Preparation method and application of azobenzene-based pH / UV intelligent response information reversible load hydrogel robot

Abstract

The invention discloses a preparation method and application of a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene, and belongs to the technical field of hydrogel. The invention aims to solve the problem that a photoresponse information loading material cannot give consideration to rewritability, high strength, high response speed and multifunctional integration. According to the azobenzene-based pH / UV intelligent response information reversible loading hydrogel robot, 4-hydroxyazobenzene needs to be synthesized through a diazo method, 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and acrylamide serve as raw materials, an azobenzene gel monomer is prepared through a Williamson ether reaction, a nucleophilic substitution reaction, ester group hydrolysis and an amide reaction, and the azobenzene-based pH / UV intelligent response information reversible loading hydrogel robot is obtained. The hydrogel is prepared by taking acrylamide and an azobenzene gel monomer as gel matrixes and N, N '-methylene bisacrylamide as a cross-linking agent through cross-linking strategies such as free radical polymerization, hydrogen bond cross-linking and hydrophobic crystallization, and is applied to intelligent information loading and rewritable password transmission.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogels, and specifically relates to a preparation method and application of an azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot. Background Art

[0002] In the current information age, paper, as the most widely used information storage medium, has the disadvantages of poor recyclability and high cost. With the advancement and development of Internet technology, multimedia transmission has alleviated the limitations of physical information media such as paper and cables, but has created new challenges in areas such as information security transmission. Information leakage and illegal transactions are increasing, causing major security risks and economic losses to society and even the entire country. Therefore, Internet technology cannot replace physical information media, and it is urgent to develop erasable physical information storage materials. Smart responsive polymer hydrogel materials can undergo reversible changes in physical / chemical properties under external stimuli (such as light, electricity, magnetism, heat, ions, etc.), which can be used to achieve information recording, erasure, encryption and decryption, and have broad application prospects in the fields of information storage and security anti-counterfeiting.

[0003] There are many types of gel excitation stimuli. Heat and ions are contact responses, and the actual application scenarios are relatively limited. Although electromagnetic signals and optical signals have the advantages of remote controllable adjustment, the detection and control of electromagnetic signals are difficult, and the entire gel must participate in the response. In contrast, optical signals are a local, instantaneous input external adjustable stimulus source, and the reaction process is simple and has few by-products. Designing intelligent photoresponsive gels with excellent performance is of great significance for the development of green, repeatable and highly secure information storage technology. However, most of the current photoresponsive information-loaded hydrogels are composites of fluorescent ink materials or based on photochemical reaction mechanisms such as photopolymerization and photolysis. Fluorescent inks are indelible and have a single function, while gels based on reactions such as photopolymerization and photolysis also have the disadvantages of poor mechanical properties, extremely slow response speed and irreversibility. Gels based on the photoisomerization mechanism (such as azobenzene) have the advantages of high reaction efficiency and reversible process, and the π-π conjugation effect of the azobenzene structure can enhance the cross-linking strength of the gel, but its poor water solubility causes barriers to the introduction of photoisomerized particles into gels. In summary, existing photoresponsive information-loaded hydrogels cannot combine the characteristics of rewritability, high strength, fast response speed, and multifunctional integration. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that light-responsive information-loaded materials cannot take into account rewritability, high strength, fast response speed and multifunctional integration, and to provide a preparation method and application of an azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot.

[0005] The present invention discloses an azobenzene-based pH / UV intelligent response information reversible load hydrogel robot. 4-hydroxyazobenzene (Azo-OH) is synthesized by diazo method. Azo-OH, potassium carbonate, methyl 6-bromohexanoate and acrylamide (AM) are used as raw materials. Azobenzene gel monomer (AzoAM) is prepared by Williamson ether reaction, nucleophilic substitution reaction, ester hydrolysis and amide reaction. Acrylamide (AM) and AzoAM are used as gel matrix, deionized water is used as solvent, N,N'-methylenebisacrylamide is used as cross-linking agent, and a pH / UV dual reversible response hydrogel is prepared by cross-linking strategies such as free radical polymerization, hydrogen bond cross-linking and hydrophobic crystallization. The specific preparation method is completed according to the following steps:

[0006] 1. Preparation of 4-hydroxyazobenzene:

[0007] ①, aniline and hydrochloric acid were mixed, magnetically stirred for a period of time under ice bath conditions, and then sodium nitrite aqueous solution was added dropwise to obtain mixed solution I;

[0008] ②, adding the sodium phenolate solution to the mixed solution I obtained in step 1①, and reacting for a period of time under low temperature magnetic stirring to obtain 4-hydroxyazobenzene;

[0009] 2. Preparation of azobenzene gel monomer:

[0010] ①, dissolving 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and potassium iodide in dimethylformamide to obtain a mixed solution II; heating the mixed solution II in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain an orange intermediate azophenyl ester derivative;

[0011] ②, dissolving the orange intermediate azophenyl ester derivative in anhydrous ethanol, adding potassium hydroxide to obtain a mixed solution III; reflux the mixed solution III in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain a yellow azobenzene carboxylic acid derivative;

[0012] ③. Dissolve a yellow azobenzenecarboxylic acid derivative, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in dimethylformamide to obtain a mixed solution IV; heat the mixed solution IV in a water bath under magnetic stirring for a period of time to activate the carboxyl group, add acrylamide monomer, and then heat in a water bath under magnetic stirring for a period of time to react. Thin layer chromatography indicates the end point of the reaction, and obtain an orange azophenyl gel monomer;

[0013] 3. Preparation of polymerized azobenzene hydrogel:

[0014] ① Dissolve the orange azophenyl gel monomer in deionized water and stir for a period of time to obtain an orange azophenyl gel monomer solution;

[0015] ②, add acrylamide, ammonium persulfate and methylenebisacrylamide to the orange azobenzene gel monomer solution in sequence, stir at room temperature until the solution is evenly dispersed to obtain a mixed solution V; drop tetramethylethylenediamine into the mixed solution V, stir vigorously and transfer to a mold to obtain a gel;

[0016] ③. Soak the gel in deionized water for cleaning to remove unreacted monomers. After cleaning, a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene is obtained.

[0017] A pH / UV intelligent responsive information reversible loading hydrogel robot based on azobenzene is used in intelligent information loading and reproducible password transmission.

[0018] Advantages of the present invention:

[0019] 1. The pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene prepared by the present invention selects polyacrylamide as the gel matrix, which has both biocompatibility and pH response characteristics;

[0020] 2. A pH / UV intelligent response information reversible load hydrogel robot based on azobenzene prepared by the present invention introduces π-π conjugation, hydrogen bonding and free radical polymerization of azobenzene groups as gel cross-linking strategies, showing good mechanical properties;

[0021] 3. A pH / UV intelligent response information reversible load hydrogel robot based on azobenzene prepared by the present invention can produce corresponding response results to the dual signals when receiving pH and UV signals, and is a multifunctional integrated material;

[0022] 4. A pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene prepared by the present invention exhibits changes in transmittance under different pH stimulations and can be used as a carrier material for second-level response information replication;

[0023] 5. A pH / UV intelligent response information reversible load hydrogel robot based on azobenzene prepared by the present invention exhibits a rapid dehydration effect under UV light irradiation by utilizing the photoisomerization and photothermal effect of azobenzene groups, and the process generates no by-products, which is green and efficient.

[0024] 6. The present invention prepares a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene. Under UV light irradiation, the template is used to cover and limit the light transmission and the convection movement of water molecules between air and gel, so as to perform pattern reversible light response information storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a reaction mechanism diagram of step 1 of Example 1;

[0026] Figure 2 is the reaction mechanism diagram of step 2 of Example 1;

[0027] Figure 3 is the reaction mechanism diagram of step 3 of Example 1;

[0028] Figure 4 is an infrared spectrum, in which a represents the infrared spectrum of phenol, a raw material in step 1 of Example 1, and b represents the infrared spectrum of Azo-OH obtained in step 1 of Example 1;

[0029] Figure 5 is the hydrogen nuclear magnetic resonance spectrum of Azo-OH obtained in step 1 of Example 1;

[0030] Figure 6 The UV absorption graphs corresponding to the heating of Azo-OH obtained in step 1 of Example 1 for different time periods; a, b, c, and d represent the UV absorption graphs corresponding to the heating of Azo-OH for 0, 0.5, 1, and 2 h, respectively;

[0031] Figure 7 is an infrared spectrum, in which a represents the infrared spectrum of Azo-OH, b represents the infrared spectrum of AzoES obtained in step 2① of Example 1, and c represents the infrared spectrum of organic carboxylate AzoCANa obtained by reacting AzoCA obtained in step 2② with sodium hydroxide;

[0032] Figure 8 is the hydrogen nuclear magnetic resonance spectrum of AzoES synthesized in step 2 of Example 1;

[0033] Fig. 9 is the hydrogen nuclear magnetic resonance spectrum of AzoAM synthesized in step 2 of Example 1;

[0034] Fig.10 is the particle size distribution diagram of Azo-OH obtained in step 1 of Example 1;

[0035] Fig.11 The particle size distribution diagram of AzoAM obtained in step 2 of Example 1;

[0036] Fig.12 This is a photo of the orange azobenzene gel monomer solution obtained in step 3① of Example 1 before gelation;

[0037] Fig.13 This is a real photo of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0038] Fig.14is an infrared spectrum, in which a represents the infrared spectrum of Azo-OH, and b represents the infrared spectrum of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0039] Fig.15 is an X-ray diffraction spectrum, in which a represents an X-ray diffraction spectrum curve of polyacrylamide gel (PAM), and b represents a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene obtained in step 3② of Example 1;

[0040] Fig.16 This is the thermogravimetric analysis diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0041] Fig.17 This is the differential scanning calorimetry spectrum of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0042] Fig.18 A scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1, magnified 30 times;

[0043] Fig.19 This is a scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③, magnified 100 times;

[0044] Fig. 20 This is a scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1, magnified 400 times;

[0045] Fig.21 This is a graph showing the change in swelling rate over time of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0046] Fig. 22 This is a graph showing the weight change over time of the azobenzene-based pH / UV intelligent response information reversible load hydrogel robot obtained in step 3③ of Example 1 in a degradation test;

[0047] Fig.23 : is a tensile stress-strain curve diagram, in which a represents the tensile stress-strain curve diagram of PAM, and b represents the tensile stress-strain curve diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0048] Fig.24is a compressive stress-strain curve diagram, in which a represents the tensile stress-strain curve diagram of PAM, and b represents the compressive stress-strain curve diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0049] Fig.25 : is a graph showing the mass change rate of gel as a function of pH, wherein a in the graph shows the mass change rate of PAM gel as a function of pH, and b in the graph shows the mass change rate of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ as a function of pH;

[0050] Fig.26 This is a result diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1 after being immersed in a pH=1 solution;

[0051] Fig. 27 This is a result diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1 after being immersed in a pH=14 solution;

[0052] Fig.28 This is a graph showing the change in the light-transmitting / light-impermeable switching time of the azobenzene-based pH / UV intelligent response information reversible load hydrogel robot as a function of the number of cycles obtained in step 3③ of Example 1;

[0053] Fig.29 This is a graph showing the test results of the pH / UV intelligent response information reversible load hydrogel robot based on azobenzene for light-transmitting / light-impermeable switching cycle obtained in step 3③ of Example 1;

[0054] Fig.30 This is a schematic diagram of the fully light-transmitting state of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot obtained in step 3③ of Example 1;

[0055] Fig.31 This is a schematic diagram of the semi-transparent state of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0056] Fig.32 This is a schematic diagram of the opaque state of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0057] Fig.33 This is a schematic diagram of the gel morphology of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot before UV response obtained in step 3③ of Example 1;

[0058] Fig.34This is the gel thermal imaging image before UV response of the pH / UV intelligent response information reversible loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0059] Fig.35 This is a schematic diagram of the gel morphology of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot after UV response obtained in step 3③ of Example 1;

[0060] Fig.36 This is the gel thermal imaging image of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot during UV response obtained in step 3③ of Example 1;

[0061] Fig.37 It is a graph showing the change of gel mass loss and gel upper / lower diameter over time during the UV response process of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot obtained in step three (3) of Example 1, in which a represents the change of mass loss rate over time, and b represents the change of gel upper / lower diameter over time of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot obtained in step three (3) of Example 1;

[0062] Fig.38 It is a result diagram of the change of gel surface temperature over time during the UV response process of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step three (3) of Example 1, in which a represents the curve of the change of the surface temperature of the PAM gel over time, and b represents the curve of the change of the surface temperature of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step three (3) of Example 1;

[0063] Fig.39 This is a schematic diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1 in front of the pH response load information;

[0064] Fig.40 This is a photo of the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene obtained in step 3③ of Example 1 after being covered with a heart-shaped template soaked in alkali solution for 12 seconds;

[0065] Fig.41 This is a photo of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene loaded with a new pattern obtained in step 3③ of Example 1 after being re-immersed in acid solution for 2 minutes;

[0066] Fig.42 This is a schematic diagram of the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene obtained in step 3③ of Example 1 in front of the light response loading information;

[0067] Fig.43 This is a schematic diagram of the arrow template covering the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene under UV light obtained in step 3③ of Example 1;

[0068] Fig.44 This is a schematic diagram of arrow information loading of the azobenzene-based pH / UV intelligent response information reversible loading hydrogel robot obtained in step three (3) of Example 1 under UV light. DETAILED DESCRIPTION

[0069] Specific implementation method 1: This implementation method is a method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene, which is specifically completed in the following steps:

[0070] 1. Preparation of 4-hydroxyazobenzene:

[0071] ①, aniline and hydrochloric acid were mixed, magnetically stirred for a period of time under ice bath conditions, and then sodium nitrite aqueous solution was added dropwise to obtain mixed solution I;

[0072] ②, adding the sodium phenolate solution to the mixed solution I obtained in step 1①, and reacting for a period of time under low temperature magnetic stirring to obtain 4-hydroxyazobenzene;

[0073] 2. Preparation of azobenzene gel monomer:

[0074] ①, dissolving 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and potassium iodide in dimethylformamide to obtain a mixed solution II; heating the mixed solution II in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain an orange intermediate azophenyl ester derivative;

[0075] ②, dissolving the orange intermediate azophenyl ester derivative in anhydrous ethanol, adding potassium hydroxide to obtain a mixed solution III; reflux the mixed solution III in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain a yellow azobenzene carboxylic acid derivative;

[0076] ③. Dissolve a yellow azobenzenecarboxylic acid derivative, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in dimethylformamide to obtain a mixed solution IV; heat the mixed solution IV in a water bath under magnetic stirring for a period of time to activate the carboxyl group, add acrylamide monomer, and then heat in a water bath under magnetic stirring for a period of time to react. Thin layer chromatography indicates the end point of the reaction, and obtain an orange azophenyl gel monomer;

[0077] 3. Preparation of polymerized azobenzene hydrogel:

[0078] ① Dissolve the orange azophenyl gel monomer in deionized water and stir for a period of time to obtain an orange azophenyl gel monomer solution;

[0079] ②, add acrylamide, ammonium persulfate and methylenebisacrylamide to the orange azobenzene gel monomer solution in sequence, stir at room temperature until the solution is evenly dispersed to obtain a mixed solution V; drop tetramethylethylenediamine into the mixed solution V, stir vigorously and transfer to a mold to obtain a gel;

[0080] ③. Soak the gel in deionized water for cleaning to remove unreacted monomers. After cleaning, a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene is obtained.

[0081] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that: the molar ratio of aniline to hydrochloric acid in step 1① is 1:(2-5); the molar ratio of aniline to sodium nitrite in step 1① is 1:(1.5-2.0); the temperature of the ice bath in step 1① is 0°C; the speed of magnetic stirring in step 1① is 800r / min-1200r / min, and the time of magnetic stirring is 40min-60min. The other steps are the same as those in specific embodiment 1.

[0082] Specific implementation method three: This implementation method is different from specific implementation method one or two in that: the concentration of the sodium phenolate solution described in step one ② is 1.0 mol / L to 1.5 mol / L; the molar ratio of the sodium phenolate in the sodium phenolate solution described in step one ② to the aniline described in step one ① is 1: (1 to 1.5); the temperature of the low-temperature magnetic stirring reaction described in step one ② is 0°C to 5°C, and the time is 8h to 12h; the speed of the magnetic stirring in step one ② is 800r / min to 1200r / min. The other steps are the same as those in specific implementation method one or two.

[0083] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the molar ratio of 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and potassium iodide described in step 2① is 1:(0.7~1.0):(0.7~1.0):(3.5~5); the concentration of 4-hydroxyazobenzene in the mixed solution II described in step 2① is 50mmol / L~80mmol / L; the time of water bath heating reflux described in step 2① is 12h, and the temperature of water bath heating reflux is 95℃; the speed of magnetic stirring described in step 2① is 800r / min~1200r / min. The other steps are the same as those of specific embodiments 1 to 3.

[0084] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the molar ratio of the orange intermediate azophenyl ester derivative to potassium hydroxide described in step 2 ② is 1: (2.5-3); the concentration of the orange intermediate azophenyl ester derivative in the mixed solution III described in step 2 ② is 20mmol / L-50mmol / L; the water bath reflux time described in step 2 ② is 6h, and the water bath reflux temperature is 65°C; the speed of the magnetic stirring described in step 2 ② is 800r / min-1200r / min. The other steps are the same as those of specific embodiments 1 to 4.

[0085] Specific implementation six: This implementation is different from specific implementations one to five in that: the time of water bath heating and stirring described in step two ③ is 1h, and the temperature of water bath heating and stirring is 55℃~65℃; the molar ratio of the yellow azobenzenecarboxylic acid derivative, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide and acrylamide described in step two ③ is 1:(1.0~1.2):(2~3):(3.5~5); the concentration of the yellow azobenzenecarboxylic acid derivative in the mixed solution IV described in step two ③ is 40mmol / L~80mmol / L; the time of water bath heating and stirring reaction after adding acrylamide monomer in step two ③ is 4h, and the temperature of water bath heating and stirring reaction is 55℃; the speed of magnetic stirring described in step two ③ is 800r / min~1200r / min. The other steps are the same as specific implementations one to five.

[0086] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that: the concentration of the orange azobenzene gel monomer solution in step 3① is 60mmol / L; the stirring speed in step 3① is 800r / min to 1200r / min, and the stirring time is 5min to 15min. The other steps are the same as those in specific embodiments 1 to 6.

[0087] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that: the mass ratio of acrylamide, ammonium persulfate and methylenebisacrylamide described in step three ② is 1g:(0.04g~0.08g):0.04g; the concentration of acrylamide in the mixed solution V described in step three ② is 0.28mol / L; the volume ratio of tetramethylethylenediamine described in step three ② to the mixed solution V is 1:1000; the speed of the vigorous stirring described in step three ② is 800r / min~1200r / min, the time of vigorous stirring is 5min~10min, and it is carried out at room temperature. The other steps are the same as those of specific embodiments one to seven.

[0088] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 3③, the gel is immersed in deionized water for cleaning, the water is changed once every 12 hours, the soaking and cleaning time is 48 hours to 96 hours, and the mass of the gel and the volume ratio of the deionized water in a single soaking is 1g:80mL. The other steps are the same as those of specific embodiments 1 to 8.

[0089] Specific embodiment ten: This embodiment is an azobenzene-based pH / UV intelligent response information reversible load hydrogel robot used in intelligent information load and reproducible password transmission.

[0090] The following examples are used to verify the beneficial effects of the present invention:

[0091] Example 1: A method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene, which is specifically completed by the following steps:

[0092] 1. Preparation of 4-hydroxyazobenzene (Azo-OH):

[0093] ①, Mix 25mmol of aniline with 40mL of 3mol / L hydrochloric acid, stir magnetically for 40min in an ice bath at 0℃, then add 25mL of 2mol / L sodium nitrite aqueous solution dropwise to obtain mixed solution I;

[0094] The speed of magnetic stirring in step 1① is 1000r / min;

[0095] ②, add 30mL of 1.0mol / L sodium phenolate solution to the mixed solution I obtained in step 1①, the reaction temperature does not exceed 5°C, and the reaction is stirred magnetically for 10h to obtain 4-hydroxyazobenzene (Azo-OH);

[0096] The speed of magnetic stirring in step 1② is 800r / min;

[0097] 2. Preparation of azophenyl gel monomer (AzoAM):

[0098] ①, 7.6mmol 4-hydroxyazobenzene (Azo-OH), 23.9mmol potassium carbonate, 11.4mmol methyl 6-bromohexanoate and 3.9mmol potassium iodide were dissolved in 100mL dimethylformamide (DMF) to obtain a mixed solution II; the mixed solution II was put into a 250mL three-necked flask, heated to reflux for 12h in a water bath at 95°C under magnetic stirring conditions, and the reaction endpoint was indicated by thin layer chromatography to obtain an orange intermediate azophenyl ester derivative (AzoES);

[0099] The speed of the magnetic stirring in step 2① is 1000r / min;

[0100] ②, dissolve 4mmol of the orange intermediate azophenyl ester derivative (AzoES) in 100mL of anhydrous ethanol, add 12mmol of potassium hydroxide (KOH) to obtain a mixed solution III; reflux the mixed solution III under magnetic stirring and in a 65°C water bath for 6h, and thin layer chromatography indicates the end point of the reaction to obtain a yellow azobenzenecarboxylic acid derivative (AzoCA);

[0101] The speed of the magnetic stirring in step 2② is 1000r / min;

[0102] ③. Dissolve 3 mmol of yellow azobenzenecarboxylic acid derivative (AzoCA), 2.5 mmol of N-hydroxysuccinimide and 2.5 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide in 50 mL of dimethylformamide to obtain a mixed solution IV; heat the mixed solution IV in a 55°C water bath under magnetic stirring for 1 h to activate the carboxyl group, add 15 mmol of acrylamide monomer, and heat and stir the mixture in a 55°C water bath under magnetic stirring for 4 h. The reaction endpoint is indicated by thin layer chromatography to obtain an orange azophenyl gel monomer (AzoAM);

[0103] The speed of the magnetic stirring described in step 2③ is 1000r / min;

[0104] 3. Preparation of polymerized azobenzene hydrogel:

[0105] ① Dissolve 0.6 mmol of orange azophenyl gel monomer in 10 mL of deionized water and stir for 10 min to obtain an orange azophenyl gel monomer solution;

[0106] The stirring speed described in step 3① is 1000r / min;

[0107] ②, add 1g acrylamide, 0.04g ammonium persulfate and 0.04g methylenebisacrylamide to the orange azobenzene gel monomer solution obtained in step 3①, stir at room temperature until the solution is uniformly dispersed to obtain a mixed solution V; drop 10μL tetramethylethylenediamine into the mixed solution V, stir at a stirring speed of 1000r / min for 10min, and then transfer to a mold to obtain a gel;

[0108] The speed of the vigorous stirring described in step 3② is 1000r / min;

[0109] ③. Soak the gel in deionized water to remove unreacted monomers, and obtain a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene after washing;

[0110] In step 3③, the gel is immersed in deionized water for cleaning, and the water is changed once every 12 hours. The soaking and cleaning time is 72 hours. The ratio of the mass of the gel to the volume of the deionized water during a single soaking is 1g:80mL.

[0111] Figure 1 is a reaction mechanism diagram of step 1 of Example 1;

[0112] pass Figure 1 It can be seen that Azo-OH is synthesized by diazo method using 4-aminobenzene, hydrochloric acid, sodium nitrite and sodium phenol as raw materials.

[0113] Figure 2 is the reaction mechanism diagram of step 2 of Example 1;

[0114] pass Figure 2 It can be seen that AzoAM monomer containing a flexible carbon segment was prepared using Azo-OH, potassium carbonate, methyl 6-bromohexanoate and potassium hydroxide as raw materials through the reaction mechanism of Williamson ether reaction, ester hydrolysis and amidation reaction.

[0115] Figure 3 is the reaction mechanism diagram of step 3 of Example 1;

[0116] pass Figure 3 It can be seen that a pH / UV dual reversible responsive hydrogel was prepared by using AM and AzoAM as gel monomers, ammonium persulfate as initiator, and N,N'-methylenebisacrylamide as cross-linking agent through cross-linking strategies such as free radical polymerization, hydrogen bond cross-linking and hydrophobic crystallization.

[0117] Figure 4 is an infrared spectrum, in which a represents the infrared spectrum of phenol, a raw material in step 1 of Example 1, and b represents the infrared spectrum of Azo-OH obtained in step 1 of Example 1;

[0118] Depend on Figure 4 It can be seen that in the infrared spectrum of phenol, 3218cm -1 The stretching vibration absorption peak of OH appears at 1592 cm -1 and 1473cm -1 The benzene ring skeleton stretching vibration peak appears at 1210cm -1 The peak of phenol CO stretching vibration is 748 cm -1 and 689cm -1 The absorption peak of Ph-H bending vibration corresponds to the characteristic absorption peak of benzene ring monosubstitution. Azo-OH still retains the original benzene ring skeleton of phenol, the CO stretching vibration absorption peak and the bending vibration absorption peak of phenol-H, but the stretching vibration absorption peak of OH tends to shift to a low wave number due to the conjugation effect, and a new peak of 836cm -1The Ph-H bending vibration absorption peak corresponds to the para-substitution of the benzene ring, indicating that Azo-OH was successfully prepared.

[0119] Figure 5 is the hydrogen nuclear magnetic resonance spectrum of Azo-OH obtained in step 1 of Example 1;

[0120] Depend on Figure 5 It can be seen that the chemical shift of the protons on the benzene ring in 4-hydroxyazobenzene is located at 6.5-8.5ppm, which is affected by π-π conjugation, p-π conjugation and the lone pair of electrons of the O atom. The protons at b and c are located at the ortho-meta positions of the azo group. Affected by the π-π conjugation, the proton NMR peaks are located at low field and have the largest chemical shift. According to the integrated area, the H atom at 7.88ppm corresponds to the H atom of benzene ring b, and the H atom at 7.50ppm corresponds to the H atom of c. d is located at the ortho-hydroxyl substitution, and the lone pair of electrons is greater than the electron-withdrawing effect of p-π conjugation. Therefore, the high-field chemical shift of the proton d is the smallest, corresponding to the NMR peak at 6.95ppm, and the integrated area is consistent with the number of H atoms. The proton NMR peak of a is located between c and d, corresponding to the NMR peak with an integrated area of ​​1 at 7.44ppm; the active H on the hydroxyl group of Azo-OH corresponds to the solitary peak at 5.19ppm, and the hydroxyl H is easily replaced by deuterium hydrogen with water molecules, and the integrated area is less than 1.

[0121] Figure 6 The UV absorption graphs corresponding to the heating of Azo-OH obtained in step 1 of Example 1 for different time periods; a, b, c, and d represent the UV absorption graphs corresponding to the heating of Azo-OH for 0, 0.5, 1, and 2 h, respectively;

[0122] Depend on Figure 6 It can be seen that the absorption peak at 340nm is the characteristic absorption of trans-azobenzene, and the absorption peak at 440nm is the characteristic absorption of cis-azobenzene. With the heating process, the absorption peak of Azo-OH at 340nm decreases significantly, and the absorption peak at 440nm increases significantly, proving that the temperature increases the excitation of the azo bond from cis to trans, and the cis to trans conversion process is slower.

[0123] Figure 7 is an infrared spectrum, in which a represents the infrared spectrum of Azo-OH, b represents the infrared spectrum of AzoES obtained in step 2① of Example 1, and c represents the infrared spectrum of organic carboxylate AzoCANa obtained by reacting AzoCA obtained in step 2② with sodium hydroxide;

[0124] Depend on Figure 7 It can be seen that AzoES retains the 1592 cm -1 and 1473cm -1 The benzene ring skeleton stretching vibration absorption peak is 2950cm -1 The new stretching vibration absorption peaks at 1720 cm-1 AzoCANa retains the C=O stretching vibration peak of the benzene ring skeleton, the characteristic absorption peaks of the benzene ring mono-substitution and the benzene ring para-substitution, and the original 1720cm -1 The C=O stretching vibration absorption peak of the AzoES ester group at 1600 cm-1 disappeared and the absorption peak at 1600 cm-2 appeared. -1 The characteristic absorption peak of organic carboxylate at .

[0125] Figure 8 is the hydrogen nuclear magnetic resonance spectrum of AzoES synthesized in step 2 of Example 1;

[0126] Depend on Figure 8 It can be seen that the NMR peaks at 7.89ppm, 7.5ppm, 7.44ppm and 6.99ppm correspond to the protons at positions b, c, a and d in the molecule respectively; due to the strong electron-withdrawing effect of the O atom, the H on the C connected to O is located in the low field due to the inductive effect, so the proton at position e is at 4.05ppm and is split into the t peak by ortho-CH2 coupling, and the solitary peak at 3.68ppm is the proton at position j; the H on the C connected to the carbonyl group is at 2.37ppm, that is, the proton at position i; 1.84ppm, 1.73ppm and 1.54ppm are all H on the C connected to the alkyl group, and correspond to the protons at positions f, h and g respectively according to the order of the inductive force received.

[0127] Fig. 9 is the hydrogen nuclear magnetic resonance spectrum of AzoAM synthesized in step 2 of Example 1;

[0128] Depend on Fig. 9 It can be seen that the NMR peaks at 7.92ppm, 7.44ppm, 7.02ppm and 6.82ppm are protons at positions b, c, a and d in the molecule; the chemical shifts at 4.08ppm, 2.43ppm, 1.88ppm, 1.80ppm and 1.53ppm have the same pattern as AzoES, and thus correspond to protons at positions e, i, f, g and h respectively; a double bond group is introduced into the molecule, and the H on the double bond C couples and splits the other H, and the double bond The coupling constant of the bond-positive H is smaller than that of the anti-positive H, so 6.82ppm, 6.38ppm and 5.87ppm correspond to l, k and l' protons respectively, among which l is split into d peak by the coupling of k proton, k is split into dd peak by the coupling of l and l' protons, and l' is split into d peak by the coupling of k proton; the active H of the amine group is connected to the carbonyl group, and the inductive effect makes it located in the low field, and the proton is also prone to deuterium hydrogen replacement, therefore, the proton peak with an integrated area less than 1 corresponds to 2.86ppm.

[0129] Fig.10 is the particle size distribution diagram of Azo-OH obtained in step 1 of Example 1;

[0130] Depend on Fig.10It can be seen that the particle size of Azo-OH is 14.8 nm and the sample size is uniform. It is speculated that the conjugated stacking of Azo makes its particle size significantly larger than the average particle size of small molecule compounds.

[0131] Fig.11 The particle size distribution diagram of AzoAM obtained in step 2 of Example 1;

[0132] Depend on Fig.11 It can be seen that the particle size of AzoAM monomer is 245.2nm, which is significantly larger than that of Azo-OH. The possible reason is that the Azo monomer material is amphiphilic: one end is a hydrophobic azobenzene, and the other end is a hydrophilic gel matrix. It has the structural basis of a surfactant and may aggregate in the solution, so the particle size is significantly increased.

[0133] Fig.12 This is a photo of the orange azobenzene gel monomer solution obtained in step 3① of Example 1 before gelation;

[0134] Fig.13 This is a real photo of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0135] pass Fig.13 and Fig.12 By comparison, it can be seen that the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot obtained in the present invention is in an orange-yellow gel state.

[0136] Fig.14 is an infrared spectrum, in which a represents the infrared spectrum of Azo-OH, and b represents the infrared spectrum of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0137] Depend on Fig.14 It can be seen that the Azo-based gel retains 1592 cm -1 The benzene ring skeleton stretching vibration has a strong absorption peak at 1660cm -1 The -C=O stretching vibration peak of PAM is 3350cm -1 and 3190cm -1 The NH bond symmetric stretching vibration and asymmetric stretching vibration peaks at.

[0138] Fig.15 is an X-ray diffraction spectrum, in which a represents an X-ray diffraction spectrum curve of polyacrylamide gel (PAM), and b represents a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene obtained in step 3② of Example 1;

[0139] Compared with PAM hydrogel, both of them showed two broad diffraction peaks characteristic of amorphous structure of composite PAM hydrogel, but the intensity of crystallization peak was significantly weakened, indicating that the non-covalent stacking of Azo groups strengthened the amorphous degree of gel and no new crystallization area was formed.

[0140] Fig.16 This is the thermogravimetric analysis diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0141] Depend on Fig.16 It can be seen that the gel thermal decomposition process is divided into three stages, with temperature ranges of room temperature-250℃, 250-400℃ and 400-800℃. The process from room temperature to 250℃ is mainly the stage of thermal volatilization of water molecules. When the temperature rises to 250-400℃, different degrees of mass loss appear again, which is the thermal decomposition process of hydrogel cross-linking bonds and side chains; when the temperature rises to 400-800℃, there is no significant mass loss, which is presumed to be the process of hydrogel carbon skeleton fracture.

[0142] Fig.17 This is the differential scanning calorimetry spectrum of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1;

[0143] Depend on Fig.17 It can be seen that the temperature ranges of the hydrogel endothermic process are room temperature to 350℃, 350-650℃ and 650-800℃, respectively. Compared with the TG curve, it can be seen that the mass loss from room temperature to 350℃ is significant, but the corresponding endothermic is not obvious, corresponding to the evaporation of water, dehydration condensation of gel side chains and depolymerization or sublimation of Azo crystal areas; the mass loss is less significant above 400℃, and the endothermic process corresponds to the breakage and decomposition of the main chain, but the network has not yet degraded; the endothermic peaks of 528℃ and 702℃ in Azo-based gels correspond to the depolymerization and decomposition of the carbon skeleton, respectively.

[0144] Fig.18 A scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1, magnified 30 times;

[0145] Fig.19 This is a scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③, magnified 100 times;

[0146] Fig. 20 This is a scanning electron microscope image of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3③ of Example 1, magnified 400 times;

[0147] Depend on Figures 18 to 20It can be seen that the Azo-based gel exhibits a typical hydrogel microstructure, with continuous and densely connected pores and pore sizes of varying sizes.

[0148] Fig.21 The pH / UV intelligent response information reversible load hydrogel robot based on azobenzene according to step 3② of Example 1 was immersed in deionized water at room temperature, removed at different time points, and weighed after absorbing the surface moisture with filter paper until the gel weight no longer changed. The results are shown in FIG. Fig.21 , Fig.21 is the graph of the swelling rate of Azo-based gel versus time, Fig.21 It can be seen that the pH / UV intelligent response information reversible load hydrogel robot based on azobenzene obtained by the present invention is immersed in deionized water for 112 hours, and its swelling rate increases to 549% and then tends to be stable, showing good swelling performance;

[0149] Fig. 22 The weight variation over time of the pH / UV intelligent response information reversible load hydrogel robot based on azobenzene obtained in step 3② of Example 1 in the degradation test is shown in FIG. Fig. 22 It can be seen that the Azo-based gel did not degrade in phosphate buffer solution, indicating that the hydrogel has good stability and is suitable for long-term use in an in vitro environment;

[0150] Fig.23 It is a tensile stress-strain curve diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene and PAM obtained in step 3② of Example 1; Fig.24 2 is a compressive stress-strain curve of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene and PAM obtained in step 3② of Example 1, a represents the stress-strain curve of PAM, and b represents the stress-strain curve of the pH / UV intelligent response information reversibly loaded hydrogel based on azobenzene obtained in step 3② of Example 1; Fig.23 and 24 It can be seen that the mechanical properties and toughness of the gel are improved, and the stress required for the same tensile / compressive deformation is significantly increased;

[0151] Fig.25 is a graph showing the mass change rate of the gel as a function of pH, wherein a in the graph shows the mass change rate of the PAM gel as a function of pH, and b in the graph shows the mass change rate of the pH / UV intelligent response information reversibly loaded hydrogel based on azobenzene obtained in step 3② of Example 1 as a function of pH, Fig.25It can be seen that compared with PAM gel, pH significantly affects the mass change of Azo-based gel. The mass loss under acidic conditions and the mass increase under alkaline conditions are higher than those of PAM gel. The mass change causes the gel to have an obvious volume change. The above phenomenon may be caused by the regulatory effect of the -NH- segment in AzoAM. Under acidic conditions, -NH2 and -NH in the gel matrix tend to form interchain hydrogen bonds. As the acidity of the solution increases, the lower the proportion of protonated groups, the stronger the hydrogen bonding effect, the smaller the gel network space, the lower the hydrophilicity and water holding capacity, and the gel shrinks. Under alkaline conditions, -NH2 and -NH in the gel matrix will be protonated, and the interchain hydrogen bonds will be broken by ionic repulsion. As the alkalinity of the solution increases, the higher the proportion of protonated groups, the stronger the interchain hydrogen bonding effect, the larger the gel network space, and the gel will be more hydrophilic and swell.

[0152] Fig.26 This is a result diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1 after being immersed in a pH=1 solution; Fig. 27 This is the result of the pH / UV dual-responsive azophenyl hydrogel obtained in step 3② of Example 1 being immersed in a pH=14 solution. Fig.26 and 27 As far as we know, the change of Azo-based gel quality causes the gel to have obvious volume change and light transmittance change. When soaked in acid solution, the gel is completely opaque; when soaked in alkaline solution, the gel has a light-transmitting area from the outer diameter to the center. The reason is speculated to be: under acidic conditions, the interchain hydrogen bonding in Azo-based gel is strong, the polymer network is more dense and conducive to the conjugated stacking of Azo groups, forming a hydrophobic crystal area, and the gel light transmittance decreases; under alkaline conditions, the interchain hydrogen bonding in the gel is weak, the loose polymer network Azo groups are not easy to contact, the hydrophobic crystal area disappears, and the gel light transmittance increases;

[0153] Fig.28 is a graph showing the change in the light-transmitting / light-impermeable switching time of the azobenzene-based pH / UV intelligent response information reversible load hydrogel robot as a function of the number of cycles obtained in step 3② of Example 1, Fig.28 It can be seen that after switching between the transparent / opaque states in alkali / acid for 25 times, the performance of the Azo-based gel remains stable, which can meet the service life requirements of its information transmission application;

[0154] Fig.29 This is a test result diagram of the pH / UV intelligent response information reversible load hydrogel robot based on azobenzene for light-transmitting / light-impermeable switching cycle obtained in step 3② of Example 1, Fig.29It can be seen that the switching time of Azo-based gel increases with the increase in the number of times it switches between the transparent and opaque states. This is because the three-dimensional network structure of the gel will store part of the solution during this process, affecting the proton exchange in the next stage; and NaCl molecules will be generated during the acid-base neutralization process and dispersed in the gel network in an ionic state, which to a certain extent hinders the H + and OH - Effective collision;

[0155] Fig.30 This is a schematic diagram of the fully light-transmitting state of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot obtained in step 3② of Example 1; Fig.31 This is a schematic diagram of the semi-transparent state of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1; Fig.32 Schematic diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1 in the opaque state; Figures 30-32 It can be seen that in the light-transmitting stage of the Azo-based gel, the letters covered can be clearly seen and information can be transmitted; in contrast, the letters covered by the opaque gel are completely hidden and information cannot be transmitted;

[0156] Fig.33 This is a schematic diagram of the gel morphology of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot before UV response obtained in step 3② of Example 1; Fig.34 This is the gel thermal imaging image before UV response of the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene obtained in step 3② of Example 1; Fig.35 This is a schematic diagram of the gel morphology of the azobenzene-based pH / UV intelligent response information reversibly loaded hydrogel robot after UV response obtained in step 3② of Example 1; Fig.36 This is the gel thermal imaging image after UV response of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1; Figures 33-36 It can be seen that the photothermal effect caused by the cis-trans isomerization of Azo induced by ultraviolet light participates in this process. At the same time, Azo isomerization causes the depolymerization of the conjugated arrangement, the cross-linking density of the irradiated surface is small, the gel network is looser, and the water encapsulated in the three-dimensional space is more easily volatilized by heat, which reduces the swelling rate of the gel toward the light side, resulting in a decrease in the photometric volume of the gel.

[0157] Fig.37It is a graph showing the change of gel mass loss and gel upper / lower diameter over time during the UV response process of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step three ② of Example 1, in which a represents the change of mass loss rate over time, and b represents the change of gel upper / lower diameter over time during the UV response process of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step three ② of Example 1; Fig.38 The graph is a result of the change of the surface temperature of the gel over time during the UV response process of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1. In the graph, a represents the curve of the surface temperature of the PAM gel over time, and b represents the curve of the surface temperature of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1. Fig.37 and 38 This further proves that the pH / UV dual-responsive azobenzene hydrogel will cause significant mass loss under UV irradiation. Even if the temperature rise is low, the decrease in gel density caused by the cis-trans isomerization of the Azo group will accelerate water loss, resulting in an experimental phenomenon in which the difference between the upper and lower radii of the gel continues to grow.

[0158] Fig.39 This is a schematic diagram of the pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene obtained in step 3② of Example 1 before the pH response load information; Fig.40 This is a photo of the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene obtained in step 3② of Example 1 after being covered with a heart-shaped template soaked in alkali solution for 12 seconds; Fig.41 This is a photo of the pH / UV intelligent response information reversibly loaded hydrogel robot loaded with azobenzene-based novel pattern obtained in step 3② of Example 1 after being re-immersed in acid solution for 2 minutes; Figures 39-41 It can be seen that the prepared pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene is placed in pH=1 acid solution to keep it in a non-light-transmitting state. After the filter paper is cut into a suitable shape, it is dipped in 1MNaOH solution and placed on the gel for 12s as a template. The information loading is observed, and it can be observed that the shape boundary is clearly printed on the gel without blurring. The gel is immersed in the acid solution again, and the gel returns to a non-light-transmitting state. This experiment proves that the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene has the functional characteristics of information loading and rewritability;

[0159] Fig.42 This is a schematic diagram of the pH / UV intelligent response information reversible load hydrogel robot based on azobenzene obtained in step 3② of Example 1 in front of the light response load information; Fig.43This is a schematic diagram of the arrow template covering the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene under UV light obtained in step 3② of Example 1; Fig.44 This is a schematic diagram of the arrow information loading of the pH / UV intelligent response information reversible loading hydrogel robot based on azobenzene under UV light obtained in step 3② of Example 1, Figures 42-44 It can be seen that based on the ultraviolet light response water loss characteristics of the prepared azobenzene-based pH / UV smart response information reversible loading hydrogel robot, after the pattern is covered on the gel surface and irradiated with ultraviolet light, the pattern template hinders the light transmission and the convection movement of water molecules between air and gel, while other areas of the surface quickly lose water, causing the covered area to bulge out of the gel surface, which can complete the light response information loading, and the loading process only involves water loss without by-products, which is green and environmentally friendly. This experiment further proves that the azobenzene-based pH / UV smart response information reversible loading hydrogel robot has multi-path information loading and rewritable functional characteristics.

Claims

1. A method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of 4-hydroxyazobenzene: ①, aniline and hydrochloric acid were mixed, magnetically stirred for a period of time under ice bath conditions, and then sodium nitrite aqueous solution was added dropwise to obtain mixed solution I; ②, adding the sodium phenolate solution to the mixed solution I obtained in step 1①, and reacting for a period of time under low temperature magnetic stirring to obtain 4-hydroxyazobenzene; 2. Preparation of azobenzene gel monomer: ①, dissolving 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and potassium iodide in dimethylformamide to obtain a mixed solution II; heating the mixed solution II in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain an orange intermediate azophenyl ester derivative; ②, dissolving the orange intermediate azophenyl ester derivative in anhydrous ethanol, adding potassium hydroxide to obtain a mixed solution III; reflux the mixed solution III in a water bath under magnetic stirring for a period of time, and thin layer chromatography indicates the end point of the reaction to obtain a yellow azobenzene carboxylic acid derivative; ③. Dissolve a yellow azobenzenecarboxylic acid derivative, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in dimethylformamide to obtain a mixed solution IV; heat the mixed solution IV in a water bath under magnetic stirring for a period of time to activate the carboxyl group, add acrylamide monomer, and then heat in a water bath under magnetic stirring for a period of time to react. Thin layer chromatography indicates the end point of the reaction, and obtain an orange azophenyl gel monomer; 3. Preparation of polymerized azobenzene hydrogel: ① Dissolve the orange azophenyl gel monomer in deionized water and stir for a period of time to obtain an orange azophenyl gel monomer solution; ②, add acrylamide, ammonium persulfate and methylenebisacrylamide to the orange azobenzene gel monomer solution in sequence, stir at room temperature until the solution is evenly dispersed to obtain a mixed solution V; drop tetramethylethylenediamine into the mixed solution V, stir vigorously and transfer to a mold to obtain a gel; ③. Soak the gel in deionized water for cleaning to remove unreacted monomers. After cleaning, a pH / UV intelligent response information reversible load hydrogel robot based on azobenzene is obtained.

2. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The molar ratio of aniline to hydrochloric acid in step 1① is 1:(2-5); the molar ratio of aniline to sodium nitrite in step 1① is 1:(1.5-2.0); the temperature of the ice bath in step 1① is 0°C; the speed of magnetic stirring in step 1① is 800r / min-1200r / min, and the time of magnetic stirring is 40min-60min.

3. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The concentration of the sodium phenolate solution described in step 1② is 1.0mol / L~1.5mol / L; the molar ratio of the sodium phenolate in the sodium phenolate solution described in step 1② to the aniline described in step 1① is 1:(1~1.5); the temperature of the low-temperature magnetic stirring reaction described in step 1② is 0℃~5℃, and the time is 8h~12h; the speed of the magnetic stirring in step 1② is 800r / min~1200r / min.

4. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The molar ratio of 4-hydroxyazobenzene, potassium carbonate, methyl 6-bromohexanoate and potassium iodide described in step 2① is 1:(0.7~1.0):(0.7~1.0):(3.5~5); the concentration of 4-hydroxyazobenzene in the mixed solution II described in step 2① is 50mmol / L~80mmol / L; the time of water bath heating reflux described in step 2① is 12h, and the temperature of water bath heating reflux is 95℃; the speed of magnetic stirring described in step 2① is 800r / min~1200r / min.

5. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The molar ratio of the orange intermediate azophenyl ester derivative described in step 2② to potassium hydroxide is 1:(2.5~3); the concentration of the orange intermediate azophenyl ester derivative in the mixed solution III described in step 2② is 20mmol / L~50mmol / L; the water bath reflux time described in step 2② is 6h, and the water bath reflux temperature is 65°C; the speed of the magnetic stirring described in step 2② is 800r / min~1200r / min.

6. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The time for water bath heating and stirring in step 2③ is 1h, and the temperature for water bath heating and stirring is 55℃~65℃; the molar ratio of the yellow azobenzenecarboxylic acid derivative, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide and acrylamide in step 2③ is 1:(1.0~1.2):(2~3):(3.5~5); the concentration of the yellow azobenzenecarboxylic acid derivative in the mixed solution IV in step 2③ is 40mmol / L~80mmol / L; the time for water bath heating and stirring reaction after adding acrylamide monomer in step 2③ is 4h, and the temperature for water bath heating and stirring reaction is 55℃; the speed of magnetic stirring in step 2③ is 800r / min~1200r / min.

7. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The concentration of the orange azobenzene gel monomer solution in step 3① is 60mmol / L; the stirring speed in step 3① is 800r / min~1200r / min, and the stirring time is 5min~15min.

8. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that The mass ratio of acrylamide, ammonium persulfate and methylenebisacrylamide described in step 3② is 1g:(0.04g~0.08g):0.04g; the concentration of acrylamide in the mixed solution V described in step 3② is 0.28mol / L; the volume ratio of tetramethylethylenediamine described in step 3② to the mixed solution V is 1:1000; the speed of the vigorous stirring described in step 3② is 800r / min~1200r / min, the time of vigorous stirring is 5min~10min, and it is carried out at room temperature.

9. The method for preparing a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene according to claim 1, characterized in that In step 3③, the gel is immersed in deionized water for cleaning, and the water is changed once every 12 hours. The soaking and cleaning time is 48 hours to 96 hours. The ratio of the mass of the gel to the volume of the deionized water during a single soaking is 1g:80mL.

10. Application of a pH / UV intelligent response information reversibly loaded hydrogel robot based on azobenzene prepared by the preparation method according to claim 1, characterized in that A pH / UV intelligent responsive information reversible loading hydrogel robot based on azobenzene is used in intelligent information loading and reproducible password transmission.

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