Hydrogel capable of controlling deformation in different directions through single-molecule optical switch and preparation method of hydrogel

Abstract

The invention relates to the technical field of hydrogel, and discloses hydrogel with deformation in different directions controlled by a single-molecule optical switch and a preparation method of the hydrogel. The preparation method comprises the following steps: preparing an optical switch TCF molecule derived from tricyanofuran, and introducing the optical switch TCF molecule into a hydrogel material to obtain the hydrogel of which the deformation in different directions is controlled by a single-molecule optical switch. The hydrogel has dual responsiveness to visible light and pH, and can generate different bending deformations in the same illumination direction.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogels, and particularly relates to a hydrogel that can be deformed in different directions controlled by a single molecular photoswitch and a preparation method thereof. Background Art

[0002] Trifuryl cyanide is a class of photoresponsive molecular switches with important research and application values. It has three isomers: ring-opening protonation, ring-opening deprotonation, and closed-loop. It is a class of photoresponsive molecular switches with important research and application values. Among them, the closed-loop structure is polar and charged, the ring-opening deprotonation structure is polar and charged, while the ring-opening protonation structure is non-polar and uncharged. The huge differences in their properties determine that trifuryl cyanide has very wide applications in many fields such as photochromism, detection imaging, analytical sensing, and dynamic materials. Under light illumination conditions, trifuryl cyanide, as a photoswitch molecule, can change from the open-ring protonated cyanine form to the closed-loop spiro form, causing a change in the net charge of the polymer material grafted to it, affecting the hydrophilic and hydrophobic properties of the polymer chain, and thus realizing the swelling of the hydrogel material, which is expected to be applied to fields such as phototactic biomimetic deformation, movement, and soft robots.

[0003] For traditional photoswitch-controlled photo-responsive hydrogels to achieve deformation in different directions, it is often necessary to change the conditions for applying the stimulus response. However, there are often many limitations in the actual application environment, making it difficult to change the stimulus response. Some research teams have used multiple molecular switches for control and achieved photo-induced deformation movement of the hydrogel from light-facing to back-light-facing without changing the light illumination conditions. However, the hydrogels controlled by multiple molecular switches have problems such as complex preparation processes and mutual interference between multiple molecular switches. Therefore, the problem of using a single molecular photoswitch to achieve multiple photo-induced deformation modes of the hydrogel has not been solved yet. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a hydrogel that can be deformed in different directions controlled by a single molecular photoswitch and a preparation method thereof. By preparing a trifuryl cyanide-derived molecular photoswitch and introducing it into the hydrogel material, the hydrogel has dual responsiveness to visible light and pH and can undergo different bending deformations in the same light illumination direction.

[0005] To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0006] A preparation method of a hydrogel that can be deformed in different directions controlled by a single molecular photoswitch, comprising the following steps:

[0007] S1. Prepare molecule A1;

[0008] Mix acrylonitrile, 3-hydroxy-3-methyl-2-butanone, sodium ethoxide, and ethanol, react, and after the reaction ends, purify to obtain molecule A1;

[0009] S2. Prepare molecule A2;

[0010] Mix 3-chloromethyl-5-nitrosalicylaldehyde, sodium acrylate, and toluene, react. After the reaction ends, perform suction filtration, take the filtrate, rotary evaporate, and purify by column chromatography to obtain molecule A2;

[0011] S3. Prepare the optical switch TCF molecule;

[0012] Mix molecule A1, molecule A2, the catalyst ammonium acetate (NH 4 Ac), and ethanol evenly, react. After the reaction ends, purify to obtain the optical switch tricyanofuran (TCF) molecule;

[0013] S4. Prepare a hydrogel with a single-molecule optical switch controlling deformation in different directions;

[0014] Mix acrylamide (AAM), acrylonitrile (AN), ascorbic acid (VC), the optical switch TCF molecule, and N-methylpyrrolidone (NMP), dissolve by ultrasonic wave, add N,N'-methylenebisacrylamide (bis-MBA) and mix evenly, then add an aqueous solution of ammonium persulfate (APS) and continue to mix evenly. Remove oxygen to obtain a prepolymer solution. Inject the prepolymer solution into a mold, polymerize and form, take out, soak in ethanol, and then displace it into an aqueous hydrochloric acid solution, and keep it away from light to obtain a hydrogel with a single-molecule optical switch controlling deformation in different directions.

[0015] Preferably, in S1, the chemical structural formula of molecule A1 is:

[0016] Preferably, in S1, the chemical reaction formula for preparing molecule A1 is:

[0017]

[0018] Among them, represents malononitrile, represents 3-hydroxy-3-methyl-2-butanone, represents molecule A1, EtONa represents sodium ethoxide, and EtOH represents ethanol.

[0019] Preferably, in S1: The molar ratio of malononitrile, 3-hydroxy-3-methyl-2-butanone, and sodium ethoxide is 1:(1 - 1.2):(1.2 - 1.5); The reaction conditions are: Stir and react at 80 °C for 6 - 8 h.

[0020] Preferably, in S1: The purification operation includes: Place the crude reaction product obtained after the reaction ends at 0 °C and cool and let it stand for 30 min to obtain a solid-liquid mixture, perform suction filtration, wash the filter cake with cold ethanol, and place it in an oven to dry.

[0021] Preferably, in the step S2, the chemical structural formula of the A2 molecule is:

[0022] Preferably, in the step S2, the chemical reaction formula for preparing the A2 molecule is:

[0023]

[0024] Among them, represents 3-chloromethyl-5-nitrosalicylaldehyde, represents sodium acrylate, toluene represents toluene, represents the A2 molecule.

[0025] Preferably, in the step S2: the molar ratio of 3-chloromethyl-5-nitrosalicylaldehyde to sodium acrylate is 1:(1.2 - 2); the reaction conditions are: stirring and reacting at a temperature of 110 °C for 10 - 12 h.

[0026] Preferably, in the step S2: the eluent used in the column purification operation is prepared by mixing dichloromethane and methanol in a volume ratio of 12:1.

[0027] Preferably, in the step S3, the chemical structural formula of the optical switch TCF molecule is:

[0028]

[0029] Preferably, in the step S3, the chemical reaction formula for preparing the optical switch TCF molecule is:

[0030]

[0031] Among them, represents the optical switch TCF molecule, represents the A1 molecule, represents the A2 molecule, NH 4 Ac represents ammonium acetate, and EtOH represents ethanol.

[0032] Preferably, in the step S3: the molar ratio of the A1 molecule, the A2 molecule, and the catalyst ammonium acetate is 1:(1 - 1.3):(0.1 - 0.2); the reaction conditions are: reacting at a temperature of 75 - 80 °C for 5 h.

[0033] Preferably, in the step S3: the purification operation includes: cooling and standing the crude reaction product obtained after the reaction at 0 °C for 30 min to obtain a solid-liquid mixture, performing suction filtration, washing the filter cake with cold ethanol, and drying it in an oven.

[0034] Preferably, in S4, the molar ratio of acrylamide, acrylonitrile, ascorbic acid, photoswitch TCF molecule, N-methylpyrrolidone, N,N'-methylenebisacrylamide, and ammonium persulfate aqueous solution is 1:(0.15 - 0.2):(0.02 - 0.03):(0.01 - 0.03):(0.03 - 0.06):(0.02 - 0.06):(0.02 - 0.03), and the ammonium persulfate aqueous solution is 20wt% ammonium persulfate aqueous solution; the polymerization and forming conditions are: polymerize and form at room temperature for 12 - 24 h.

[0035] Preferably, in S4, the soaking time in ethanol is 2 h; the light shielding time is 12 h; the hydrochloric acid aqueous solution is 5 mmol / L hydrochloric acid aqueous solution.

[0036] Preferably, a hydrogel with different-direction deformation controlled by a single molecular photoswitch prepared by the preparation method of a hydrogel with different-direction deformation controlled by a single molecular photoswitch as described above.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The present invention utilizes the nucleophilicity of the carbon on the methylene group in malononitrile and the electrophilicity of the cyano group, and synthesizes A1 molecule by a one-step method. At the same time, the method of introducing acrylate structure on the benzene ring is developed by using the nucleophilicity of sodium acrylate, avoiding the side reactions caused by the reaction of hydroxyl group and acyl chloride structure in the past.

[0039] 2. The synthesis of the photoswitch TCF molecule can be obtained by the mutual reaction between the methyl group in A1 molecule and the aldehyde group in A2 molecule, and the subsequent separation only requires simple suction filtration and washing, without complex column chromatography purification.

[0040] 3. Hydrogel materials can be efficiently obtained by free radical polymerization. In the present invention, functional groups of the TCF molecular photoswitch are modified, and the acrylate structure enables the TCF molecular photoswitch to be covalently grafted into the polymer, and at the same time endows the hydrogel with light responsiveness.

[0041] 4. The present invention designs and synthesizes a polymerizable photoswitch TCF molecule, covalently grafts it into a polymer hydrogel, and utilizes the change in hydrophilic-hydrophobic properties brought about by the open-closed loop isomerization of the TCF molecular photoswitch under light and pH change conditions to realize the light-induced deformation of the hydrogel with a single molecular switch regulation in different directions under the same light direction, overcoming the dependence on multiple molecular switches during the actuation process of the light-responsive hydrogel material, expanding the light-induced deformation response of the light-responsive hydrogel, and is expected to realize the development of a new generation of solar catalytic actuators. Description of the Drawings

[0042] Figure 1It is the process flow diagram for preparing a hydrogel with a single-molecule photoswitch controlling deformations in different directions in the present invention;

[0043] Figure 2 It is the schematic diagram of the detection by an ultraviolet fiber spectrometer during the responsiveness test of the photoswitch TCF molecule prepared in Example 1 of the present invention;

[0044] Figure 3 It is the photo-response / pH-response / dark recovery kinetic curve of the photoswitch TCF molecule prepared in Example 1 of the present invention;

[0045] Figure 4 It is the schematic diagram of the illumination experiment during the photo-induced deformation test of the hydrogel with a single-molecule photoswitch controlling deformations in different directions prepared in Example 2 of the present invention;

[0046] Figure 5 It is the physical diagram of the light response during the photo-induced deformation test of the hydrogel with a single-molecule photoswitch controlling deformations in different directions prepared in Example 2 of the present invention. Detailed implementation manners

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0048] Example 1

[0049] This example discloses a preparation method of a photoswitch TCF molecule, including the following steps:

[0050] S1. Prepare A1 molecule;

[0051] Mix 2 g of acrylonitrile, 2.5 g of 3-hydroxy-3-methyl-2-butanone, and 0.2 g of sodium ethoxide in 20 mL of ethanol, stir and react at 80 °C for 6 h. After the reaction ends, obtain the crude reaction product, cool and let stand the crude reaction product at 0 °C for 30 min to obtain a solid-liquid mixture, perform suction filtration, wash the filter cake with cold ethanol, and dry it in an oven to obtain A1 molecule, with a yield of about 70%;

[0052] S2. Prepare A2 molecule;

[0053] 3-chloromethyl-5-nitro-salicylaldehyde and sodium acrylate were mixed in 50 mL of toluene. The molar ratio of 3-chloromethyl-5-nitro-salicylaldehyde, sodium acrylate, and toluene was 1:1.2:0.5. The mixture was stirred and reacted at 110 °C for 12 h. After the reaction, filtration was carried out. The filtrate was taken, the solvent was removed by rotary evaporation, and then purified by column chromatography to obtain A2 molecules, with a yield of about 40%;

[0054] Among them, the eluent used in the column purification operation was prepared by mixing dichloromethane and methanol at a volume ratio of 12:1;

[0055] S3. Prepare the optical switch TCF molecule;

[0056] A1 molecules, A2 molecules and the catalyst ammonium acetate (NH 4 Ac) were mixed evenly in 6 ml of ethanol. The molar ratio of A1 molecules, A2 molecules, the catalyst ammonium acetate, and ethanol was 1:1:0.1:0.07. The reaction was carried out at 80 °C for 5 h. After the reaction, the crude reaction product was obtained. The crude reaction product was cooled and allowed to stand at 0 °C for 30 min to obtain a solid-liquid mixture. Filtration was carried out, and the filter cake was washed with cold ethanol and then dried in an oven to obtain the optical switch TCF molecule, with a yield of about 40%.

[0057] Example 2

[0058] This example discloses a preparation method of a hydrogel controlled by a single-molecule optical switch to deform in different directions, including the following steps:

[0059] 200 mg of acrylamide (AAM), 30 μL of acrylonitrile (AN), 20 mg of ascorbic acid (VC), 30 mg of the optical switch TCF molecule, and 1000 μL of N-methylpyrrolidone (NMP) were mixed. After ultrasonic dissolution, 5 mg of N,N'-methylenebisacrylamide (bis-MBA) was added and mixed evenly. Then 200 μL of a 20 wt% aqueous solution of ammonium persulfate (APS) was added and mixed evenly. Argon was introduced to remove oxygen for 3 min to obtain a prepolymer solution. The prepolymer solution was injected into a mold and polymerized at room temperature for 24 h. After molding, a gel was obtained. The gel was taken out, soaked in ethanol for 2 h, and then replaced into a 5 mmol / L hydrochloric acid aqueous solution and kept in the dark for 12 h to obtain a hydrogel controlled by a single-molecule optical switch to deform in different directions.

[0060] Test example

[0061] 1. Responsiveness test of the optical switch TCF molecule:

[0062] As Figure 2 shown, the response properties of the optical switch TCF molecule prepared in Example 1 under illumination and changing pH conditions were detected;

[0063] The specific test method is as follows: Dissolve the optical switch TCF molecule in N-methylpyrrolidone (NMP), balance it overnight in the dark to obtain a TCF-NMP solution with a concentration of 0.05 mmol / L. Take 2 mL of the TCF-NMP solution and add it to a four-way cuvette, irradiate it with blue light (450 nm), and detect it with an ultraviolet fiber spectrometer; then take another 2 mL of the TCF-NMP solution and add it to a four-way cuvette, acidify it with 20 μL of 1 mol / L hydrochloric acid aqueous solution, and detect it with an ultraviolet fiber spectrometer.

[0064] According to Figure 2 the detection results, under the condition of light intensity (50 mW / cm 2 ), the absorption curve of the TCF-NMP solution containing the optical switch TCF molecule changes from a blue line to a gray line, the absorption value in the visible region decreases, and the absorption value in the ultraviolet region increases; the characteristic absorption peak value of the TCF-NMP solution containing the optical switch TCF molecule at 540 nm decreases from 0.9 (blue line) before illumination to about 0.0 (gray line), and during the acidification process, the characteristic absorption peak value of the TCF-NMP solution containing the optical switch TCF molecule at 540 nm decreases from 0.9 (blue line) before acidification to about 0.0 (gray line), and the characteristic absorption peak at 380 nm increases from 0.5 (blue line) before acidification to about 0.9 (yellow line);

[0065] In summary, under the NMP condition, when the optical switch TCF molecule is irradiated with blue light, the ultraviolet absorption changes. This is because the TCF molecular switch is converted from the open-ring deprotonated long-wavelength form (540 nm) to the closed-ring short-wavelength form (380 nm), which proves that the optical switch TCF molecule has a blue light response behavior; under the NMP condition, when the optical switch TCF molecule is acidified, the ultraviolet absorption changes. This is because the TCF molecular switch changes from the open-ring deprotonated form (540 nm) to the open-ring protonated form (380 nm), and the acidification causes changes in the long conjugated form of the molecule, which proves that the optical switch TCF molecule has a pH response behavior.

[0066] 2. Test on the photo-response / pH-response kinetic curve of the optical switch TCF molecule:

[0067] As Figure 3 shown, detect the photo-response / pH-response kinetic curve of the optical switch TCF molecule prepared in Example 1.

[0068] According to Figure 3 the test results, monitor the characteristic absorption peak value of the 0.05 mmol / L TCF-NMP solution at 540 nm. Under the light intensity (50 mW / cm 2) Under the condition of , after the photoswitch TCF molecule is irradiated in the solution, the absorption value rapidly drops from 0.9 to 0 (the blue area is the light-irradiation time period). After turning off the light irradiation, the absorption value gradually returns to the initial value. Then, 25 μL of 1 mol / L hydrochloric acid aqueous solution is added to the solution. At this time, the characteristic absorption peak at 540 nm rapidly drops to 0, while the characteristic absorption peak at 380 nm rises from 0.5 to 0.9 (the dotted-line box is the acidification time period). Then, light irradiation (50 mW / cm 2 ) is applied again, and the characteristic absorption peak at 380 nm drops from 0.9 to about 0.4 (the blue area is the light-irradiation time period). After turning off the light irradiation, the absorption value gradually returns to the initial value. Then, 25 μL of 1 mol / L sodium hydroxide solution is added to the solution. The characteristic absorption peak at 380 nm drops from 0.9 to about 0.4, while the characteristic absorption peak at 540 nm rises from 0 to 0.9.

[0069] From the above test results, it can be seen that the photoswitch TCF molecule exhibits extremely strong photosensitivity when tested on the characteristic absorption peaks without acidification (540 nm) or after acidification (380 nm). The open-ring state of the molecule will be converted into a closed-ring form under light irradiation, resulting in changes in the absorption peak; in the dark environment / light-shielded conditions, the solution of the photoswitch TCF molecule after light irradiation can quickly return to the original state, that is, spontaneously return from the closed-ring state to the open-ring state, and the absorption peak also recovers accordingly; the solution of the acidified photoswitch TCF molecule can quickly return to the original state after adding alkali for neutralization, which is also because the different structures between open-ring protonation and open-ring deprotonation lead to different characteristic absorption peaks of the molecule. The absorbance change of the ultraviolet acid-base change proves the reversibility of the pH response of the photoswitch TCF molecule; in summary, the photoswitch TCF molecule designed in the present invention can achieve its stable open-ring and photo-isomerization under light irradiation or pH regulation conditions.

[0070] 3. Photo-induced deformation test of hydrogels with different-direction deformations controlled by a single-molecule photoswitch:

[0071] As Figure 4 , Figure 5 shown, detect the photo-induced deformation properties in different directions of the hydrogel with different-direction deformations controlled by the single-molecule photoswitch prepared in Example 2 under different light intensities and pH regulation;

[0072] The specific test method is as follows: Cut the hydrogel that can control deformation in different directions prepared in Example 2 into strip-shaped samples with equal thickness, different lengths and widths, transfer it from a 5 mmol / L hydrochloric acid aqueous solution to the bottom of a glass container filled with deionized water, or suspend it vertically by wrapping it with tin foil, irradiate light from the middle part of the strip-shaped sample, and verify the response of the material to light by whether it produces macroscopic mechanical deformation after illumination; among them, the test schematic diagram is as shown in Figure 4 shown, where Figure 4 The left set of schematic diagrams in represent the initial state of the gel, Figure 4 The three sets of schematic diagrams on the right in represent the final different states of the gel under different conditions. The regulatory effect of pH is represented in red. The three sets of pH values all represent the process of changing from a 5 mmol / L hydrochloric acid aqueous solution to water, and the weaker light intensity means irradiating light at a light intensity of 20 mW / cm 2 , the appropriate light intensity means irradiating light at a light intensity of 50 mW / cm 2 , and the stronger light intensity means irradiating light at a light intensity of 100 mW / cm 2 ; The light source illumination direction for the three groups of experiments is from the left side of the gel; Figure 4 The light source used in is a 450 nm blue light source conducted through an optical fiber, and the light intensity range is 20 - 100 mW / cm 2 .

[0073] According to Figure 5 the test results, it can be seen that when a spline with a thickness of 0.5 mm, a width of 1 mm, and a length of 4 cm is wrapped with tin foil and suspended vertically in deionized water, as shown in Figure 5 (a), after irradiating light from the left side, under the illumination of a light intensity of 20 mW / cm 2 , the gel shows a behavior of bending towards the light source (left side). After irradiating light for 3 h, the gel has an obvious bend, and the bending angle is about 15°; under the illumination of a light intensity of 50 mW / cm 2 on the left side, as shown in Figure 5 (b), the gel shows a vertically uniform bending behavior; under the illumination of a light intensity of 100 mW / cm 2 on the left side, as shown in Figure 5 (c), the gel shows a bending behavior away from the light source. After irradiating light for 3 h, the gel has an obvious bend, and the bending angle is about 20°.

[0074] As can be seen from the above test results, when the hydrogel with a single-molecule photoswitch for controlling deformations in different directions prepared in Example 2 was irradiated with light after being transferred from 5 mmol / L hydrochloric acid to deionized water, the photoswitch TCF molecules therein simultaneously underwent a process of changing from the open-loop protonated form controlled by light to the closed-loop form and a process of changing from the open-loop protonated form controlled by pH to the closed-loop form. The different rate competitions between the two led to a process of bending deformations in different directions; when the rate controlled by pH was faster than the process of light irradiation, the gel bent towards the light; when the rate controlled by pH was similar to the light irradiation rate, the gel bent vertically and uniformly; when the rate controlled by pH was slower than the light irradiation rate, the gel bent away from the light. In summary, in the synergistic process of light irradiation and pH regulation, the designed photoswitch TCF molecules of the present invention achieve photoinduced deformations in different directions, overcoming the dependence of photo-responsive hydrogels on multiple molecular switches, thus simplifying the control of photo-responsive hydrogels and providing a new preparation method and direction for the development of a new generation of bionic actuators.

[0075] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions, characterized in that: The following steps are involved: S1, preparing A1 molecule; acrylonitrile, 3-hydroxy-3-methyl-2-butanone, sodium ethoxide and ethanol are mixed and reacted, and after the reaction is completed, the mixture is purified to obtain the A1 molecule; S2, preparing A2 molecules; 3-chloromethyl-5-nitrosalicylicylaldehyde, sodium acrylate and toluene are mixed and reacted. After the reaction is completed, the filtrate is filtered and the filtrate is taken, rotary evaporated and purified by column to obtain A2 molecule; S3, preparing photoswitch TCF molecules; The A1 molecule, the A2 molecule, ammonium acetate and ethanol are uniformly mixed and reacted, and after the reaction is completed, the molecule is purified to obtain the optical switch TCF molecule; S4. Prepare hydrogels with single molecular optical switches to control deformation in different directions; Acrylamide, acrylonitrile, ascorbic acid, optical switch TCF molecules, and N-methylpyrrolidone are mixed and dissolved by ultrasonication, N,N'-methylenebisacrylamide is added and mixed evenly, and then an aqueous solution of ammonium persulfate is added and mixed evenly to deoxygenate to obtain a prepolymer solution. The prepolymer solution is injected into a mold, polymerized, taken out, soaked in ethanol, and replaced in an aqueous solution of hydrogen chloride to avoid light to obtain a hydrogel with deformation in different directions controlled by a single molecule optical switch.

2. The method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions according to claim 1, characterized in that: In S1: The chemical structure of A1 molecule is: The chemical reaction formula for preparing A1 molecule is: in, represents malononitrile, represents 3-hydroxy-3-methyl-2-butanone, represents the A1 molecule, EtONa represents sodium ethoxide, and EtOH represents ethanol.

3. The method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions according to claim 1, characterized in that: In S1, the molar ratio of malononitrile, 3-hydroxy-3-methyl-2-butanone and sodium ethoxide is 1:(1-1.2):(1.2-1.5); the reaction conditions are: stirring the reaction at 80° C. for 6-8 hours.

4. The method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions according to claim 1, characterized in that: In S2: The chemical structure of A2 molecule is: The chemical reaction formula for preparing A2 molecule is: in, represents 3-chloromethyl-5-nitrosalicylicylaldehyde, represents sodium acrylate, toluene represents toluene, Represents A2 molecule.

5. According to the method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions as described in claim 1, in said S2: the molar ratio of 3-chloromethyl-5-nitrosalicylicylaldehyde and sodium acrylate is 1:(1.2-2); the reaction conditions are: stirring the reaction at a temperature of 110°C for 10-12h.

6. The method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions according to claim 1, wherein in S3: The chemical structure of the optical switch TCF molecule is: The chemical reaction formula for preparing the optical switch TCF molecule is: in, represents the optical switch TCF molecule, represents the A1 molecule, represents the A2 molecule, NH4Ac represents ammonium acetate, and EtOH represents ethanol.

7. According to the method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions as described in claim 1, in said S3: the molar ratio of A1 molecule, A2 molecule and catalyst ammonium acetate is 1:(1-1.3):(0.1-0.2); the reaction conditions are: reacting at a temperature of 75-80°C for 5 hours.

8. According to the method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions as claimed in claim 1, in said S4: the molar ratio of acrylamide, acrylonitrile, ascorbic acid, optical switch TCF molecule, N-methylpyrrolidone, N,N'-methylenebisacrylamide, and ammonium persulfate aqueous solution is 1:(0.15-0.2):(0.02-0.03):(0.01-0.03):(0.03-0.06):(0.02-0.06):(0.02-0.03); the ammonium persulfate aqueous solution is a 20wt% ammonium persulfate aqueous solution.

9. The method for preparing a hydrogel with a single molecule optical switch controlling deformation in different directions according to claim 1, wherein in S4: the polymerization molding condition is: polymerization molding at room temperature for 12-24 hours.

10. A hydrogel with deformation in different directions controlled by a single molecule optical switch, prepared by the method for preparing a hydrogel with deformation in different directions controlled by a single molecule optical switch as described in any one of claims 1 to 9.

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