Multi-stimulus responsive fluorescent color-changing material as well as preparation method and application thereof

Abstract

The invention discloses a multi-stimulus responsive fluorescent color-changing material as well as a preparation method and application thereof, and belongs to the technical field of fluorescent color-changing materials. The substance composition of the multi-stimulus responsive fluorescent color-changing material disclosed by the invention is a maleimide-isopropylacrylamide copolymer. According to the multi-stimulus responsive fluorescent color-changing material, through copolymerization of carboxylic acid maleimide and isopropylacrylamide, a synergistic effect is formed between carboxylic acid maleimide and isopropylacrylamide molecules to generate an AIE effect, so that the copolymer is endowed with excellent fluorescence ability; moreover, the interaction among copolymer molecules can be specifically changed under thermal stimulation, alkali stimulation and thermal-alkali stimulation, so that the fluorescence color or fluorescence emission peak position / intensity is subjected to conversion regulation, and multi-stimulation responsive fluorescence discoloration is effectively achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of organic fluorescent color-changing materials, and in particular relates to a multi-stimulus responsive fluorescent color-changing material, a preparation method thereof, and an application thereof. Background Art

[0002] Stimuli-responsive fluorescent materials refer to new functional materials whose color and fluorescence emission peak position / intensity can be converted / adjusted under the action of external environmental stimuli (such as temperature, force, light, electricity, magnetism, etc.). They have shown great development potential in the fields of anti-counterfeiting marking, information storage, optical coding / switching, bioimaging and fluorescent sensors. However, with the increasing demand for the application of stimuli-responsive fluorescent materials, stimuli-responsive fluorescent materials should have strong luminescence properties in solution or solid state. Therefore, the design and preparation of stimuli-responsive fluorescent color-changing materials with AIE effect is of great practical value.

[0003] At present, related fields have designed and prepared many fluorescent color-changing materials with single stimulus response, such as temperature stimulus response, light stimulus response, ion stimulus response, pressure stimulus response and acid / base stimulus response, to meet the application needs in different fields.

[0004] However, with the continuous expansion of the application of stimulus-responsive fluorescent color-changing materials, single stimulus-responsive fluorescent color-changing materials no longer meet the application requirements, and existing multi-stimulus-responsive fluorescent color-changing materials are generally prepared by free radical polymerization, polycondensation and other methods using special structural monomers, and the synthesis steps are cumbersome and costly. Therefore, it is extremely important to develop multi-stimulus-responsive fluorescent color-changing materials with simple synthesis, fast response speed and obvious fluorescence color change. Summary of the invention

[0005] The present application discloses a multi-stimulus responsive fluorescent color-changing material, a preparation method thereof and an application thereof, aiming to solve the technical problems of complicated synthesis steps and high cost of existing multi-stimulus responsive fluorescent color-changing materials.

[0006] In order to achieve the above objectives, the technical solution adopted in this application is:

[0007] The first aspect of the present application provides a multi-stimulus responsive fluorescent color-changing material, wherein the material composition of the multi-stimulus responsive fluorescent color-changing material of the present application is carboxylic acid maleimide-isopropyl acrylamide copolymer.

[0008] The second aspect of the present application provides a method for preparing the multi-stimulus responsive fluorescent color-changing material described in the present application, the preparation method comprising the steps of:

[0009] providing a polar solvent in which isopropyl acrylamide is dissolved;

[0010] After adding carboxylic acid maleimide monomer and initiator to the polar solvent, copolymerization reaction is carried out in an inert atmosphere, solid products are separated and collected, and the solid products are dialyzed in deionized water, and the dialyzate is vacuum freeze-dried to obtain a multi-stimulus responsive fluorescent color-changing material;

[0011] The carboxylic acid maleimide monomer has the chemical structure of formula [i]:

[0012]

[0013] Here, R is any one of C1-C6 straight-chain alkyl groups.

[0014] In a possible embodiment, when the carboxylic acid maleimide monomer and the initiator are added to the polar solvent, the molar ratio of the carboxylic acid maleimide monomer to the isopropyl acrylamide is 1:(1-50).

[0015] In a possible implementation, when the carboxylic acid maleimide monomer and the initiator are added to the polar solvent, the molar ratio of the carboxylic acid maleimide monomer to the isopropyl acrylamide is 1:20.

[0016] In a possible embodiment, the initiator comprises azobisisobutyronitrile.

[0017] In a possible embodiment, the polar solvent is toluene.

[0018] In a possible embodiment, the dialysis is performed at a molecular weight cut-off of 4000-6000.

[0019] In a possible embodiment, the maleimide is any one of 2-maleimidoacetic acid, 3-maleimidopropionic acid, 4-maleimidobutyric acid, 5-maleimidopentanoic acid or 6-maleimidohexanoic acid.

[0020] In a possible embodiment, when the copolymerization reaction is carried out, the reaction temperature is 60-70° C. and the time is 12-24 hours.

[0021] The third aspect of the present application provides the application of the multi-stimulus responsive fluorescent color-changing material described in the present application in anti-counterfeiting marking, information storage, biological imaging, and sensors.

[0022] Compared with the prior art, the advantages or beneficial effects of the present application include at least:

[0023] The multi-stimulus responsive fluorescent color-changing material provided in the present application is a carboxylic acid maleimide-isopropyl acrylamide copolymer, and the carboxylic acid maleimide-isopropyl acrylamide copolymer is copolymerized by carboxylic acid maleimide and isopropyl acrylamide contained in its molecular structure, so that the carboxylic acid maleimide and isopropyl acrylamide molecules form a synergistic effect to produce an AIE effect, which not only gives the obtained copolymer excellent fluorescence ability in solution or solid state, but also the obtained copolymer can be based on intermolecular interactions and cause specific changes under thermal stimulation, alkali stimulation and heat-alkali stimulation, so that the fluorescence color or fluorescence emission peak position / intensity is converted and adjusted, and multi-stimulus responsive fluorescent color change is effectively achieved. In addition, the synthetic monomers of the copolymer are common carboxylic acid maleimide and isopropyl acrylamide, which are widely available, low cost, and omit the complex synthesis process, and have good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 The infrared spectrum of the (MPA-NIPAM) copolymer P4 provided in the examples of the present application;

[0026] Figure 2 This is a fluorescence color diagram of the (MPA-NIPAM) copolymer P4 in solution provided in an embodiment of the present application;

[0027] Figure 3 The liquid fluorescence emission spectrum of the (MPA-NIPAM) copolymer P4 provided in the examples of the present application;

[0028] Figure 4 This is a fluorescence color diagram of the (MPA-NIPAM) copolymer P4 solution provided in the examples of the present application after being treated with different stimuli;

[0029] Figure 5 This is a fluorescence color diagram of the (MPA-AM) copolymer in solution state provided in the examples of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] In the following description of this specification, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. Among them, A and B can be singular or plural; the symbol " / " means "or".

[0032] In the following description of this specification, the term "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of A, B or C", or "at least one of A, B and C" can mean any one of A, B, C, or A+B, or A+C, or B+C, or A+B+C, where A, B, C can be single or multiple, respectively.

[0033] In the following description of this specification, the order of serial numbers does not mean the order of execution. Some or all of the steps can be executed in parallel or one after the other. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this embodiment.

[0034] In the following description of this specification, the numerical range should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value in the stated range and any other stated value or each smaller range between the intermediate values ​​in the range are also included in this embodiment, and the upper and lower limits of the smaller range can be independently included or excluded in the range.

[0035] Unless otherwise specified, the technical / scientific terms used in this specification have the meanings commonly understood by those skilled in the art. Although this specification only describes preferred materials and methods, any similar or equivalent methods and materials may also be used in specific embodiments or test cases. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0036] In a first aspect, the embodiments of the present application provide a multi-stimulus responsive fluorescent color-changing material. The material composition of the multi-stimulus responsive fluorescent color-changing material of the embodiments of the present application is carboxylic acid maleimide-isopropyl acrylamide copolymer.

[0037] It should be noted that the carboxylic acid maleimide-isopropyl acrylamide copolymer of the embodiment of the present application refers to a polymer containing carboxylic acid maleimide and isopropyl acrylamide in the molecular chain generated by copolymerization of carboxylic acid maleimide and isopropyl acrylamide, and its chemical structure can be represented by [ii].

[0038]

[0039] Wherein, R is any one of C1-C6 straight-chain alkyl groups, which can be exemplified by any one of methyl, ethyl, propyl, butyl, n-pentyl and n-hexyl. The embodiments of the present application have no special limitation on the carbon chain, and the multi-stimulus responsive fluorescent color-changing material can be prepared. Specifically, it can be reasonably selected according to the structure of the carboxylic acid maleimide monomer; m and n both represent the degree of polymerization. The embodiments of the present application have no special limitation on the specific value of the degree of polymerization, and can be reasonably regulated according to the molar ratio of the carboxylic acid maleimide monomer and isopropyl acrylamide during copolymerization. However, in order to ensure reasonable costs, a lower value range can be selected, for example, the values ​​of m and n are both 1-50.

[0040] The multi-stimulus responsive fluorescent color-changing material provided in the embodiment of the present application is a carboxylic acid maleimide-isopropyl acrylamide copolymer, and the carboxylic acid maleimide-isopropyl acrylamide copolymer is copolymerized by the carboxylic acid maleimide and isopropyl acrylamide contained in its molecular structure, so that the carboxylic acid maleimide and isopropyl acrylamide molecules form a synergistic effect and produce an AIE effect, which not only gives the obtained copolymer excellent fluorescence ability in a solution or solid state, but also the obtained copolymer can be based on intermolecular interactions and cause specific changes under thermal stimulation, alkali stimulation and heat-alkali stimulation, so that the fluorescence color or the fluorescence emission peak position / intensity is converted and adjusted, and multi-stimulus responsive fluorescent color change is effectively achieved. In addition, the synthetic monomers of the copolymer are commercially available carboxylic acid maleimide and isopropyl acrylamide, which are widely available, low cost, and omit the complex synthesis process, and have good industrial prospects.

[0041] In a second aspect, the present application provides a method for preparing the multi-stimulus responsive fluorescent color-changing material according to the present application, preferably comprising the steps of:

[0042] providing a polar solvent in which isopropyl acrylamide is dissolved;

[0043] After adding carboxylic acid maleimide monomer and initiator to the polar solvent, copolymerization reaction is carried out in an inert atmosphere, solid products are separated and collected, and the solid products are dialyzed in deionized water, and the dialyzate is dried to obtain a multi-stimulus responsive fluorescent color-changing material;

[0044] The carboxylic acid maleimide monomer has the chemical structure of formula [i]:

[0045]

[0046] Wherein, R is any one of C1-C6 alkyl groups.

[0047] It should be noted that "R" in the chemical structures of formula [i] and formula [ii] is the same substituent group, so it will not be repeated here; the embodiment of the present application does not specifically limit the specific source of the carboxylic acid maleimide monomer, and it is preferably obtained through commercial sources; at the same time, the embodiment of the present application does not limit the specific process of dialysate drying, and is based on the ability to completely remove the solvent component. The embodiment of the present application preferably performs vacuum freeze drying on the dialysate, for example, the vacuum freeze drying parameters are: temperature is -50°C, and time is 72h.

[0048] Based on the above description, in the embodiment of the present application, a multi-stimulus responsive fluorescent color-changing material can be prepared by copolymerizing isopropyl acrylamide and carboxylic acid maleimide monomers under the action of an initiator. The synthesis method is simple and easy to commercialize.

[0049] In an exemplary embodiment, when the initiator and the carboxylic acid maleimide monomer are added to the polar solvent, the molar ratio of the carboxylic acid maleimide monomer to the isopropyl acrylamide is 1:(1-50). Among them, the preferred molar ratio is 1:1, 1:3, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50 or any one within the molar ratio range, more preferably 1:20.

[0050] In an exemplary embodiment, the initiator is preferably azobisisobutyronitrile.

[0051] In an exemplary embodiment, the polar solvent is preferably toluene.

[0052] In an exemplary embodiment, the molecular weight cutoff for the dialysis is 4000-6000, so that the unreacted monomers / materials can be fully separated and removed to avoid the unreacted monomers / materials interfering with the fluorescent color-changing properties of the prepared copolymer.

[0053] In an exemplary embodiment, the maleimide is preferably any one of 2-maleimidoacetic acid, 3-maleimidopropionic acid, 4-maleimidobutyric acid, 5-maleimidopentanoic acid or 6-maleimidohexanoic acid.

[0054] In the exemplary embodiment, when the copolymerization reaction is carried out, the reaction temperature is preferably 60-70°C, and the time is preferably 12-24h. The reaction temperature may be 60°C, 65°C, 70°C or any one in the temperature range; the time may be 12h, 15h, 18h, 20h, 22h, 24h or any one in the time range.

[0055] On the third aspect, the embodiments of the present application also provide applications of the multi-stimulus responsive fluorescent color-changing materials described above in anti-counterfeiting markings, information storage, bio-imaging, and sensors.

[0056] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0057] Example 1

[0058] This example provides the preparation of (MPA-NIPAM) copolymer P1, and the specific steps include:

[0059] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 1690 mg (10 mmol) of 3-maleimidopropionic acid (MPA) monomer and 1131.6 mg (10 mmol) of isopropylacrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65 ° C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50 ° C, time 72 hours) to obtain (MPA-NIPAM) copolymer P1.

[0060] Example 2

[0061] This embodiment provides the preparation of (MPA-NIPAM) copolymer P2, and the specific steps include:

[0062] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 169 mg (1 mmol) of 3-maleimidopropionic acid (MPA) monomer and 1131.6 mg (10 mmol) of isopropylacrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65 ° C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50 ° C, time 72 hours) to obtain (MPA-NIPAM) copolymer P2.

[0063] Example 3

[0064] This embodiment provides the preparation of (MPA-NIPAM) copolymer P3, and the specific steps include:

[0065] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 169 mg (1 mmol) of 3-maleimidopropionic acid (MPA) monomer and 1697.4 mg (15 mmol) of isopropylacrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65 ° C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50 ° C, time 72 hours) to obtain (MPA-NIPAM) copolymer P3.

[0066] Example 4

[0067] This example provides the preparation of (MPA-NIPAM) copolymer P4, and the specific steps include:

[0068] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 169 mg (1 mmol) of 3-maleimidopropionic acid (MPA) monomer and 2263.2 mg (20 mmol) of isopropylacrylamide (NIPAM) monomer, vacuumize and replace nitrogen three times, copolymerize at 65 ° C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50 ° C, time 72 hours) to obtain (MPA-NIPAM) copolymer P4.

[0069] Example 5

[0070] This example provides the preparation of (MPA-NIPAM) copolymer P5, and the specific steps include:

[0071] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 169 mg (1 mmol) of 3-maleimidopropionic acid (MPA) monomer and 5658.0 mg (50 mmol) of isopropylacrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65°C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50°C, time 72 hours) to obtain (MPA-NIPAM) copolymer P5.

[0072] Example 6

[0073] This example provides the preparation of (MBA-NIPAM) copolymer P6, and the specific steps include:

[0074] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 138 mg (1 mmol) of 4-maleimidobutyric acid (MBA) monomer and 2263.2 mg (20 mmol) of isopropyl acrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65°C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50°C, time 72 hours) to obtain (MBA-NIPAM) copolymer P6.

[0075] Example 7

[0076] This example provides the preparation of (MCA-NIPAM) copolymer P7, and the specific steps include:

[0077] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 211.2 mg (1 mmol) of 6-maleimidocaproic acid (MCA) monomer and 2263.2 mg (20 mmol) of isopropylacrylamide (NIPAM) monomer, evacuate and replace nitrogen three times, copolymerize at 65°C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50°C, time 72 hours) to obtain (MCA-NIPAM) copolymer P7.

[0078] Comparative Example 1

[0079] This embodiment provides the preparation of (MPA-AM) copolymer, and the specific steps include:

[0080] In 6 mL of anhydrous toluene, add 16 mg of azobisisobutyronitrile, 169.0 mg (1 mmol) of 3-maleimidopropionic acid (MPA) monomer and 1421.6 mg (20 mmol) of acrylamide (AM) monomer, evacuate and replace with nitrogen 3 times, copolymerize at 65 ° C for 12 hours; then cool to room temperature, and filter the reaction solution to obtain a crude solid. The obtained crude solid is dialyzed in deionized water (dialysis bag molecular weight cutoff is 4000-6000), and the obtained dialyzate is vacuum freeze-dried (temperature -50 ° C, time 72 hours) to obtain (MPA-AM) copolymer, whose chemical structure is:

[0081]

[0082] In order to illustrate the fluorescence properties of the carboxylic acid maleimide-isopropylacrylamide copolymer prepared in the examples of the present application, the (MPA-NIPAM) copolymer P4 will be used as a test sample for verification analysis.

[0083] 1. Infrared spectroscopy characterization

[0084] The (MPA-NIPAM) copolymer P4 was characterized by infrared spectroscopy, and the results were Figure 1 As shown. Among them, Figure 1 This is the infrared spectrum of (MPA-NIPAM) copolymer P4.

[0085] according to Figure 1 It can be seen that the carboxyl peak of 3-maleimidopropionic acid appears at 1686 cm -1 The amide peak of isopropyl acrylamide appears at 1399.3 cm -1 It shows that the 3-maleimidopropionic acid-isopropylacrylamide copolymer was successfully synthesized in the examples of the present application.

[0086] 2. Fluorescence performance measurement

[0087] The (MPA-NIPAM) copolymer P4 was dissolved in N,N-dimethylformamide to prepare a 100 mg / mL (MPA-NIPAM) copolymer P4 solution and its fluorescence color was observed. The results were as follows: Figure 2 As shown. Among them, Figure 2 This is the fluorescence color diagram of (MPA-NIPAM) copolymer P4 in solution.

[0088] according to Figure 2 It can be seen that the DMF solution state of the (MPA-NIPAM) copolymer P4 has an obvious fluorescent color, and the fluorescence is blue, indicating that the solution state of the carboxylic acid maleimide-isopropylacrylamide copolymer has strong fluorescence properties and has an AIE effect.

[0089] Further, the fluorescence of the (MPA-NIPAM) copolymer P4 solution was tested using a fluorescence spectrometer, and the results were Figure 3 As shown. Among them, Figure 3 This is the liquid fluorescence emission spectrum of (MPA-NIPAM) copolymer P4.

[0090] according to Figure 3 It can be seen that the DMF solution state of the (MPA-NIPAM) copolymer P4 has a very obvious fluorescence emission peak, which further confirms that the (MPA-NIPAM) copolymer P4 has strong luminescence properties in the liquid state.

[0091] 2.3 Stimulus-responsive fluorescence

[0092] The (MPA-NIPAM) copolymer P4 solution was subjected to different stimulation treatments, namely:

[0093] A: The (MPA-NIPAM) copolymer P4 solution was heated at 71°C for 1 h;

[0094] B: adding KOH solution (pH=12) to the (MPA-NIPAM) copolymer P4 solution, the amount of KOH solution added is 100 μL per 3 mL of the (MPA-NIPAM) copolymer P4 solution; and,

[0095] C: After heating the (MPA-NIPAM) copolymer P4 solution at 71°C for 1 hour, KOH solution (pH = 12) was added, with 100 μL of KOH solution added for every 3 mL of (MPA-NIPAM) copolymer P4 solution.

[0096] After each treatment, observe the fluorescent color of each treatment solution. The results are: Figure 4 As shown. Among them, Figure 4 This is the fluorescence color diagram of the (MPA-NIPAM) copolymer P4 solution after being treated with different stimuli.

[0097] according to Figure 4 It can be seen that the initial state of the (MPA-NIPAM) copolymer P4 solution is colorless and transparent; after heat stimulation treatment, the fluorescence color of the (MPA-NIPAM) copolymer P4 solution begins to shift to the infrared region and becomes slightly pink; after alkali stimulation treatment, the fluorescence wavelength of the (MPA-NIPAM) copolymer P4 solution further increases, and the pink color becomes more obvious; after heat-alkali multi-stimulation treatment, the color of the (MPA-NIPAM) copolymer P4 solution further deepens to dark purple.

[0098] At the same time, the (MPA-AM) copolymer prepared in Comparative Example 1 was dissolved in N,N-dimethylformamide to prepare a 100 mg / mL (MPA-AM) copolymer solution and its fluorescence color was observed. The results were: Figure 5 As shown. Among them, Figure 5 This is the fluorescence color diagram of (MPA-AM) copolymer in solution state.

[0099] according to Figure 5 It can be seen that the fluorescent color of the (MPA-AM) copolymer solution is extremely weak and can hardly be seen by the naked eye. At the same time, no fluorescent color was measured in the fluorescence emission spectrum, indicating that the maleimide-acrylamide copolymer does not have fluorescent color-changing properties.

[0100] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0101] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A multi-stimulus responsive fluorescent color-changing material, characterized in that: The material composition is carboxylic acid maleimide-isopropyl acrylamide copolymer.

2. A method for preparing the multi-stimulus responsive fluorescent color-changing material according to claim 1, characterized in that: Contains steps: providing a polar solvent in which isopropyl acrylamide is dissolved; After adding carboxylic acid maleimide monomer and initiator to the polar solvent, copolymerization reaction is carried out in an inert atmosphere, solid products are separated and collected, and the solid products are dialyzed in deionized water, and the dialyzate is vacuum freeze-dried to obtain a multi-stimulus responsive fluorescent color-changing material; The carboxylic acid maleimide monomer has the chemical structure of formula [i]: Here, R is any one of C1-C6 straight-chain alkyl groups.

3. The preparation method according to claim 2, characterized in that: When the carboxylic acid maleimide monomer and the initiator are added to the polar solvent, the molar ratio of the carboxylic acid maleimide monomer to the isopropyl acrylamide is 1:(1-50).

4. The preparation method according to claim 3, characterized in that: When the carboxylic acid maleimide monomer and the initiator are added to the polar solvent, the molar ratio of the carboxylic acid maleimide monomer to the isopropyl acrylamide is 1:

20.

5. The preparation method according to claim 2, characterized in that: The initiator comprises azobisisobutyronitrile.

6. The preparation method according to claim 2, characterized in that: The polar solvent is toluene.

7. The preparation method according to claim 2, characterized in that: The dialysis was performed at a molecular weight cut-off of 4000-6000.

8. The preparation method according to claim 2, characterized in that: The maleimide is any one of 2-maleimidoacetic acid, 3-maleimidopropionic acid, 4-maleimidobutyric acid, 5-maleimidopentanoic acid or 6-maleimidohexanoic acid.

9. The preparation method according to claim 2, characterized in that: When the copolymerization reaction is carried out, the reaction temperature is 60-70° C. and the reaction time is 12-24 hours.

10. Application of the multi-stimulus responsive fluorescent color-changing material according to claim 1 in anti-counterfeiting labels, information storage, bio-imaging, and sensors.

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