Azobenzene polymer with light-operated reversible phase change as well as preparation method and application of azobenzene polymer

Abstract

The invention discloses an azobenzene polymer with light-operated reversible phase change as well as a preparation method and application of the azobenzene polymer. The azobenzene polymer has a first repetitive unit as shown in a general formula 1 and a second repetitive unit as shown in a general formula 2. The azobenzene polymer disclosed by the invention has excellent adhesion performance and light-operated reversible solid-liquid phase change performance, can be used as an adhesive, and can be reversibly switched between a solid state and a liquid state through a light-emitting adhesive, so that the adhesive can be debonded through illumination after being used, and the adhesive has the advantages of simple preparation process and low cost. The harsh conditions such as high temperature, strong acid or strong alkali required during debonding of a traditional adhesive are avoided, so that environmental pollution and resource waste are reduced; after the adhesive is debonded, the adhesion performance can be recovered through simple light treatment, so that the adhesive can be recycled and reused, the material cost is reduced, and the concept of environmental protection and sustainable development is met.

Description

Technical Field

[0001] This application belongs to the technical field of adhesives, and particularly relates to an azobenzene-based polymer with photo-controlled reversible phase change, its preparation method and application. Background Art

[0002] Commercial adhesives are widely used in various fields such as handicraft manufacturing, cultural relic restoration, and real estate decoration. However, current commercial adhesives generally have the problem of difficult debonding and cannot be recycled, resulting in a large amount of waste. Moreover, the debonding process often requires a high-temperature, strong acid or strong alkali environment, which will cause serious environmental pollution and high debonding costs. Therefore, traditional commercial adhesives no longer meet the current concept of green environmental protection and sustainable development.

[0003] In addition, with the rapid development of high-tech industries, new requirements have also been put forward for adhesive materials. For example, current electronic products are gradually developing towards being thinner, lighter, and more complex, requiring adhesives to provide better flexibility and reliability when bonding micro-components, while existing commercial adhesives are difficult to meet these conditions. Summary of the Invention

[0004] The purpose of this application is to provide an azobenzene-based polymer with photo-controlled reversible phase change, its preparation method and application, so as to solve the technical problems existing in the prior art, such as difficult debonding of commercial adhesives, inability to be recycled, resulting in a large amount of waste, and the debonding process often requiring a high-temperature, strong acid or strong alkali environment, causing environmental pollution and high debonding costs.

[0005] To achieve the above purpose, in the first aspect of this application, an azobenzene-based polymer with photo-controlled reversible phase change is provided, which has a first repeating unit shown in the following general formula 1 and a second repeating unit shown in the following general formula 2;

[0006]

General Formula 1

[0007]

[0008]

General Formula 2

[0009]

[0010] In one or more embodiments, it has a structure shown in the following general formula 3;

[0011]

General Formula 3

[0012]

[0013] In the formula, n and m are integers greater than 1.

[0014] In one or more embodiments, the molar ratio of the first repeating unit to the second repeating unit is 1.0:(1.0 - 2.5).

[0015] To achieve the above object, a second aspect of the present application provides a method for preparing an azobenzene polymer with photo-controlled reversible phase change, including:

[0016] Diazo-coupling 4-butoxy-2,6-difluoroaniline with 2,6-difluorophenol after diazotization to obtain a first intermediate product with general formula 4;

[0017] Performing an esterification reaction on the first intermediate product with acryloyl chloride to obtain a second intermediate product with general formula 5;

[0018] Initiating polymerization of the second intermediate product and N-tert-butylacrylamide to obtain an azobenzene polymer with photo-controlled reversible phase change, where the azobenzene polymer has a first repeating unit shown in the following general formula 1 and a second repeating unit shown in the following general formula 2;

[0019] [General formula 4]

[0020]

[0021] [General formula 5]

[0022]

[0023] [General formula 1]

[0024]

[0025] [General formula 2]

[0026]

[0027] In one or more embodiments, the step of diazo-coupling 4-butoxy-2,6-difluoroaniline with 2,6-difluorophenol after diazotization includes:

[0028] Reacting 4-butoxy-2,6-difluoroaniline with sodium nitrite under low-temperature acidic conditions to generate a diazonium salt;

[0029] Adding 2,6-difluorophenol and sodium hydroxide to the reaction system, stirring and reacting, and after the reaction is completed, adjusting the pH value of the reaction system to 4 - 5, filtering and collecting the precipitate to obtain the first intermediate product.

[0030] In one or more embodiments, in the step of reacting 4-butoxy-2,6-difluoroaniline with sodium nitrite under low-temperature acidic conditions, the reaction temperature is 0 to 5 °C, the pH value of the reaction system is 1 to 3, the reaction time is 0.5 to 1 h, and the molar ratio of 4-butoxy-2,6-difluoroaniline to sodium nitrite is 1.0:(1.0 to 1.6); and / or.

[0031] In one or more embodiments, the molar ratio of 4-butoxy-2,6-difluoroaniline to 2,6-difluorophenol is 1.0:(1.0 to 1.5).

[0032] In one or more embodiments, the molar ratio of 2,6-difluorophenol to sodium hydroxide is 1.0:(1.5 to 2.5).

[0033] In one or more embodiments, the reaction time of the stirring reaction is 1.5 to 2 h.

[0034] In one or more embodiments, the step of esterifying the first intermediate with acryloyl chloride includes:

[0035] Dissolve the first intermediate in anhydrous dichloromethane, add triethylamine dropwise, add acryloyl chloride under stirring for esterification reaction. After the reaction is completed, distill off the solvent to obtain a crude product, and purify the crude product by column chromatography to obtain the second intermediate;

[0036] Among them, the molar ratio of the first intermediate to acryloyl chloride is 1.0:(1.5 to 2.0).

[0037] In one or more embodiments, the step of polymerizing the second intermediate and N-tert-butylacrylamide includes:

[0038] Dissolve the second intermediate and N-tert-butylacrylamide in a solvent, deoxygenate, add a thermal initiator, react at a first temperature under an inert atmosphere, then raise the temperature to a second temperature for continuous reaction. After the reaction is completed, cool to room temperature, precipitate a colloidal precipitate, wash, and dry to obtain the azobenzene-based polymer.

[0039] In one or more embodiments, the first temperature is 50 to 60 °C, and the reaction time at the first temperature is 2 to 4 h.

[0040] In one or more embodiments, the second temperature is 70 to 75 °C, and the reaction time at the second temperature is 24 to 36 h.

[0041] In one or more embodiments, the thermal initiator is azobisisobutyronitrile, and the molar ratio of the second intermediate product, N-tert-butylacrylamide, and azobisisobutyronitrile is 1.0:(1.0 to 2.5):(0.1 to 0.4).

[0042] In one or more embodiments, the solvent is toluene.

[0043] To achieve the above object, a third aspect of the present application provides an application of the azobenzene polymer described in any one of the above embodiments or the azobenzene polymer prepared by the preparation method described in any one of the above embodiments as an adhesive. The adhesive has a photo-controlled reversible phase change and can be transformed from a solid state to a liquid state under ultraviolet light irradiation conditions, and can be transformed from a liquid state to a viscous solid state under visible light irradiation conditions.

[0044] Different from the prior art, the beneficial effects of the present application are as follows:

[0045] The azobenzene polymer of the present application has excellent adhesion performance and photo-controlled reversible solid-liquid phase change performance and can be used as an adhesive. Through the irradiation of ultraviolet light / visible light, the adhesive can be reversibly switched between a solid state and a liquid state. This characteristic enables the adhesive to be debonded by light irradiation after use, avoiding the need for harsh conditions such as high temperature, strong acid or strong base during debonding of traditional adhesives, thereby reducing environmental pollution and resource waste;

[0046] When the azobenzene polymer of the present application is used as an adhesive, its adhesion performance can be restored by simple light treatment after debonding, thereby realizing the recyclability and reusability of the adhesive. This not only reduces the material cost but also conforms to the concepts of green environmental protection and sustainable development;

[0047] The preparation method of the present application efficiently synthesizes an azobenzene polymer with photo-controlled reversible phase change through three-step reactions. The reaction conditions are mild, the operation is simple, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0049] Figure 1 It is a schematic flowchart of an embodiment of the preparation method of the azobenzene polymer with photo-controlled reversible phase change of the present application;

[0050] Figure 21H NMR spectrum of the product of Step 1 in Example 1 of the present application;

[0051] Figure 3 1H NMR spectrum of the product of Step 2 in Example 1 of the present application;

[0052] Figure 4 1H NMR spectrum of the azobenzene-based polymer Azo-PC1 in Example 1 of the present application;

[0053] Figure 5 Morphological photos of the azobenzene-based polymer before and after ultraviolet light irradiation and after visible light irradiation in Effect Example 1 of the present application;

[0054] Figure 6 Displacement-stress curve of the single-lap shear experiment in Effect Example 2 of the present application. Detailed implementation manners

[0055] To enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0056] Traditional commercial adhesives have the problem of difficult debonding, are difficult to recycle, and the debonding process often requires a high-temperature, strong acid or strong alkali environment, which will cause serious environmental pollution and high debonding costs.

[0057] To solve the above problems, the applicant has developed a new type of azobenzene-based polymer, which can be used as an adhesive and has photo-controlled reversible phase change. It can be transformed from a solid state to a liquid state under light irradiation, so as to achieve rapid debonding and recycling, avoiding the problems existing in traditional adhesives.

[0058] Specifically, the azobenzene-based polymer with photo-controlled reversible phase change in the present application has a first repeating unit shown in the following General Formula 1 and a second repeating unit shown in the following General Formula 2;

[0059]

General Formula 1

[0060]

[0061]

General Formula 2

[0062]

[0063] In one embodiment, the azobenzene-based polymer with photo-controlled reversible phase change of the present application may have the structure shown in the following general formula 3;

[0064]

[0065] In the formula, n and m are integers greater than 1.

[0066] Of course, in other embodiments, the azobenzene-based polymer of the present application can also be obtained by randomly connecting the first repeating unit and the second repeating unit, and the effects of this embodiment can be achieved.

[0067] In one embodiment, in the azobenzene-based polymer of the present application, the molar ratio of the first repeating unit to the second repeating unit can be 1.0:(1.0 - 2.5).

[0068] Based on the azobenzene-based polymers of the above embodiments, they have excellent adhesion performance and photo-controlled reversible solid-liquid phase change performance. By irradiating with ultraviolet / visible light, the adhesive can be reversibly switched between the solid state and the liquid state. This characteristic enables the adhesive to be debonded by light irradiation after use, avoiding the harsh conditions such as high temperature, strong acid or strong base required for debonding traditional adhesives, thereby reducing environmental pollution and resource waste.

[0069] At the same time, due to the photo-controlled reversible phase change performance of the adhesive, its adhesion performance can be restored by simple light treatment after debonding, thus realizing the recyclability and reusability of the adhesive. This not only reduces the material cost, but also conforms to the concepts of green environmental protection and sustainable development.

[0070] The present application also provides a preparation method of the above azobenzene-based polymer. Please refer to Figure 1 , Figure 1 which is a schematic flow chart of an embodiment of the preparation method of the azobenzene-based polymer with photo-controlled reversible phase change of the present application.

[0071] As Figure 1 shown, the preparation method includes:

[0072] S100. Diazotize 4-butoxy-2,6-difluoroaniline and then carry out a coupling reaction with 2,6-difluorophenol to obtain a first intermediate product with the general formula 4.

[0073]

General formula 4

[0074]

[0075] Specifically, the reaction formula is as follows:

[0076]

[0077] In S100, the target azo compound is synthesized by coupling 4-butoxy-2,6-difluoroaniline with 2,6-difluorophenol using a diazotization-coupling reaction.

[0078] Specifically, in one embodiment, the method for diazotizing 4-butoxy-2,6-difluoroaniline can be: reacting 4-butoxy-2,6-difluoroaniline with sodium nitrite under low-temperature acidic conditions to form a diazonium salt.

[0079] In one embodiment, the reaction temperature of the above diazotization reaction can be 0 to 5 °C. The reaction system can ensure acidic conditions by adding concentrated sulfuric acid, and the pH value of the reaction system can be 1 to 3. Exemplarily, 4-butoxy-2,6-difluoroaniline can be dissolved in water, ice-bathed and concentrated sulfuric acid is added, and then sodium sulfite is added for reaction.

[0080] In one embodiment, the reaction time of the above diazotization reaction can be 0.5 to 1 h.

[0081] In one embodiment, the molar ratio of 4-butoxy-2,6-difluoroaniline to sodium nitrite can be 1.0:(1.0 to 1.6).

[0082] After diazotization, a coupling reaction can be carried out. The reaction method can be to add 2,6-difluorophenol and sodium hydroxide to the above diazotized reaction system, stir and react. After the reaction is completed, the pH value of the reaction system is adjusted to 4 to 5, and the precipitate is filtered and collected to obtain a first intermediate product.

[0083] 2,6-Difluorophenol and sodium hydroxide can react to form a phenolate salt, and the diazonium salt and the phenolate salt undergo an electrophilic substitution reaction under weakly basic conditions to form an azo compound.

[0084] In one embodiment, the molar ratio of 4-butoxy-2,6-difluoroaniline to 2,6-difluorophenol can be 1.0:(1.0 to 1.5).

[0085] In one embodiment, the molar ratio of 2,6-difluorophenol to sodium hydroxide can be 1.0:(1.5 to 2.5).

[0086] In one embodiment, the reaction time of the above coupling reaction can be 1.5 to 2 h.

[0087] S200: Esterify the first intermediate product with acryloyl chloride to obtain a second intermediate product with General Formula 5.

[0088]

General Formula 5

[0089]

[0090] Specifically, the reaction formula of S200 can be as follows:

[0091]

[0092] In one embodiment, the method of the esterification reaction can be specifically as follows:

[0093] Dissolve the first intermediate product in anhydrous dichloromethane, add triethylamine dropwise, add acryloyl chloride under stirring for the esterification reaction. After the reaction is completed, distill off the solvent to obtain a crude product, and purify the crude product by column chromatography to obtain the second intermediate product.

[0094] Among them, triethylamine neutralizes the generated HCL in the reaction and promotes the forward reaction.

[0095] S300: Polymerize the second intermediate product and N-tert-butylacrylamide to obtain an azobenzene polymer with photo-controlled reversible phase transition.

[0096] Among them, the azobenzene polymer has the first repeating unit shown in the above general formula 1 and the second repeating unit shown in the above general formula 2.

[0097] In one embodiment, a thermal initiator can be used for the polymerization initiation. The method of the polymerization initiation can be specifically as follows: Dissolve the second intermediate product and N-tert-butylacrylamide in a solvent, add a thermal initiator after deoxygenation, react at a first temperature under an inert atmosphere, then raise the temperature to a second temperature for continuous reaction. After the reaction is completed, cool to room temperature, precipitate a colloidal precipitate, wash, and dry to obtain the azobenzene polymer.

[0098] In one embodiment, the deoxygenation can specifically adopt the freeze-thaw cycle deoxygenation method.

[0099] In one embodiment, the first temperature can be 50 - 60 °C, and the reaction time at the first temperature can be 2 - 4 h.

[0100] In one embodiment, the second temperature can be 70 - 75 °C, and the reaction time at the second temperature can be 24 - 36 h.

[0101] In one embodiment, the thermal initiator can be azobisisobutyronitrile, and the molar ratio of the second intermediate product, N-tert-butylacrylamide, and azobisisobutyronitrile can be 1.0:(1.0 - 2.5):(0.1 - 0.4).

[0102] In one embodiment, the solvent can be toluene.

[0103] Based on the preparation methods of the above embodiments, an azobenzene polymer with photo-controlled reversible phase transition can be efficiently synthesized through three-step reactions. The reaction conditions are mild, the operation is simple, and it is suitable for large-scale production.

[0104] The effects of the technical solution of the present application will be further elaborated in detail below in conjunction with specific embodiments.

[0105] Example 1:

[0106] An azobenzene-based polymer Azo-PC1 with photo-controlled reversible phase change is prepared by the following steps:

[0107] 1) Weigh 2.0 g of 4-butoxy-2,6-difluoroaniline (9.9 mmol) into a round-bottom flask, add 20 mL of deionized water, cool to 0 °C, then add 4.0 mL of concentrated hydrochloric acid. Then weigh 0.8 g of NaNO2 (11 mmol) and dissolve it in 10 mL of deionized water, cool to 0 °C, and slowly drop it into the above reaction system. Stir for 1 h under an ice bath. Then weigh 1.6 g of 2,6-difluorophenol (12 mmol) and 0.7 g of NaOH (18 mmol) and dissolve them in 20 mL of deionized water, and drop it into the above reaction system. Continue to stir for 2 h, then acidify the reaction mixture to pH 4 with dilute hydrochloric acid, filter the precipitate, wash the precipitate with a small amount of methanol, and then dry it under vacuum to obtain 2.45 g of a brown solid compound, namely 4-hydroxy-2,6-difluoro-4'-butoxy-2,6-difluoroazobenzene, with a yield of 72%.

[0108] Perform nuclear magnetic resonance hydrogen spectrum analysis on the reaction product to obtain Figure 2 , Figure 2 which is the nuclear magnetic resonance hydrogen spectrum of the product of step 1 of Example 1 of the present application. The chemical shift and integral data of the nuclear magnetic hydrogen spectrum of the product are: δ = 8.98 (s, 1H), 7.92–7.84 (m, 2H), 7.60–7.50 (m, 2H), 4.05 (t, J = 6.5 Hz, 2H), 1.81 (m, 2H), 1.58–1.47 (m, 2H), 1.00 (t, J = 7.4 Hz, 3H), all corresponding exactly to the target substance.

[0109] 2) Weigh 2.0 g of 4-hydroxy-2,6-difluoro-4'-butoxy-2,6-difluoroazobenzene (5.8 mmol) into a round-bottom flask, add 20 mL of anhydrous CH2Cl2, then drop 1.8 g of triethylamine (18 mmol) into the solution, add 0.8 g of acryloyl chloride (8.7 mmol) under stirring, and then react at room temperature for 12 h.

[0110] After the reaction is completed, remove the solvent by distillation under reduced pressure to obtain a yellow crude product. The crude product is purified by column chromatography (mobile phase: DCM:N-hexane = 1:3) to obtain 1.16 g of a pale yellow crystal, namely compound 4-hydroxy-2,6-difluoro-4'-acryloyl-2,6-difluoroazobenzene, with a yield of 50%.

[0111] The reaction product was analyzed by 1H NMR spectroscopy to obtain Figure 3 , Figure 3 which is the 1H NMR spectrum of the product in Step 2 of Example 1 of this application. The chemical shift and integral data of the 1H NMR of the product are: δ = 7.86 (d, J = 8.1 Hz, 2H), 7.28 (t, J = 7.8 Hz, 2H), 6.76 (m, 1H), 6.41 (m, 1H), 5.67 (m, 1H), 4.03 (t, J = 6.5 Hz, 2H), 1.82 (m, 2H), 1.57 - 1.43 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H), all corresponding one by one to the target substance.

[0112] 3) Weighed 1.0 g of 4-hydroxy-2,6-difluoro-4'-acryloyloxy-2,6-difluoroazobenzene (3.8 mmol) and 0.5 g of N-tert-butylacrylamide (3.8 mmol) into a round-bottom flask, added 10 mL of toluene, deoxygenated by the freeze-thaw cycle method, then added 0.06 g of azobisisobutyronitrile (0.4 mmol), reacted at 50 °C for 2 h under a N2 atmosphere, then raised the temperature to 70 °C and continued to react for 36 h. After the reaction was completed, the reaction mixture was cooled to room temperature, 50 mL of ice methanol was added, and the bright yellow solid was obtained by filtration. The solid was dried at 50 °C for 24 h to obtain the azobenzene-based polymer, denoted as Azo-PC1.

[0113] The reaction product was analyzed by 1H NMR spectroscopy to obtain Figure 4 , Figure 4 which is the 1H NMR spectrum of the azobenzene-based polymer Azo-PC1 in Example 1 of this application, conforming to the characteristics of the target product.

[0114] Example 2:

[0115] An azobenzene-based polymer Azo-PC2 with photo-controlled reversible phase transition, the preparation method is basically the same as that of Example 1, except that:

[0116] In Step 1, the reaction temperature was 3 °C, the amount of NaNO2 used was 1.1 g (15 mmol), the reaction time of 4-butoxy-2,6-difluoroaniline with sodium nitrite was 0.5 h, the reaction time after adding 2,6-difluorophenol and sodium hydroxide was 1.5 h, the amount of 2,6-difluorophenol used was 1.35 g (10 mmol), and the amount of sodium hydroxide used was 1.0 g (25 mmol);

[0117] In Step 2, the reaction time was 14 h, and the amount of acryloyl chloride used was 1.1 g (11.6 mmol);

[0118] In Step 3, the amount of N-tert-butylacrylamide used is 1.25 g (9.5 mmol), and the amount of azobisisobutyronitrile used is 0.23 g (1.5 mmol). The specific reaction process is as follows: React at 55 °C for 4 h, and then raise the temperature to 72 °C and continue to react for 30 h.

[0119] Example 3:

[0120] A kind of azobenzene-based polymer Azo-PC3 with photo-controlled reversible phase transition, the preparation method is basically the same as that of Example 1, the differences are as follows:

[0121] In Step 1, the reaction temperature is 5 °C, the amount of 2,6-difluorophenol used is 2 g (15 mmol), and the amount of sodium hydroxide used is 1.2 g (30 mmol);

[0122] In Step 2, the reaction time is 16 h, and the amount of acryloyl chloride used is 0.9 g (10.0 mmol);

[0123] In Step 3, the amount of N-tert-butylacrylamide used is 1 g (7.6 mmol), and the amount of azobisisobutyronitrile used is 0.12 g (0.8 mmol). The specific reaction process is as follows: React at 55 °C for 3 h, and then raise the temperature to 75 °C and continue to react for 36 h.

[0124] Effect Example 1: Verification of photo-controlled reversible phase transition

[0125] Take 0.2 g of Azo-PC1 prepared in Example 1 on a white plastic hard board, and irradiate the solid azobenzene-based copolymer with 355 nm ultraviolet light at room temperature. The irradiation power is 30 Mw / cm 2 , starting from the start of irradiation, when Azo-PC1 is completely transformed into a liquid state, stop timing. At this time, the recorded time t1 is the solid-liquid transition time of Azo-PC1.

[0126] When Azo-PC1 is completely transformed into a liquid state, start timing again until it is completely transformed into a solid state. At this time, the recorded time t2 is the liquid-solid transition time of Azo-PC1.

[0127] In the experiment, t1 was measured three times and the average value was 2.5 min, and t2 was measured three times and the average value was 3.8 min. Then, the liquid Azo-PC1 was irradiated with visible light until Azo-PC1 became a viscous solid state. The whole process recorded the macroscopic states of Azo-PC1 before and after ultraviolet light irradiation and after visible light irradiation through digital photos, and obtained Figure 5 , Figure 5 are the morphological photos of the azobenzene-based polymer in Effect Example 1 of this application before and after ultraviolet light irradiation and after visible light irradiation.

[0128] From the above data, it can be seen that Azo-PC1 in Example 1 has photo-controlled reversible phase change. It can be transformed from a solid state to a liquid state under ultraviolet light irradiation. When used as an adhesive, debonding can be achieved through ultraviolet light irradiation. It can be transformed from a liquid state to a sticky solid state under visible light irradiation, and the adhesion performance can be restored through simple light treatment after debonding.

[0129] Effect Example 2: Analysis of Adhesion Performance

[0130] Take 10 mg of the Azo-PC1 solid prepared in Example 1, convert it into a liquid state through light irradiation, and coat it on a glass substrate with dimensions of 60 mm × 20 mm (the glass plate has been ultrasonically cleaned twice with dichloromethane and absolute ethanol before use). Then, place another glass plate on the liquefied Azo-PC1 to form an adhesion area with an area of 15 mm × 20 mm and an adhesion thickness of 0.1 mm.

[0131] Wait for several minutes for Azo-PC1 to cure. Through a single-lap shear experiment, at a tensile speed of 0.2 mm / min, test the bonding strength of Azo-PC1 to obtain Figure 6 data Figure 6 is the displacement-stress curve of the single-lap shear experiment in Effect Example 2 of this application.

[0132] As Figure 6 shown, the maximum bonding strength of Azo-PC1 on the glass substrate is 4.01 Mpa, and it has excellent adhesion performance.

[0133] For those skilled in the art, it is obvious that this application is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of this application, this application can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of this application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in this application. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0134] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An azobenzene-based polymer with photo-controlled reversible phase transition, characterized in that, It has a first repeating unit represented by the following general formula 1 and a second repeating unit represented by the following general formula 2; 【General formula 1】 【General formula 2】 2. The azobenzene-based polymer according to claim 1, wherein It has a structure represented by the following general formula 3; 【General formula 3】 In the formula, n and m are integers greater than 1.

3. The azobenzene-based polymer according to claim 1 or 2, characterized in that, The molar ratio of the first repeating unit to the second repeating unit is 1.0:(1.0 - 2.5).

4. A preparation method of an azobenzene-based polymer with photo-controlled reversible phase transition, characterized in that, It includes: After diazotizing 4-butoxy-2,6-difluoroaniline and carrying out a coupling reaction with 2,6-difluorophenol, a first intermediate product with the general formula 4 is obtained; Carrying out an esterification reaction on the first intermediate product and acryloyl chloride to obtain a second intermediate product with the general formula 5; Initiating the polymerization of the second intermediate product and N-tert-butylacrylamide to obtain an azobenzene polymer with photo-controlled reversible phase change, and the azobenzene polymer has a first repeating unit represented by the following general formula 1 and a second repeating unit represented by the following general formula 2; 【General formula 4】 【General formula 5】 【General formula 1】 【General formula 2】 5. The preparation method according to claim 4, characterized in that, The step of diazotizing 4-butoxy-2,6-difluoroaniline and then carrying out a coupling reaction with 2,6-difluorophenol includes: Reacting 4-butoxy-2,6-difluoroaniline with sodium nitrite under low-temperature acidic conditions to generate a diazonium salt; Adding 2,6-difluorophenol and sodium hydroxide to the reaction system, stirring and reacting, after the reaction is completed, adjusting the pH value of the reaction system to 4 - 5, filtering and collecting the precipitate to obtain the first intermediate product.

6. The preparation method according to claim 5, characterized in that, In the step of reacting 4-butoxy-2,6-difluoroaniline with sodium nitrite under low-temperature acidic conditions, the reaction temperature is 0 - 5 °C, the pH value of the reaction system is 1 - 3, the reaction time is 0.5 - 1 h, and the molar ratio of 4-butoxy-2,6-difluoroaniline to sodium nitrite is 1.0:(1.0 - 1.6); and / or; The molar ratio of 4-butoxy-2,6-difluoroaniline to 2,6-difluorophenol is 1.0:(1.0 - 1.5); and / or, The molar ratio of 2,6-difluorophenol to sodium hydroxide is 1.0:(1.5 - 2.5); and / or, The reaction time of the stirring reaction is 1.5 - 2 h.

7. The preparation method according to claim 4, characterized in that, The step of carrying out an esterification reaction on the first intermediate product and acryloyl chloride includes: Dissolving the first intermediate product in anhydrous dichloromethane, dropping triethylamine, adding acryloyl chloride under stirring for esterification reaction, after the reaction is completed, distilling off the solvent to obtain a crude product, and purifying the crude product by column chromatography to obtain the second intermediate product; Among them, the molar ratio of the first intermediate product to acryloyl chloride is 1.0:(1.5 - 2.0).

8. The preparation method according to claim 4, characterized in that, The step of initiating the polymerization of the second intermediate product and N-tert-butylacrylamide includes: Dissolving the second intermediate product and N-tert-butylacrylamide in a solvent, deoxygenating, adding a thermal initiator, reacting at a first temperature under an inert atmosphere, then raising the temperature to a second temperature for continuous reaction, after the reaction is completed, cooling to room temperature, precipitating a colloidal precipitate, washing, and drying to obtain the azobenzene polymer.

9. The preparation method according to claim 8, characterized in that, The first temperature is 50 - 60 °C, and the reaction time at the first temperature is 2 - 4 h; and / or, The second temperature is 70 to 75 °C, and the reaction time at the second temperature is 24 to 36 h; and / or, The thermal initiator is azobisisobutyronitrile, and the molar ratio of the second intermediate product, N-tert-butylacrylamide and azobisisobutyronitrile is 1.0:(1.0 to 2.5):(0.1 to 0.4); and / or, The solvent is toluene.

10. Use of an azobenzene polymer according to any one of claims 1 to 3 or an azobenzene polymer prepared by the preparation method according to any one of claims 4 to 9 as an adhesive, characterized in that, The adhesive has photo-controlled reversible phase change, and can be transformed from a solid state to a liquid state under ultraviolet light irradiation conditions, and from a liquid state to a viscous solid state under visible light irradiation conditions.

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