A multi-stimulus responsive fluorescent color-changing material, its preparation method and application

Abstract

This application discloses a multi-stimulus responsive fluorescent color-changing material, its preparation method, and its application, belonging to the technical field of fluorescent color-changing materials. The multi-stimulus responsive fluorescent color-changing material of this application is composed of a maleimide-isopropylacrylamide copolymer. Through the copolymerization of carboxylic acid maleimide and isopropylacrylamide, a synergistic effect is formed between the carboxylic acid maleimide and isopropylacrylamide molecules, resulting in an AIE (Alternating Induction Emission) effect. This not only endows the copolymer with excellent fluorescence ability, but also allows the intermolecular interactions of the copolymer to undergo specific changes under thermal stimulation, alkaline stimulation, and thermal-alkaline stimulation, resulting in the conversion and regulation of fluorescence color or fluorescence emission peak position / intensity, effectively achieving multi-stimulus responsive fluorescent color-changing.

Description

Technical Field

[0001] This application belongs to the field of organic fluorescent color-changing materials technology, and specifically relates to a multi-stimulus responsive fluorescent color-changing material, its preparation method and application. Background Technology

[0002] Stimulus-responsive fluorescent materials are novel functional materials whose color and fluorescence emission peak position / intensity can be switched / regulated under the influence of external environmental stimuli (such as temperature, force, light, electricity, magnetism, etc.). They have shown great development potential in fields such as anti-counterfeiting marking, information storage, optical encoding / switching, bioimaging, and fluorescence sensors. However, with the increasing demand for stimulus-responsive fluorescent materials, these materials should possess strong luminescent properties in solution or solid states. Therefore, designing and preparing stimulus-responsive fluorescent color-changing materials with the AIE effect is of great practical value.

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

[0004] However, with the expanding applications of stimulus-responsive fluorescent materials, single-stimulus-responsive fluorescent materials no longer meet the demands. Furthermore, existing multi-stimulus-responsive fluorescent materials are generally prepared using specialized monomers via free radical polymerization and polycondensation, which are cumbersome and costly. Therefore, developing multi-stimulus-responsive fluorescent materials that are simple to synthesize, have fast response times, and exhibit significant fluorescence color changes is extremely important. Summary of the Invention

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

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

[0007] The first aspect of this application provides a multi-stimulus responsive fluorescent color-changing material. The multi-stimulus responsive fluorescent color-changing material of this application is composed of a carboxylic acid maleimide-isopropylacrylamide copolymer.

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

[0009] Provides a polar solvent for dissolving isopropylacrylamide;

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

[0011] The carboxylic acid maleimide monomer possesses the chemical structural formula of formula [i]:

[0012]

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

[0014] 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 isopropylacrylamide 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 isopropylacrylamide is 1:20.

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

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

[0018] In a possible implementation, the molecular weight cutoff for the dialysis is 4000-6000.

[0019] In a possible implementation, the maleimide is any one of 2-maleimideacetic acid, 3-maleimidepropionic acid, 4-maleimidebutyric acid, 5-maleimidevallic acid, or 6-maleimidehexanoic acid.

[0020] In a possible implementation, the copolymerization reaction is carried out at a temperature of 60-70°C for a time of 12-24 hours.

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

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

[0023] The multi-stimulus responsive fluorescent color-changing material provided in this application is a carboxylic acid maleimide-isopropylacrylamide copolymer. This carboxylic acid maleimide-isopropylacrylamide copolymer, through the copolymerization of carboxylic acid maleimide and isopropylacrylamide in its molecular structure, achieves a synergistic effect between the carboxylic acid maleimide and isopropylacrylamide molecules, resulting in AIE (Average Electrophoretic Emission) activity. This not only endows the resulting copolymer with excellent fluorescence ability in solution or solid states, but also allows the copolymer to undergo specific changes under thermal, alkaline, and thermal-alkaline stimuli based on intermolecular interactions, resulting in a transformation and regulation of fluorescence color or fluorescence emission peak position / intensity, effectively achieving multi-stimulus responsive fluorescent color-changing. Furthermore, the monomers used in the synthesis of this copolymer are common carboxylic acid maleimide and isopropylacrylamide, which are widely available, low in cost, and eliminate complex synthesis processes, thus possessing excellent industrialization prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0026] Figure 2 The fluorescence color diagram of (MPA-NIPAM) copolymer P4 in solution provided in the embodiments of this application;

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

[0028] Figure 4 The fluorescence color diagrams of the (MPA-NIPAM) copolymer P4 solution provided in the embodiments of this application after different stimulation treatments;

[0029] Figure 5 The fluorescence color diagram of the (MPA-AM) copolymer in solution provided in the embodiments of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort 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 relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and both A and B existing simultaneously. 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 "more than one" means two or more. "At least one of the following" or similar expressions mean any combination of such items, including any combination of single or multiple 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, and C can be single or multiple.

[0033] In the following description of this specification, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. 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, numerical ranges 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 within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this embodiment, and the upper and lower limits of the smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, the technical / scientific terms used in this specification have the meanings commonly understood by one of ordinary skill in the art. While this specification describes only preferred materials and methods, any similar or equivalent methods and materials may be used in specific embodiments or test examples. All references to this specification are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] In a first aspect, embodiments of this application provide a multi-stimulus responsive fluorescent color-changing material. The multi-stimulus responsive fluorescent color-changing material of this application embodiment is composed of a carboxylic acid maleimide-isopropylacrylamide copolymer.

[0037] It should be noted that the carboxylic acid maleimide-isopropylacrylamide copolymer in the embodiments of this application refers to a polymer whose molecular chain contains carboxylic acid maleimide and isopropylacrylamide, which is generated by copolymerization of carboxylic acid maleimide and isopropylacrylamide, and its chemical structural formula can be represented by [ii].

[0038]

[0039] Wherein, R is any one of the C1-C6 straight-chain alkyl groups, such as methyl, ethyl, propyl, butyl, n-pentyl, and n-hexyl. The embodiments of this application do not have a special limitation on the carbon chain, as long as it can prepare a multi-stimulus responsive fluorescent color-changing material. 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 this application do not have a special limitation on the specific value of the degree of polymerization. It can be reasonably controlled according to the molar ratio of the carboxylic acid maleimide monomer and isopropyl acrylamide copolymerization. However, in order to ensure reasonable cost, 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 this application is a carboxylic acid maleimide-isopropylacrylamide copolymer. This carboxylic acid maleimide-isopropylacrylamide copolymer, through the copolymerization of carboxylic acid maleimide and isopropylacrylamide in its molecular structure, achieves a synergistic effect between the carboxylic acid maleimide and isopropylacrylamide molecules, resulting in AIE (Average Electrophoretic Emission) activity. This not only endows the resulting copolymer with excellent fluorescence ability in solution or solid states, but also allows the copolymer to undergo specific changes under thermal, alkaline, and thermal-alkaline stimuli based on intermolecular interactions, resulting in a transformation and regulation of fluorescence color or fluorescence emission peak position / intensity, effectively achieving multi-stimulus responsive fluorescent color-changing. Furthermore, the monomers for synthesizing this copolymer are commercially available carboxylic acid maleimide and isopropylacrylamide, which are widely available, low in cost, and eliminate complex synthesis processes, thus possessing excellent industrialization prospects.

[0041] Secondly, embodiments of this application provide a method for preparing the multi-stimulus responsive fluorescent color-changing material described in the embodiments of this application, preferably including the following steps:

[0042] Provides a polar solvent for dissolving isopropylacrylamide;

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

[0044] The carboxylic acid maleimide monomer possesses the chemical structural formula 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 structural formulas of formulas [i] and [ii] are the same substituent group, so it will not be repeated here; the embodiments of this application do not have a specific limitation on the specific source of the carboxylic acid maleimide monomer, and it is preferred to obtain it through commercial means; at the same time, the embodiments of this application do not limit the specific process of drying the dialysate, as long as the solvent components can be completely removed. The embodiments of this application preferably perform vacuum freeze-drying on the dialysate. For example, the vacuum freeze-drying parameters are: temperature of -50°C and time of 72h.

[0048] Based on the above description, the embodiments of this application can prepare multi-stimulus responsive fluorescent color-changing materials by copolymerizing isopropylacrylamide with carboxylic acid maleimide monomer 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 isopropylacrylamide is 1:(1-50). Preferably, the molar ratio is 1:1, 1:3, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, or any of the above molar ratio ranges, more preferably 1:20.

[0050] In the example implementation, the initiator is preferably azobisisobutyronitrile (AIBN).

[0051] In the example implementation, the polar solvent is preferably toluene.

[0052] In the example implementation, the molecular weight cutoff for dialysis is 4000-6000, thereby enabling sufficient separation and removal of unreacted monomers / materials and avoiding interference with the fluorescence color-changing properties of the prepared copolymer.

[0053] In the example embodiments, the maleimide is preferably any one of 2-maleimideacetic acid, 3-maleimidepropionic acid, 4-maleimidebutyric acid, 5-maleimidevallic acid, or 6-maleimidehexanoic acid.

[0054] In the example implementation, the copolymerization reaction is preferably carried out at a temperature of 60-70°C and a time of 12-24 hours. The example reaction temperature can be 60°C, 65°C, 70°C, or any temperature within the range mentioned above; the example time can be 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 24 hours, or any time within the range mentioned above.

[0055] Thirdly, embodiments of this application also provide the application of the multi-stimulus responsive fluorescent color-changing materials described above in anti-counterfeiting marks, information storage, bioimaging, and sensors.

[0056] The technical solution of this application will be further described below with reference to specific embodiments.

[0057] Example 1

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

[0059] In 6 mL of anhydrous toluene, 16 mg of azobisisobutyronitrile (AIB), 1690 mg (10 mmol) of 3-maleimide propionic acid (MPA) monomer, and 1131.6 mg (10 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (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, 16 mg of azobisisobutyronitrile (AIB), 169 mg (1 mmol) of 3-maleimide propionic acid (MPA) monomer, and 1131.6 mg (10 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (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, 16 mg of azobisisobutyronitrile (AIB), 169 mg (1 mmol) of 3-maleimide propionic acid (MPA) monomer, and 1697.4 mg (15 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (MPA-NIPAM) copolymer P3.

[0066] Example 4

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

[0068] In 6 mL of anhydrous toluene, 16 mg of azobisisobutyronitrile (AIB), 169 mg (1 mmol) of 3-maleimide propionic acid (MPA) monomer, and 2263.2 mg (20 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (MPA-NIPAM) copolymer P4.

[0069] Example 5

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

[0071] In 6 mL of anhydrous toluene, 16 mg of azobisisobutyronitrile (AIB), 169 mg (1 mmol) of 3-maleimide propionic acid (MPA) monomer, and 5658.0 mg (50 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (MPA-NIPAM) copolymer P5.

[0072] Example 6

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

[0074] In 6 mL of anhydrous toluene, 16 mg of azobisisobutyronitrile (AIB), 138 mg (1 mmol) of 4-maleimide-butyric acid (MBA) monomer, and 2263.2 mg (20 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (MBA-NIPAM) copolymer P6.

[0075] Example 7

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

[0077] In 6 mL of anhydrous toluene, 16 mg of azobisisobutyronitrile (AIBN), 211.2 mg (1 mmol) of 6-maleimide hexanoic acid (MCA) monomer, and 2263.2 mg (20 mmol) of isopropylacrylamide (NIPAM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times and copolymerized at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (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, 16 mg of azobisisobutyronitrile (AIB), 169.0 mg (1 mmol) of 3-maleimide propionic acid (MPA) monomer, and 1421.6 mg (20 mmol) of acrylamide (AM) monomer were added. The mixture was subjected to vacuum purging with nitrogen three times, and copolymerization was carried out at 65 °C for 12 h. The mixture was then cooled to room temperature, and the reaction solution was filtered to obtain a crude solid. The crude solid was dialyzed in deionized water (dialysis bag molecular weight cutoff 4000-6000), and the dialysate was freeze-dried under vacuum (temperature -50 °C, time 72 h) to obtain the (MPA-AM) copolymer, whose chemical structural formula is:

[0081]

[0082] To clarify the fluorescence properties of the carboxylic acid maleimide-isopropylacrylamide copolymer prepared in the embodiments of this application, the (MPA-NIPAM) copolymer P4 will be used as the test sample for verification analysis below.

[0083] 1. Infrared spectroscopy characterization

[0084] The (MPA-NIPAM) copolymer P4 was characterized by infrared spectroscopy, and the results were as follows: 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-maleimide propionic acid appears at 1686 cm⁻¹. -1 The amide peak of isopropyl acrylamide appears at 1399.3 cm⁻¹. -1 The presence of this information indicates that the embodiments of this application successfully synthesized a 3-maleimide propionic acid-isopropylacrylamide copolymer.

[0086] 2. Fluorescence performance determination

[0087] (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 of (MPA-NIPAM) copolymer P4 exhibits obvious fluorescence, which is blue, indicating that the solution of carboxylic acid maleimide-isopropylacrylamide copolymer has strong fluorescence properties and exhibits the AIE effect.

[0089] Furthermore, the fluorescence of the (MPA-NIPAM) copolymer P4 solution was tested using a fluorescence spectrometer, and the results were as follows: 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 (MPA-NIPAM) copolymer P4 has a very obvious fluorescence emission peak in the DMF solution state, which further confirms that the (MPA-NIPAM) copolymer P4 has strong luminescence properties in the liquid state.

[0091] 2.3 Stimulus-Response Fluorescence

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

[0093] A: Heat the (MPA-NIPAM) copolymer P4 solution at 71°C for 1 hour;

[0094] B: Add KOH solution (pH=12) to the (MPA-NIPAM) copolymer P4 solution, at a rate of 100 μL of KOH solution per 3 mL of (MPA-NIPAM) copolymer P4 solution; and,

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

[0096] After each treatment was completed, the fluorescence color of the treated solution was observed, and the results were as follows: Figure 4 As shown. Among them, Figure 4 This is a fluorescence color diagram of the (MPA-NIPAM) copolymer P4 solution after treatment 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 change to the infrared region, turning into a light 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 a deep purple.

[0098] Meanwhile, 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 as follows: Figure 5 As shown. Among them, Figure 5 This is the fluorescence color diagram of the (MPA-AM) copolymer in solution.

[0099] according to Figure 5 It can be seen that the fluorescence color of the (MPA-AM) copolymer solution is extremely weak and can hardly be seen with the naked eye. At the same time, the fluorescence emission spectrum was not detected, 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. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0101] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A multi-stimulus responsive fluorescent color-changing material, characterized in that, The material composition is a copolymer of carboxylic acid maleimide and isopropyl acrylamide; The carboxylic acid maleimide-isopropylacrylamide copolymer is prepared by copolymerizing carboxylic acid maleimide monomer and isopropylacrylamide in a molar ratio of 1:

20.

2. A method for preparing the multi-stimulus responsive fluorescent color-changing material according to claim 1, characterized in that, Includes the following steps: Provides a polar solvent for dissolving isopropylacrylamide; After adding carboxylic acid maleimide monomer and initiator to the polar solvent, a copolymerization reaction is carried out in an inert atmosphere. The solid product is separated and collected, and then dialyzed in deionized water. The dialysate is then freeze-dried under vacuum to obtain a multi-stimulus responsive fluorescent color-changing material. The carboxylic acid maleimide monomer possesses the chemical structural formula of formula [i]: [i] Wherein, R is any one of the C1-C6 straight-chain alkyl groups.

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

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

5. The preparation method according to claim 2, characterized in that, The molecular weight cutoff for the dialysis is 4000-6000.

6. The preparation method according to claim 2, characterized in that, The maleimide is any one of 2-maleiminoacetic acid, 3-maleiminopropionic acid, 4-maleiminobutyric acid, 5-maleiminovalerate, or 6-maleiminohexanoic acid.

7. The preparation method according to claim 2, characterized in that, The copolymerization reaction is carried out at a temperature of 60-70 ℃ for 12-24 h.

8. The application of the multi-stimulus responsive fluorescent color-changing material of claim 1 in anti-counterfeiting marking, information storage, bioimaging, and sensors.

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