carbonyl group and the nitrogen atom in the amide group, its CN bond strength is as high as 90-100 kcal / mol and has extremely high stability. Therefore, developing amide bonds into dynamic covalent bonds can bring more opportunities for the development of dynamic covalent chemistry and smart materials. However, there are still few reports on degradable and recyclable cross-linked polymers constructed using dynamic amide bonds, and there is no wide range of application. For example, the literature ( Nat. Commun. 2014, 5 , 3218) By introducing large steric groups to construct dynamic urea bonds, self-healing and recyclable polymer materials were obtained. ACS Macro Lett. 2019, 8 , 233−238) constructed a dynamic amide bond based on ethyl acetoacetate to prepare a thermoplastic cross-linked polymer that can be processed and recycled. Nat. Commun.2022, 13 , 7595) A class of polymer cross-linked networks with controllable mechanical properties and closed-loop recycling capabilities were constructed based on the reversible amidation reaction between maleic anhydride and secondary amines. The dynamic covalent polymers constructed using dynamic amide bonds in the above examples are permanently dynamic, and their reversibility is easily affected by external stimuli such as acid. They are insufficient in inherent stability, thus losing the advantage of high stability of amide bonds, thus limiting the practical application of materials. Therefore, it is of great significance to develop a system that can control the dynamics of amide bonds in situ and achieve efficient regulation through light irradiation for controllable cross-linking density of polymers and degradation and recycling. Summary of the invention

[0005] Photo-controlled reversible crosslinking agent, preparation method thereof and application in amide polymer

[0006] This application adopts the following technical solutions:

[0007] According to one aspect of the present application, a photo-controlled reversible cross-linking agent is provided, wherein the photo-controlled reversible cross-linking agent has a structure shown in Formula Ia or Formula Ib:

[0008] Formula Ia;

[0009] Formula Ib;

[0010] Wherein, R2 and R3 are selected from CH3, R4 is selected from one of CF3, H, and CH3O; R1 is selected from a structure in Formula II:

[0011] Formula II.

[0012] The light-controlled reversible cross-linking agent is a compound formed by coupling a diarylethene photoswitch molecule with maleic anhydride.

[0013] According to another aspect of the present application, a photo-controlled reversible cross-linking agent is provided, comprising the following steps:

[0014] S1. Preparation of intermediate 3: a dichloroimide derivative, arylboronic acid, BnEt3N + Cl - , a mixture of PdCl2(PPh3)2, toluene, cesium fluoride and water, to carry out reaction I, and to obtain intermediate 3 after extraction, drying and separation;

[0015] S2, containing intermediate 3, aryl borate, BnEt3N + Cl - , a mixture of PdCl2(PPh3)2, toluene, cesium fluoride and water, to carry out reaction II, and to obtain intermediate 4 after extraction, drying and separation;

[0016] S3. The mixture containing intermediate 4, DMAP and dichloromethane is subjected to reaction III, and then EDCI is added to carry out reaction IV, and then an amine-containing compound is added to carry out reaction V. After extraction, drying and separation, the product is dissolved in alcohol and an alkaline solution is added to carry out reaction VI. After neutralization by adding an acid solution, the light-controlled reversible cross-linking agent is obtained after extraction, drying and separation.

[0017] The preparation method of the light-controlled reversible cross-linking agent in the present application is through step-by-step Suzuki coupling, followed by nucleophilic substitution or esterification / amidation reactions, and the multifunctional diarylethene maleic anhydride compounds can be prepared in an integrated manner.

[0018] Optionally, in step S1, a derivative of dichloroimide, arylboronic acid, BnEt3N + Cl - The molar ratio of PdCl2(PPh3)2 and cesium fluoride is 1: (0.1~2): (0.1~1): (0.05~0.5): (0.5~5.0).

[0019] Optionally, in step S1, the conditions of reaction I include: reacting at 50-150 °C for 5-14 h.

[0020] Optionally, in step S1, the derivative of dichloroimide is one of the compounds having a structure shown in formula III-a:

[0021] Formula III-a; wherein R5 is selected from C6H5CH2, C2H5, C3H7, C n H 2n+1 One of them.

[0022] Optionally, in step S1, the aryl boronic acid is one of the compounds having a structure shown in formula III-b:

[0023] Formula III-b;

[0024] R4 is selected from one of CF3, H, and CH3O.

[0025] Optionally, in step S2, intermediate 3, aryl borate, BnEt3N + Cl - The molar ratio of PdCl2(PPh3)2 and cesium fluoride is 1: (0.1~2): (0.1~1): (0.05~0.5): (0.5~5.0).

[0026] Optionally, in step S2, the conditions of reaction II include: reacting at 50-150° C. for 3-8 h.

[0027] Optionally, in step S2, the aryl borate ester is one of the compounds having a structure shown in formula III-c:

[0028] Formula III-c;

[0029] Wherein, R6 is selected from one of the following structures:

[0030] .

[0031] Optionally, in step S3, the molar ratio of intermediate 4, DMAP, dichloromethane, EDCI, octanediamine, and the alkali in the alkali solution is 1: (0.1-0.5): (10-50): (0.01-0.2): (0.1-2.0): (0.1-2.0).

[0032] Optionally, in step S3, the conditions of reaction III to reaction VI independently include: reacting at 15-30 °C for 0.5-3h.

[0033] Optionally, in step S3, the amine-containing compound is one of the compounds having a structure shown in formula III-d:

[0034] Formula III-d;

[0035] Wherein, R7 is selected from C2H5, C3H7, C n H 2n+1 One of them.

[0036] Optionally, in step S3, the alcohol is preferably methanol or ethanol.

[0037] In step S3, those skilled in the art can select the alkaline solution as required, for example, the alkaline solution is selected from a NaOH aqueous solution and a KOH aqueous solution.

[0038] In step S3, those skilled in the art can select the acid solution as required. For example, the acid solution is selected from hydrochloric acid, sulfuric acid, and nitric acid.

[0039] According to another aspect of the present application, there is also provided a use of the above-mentioned photo-controlled reversible cross-linking agent or the photo-controlled reversible cross-linking agent obtained according to any of the above-mentioned preparation methods in the preparation of an amide polymer, wherein the amide polymer is a polymer network formed by cross-linking the photo-controlled reversible cross-linking agent;

[0040] The applications include:

[0041] Regulating the crosslinking density of amide polymers by photo-controlled reversible crosslinkers; or,

[0042] Under external stimuli, the degradation of amide polymers is regulated by photocontrolled reversible cross-linkers.

[0043] Optionally, the wavelength of the light controlled reversible crosslinker is 440 nm and 620 nm;

[0044] Under 440 nm wavelength light, the photo-controlled reversible cross-linker changes from an open-ring state to a closed-ring state;

[0045] Under light of 620 nm wavelength, the photo-controlled reversible cross-linker changes from a closed-ring state to an open-ring state;

[0046] In the open-loop state and the closed-loop state, the light-controlled reversible crosslinking agent is respectively a structure represented by the above-mentioned formula Ia or formula Ib;

[0047] Optionally, the external stimulus includes placing the amide polymer in hydrochloric acid, and when the light-controlled reversible cross-linking agent is in an open-ring state, the amide polymer degrades;

[0048] When the photo-controlled reversible cross-linking agent is in a closed-ring state, the amide polymer does not degrade.

[0049] The beneficial effects of this application include:

[0050] The light-controlled reversible cross-linker provided in the present application is a multifunctional cross-linker based on the coupling of diarylethene photoswitch and maleic anhydride, which can realize the regulation of the electronic effect and ring tension of the anhydride part by bidirectional visible light, thereby controlling its reactivity with secondary amines, and is used for the variable cross-linking density of amide polymers and photo-activated recycling and reuse. The diarylethene part in the light-controlled reversible cross-linker has stimulus responsiveness to light of a specific wavelength, and the anhydride ring tension is greatly changed by bidirectional visible light irradiation, thereby causing a more significant change in the reactivity of the anhydride part, which can be used for rapid reversible binding and selective release of secondary amines, and realizes the reaction kinetics and thermodynamic equilibrium constants of dynamic amides controlled by light switches. Through the reversible light regulation of the diarylethene units at multiple anhydride sites in the light-controlled reversible cross-linker, the cross-linking of various types of nucleophilic reagents containing multiple secondary amines by such molecules is realized, and a polymer network with controllable cross-linking density is obtained. Further, the light-controlled activation and closure of the above-mentioned amide bonds are used to realize the controllable degradation recovery of polymers and the selective switching of high stability, thereby realizing the selective customization of material properties. Therefore, the light-controlled reversible crosslinker provided in the present application has a good application prospect in the selective in-situ customization of polymer material properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound 19 of the present application.

[0052] Figure 2Schematic diagram of bidirectional visible light regulation of the photo-controlled reversible cross-linker of the present application, wherein Figure 2 (a) is a schematic diagram of reversible photocyclization, with the structure before and after light control on the right and the actual picture corresponding to the structure on the right; Figure 2 (b) is a reversible photocyclization process 1 H NMR spectrum.

[0053] Figure 3 The absorption spectra of the acetonitrile solution of compound 19 of the present application before (dashed line) and after (solid line) irradiation at 440 nm, with a concentration of 50 μM.

[0054] Figure 4 Bidirectional visible light regulated amidation for this application: amidation and process hydrogen spectrum under 620 nm irradiation.

[0055] Figure 5 Bidirectional visible light regulated amidation for this application: amidation and process hydrogen spectrum under 440 nm irradiation.

[0056] Figure 6 Bidirectional visible light regulated amidation for this application: o -19 and c Kinetic curve of the reaction of -19 with diethylamine.

[0057] Figure 7 Schematic diagram of the photo-controlled reversible cross-linker and amide polymer under bidirectional light regulation in this application: Schematic diagram of the opening and closing rings and cross-linking density changes of the photo-controlled reversible cross-linker.

[0058] Figure 8 Schematic diagram of the photo-controlled reversible cross-linker and amide polymer under bidirectional light regulation in this application: Schematic diagram of the photo-controlled reversible cross-linker regulating polyamines (secondary amines) to produce a polymer network with adjustable cross-linking density through amidation reaction.

[0059] Fig. 9 Schematic diagram of the bidirectional visible light reversible regulation of viscosity changes of cross-linked polymers in this application.

[0060] Fig.10 The crosslinking / degradation process of the crosslinker and LCE can be reversibly regulated by visible light in the present application, wherein Fig.10 (a) o -19 and LCE structural diagram (left) and simplified structural diagram (right), 10(b) is o -19 and c -19 is a simplified schematic diagram of the structural transformation, and 10(c) is a schematic diagram of the cross-linking / degradation regulation process of the cross-linked polymer and LCE.

[0061] Fig.11 For this application, the degradation of the cross-linked polymer between this type of molecule and LCE is regulated by bidirectional visible light.

[0062] Fig.12 Schematic diagram of the bidirectional visible light reversible regulation of cross-linker and LCE self-repair in this application.

[0063] Fig.13 For this application, bidirectional visible light is used to regulate the cross-linking polymerization self-repair of this type of molecules and LCE.

[0064] Fig.14 For the present application, the storage modulus G' and loss modulus G" of the cross-linked polymer network are recycled. DETAILED DESCRIPTION

[0065] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0066] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0067] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0068] Example 1 Preparation of light-controlled reversible crosslinking agent

[0069] The preparation route of the photo-controlled reversible cross-linking agent is shown in Formula V:

[0070] Formula V, wherein R is , R1 is .

[0071] (1) Synthesis of intermediate 3: Weigh 1 equivalent of dichloroimide derivative, 1 equivalent of arylboronic acid, 0.05 equivalent of BnEt3N + Cl - and 0.05 equivalent of PdCl2(PPh3)2 in a double-necked round-bottom flask, install a reflux device and a nitrogen protection device, evacuate and replace with nitrogen three times, add toluene and an aqueous solution containing 4 equivalents of cesium fluoride (V 水 : V 甲苯 = 1:10), react at 95 °C for 12 hours. The reaction solution was extracted with dichloromethane three times, the organic phases were combined and dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporator and then separated by column chromatography (SiO2), the eluent was petroleum ether: ethyl acetate = 10:1. Intermediate 3 was obtained with a yield of 73%.

[0072] (2) Synthesis of intermediate 4: Weigh 1 equivalent of compound 3, 3 equivalents of aryl borate, 0.05 equivalent of BnEt3N + Cl -and 0.05 equivalent of PdCl2(PPh3)2 in a double-necked round-bottom flask, install a reflux device and a nitrogen protection device, evacuate and replace with nitrogen three times, add toluene and an aqueous solution containing 4 equivalents of cesium fluoride (V 水 : V 甲苯 = 1:10), heated to 95°C for 4 hours. After the reaction solution was cooled to room temperature, it was extracted with dichloromethane three times, the organic phases were combined and dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporator, and then separated by column chromatography (SiO2), the eluent was petroleum ether: ethyl acetate = 10:1. Intermediate 4 was obtained with a yield of 66%.

[0073] (3) Synthesis of photo-controlled reversible cross-linker compound 19: Weigh 1 equivalent of compound 4 and 0.1 equivalent of DMAP in a round-bottom flask, add dichloromethane, react at room temperature for 1 hour, add 1 equivalent of EDCI, react at room temperature for 1 hour, add 0.5 equivalent of octanediamine, react at room temperature for 1 hour. Extract with ethyl acetate three times, combine the organic phases and dry them with anhydrous sodium sulfate, remove the solvent on a rotary evaporator, dissolve in methanol, add 2 mol / L NaOH solution, and react at room temperature for 2 hours. Add concentrated hydrochloric acid to neutralize, cool the reaction solution to room temperature, extract with dichloromethane three times, combine the organic phases and dry them with anhydrous sodium sulfate, remove the solvent on a rotary evaporator, and separate by column chromatography (SiO2), with the eluent being petroleum ether: ethyl acetate = 2:1. Compound 19 based on the coupling of diarylethene optical switch and maleic anhydride was obtained with a yield of 65%.

[0074] The chemical formula of compound 19 is shown in Formula I, wherein the diarylethene photoswitch portion is in an open ring state, and compound 19 is marked as o -19. o -19 The ring-closed compound is labeled c -19.

[0075] Formula 1.

[0076] H NMR spectroscopy (eg Figure 1 shown): 1 H NMR (CDCl3): δ = 7.78 (d, J = 8.5 Hz, 4H),7.64 (s, 8H), 7.58 (d, J = 8.3 Hz, 4H), 7.41 (s, 2H), 7.41 (s, 2H), 6.19 (t, J =5.7 Hz, 2H), 3.46 (q, 4H), 2.10 (s, 6H), 2.08 (s, 6H), 1.65 – 1.61 (m, 12H).

[0077] Test Example 1 Reversible Photocyclization Properties

[0078] Compound 19 was prepared into a 50 μM acetonitrile standard solution, and its absorption spectrum was measured. After it was irradiated with 440 nm visible light to achieve photostable state, its absorption spectrum was measured again. Figure 2 As shown in (a), when irradiated with 440 nm visible light, the structure of compound 19 changes from an open ring to a o -19 (the actual object is light yellow) form halo c -19 (light blue in real life) form, such as Figure 3 As shown, its ultraviolet absorption spectrum has a new peak in the visible region.

[0079] Test Example 2: Changes in hydrogen spectrum during bidirectional visible light regulation

[0080] Compound 19 was prepared into a 5.0 mM deuterated chloroform standard solution, and its hydrogen spectrum was measured. After it was irradiated with 440 nm visible light to achieve photostable state, its hydrogen spectrum was measured again. After it was irradiated with 620 nm visible light to achieve photostable state, its hydrogen spectrum was measured again. The results are shown in Figure 2 As shown in (b), the compound o -19 was irradiated with 440 nm visible light. o The peak of -19 weakens and produces a group of corresponding cyclized forms c -19 peak, c -19 forms account for more than 95%; then irradiated with 620 nm light, c The peak of -19 disappeared, o The peak of -19 returned to the initial intensity.

[0081] Test Example 3 Reversible photoregulation of amidation reaction

[0082] 3 mg of compound 19 was dissolved in a mixed solution of 0.4 ml of deuterated acetonitrile and 0.1 ml of deuterated chloroform and the mixture was observed under visible light (λ irr = 620 nm) to the photostable state, and measure its hydrogen spectrum. Then, add 2.4 equivalents of diethylamine, and measure its hydrogen spectrum every 10 minutes until the reaction reaches equilibrium (e.g. Figure 4 ). Then 3 mg of compound 19 was dissolved in a mixed solution of 0.4 ml of deuterated acetonitrile and 0.1 ml of deuterated chloroform and the mixture was illuminated by visible light (λ irr = 440 nm) to the photostable state, and measure its hydrogen spectrum. Then, add 2.4 equivalents of diethylamine, and measure its hydrogen spectrum every 10 minutes until the reaction reaches equilibrium (e.g. Figure 5 ). and draw o -19 and c Kinetic curve of the reaction of -19 with diethylamine (such as Figure 6 ). c -19 and diethylamine reaction rate ratio o -19 is faster and has a larger equilibrium constant, which can be used to prepare polymer networks with adjustable photo-controlled cross-linking density.

[0083] Example 2 Application of light-controlled reversible crosslinker and polyamines (secondary amines) to adjust crosslink density through amidation reaction

[0084] Schematic diagram of the opening and closing rings and crosslinking density changes of the light-controlled reversible crosslinker under bidirectional light regulation Figure 7 As shown, the specific o -19 as an example to prepare and regulate amide polymers. Figure 8 As shown, o -19 (84 mg) was dissolved in chloroform (1.0 mL) and placed under visible light (λ irr = 440 nm) for 2 h, o -19 Halo c After -19 reached the photostable state, a chloroform solution of LCE (500 mg LCE dissolved in 1.0 mL chloroform) was added, and the high cross-linking density polymer 25 was obtained after the reaction reached thermodynamic equilibrium. irr = 620 nm) for 6 h can switch the high cross-linking density polymer 25 to the low cross-linking density polymer 26.

[0085] Will o -19 (84 mg) was dissolved in chloroform (1.0 mL), and then a chloroform solution of LCE (500 mg LCE dissolved in 1.0 mL chloroform) was added. After the reaction reached thermodynamic equilibrium, a low cross-linking density polymer 26 was obtained. The cross-linking density of the polymer 26 was determined by visible light (λ irr = 440nm) for 12 hours to switch the low cross-linking density polymer 26 into the high cross-linking density polymer 25.

[0086] Test Example 4

[0087] like Fig. 9 As shown, a small piece of polymer 26 is placed between two glass slides, and the two slides are tightly pressed together for 5 minutes under the action of external force. The polymer 26 adheres the glass slides together. The polymer 26 is exposed to visible light (λ irr = 440 nm) for 12 hours, and then placed between two glass slides. They were pressed tightly together for 5 minutes under the action of external force, but the glass slides could not be bonded. A small piece of polymer 25 was placed between two glass slides. They were pressed tightly together for 5 minutes under the action of external force, but the glass slides could not be bonded. Polymer 25 was irradiated with visible light (λ irr= 620 nm) for 6 hours, and then placed between two glass slides, which were tightly pressed together for 5 minutes under the action of external force to bond the slides together.

[0088] Example 3 Bidirectional visible light and external stimulation to regulate the recycling of amide polymers

[0089] Crosslinking / degradation of LCE with photo-controlled reversible crosslinker: A small piece of crosslinked polymer 25 was placed in 1 M hydrochloric acid and remained intact after one week. irr = 620 nm) for 6 h, the polymer was completely degraded again to o -19; using visible light (λ irr = 620 nm) for 6 hours to convert polymer 25 into polymer 26. Then a small piece of the polymer was placed in 1 M hydrochloric acid and completely degraded into o -19. A small piece of polymer 26 was placed in 1 M hydrochloric acid and completely degraded to o -19, the schematic diagram of the above process is as follows Fig.10 As shown in the actual picture Fig.11 shown.

[0090] Photo-controlled reversible crosslinker and LCE self-repair: Polymer 25 was heated and melted and placed in a circular mold. After solidification, it was taken out and cut into two pieces with a blade. The two pieces of polymer were placed close together. After one week, self-repair was not completed. irr = 620 nm) for 6 hours to switch polymer 25 to polymer 26. Bring the two polymers close together and the self-healing is completed after 120 minutes. Heat and melt polymer 26 and place it in a circular mold. After it solidifies and forms, take it out. Similarly, use a blade to evenly cut it into two pieces. Bring the two polymers close together and the self-healing is completed after 120 minutes. The schematic diagram of the above process is shown in the figure. Fig.12 As shown in the figure, the actual process is as follows Fig.13 shown.

[0091] Recycling and reuse of cross-linked polymer networks and rheological tests before recycling: Rheological tests were performed on polymer 25 and polymer 26 to determine their storage modulus G' and loss modulus G". Polymer 25 (584 mg) was exposed to visible light at 620 nm for 12 hours to the open-ring form 26, and then 100 ml of 1 mol / L hydrochloric acid was added and decomposed at room temperature for 24 hours. The dichloromethane was extracted three times, and the organic phases were combined and dried over anhydrous sodium sulfate. The solvent was removed by rotary evaporation, separated and purified, and washed with n-hexane to obtain the monomer o-19, with a recovery rate of 85%; the n-hexane used for washing was combined, acetonitrile was added for extraction three times, the n-hexane phases were combined, and the solvent was removed by rotary evaporation to obtain LCE, with a recovery rate of 83%. Similarly, polymer 26 was placed in 1 mol / L hydrochloric acid for decomposition, and separated and purified to obtain o -19 monomer and LCE. o -19 monomer and LCE were used to prepare polymer 25-recycle and polymer 26-recycle according to Example 2, and rheological tests were performed to determine their storage modulus G' and loss modulus G", and the results are as follows Fig.14 As shown, it is consistent with the polymer before decomposition, thereby achieving polymer recycling.

[0092] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A light-controlled reversible crosslinking agent, characterized in that: The photo-controlled reversible cross-linking agent has a structure shown in Formula Ia or Formula Ib: Wherein, R2 and R3 are selected from CH3, R4 is selected from one of CF3, H, and CH3O; R1 is selected from a structure in Formula II: The light-controlled reversible cross-linking agent is a compound formed by coupling a diarylethene light switch molecule with maleic anhydride.

2. The method for preparing the light-controlled reversible crosslinking agent according to claim 1, characterized in that: The steps include: S1. Preparation of intermediate 3: a dichloroimide derivative, arylboronic acid, BnEt3N + Cl - , a mixture of PdCl2(PPh3)2, toluene, cesium fluoride and water, to carry out reaction I, and to obtain intermediate 3 after extraction, drying and separation; S2, containing intermediate 3, aryl borate, BnEt3N + Cl - , a mixture of PdCl2(PPh3)2, toluene, cesium fluoride and water, to carry out reaction II, and to obtain intermediate 4 after extraction, drying and separation; S3, subjecting the mixture containing intermediate 4, DMAP, and dichloromethane to reaction III, then adding EDCI to react IV, then adding an amine-containing compound to react V, extracting, drying, and separating, dissolving the product in alcohol and adding an alkaline solution to react VI, adding an acid solution to neutralize, and extracting, drying, and separating to obtain the light-controlled reversible crosslinking agent; In step S1, the derivative of dichloroimide is one of the compounds having the structure shown in formula III-a: Wherein, R5 is selected from one of C6H5CH2, C2H5, and C3H7; In step S1, the aryl boronic acid is one of the compounds having a structure shown in formula III-b: R4 is selected from one of CF3, H, and CH3O; In step S2, the aryl borate ester is a compound having a structure shown in formula III-c: Wherein, R6 is selected from the following structures:

3. The preparation method according to claim 2, characterized in that: In step S1, a dichloroimide derivative, an arylboronic acid, BnEt3N + Cl - The molar ratio of PdCl2(PPh3)2 and cesium fluoride is 1:(0.1-2):(0.1-1):(0.05-0.5):(0.5-5.0); In step S1, the conditions of reaction I include: reacting at 50-150° C. for 5-14 hours.

4. The preparation method according to claim 2, characterized in that: In step S2, intermediate 3, aryl borate, BnEt3N + Cl - The molar ratio of PdCl2(PPh3)2 and cesium fluoride is 1:(0.1-2):(0.1-1):(0.05-0.5):(0.5-5.0); In step S2, the conditions of reaction II include: reacting at 50-150° C. for 3-8 hours.

5. The preparation method according to claim 2, characterized in that: In step S3, the molar ratio of intermediate 4, DMAP, dichloromethane, EDCI, octanediamine, and the alkali in the alkali solution is 1: (0.1-0.5): (10-50): (0.01-0.2): (0.1-2.0): (0.1-2.0); In step S3, the conditions of reaction III to reaction VI independently include: reacting at 15 to 30° C. for 0.5 to 3 h.

6. Use of the photo-controlled reversible crosslinking agent according to claim 1 or the photo-controlled reversible crosslinking agent obtained according to the preparation method according to any one of claims 2 to 5 in the preparation of amide polymers, characterized in that: Amide polymers are polymer networks formed by cross-linking with a photo-controlled reversible cross-linker; The applications include: Regulating the crosslinking density of amide polymers by photo-controlled reversible crosslinkers; or, Under external stimuli, the degradation of amide polymers is regulated by photocontrolled reversible cross-linkers.

7. The use according to claim 6, characterized in that: The wavelength of the light controlled reversible crosslinker is 440nm and 620nm; Under 440 nm wavelength light, the photo-controlled reversible cross-linking agent changes from an open-ring state to a closed-ring state; Under light of 620 nm wavelength, the photo-controlled reversible cross-linking agent changes from a closed-ring state to an open-ring state; In the open-loop state and the closed-loop state, the light-controlled reversible cross-linking agent is respectively a structure represented by Formula Ia or Formula Ib as described in claim 1.

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