CN116874703A - Photoresponse benzoxazine material and preparation method thereof - Google Patents

Abstract

The invention discloses a photoresponsive benzoxazine material and a preparation method thereof, which belong to the technical field of photoresponsive materials, and are obtained by thermal curing reaction of benzoxazine prepolymer containing azobenzene structures at the temperature of 120-200 ℃; the benzoxazine prepolymer containing the azobenzene structure is prepared by refluxing and stirring diamine containing the azobenzene structure, diphenol and paraformaldehyde in a mixed solvent of toluene and ethanol according to a certain molar ratio; the diamine containing the azobenzene structure is obtained by reacting azobenzene diacid chloride with long-chain diamine. The benzoxazine material provided by the invention is introduced with an optically active azobenzene structure, and the quick photoresponse deformation of the benzoxazine material is realized through the photoreversible isomerization of the azobenzene structure. The prepared benzoxazine material has rapid light response capability and excellent shape memory performance under the irradiation of ultraviolet light with the wavelength of 340-380 nm. Can be applied to the fields of biosensors, intelligent biological switches, soft robots and the like.

Description

A kind of light-responsive benzoxazine material and preparation method thereof

Technical field

The invention relates to the technical field of photoresponsive materials, in particular to a photoresponsive benzoxazine material and its preparation method.

Background technique

As a type of polymer-based smart material, light-responsive polymer materials refer to functional polymer materials whose molecules contain structures that can absorb light energy and undergo specific physical or chemical changes under the action of light. This physical or chemical change can cause changes in the polymer structure or morphology, causing the material to change macroscopically. For example, the material changes shape, color, transparency or refractive index under light. Light as a stimulus source has the advantages of rapid response, remote control, no by-products, and safety and reliability. These advantages make light-responsive polymer materials have broad applications in the fields of biosensors, intelligent biological switches, microfluidic conduction soft robots, and artificial muscles. application prospects.

Benzoxazine resin is a thermosetting resin with high heat resistance, high mechanical properties, low water absorption, low dielectric properties, and flexible molecular design. Therefore, it has a very wide range of application prospects in the field of functional materials. At this stage, research on benzoxazines containing azo structures is mainly focused on benzoxazines (CN 108997547 A, CN 108997548 A) synthesized from phenolic compounds containing azo structures and aromatic amine compounds, and benzoxazines containing azo structures. Benzoxazine (CN 108997546 A) synthesized from nitrogen-structured aniline compounds and phenol compounds. Since the synthesized benzoxazine resin has a large cross-linking density and relatively large rigidity, this type of benzoxazine It has poor toughness, low elongation at break, cannot realize the orientation of azo groups, and does not have the ability to photo-induced deformation. In order to improve the flexibility of benzoxazine resin, our research group also reacted azo-structure-containing phenol with long-chain diamine to prepare a flexible azo-structure-containing benzoxazine elastomer (CN 110105517 A). Although the toughness of this type of benzoxazine has been improved, this type of benzoxazine has a low glass transition temperature and the shape after stretching cannot be fixed. At the same time, since the azo group is connected to phenol, after cross-linking and solidification, the azo group is close to the cross-linking center. For these two reasons, the azo groups in the synthesized azo-structure-containing benzoxazine elastomer cannot be oriented and do not have the ability to photo-induced deformation.

The present invention uses azobenzenedicarboxylic acid as raw material, reacts with long-chain diamines to obtain diamines containing azo structures, and then reacts with common diphenols to obtain benzoxazine prepolymers containing azo structures. After ring-opening solidification, benzoxazine resin is obtained. Due to the flexible long-chain diamine between the azo group and the generated oxazine ring, the cured benzoxazine can smoothly orient the azo structure by stretching under heating conditions, realizing azo-containing Photodeformation of structural benzoxazines.

Contents of the invention

In order to solve the problem that the current benzoxazine materials containing azobenzene structure cannot orient the azo structure, resulting in the inability to achieve photodeformation, the present invention uses long-chain diamines containing azo structures as raw materials, which can be irradiated with ultraviolet light Light actuation is performed below.

The invention provides a fast light-responsive benzoxazine material, which is obtained by curing a benzoxazine prepolymer containing an azobenzene structure at 120-200°C; the benzoxazine prepolymer The product is prepared by refluxing and stirring diamine, diphenol and paraformaldehyde containing azobenzene structure in toluene for 12 hours in a molar ratio of 1:1:4.1~4.4. The structural formula of the benzoxazine prepolymer is as follows:

;

In the formula, R ₁ is one of the following structural formulas:

;

Among them, the value range of m is 1-14;

In the formula, R ₂ is one of the following structural formulas:

.

The azobenzene structure-containing diamine is obtained by reacting azobenzenedioyl chloride and a long-chain diamine in a molar ratio of 2:1:3 under the catalysis of triethylamine. The long-chain diamine is one of polysiloxane, polyetheramine, polyethylene glycol diamine and alkyl diamine with a molecular weight of 100-1000. The structural formula of the diamine containing azobenzene structure is as follows:

;

In the formula, R ₁ is one of the following structural formulas:

;

Among them, the value range of m is 1-14.

The preparation method of the above-mentioned photoresponsive benzoxazine material includes the following steps:

Add the long-chain diamine to the round-bottomed flask, dissolve it in dichloromethane and add the catalyst triethylamine. After cooling to 0°C, add the dichloromethane solution of azobenzoyl chloride using a dropping funnel. After the dropwise addition was completed, stirring was continued at room temperature for 24 h. After the reaction is completed, the solvent is removed by extraction, drying, and rotary evaporation to obtain a diamine containing an azobenzene structure;

Mix diamine, diphenol and paraformaldehyde containing azobenzene structure in a mixed solution of toluene and ethanol in a molar ratio of 1:1:4.1~4.4, then fully react at 100-130°C for 12 hours, and then rotary evaporate The solvent is removed to obtain a benzoxazine prepolymer containing an azobenzene structure;

Dissolve the benzoxazine prepolymer in N,N-dimethylformamide and pour it into the mold. The solvent is dried at 60°C and then the temperature is raised to 120-200°C for curing reaction. Finally, azobenzene containing Structural benzoxazine materials;

Compared with the prior art, the benefits of the present invention are:

First, the photoresponsive benzoxazine material of the present invention is prepared by using long-chain diamines containing azobenzene structures, which solves the problem of using aromatic amines containing azo structures or phenols containing azo structures to prepare benzo Oxazine causes the azo structure to be close to the cross-linking point after thermal curing, making it difficult to orient for photoactivation;

Secondly, the present invention utilizes a diamine of moderate length as the raw material for synthesizing photo-activated benzoxazine resin. The synthesized benzoxazine resin has a glass transition temperature of 20-80°C and high elongation at break. The efficiency solves the existing problems of poor toughness and low glass transition temperature of benzoxazines containing azo structures, and can realize optical braking of benzoxazine materials containing azo structures;

Other advantages, objects, and features of the present invention will be apparent in part from the description below, and in part will be understood by those skilled in the art through study and practice of the present invention.

Description of the drawings

Figure 1. NMR spectrum of sodium azobenzenedicarboxylate;

Figure 2. Infrared spectrum of azobenzenedicarboxylic acid;

Figure 3. NMR spectrum of azophenylenediamine;

Figure 4. Infrared spectrum of azophenylenediamine;

Figure 5. Infrared spectrum of azobenzoxazine prepolymer;

Figure 6. Infrared spectrum of azobenzoxazine after self-curing;

Figure 7. DSC image of azobenzoxazine prepolymer before curing;

Figure 8. DSC image of azobenzoxazine prepolymer after curing;

Figure 9. Test chart of tensile properties of light-responsive azobenzobenzoxazine materials;

Figure 10. Photo-responsive azobenzoxazine material shape memory test chart. (a) is a photo of the original length of the spline, (b) is a photo of the spline with a fixed stretching orientation, (c) is the light deformation of the spline. The photo of (d) is the photo of spline thermal shape recovery;

Figure 11. Light braking diagram of light-responsive azobenzoxazine material.

Detailed ways

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Example 1

A fast light-responsive benzoxazine material and a preparation method, including the following steps:

(1) Preparation of azobenzene-4,4-dicarboxylic acid

The first step of synthesizing azobenzene-4,4-dicarboxylic acid requires p-nitrobenzoic acid, sodium hydroxide solid, glucose, glacial acetic acid and other drugs. Mix 8 g of p-nitrobenzoic acid and 26.8 g of sodium hydroxide in 120 mL of deionized water into a 2000 mL round bottom flask. The solution was heated in a water bath until the solids dissolved, then the temperature of the water bath was maintained at 50°C. Dissolve 53.32g of glucose in 80ml of deionized water to form an aqueous solution and add it dropwise to the above solution to obtain a yellow precipitate, which immediately turns into a brown solution after further addition of glucose. Then, the mixture solution was stored in a water bath at 50°C and bubbled continuously for 8 h to obtain a light brown precipitate. The precipitate was collected by filtration and dissolved in deionized water. The solution was then acidified by adding a large amount of glacial acetic acid, producing a light pink precipitate. Finally, rinse, filter and purify the precipitate with plenty of deionized water. The final product is vacuum dried, resulting in a pink powder. The reaction equation is:

;

Figure 1 shows the hydrogen nuclear magnetic spectrum of sodium azobenzenedicarboxylate. Since the obtained dicarboxylic acid cannot be dissolved in water, it was reacted with sodium hydroxide to convert it into a sodium salt before testing. The displacements in the figure are: 7.78-7.85 ppm, and 7.91-7.99 ppm respectively correspond to the characteristic hydrogens at the a and b positions on azobenzenedicarboxylic acid;

Figure 2 is the infrared spectrum of azobenzenedicarboxylic acid. In the figure: 1283 cm ^-1 is the stretching vibration peak of the carboxyl group; 1425 cm ^-1 is the stretching vibration peak of the benzene ring skeleton; 1605 cm ^-1 is the vibration peak of -N=N-; 1684 cm ^-1 is the stretching vibration peak of the carboxyl carbonyl group ; 2661cm ^-1 is the stretching vibration peak of hydrogen in the carboxyl group;

(2) Preparation of azobenzene-4,4-dioic acid chloride;

Weigh out 5 g of azobenzene dicarboxylic acid ground into powder and pour it into a flask. Place the flask on the reaction table. Under an _N2 atmosphere, slowly add 75 mL of thionyl chloride dropwise into the flask. Stir. After the dropwise addition is completed, set the oil bath temperature to 78°C and the reaction table temperature to 120°C. Then set up the condenser tube and reflux for 12 hours. The reaction ends the next day, and the product is the mixture azobenzoyl chloride. The mixture was then suction filtered using a Buchner funnel to obtain a red clear liquid. The solvent was evaporated from the obtained liquid using a rotary distillation instrument to obtain pure azobenzene-4,4-dioic acid chloride. The reaction equation is as follows:

;

(3) Preparation of azobenzene polyetherdiamine

Weigh the product of the previous reaction, azobenzene-4,4-dioic acid chloride, and the mass of the product is 5.5g. Dissolve it in 150 mL of dichloromethane. Weigh polyetheramine D400 with a molar ratio of azophthalic acid chloride and polyetheramine D400 of 1:2, pour it into the round-bottomed sesame cake, add 15 mL of methylene chloride to the flask, and then add 10 mL of triethylamine ( Eliminate the hydrogen chloride gas produced in the subsequent reaction). Pour the mixed solution of azobenzoyl chloride and methylene chloride into the constant pressure funnel, place the flask containing the polyetheramine D400 solution on the operating table, and then use the constant pressure funnel to add polyetheramine D400 solution at 0°C. Slowly add the azobenzoyl chloride solution dropwise into the solution, add N ₂ during the process, stir slowly, close the nitrogen valve after the dropwise addition, and react at room temperature for 24 hours. The next day a mixture of azophenylenediamine was obtained. Use a rotary evaporator to evaporate the solvent from the obtained initial product of azophenylenediamine, and then wash and extract with ethyl acetate and water. After washing, the azophenylenediamine is rotary evaporated again to obtain pure azophenylenediamine. The reaction equation is as follows:

;

Figure 3 shows the NMR spectrum of azophenylenediamine; 8.20-7.77 ppm is the hydrogen atom on the benzene ring of the azobenzene structure; 4.46-4.27 ppm is the hydrogen on the amide; 3.85-3.02 ppm is the polyetheramine methylene Hydrogen on the base; 1.44-1.12 ppm is hydrogen on the methine group of polyetheramine; 1.19-0.90ppm is hydrogen on the branched methyl group of polyetheramine;

Figure 4 is the infrared spectrum of azophenylenediamine. In the figure, 3300 cm ^-1 is the stretching vibration peak of -NH ₂ and -NH-, 2960 cm ^-1 and 2868 cm ^-1 are the stretching vibration peaks of methyl and methylene respectively, and 1633 cm ^-1 is the amide The carbonyl peak of the group at 1096 cm ^-1 is the stretching vibration of the ether bond; the characteristic vibration bands of the amide in azophenylenediamine are located near 1633 cm ^-1 , 1279 cm ^-1 , and 670 cm ^-1 respectively, proving that the amide bond formation;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azophenylenediamine, bisphenol A, and paraformaldehyde 1:1:4.3. Mix each gram of azophenylenediamine with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene to ethanol 2:1). After thoroughly mixing in the flask, place the flask on a magnetic stirrer for stirring and reflux at 120°C. Reaction 12 hours. The initial product was obtained the next day. The initial product was filtered with cotton to remove the solidified solid impurities. Then the liquid part was evaporated with a rotary evaporator. After removing the solvent, the final product benzoxazine was obtained. The reaction equation is:

;

Figure 5 shows the infrared spectrum of azobenzoxazine prepolymer; in the figure, the stretching vibration peaks of -NH ₂ and -NH- are at 3296 cm ^-1 , and the stretching vibration peaks at 2985 cm ^-1 and 2866 cm ^-1 are respectively The stretching vibration peaks of methyl and methylene groups, 1636 cm ^-1 is the carbonyl peak of the amide group, 1099 cm ^-1 is the stretching vibration of the ether bond, and 958 cm ^-1 is the characteristic peak of the oxazine ring;

Figure 6 shows the infrared spectrum of azobenzoxazine after curing; in the figure, 3301 cm ^-1 is the stretching vibration peak of -NH ₂ and -NH-, 2974cm ^-1 and 2866cm ^-1 are methyl and methyl respectively. The stretching vibration peak of methylene group is the carbonyl peak of the amide group at 1641 cm ^-1 , and the stretching vibration of the ether bond is at 1099 cm ^-1 ; due to the strong stretching vibration of the ether bond, the characteristic peak of the oxazine ring is not so obvious. . However, through infrared comparison before and after curing, it can be found that the intensity of the peak has changed significantly, which can also prove that benzoxazine is cured;

Figure 7 shows the DSC image of azobenzoxazine prepolymer before curing. The information in the figure proves that the self-curing temperature of the benzoxazine prepolymer belongs to a large range, with a peak temperature of 232°C. Subsequently, it was proved that benzoxazine prepolymer can be successfully cured by long-term curing at 200°C;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5 g of benzoxazine and add 4 mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it begins to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. The DSC tested before curing shows that the curing temperature is about 200℃-250℃ (it can be cured at 200℃ for a long time). Put the film into the oven and continue to dry it at 80℃ for 1 hour, and then dry it at 120℃ for 1 hour. , then cured at 180°C for 2 hours and 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, take off the mold (it can be heated appropriately to facilitate demoulding), and a benzoxazine film is obtained;

Figure 8 shows the DSC image of the azobenzoxazine prepolymer after curing. The information in the figure proves that the glass transition temperature of the film formed by self-curing of the azobenzoxazine-containing prepolymer is 28°C;

Figure 9 is a test chart of the tensile properties of light-responsive benzoxazine materials. According to the strain-tensile strength diagram, the elongation at break and tensile strength of the three sets of data are read, and the elastic modulus is calculated. Based on the average of the three sets of data, the average elongation at break of the material is 294%, and the average breaking strength is 15.54 MPa;

Figure 10 is the thermal shape memory test chart of the photoresponsive benzoxazine material. After testing: (a) in the figure, the film spline with an original length of 2.1cm was stretched to 3.2cm by applying stress at a certain temperature, as shown in the figure ( b) shown. After the stress is removed, the film is fixed at 3cm, and is bent at a certain angle after illumination, as shown in (c) in the figure. The sample is then heated, and the sample returns to 2.3cm, as shown in (d) in the figure. Therefore, after calculation: the shape fixation rate of the thin film spline is 93.8%, and the shape recovery rate is 90.5%. This sample achieves the effects of light actuation and thermal shape recovery;

Figure 11 shows the light braking diagram of the light-responsive benzoxazine material. The obtained light-responsive azobenzobenzoxazine film is stretched and oriented above the glass transition temperature. After cooling and setting, the orientation position is irradiated under a 365nm point light source, and the material bends to achieve a braking effect. It can be found from the figure that the light braking effect of the material is relatively obvious: it can achieve a 67° bend within 6 seconds of irradiation with a 365nm light source.

Example 2

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

(3) Preparation of azobenzene polysiloxane diamine

Weigh 3.07g of azobenzene-4,4-dioic acid chloride, dissolve it in 100 mL of methylene chloride, and purge it with nitrogen for later use. Weigh 20g of aminopropyl-terminated polysiloxane (Mn=1000g/mol) according to the molar ratio of 1:2 and pour it into the round-bottomed sesame cake. Add 12 mL of methylene chloride to the flask, and then add 10 mL of triethylamine ( Eliminate the hydrogen chloride produced in the subsequent reaction). Pour the mixed solution of azophthalic acid chloride and dichloromethane into the constant pressure funnel, place the flask containing the polysiloxane 1000 solution on the operating table, and then use the constant pressure funnel to pour the polysiloxane 1000 solution into the constant pressure funnel at 0°C. Slowly add azobenzoyl chloride solution into the solution of alkane 1000, add N ₂ during the process, stir slowly, close the nitrogen valve after the dropwise addition, and react at room temperature for 24 hours. The next day a mixture of azophenylenediamine was obtained. Use a rotary evaporator to evaporate the solvent from the obtained initial product of azophenylenediamine, and then wash and extract with ethyl acetate and water. After washing, the azophenylenediamine is rotary evaporated again to obtain pure azophenylenediamine. The reaction equation is as follows:

;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polysiloxane diamine, bisphenol A, and paraformaldehyde 1:1:4.4. Mix each gram of azophenylenediamine with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene to ethanol 2:1). After thoroughly mixing in the flask, place the flask on a magnetic stirrer for stirring and reflux at 120°C. Reaction 12 hours. The initial product was obtained the next day. The initial product was filtered with cotton to remove the solidified solid impurities. Then the liquid part was evaporated with a rotary evaporator. After removing the solvent, the final product benzoxazine was obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of DMF to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

Example 3

(1) The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

(2) The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

(3) Preparation of azobenzene dodecyldiamine

Weigh 3.07g of azobenzene-4,4-dioic acid chloride, dissolve it with 50 mL of dehydrated N,N-dimethylformamide, and purge it with nitrogen for later use. Weigh 4g of dodecyldiamine into the round-bottomed sesame cake according to the molar ratio of 1:2, add 30mL of N,N-dimethylformamide to the flask, and then add 10mL of triethylamine (to eliminate the subsequent reaction hydrogen chloride produced). Pour the mixed solution of azobenzoyl chloride and N,N-dimethylformamide into a constant pressure funnel, place the flask containing the dodecyldiamine solution on the operating table, and then use The azobenzoyl chloride solution was slowly dropped into the dodecyldiamine solution from a constant pressure funnel. During the process, N ₂ was introduced and stirred slowly. After the dropwise addition, the nitrogen valve was closed and the solution was refluxed at 60°C for 24 hours. The next day a mixture of azophenylenediamine was obtained. Directly add water to the mixture, stir and wash away impurities, and then use vacuum filtration to filter, and then dry the water in a vacuum oven at 60°C to obtain azobenzene-containing dodecyldiamine. The reaction equation is:

;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene dodecyldiamine, bisphenol A, and paraformaldehyde 1:1:4.3. The mixture was mixed with 10 mL of chloroform per gram of azophenylenediamine. After thorough mixing in the flask, the flask was stirred on a magnetic stirrer and refluxed for 24 h. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

Example 4

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

The method for preparing azobenzene polyetherdiamine is the same as step (3) in Example 1;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polyetherdiamine, bisphenol F, and paraformaldehyde 1:1:4.4. Mix each gram of azobenzene polyetherdiamine with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene to ethanol 2:1). After thoroughly mixing in the flask, place the flask on a magnetic stirrer and stir at 120°C. Reflux reaction for 12 h. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

Example 5

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

The method for preparing azobenzene polyetherdiamine is the same as step (3) in Example 1;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polyetherdiamine, bisphenol AF, and paraformaldehyde 1:1:4.3. Mix each gram of azobenzene polyetherdiamine with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene to ethanol 2:1). After thoroughly mixing in the flask, place the flask on a magnetic stirrer and stir at 120°C. Reflux reaction for 12 hours. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

Example 6

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

The method for preparing azobenzene polyetherdiamine is the same as step (3) in Example 1;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polyetherdiamine, 3,3-bis(4-hydroxyphenyl)butyric acid, and paraformaldehyde 1:1:4.3. Mix each gram of azobenzene polyetherdiamine with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene to ethanol 2:1). After thoroughly mixing in the flask, place the flask on a magnetic stirrer and stir at 120°C. Reflux reaction for 12 hours. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing.

Example 7

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

The method for preparing azobenzene polyetherdiamine is the same as step (3) in Example 1;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polyetherdiamine, 4,4'-dihydroxybenzophenone, and paraformaldehyde 1:1:4.3. The mixture is mixed with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene and ethanol 2:1) per gram of azobenzene polyetherdiamine. After thorough mixing in the flask, place the flask on a magnetic stirrer and stir at 120°C. Reflux reaction for 12 hours. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4mL of N, N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

Example 8

The method for preparing azobenzene-4,4-dicarboxylic acid is the same as step (1) in Example 1;

The method for preparing azobenzene-4,4-dioic acid chloride is the same as step (2) in Example 1;

The method for preparing azobenzene polysiloxane diamine is the same as step (3) in Example 2;

(4) Preparation of azobenzobenzoxazine-containing prepolymer

The raw materials are mixed according to the molar ratio of azobenzene polyetherdiamine, 4,4'-dihydroxybenzylthione, and paraformaldehyde 1:1:4.3. The mixture is mixed with 15 mL of a mixture of toluene and ethanol (volume ratio of toluene and ethanol 2:1) per gram of azobenzene polyetherdiamine. After thorough mixing in the flask, place the flask on a magnetic stirrer and stir for 120 Reflux reaction at ℃ for 12 h. The initial product is obtained the next day, and then the liquid part is evaporated using a rotary evaporator. After removing the solvent, the final product benzoxazine is obtained. The reaction equation is:

;

(5) Preparation of photoresponsive benzoxazine films

Take 0.5g benzoxazine and add 4 mL of N,N-dimethylformamide to dissolve it, pour it into a polytetrafluoroethylene membrane, and dry it. After it is completely dried, it starts to solidify. After dissolving, pour the solution evenly into the film-forming film tool, and put the film tool into an oven at 60°C for the first drying, but after complete drying, it will begin to solidify. Put the film into the oven and continue drying at 80°C for 1 hour, dry at 120°C for 1 hour, then cure at 180°C for 2 hours, and cure at 200°C for 6 hours. After completion, take out the mold and cool to room temperature to complete curing. After the mold is completely cooled, the mold is removed and a benzoxazine film is obtained.

To sum up, the present invention solves the problem of traditional azobenzene-containing benzoxazine by using azobenzene-containing diamine instead of traditional azobenzene monophenol or azobenzodiphenol to synthesize azo-containing benzoxazine. Oxazine resin is not prone to orientation and does not have the problem of light braking.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed above in preferred embodiments, they are not intended to limit the present invention. Anyone familiar with this field will Skilled persons can make some changes or modifications to equivalent embodiments using the technical content disclosed above without departing from the scope of the technical solution of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the invention still fall within the scope of the technical solution of the present invention.

Claims (3)

1. A photoresponsive benzoxazine material is characterized in that the photoresponsive benzoxazine material is obtained by thermal curing reaction of a benzoxazine prepolymer containing an azobenzene structure at the temperature of 120-200 ℃; the benzoxazine prepolymer is prepared by refluxing and stirring diamine containing an azobenzene structure, diphenol and paraformaldehyde in a molar ratio of 1:1:4.1-4.4 in toluene for 12 hours; the benzoxazine prepolymer has the following structural formula:

；

wherein R is ₁ Is one of the following structural formulas:

；

wherein, the value range of m is 1-14;

wherein R is ₂ Is one of the following structural formulas:

。

2. the photoresponsive benzoxazine material according to claim 1, wherein the diamine containing an azobenzene structure is obtained by reacting azobenzene diacid chloride with long-chain diamine under the catalysis of triethylamine according to a molar ratio of 2:1:3; the long-chain diamine is one of polysiloxane, polyether amine, polyethylene glycol diamine and alkyl diamine with the molecular weight of 100-1000; the structural formula of the diamine containing the azobenzene structure is as follows:

；

wherein R is ₁ Is one of the following structural formulas:

；

wherein, the value range of m is 1-14.

3. A method of preparing a photoresponsive benzoxazine material according to any one of claims 1 to 2, comprising the steps of:

s1, preparing diamine containing an azobenzene structure: adding long-chain diamine into a round bottom flask, dissolving with dichloromethane, adding triethylamine as a catalyst, cooling to 0 ℃, and adding dichloromethane solution of azobenzene diacid chloride with a dropping funnel; after the dripping is finished, stirring is continued for 24 hours at room temperature; after the reaction is finished, extracting, drying and spin-evaporating to remove the solvent to obtain diamine containing an azobenzene structure;

s2, preparing a benzoxazine prepolymer containing an azobenzene structure: diamine containing an azobenzene structure, diphenol and paraformaldehyde are uniformly mixed in a mixed solution of toluene and ethanol according to the molar ratio of 1:1:4.1-4.4, then fully reacted for 12 hours at 100-130 ℃, and the solvent is removed by rotary evaporation to obtain a benzoxazine prepolymer;

s3, preparing a light-response benzoxazine material: and (3) dissolving the benzoxazine prepolymer in DMF, pouring the DMF into a mold, drying the solvent at 60 ℃, and then raising the temperature to 120-200 ℃ for curing reaction to obtain the benzoxazine material containing the azobenzene structure.