Stimulus-responsive color-changing material as well as preparation method and application thereof

Abstract

The invention discloses a stimuli-responsive color-changing material and a preparation method and application thereof, and belongs to the technical field of anti-counterfeiting materials, the preparation method comprises the following steps: soaking a cross-linked indolyl polyvinyl alcohol polymer in an escherichia coli solution, and collecting solid insoluble substances; the solid insoluble substance is dissolved in a solvent, then indole small molecules are added into the solvent, and the compound is prepared after reaction. The material has a high-contrast color switching behavior under external stimulation, and the problems that an existing anti-counterfeiting material is high in preparation cost and complex in preparation method can be effectively solved.

Description

Technical Field

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

[0002] With the acceleration of global economic integration, the proliferation of counterfeit and shoddy products and information leakage have become undeniable global problems. This phenomenon not only seriously erodes the value of intellectual property rights, but also poses a serious challenge to the market order and causes inestimable economic losses. In this context, it is urgent to strengthen anti-counterfeiting and encryption technology. With the acceleration of technological progress, counterfeiting methods are evolving into more complex forms. Traditional anti-counterfeiting technologies such as watermarks, lasers, inkjet printing, and fluorescence have begun to expose their limitations - poor adaptability, easy to be imitated, high technical barriers, and high costs. Therefore, there is an urgent need to explore and develop new anti-counterfeiting and encryption technologies that are efficient, anti-copying, and cost-effective. This pursuit is essential to promote strong and sustainable market development while safeguarding consumer rights.

[0003] Among the numerous anti-counterfeiting materials, stimuli-responsive color-changing polymers stand out for their unique properties such as stimulus responsiveness, structural design flexibility, low specific gravity, excellent chemical stability, easy processing and cost-effectiveness, making them the focus of research and cutting-edge applications in the field of anti-counterfeiting. These materials exhibit distinct color changes in response to specific external stimuli, such as light, temperature changes and pH fluctuations, providing simple and recognizable anti-counterfeiting markings. However, current strategies for preparing color-changing polymer materials face significant challenges. Complex chemical synthesis methods involve covalently bonding color-changing groups to polymers while enhancing stability, but have proven to be costly and require complex synthetic pathways. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a stimulus-responsive color-changing material and a preparation method and application thereof. The material has high-contrast color switching behavior under external stimulation, which can effectively solve the problems of high preparation cost and complex preparation method of existing anti-counterfeiting materials.

[0005] To achieve the above purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0006] A method for preparing a stimulus-responsive color-changing material comprises the following steps:

[0007] (1) soaking the cross-linked indole polyvinyl alcohol polymer in an Escherichia coli solution and collecting the solid insoluble matter;

[0008] (2) The solid insoluble matter is dissolved in a polar solvent, and then an indole reagent is added thereto. The mixture is mechanically stirred and mixed, and then dried to obtain the product.

[0009] Furthermore, the cross-linked indole polyvinyl alcohol polymer in step (1) is prepared by the following method:

[0010] S1: Under an inert atmosphere, IPDI is dissolved in dichloromethane to obtain an IPDI solution; Tryp and DBTDL are dissolved in dichloromethane to obtain a mixed solution, the mixed solution is added dropwise to the IPDI solution, and then heated to complete the reaction, purified, and dried to obtain ITr;

[0011] S2: Under an inert atmosphere, PVA is dissolved in DMSO to prepare a PVA solution, ITr and DBTDL are added thereto, and stirred until dissolved in dichloromethane, the mixture is heated to react, and after the reaction is completed, the mixture is poured into dichloromethane, the solid polymer is collected and impurities are removed to prepare PIVA;

[0012] S3: Dissolve PIVA in DMSO, dissolve MDI-TAD in DMAc, pour the MDI-TAD solution into the PIVA solution under high-speed stirring to prepare a cross-linked indole polyvinyl alcohol polymer.

[0013] Furthermore, the soaking time in step (1) is 50-100 days.

[0014] Furthermore, in step S1, the mass ratio of IPDI:Tryp:DBTDL in the mixture solution is 10-30:10-30:1; the mass concentration of the IPDI solution is 100-200 g / L; the mass concentration of Tryp in the mixture solution is 100-200 g / L; the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

[0015] Furthermore, in the reaction solution of step S2, the mass concentration of PVA is 40-200 g / L, the mass concentration of ITr is 190-770 g / L, and the mass concentration of DBTDL is 6-12 g / L; the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

[0016] Furthermore, in step S3, the mass ratio of PIVA to MDI-TAD is 1000:1-75, and the reaction temperature is 0-25°C.

[0017] Furthermore, in step (2), the polar solvent is dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

[0018] Furthermore, the amount of the indole reagent added is 0.1-20% of the amount of the solid insoluble matter.

[0019] A stimulus-responsive color-changing material is prepared by the above method.

[0020] The application of the above-mentioned stimulus-responsive color-changing material in the preparation of anti-counterfeiting labels.

[0021] The beneficial effects produced by the present invention are:

[0022] 1. The stimulus-responsive color-changing material of the present invention is made of thermosetting polymer as raw material through processing. The raw material is widely available and easy to obtain, and the preparation process is simple and easy to operate.

[0023] 2. The stimulus-responsive color-changing material of the present invention has a high-contrast color switching behavior and can be used as an anti-counterfeiting material to improve the anti-counterfeiting effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of the processing of CPIVA;

[0025] Figure 2 Figure 2 is the detection result of the treatment process of CPIVA, 2a is the ultraviolet absorption spectrum of the liquid culture medium after CPIVA was treated with E. coli, 2b is the fluorescence spectrum of the liquid culture medium after CPIVA was treated with E. coli, and 2c is the fluorescence spectrum of the liquid culture medium after CPIVA was treated with E. coli. 1 H-NMR graph, 2d is the fluorescence spectrum before and after CPIVA film treatment, 2e is the FTIR graph before and after CPIVA film treatment, and 2f is the FTIR graph after CPIVA film treatment. 1 H-NMR graph, 2g is a schematic diagram of the E. coli treatment process;

[0026] Figure 3 3a is a schematic diagram of the anti-counterfeiting function of IPVA, 3b is a schematic diagram of the color change in an acid-base environment, 3c is a schematic diagram of the color change of the IPVA film in an acid-base environment, and 3d is a stress change curve of the IPVA film before and after alkaline stimulation;

[0027] Figure 4 Figure 2 shows the composite structure of the model and the calculation results. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0029] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0030] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0031] The features and performance of the present invention are further described in detail below in conjunction with the embodiments and drawings.

[0032] Example 1

[0033] A stimulus-responsive color-changing material, the preparation method of which comprises the following steps:

[0034] (1) soaking the cross-linked indole polyvinyl alcohol polymer in an Escherichia coli solution for 100 days and collecting the solid insoluble matter;

[0035] (2) The solid insoluble matter is dissolved in dimethyl sulfoxide solvent, and then an indole reagent is added thereto. The amount of the indole reagent added is 0.1% of the mass of the solid insoluble matter. After reaction, the product is obtained.

[0036] Wherein, the cross-linked indole polyvinyl alcohol polymer is prepared by the following method:

[0037] S1: Synthesis of ITr: Under an inert atmosphere, 10 g of isophorone diisocyanate (IPDI) was dissolved in 100 ml of dichloromethane to obtain an IPDI solution; 10 g of tryptone (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to obtain a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 45°C for reaction. After reacting for 4 hours, the mixture was purified by column chromatography, and the solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder;

[0038] S2: Synthesis of indole functionalized polyvinyl alcohol (PIVA): 4 g of PVA was dissolved in 100 ml of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 19 g of ITr and 0.6 g of DBTDL solution were added thereto. The mixture was stirred at 40 °C for 4 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA.

[0039] S3: Synthesis of cross-linked indole polyvinyl alcohol polymer (CPIVA): dissolve 2 g PIVA in 10 ml DMSO to prepare PIVA solution; dissolve 2 mg MDI-TAD in 2 ml DMAc solvent to prepare MDI-TAD solution; pour the pre-cooled MDI-TAD solution into the PIVA solution under stirring at 1000 rpm to prepare a cross-linked indole polyvinyl alcohol polymer (CPIVA).

[0040] Example 2

[0041] A stimulus-responsive color-changing material, the preparation method of which comprises the following steps:

[0042] (1) soaking the cross-linked indole polyvinyl alcohol polymer in an Escherichia coli solution for 50 days and collecting the solid insoluble matter;

[0043] (2) The solid insoluble matter is dissolved in N,N-dimethylformamide solvent, and then an indole reagent is added thereto. The amount of the indole reagent added is 20% of the mass of the solid insoluble matter. After the reaction, the product is obtained.

[0044] Wherein, the cross-linked indole polyvinyl alcohol polymer is prepared by the following method:

[0045] S1: Synthesis of ITr: Under an inert atmosphere, 20 g of isophorone diisocyanate (IPDI) was dissolved in 140 ml of dichloromethane to obtain an IPDI solution; 20 g of tryptophan (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to obtain a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 40°C for reaction. After reacting for 5 hours, the mixture was purified by column chromatography, and the solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder;

[0046] S2: Synthesis of indole functionalized polyvinyl alcohol (PIVA): Under an inert atmosphere, 10 g of PVA was dissolved in 100 mL of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 47.5 g of ITr and 0.8 g of DBTDL solution were added thereto. The mixture was stirred at 40 °C for 5 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA.

[0047] S3: Synthesis of cross-linked indole polyvinyl alcohol polymer (CPIVA): dissolve 2g PIVA in 10ml DMSO to prepare PIVA solution, and dissolve 18mg MDI-TAD in 2ml DMAc solvent to prepare MDI-TAD solution; under stirring at 1000rpm, pour the pre-cooled MDI-TAD solution into the PIVA solution to prepare a cross-linked indole polyvinyl alcohol polymer (CPIVA).

[0048] Example 3

[0049] A stimulus-responsive color-changing material, the preparation method of which comprises the following steps:

[0050] (1) soaking the cross-linked indole polyvinyl alcohol polymer in an Escherichia coli solution for 70 days and collecting the solid insoluble matter;

[0051] (2) The solid insoluble matter is dissolved in N,N-dimethylacetamide solvent, and then an indole reagent is added thereto. The amount of the indole reagent added is 10% of the mass of the solid insoluble matter. After the reaction, the product is obtained.

[0052] Wherein, the cross-linked indole polyvinyl alcohol polymer is prepared by the following method:

[0053] S1: Under an inert atmosphere, 30 g of isophorone diisocyanate (IPDI) was dissolved in 150 ml of dichloromethane to obtain an IPDI solution; 30 g of tryptophan (Tryp) and 1 g of dibutyltin dilaurate (DBTDL) were dissolved in dichloromethane to obtain a mixture solution, and then the mixture solution was added dropwise to the IPDI solution, and then the temperature was raised to 50° C. for reaction, and after reacting for 3 hours, it was purified by column chromatography, and the solvent system of the column chromatography was petroleum ether: ethyl acetate = 1:1, and then the solvent was removed under reduced pressure to obtain a light yellow powder;

[0054] S2: Synthesis of indole functionalized polyvinyl alcohol (PIVA): Under an inert atmosphere, 20 g of PVA was dissolved in 100 ml of dimethyl sulfoxide (DMSO) to prepare a PVA solution, and then 77 g of ITr and 1.2 g of DBTDL solution were added thereto. The mixture was stirred at 50 °C for 3 h. After the reaction was completed, the mixture was poured into dichloromethane to suspend the polymer in dichloromethane. The polymer was collected and vacuum dried, and then the polymer was purified using acetone to remove impurities to prepare PIVA.

[0055] S3: Synthesis of cross-linked indole polyvinyl alcohol polymer (CPIVA): dissolve 2g PIVA in 10ml DMSO to prepare PIVA solution, and dissolve 150mg MDI-TAD in 2ml DMAc solvent to prepare MDI-TAD solution; under stirring at 1000rpm, pour the pre-cooled MDI-TAD solution into the PIVA solution to prepare a cross-linked indole polyvinyl alcohol polymer (CPIVA).

[0056] Test example

[0057] Taking CPIVA in Example 1 as an example, CPIVA polymer (6 cm × 3 cm, 0.05 mm thick) was immersed in the liquid culture medium of E. coli to observe the changes of CPIVA polymer. The specific results are shown in Figure 1 The results showed that after being immersed in E. coli, the polymer dissolved. The liquid culture medium and residual plastic were characterized. Figure 2 a shows the UV absorption spectra of the liquid culture medium in the absence and presence of CPIVA plastic. The liquid culture medium cut through CPIVA plastic produced a strong UV absorption peak at 256 nm, which is the obvious π-π* transition absorption peak of the indole group (ITAD) ( Figure 2 a). In addition, the fluorescence spectrum also shows a strong fluorescence emission peak at 338nm ( Figure 2 b) Liquid culture medium 1 H-NMR spectroscopy further revealed the above transformation ( Figure 2 c). The characteristic H in the indole group is marked on the figure. 1 H-NMR spectroscopy showed that the ITAD fragment was cleaved from CPIVA by E. coli and then dropped into the liquid culture medium.

[0058] The residual plastic was further characterized. First, the fluorescence spectrum of the CPIVA plastic before and after cutting was tested. The spectrum clearly showed that the fluorescence intensity at 338nm was significantly reduced ( Figure 2d), this is because CPIVA plastic has a large number of indole luminescent groups. As the E. coli cuts, the indole groups gradually fall off, causing the fluorescence intensity of the plastic to drop significantly. The FTIR spectra of CPIVA plastic before and after cutting also obtained the same results ( Figure 2 e). First, the 740 cm-1 -1 The characteristic CH out-of-plane deformation vibration peak at 1600 cm -1 The vibration changes of benzene in the indole structure disappeared in the residual plastic. In addition, the 1770cm -1 The characteristic carbonyl stretching vibration peak at 20° disappears in the residual plastic. 1 H-NMR spectrum further revealed the above transformation ( Figure 2 f). 1 H-NMR spectroscopy showed that E. coli cleaved the indole group (ITAD) from the CPIVA plastic and fell into the liquid culture medium due to gravity.

[0059] The reaction process of CPIVA in E. coli solution is shown in the schematic diagram Figure 2 g, first, the indole groups in the CPIVA cross-linked network can be accurately recognized by E. coli, and the alkane side chain at the C3 position of the indole is cut, thereby cutting the cross-linked network into a new linear polymer (NPVA) and an indole group (ITAD) ( Figure 2 g). Meanwhile, ITAD easily separated from CPIVA plastic and fell into the liquid medium. NPVA still retained large fragments and floated in the liquid medium.

[0060] Based on the linear polymer (NPVA) formed by E. coli cutting, it was dissolved, and then ITAD was added to the solution to form a polymer (IPVA) with a color switching effect. The schematic diagram of the reaction process is shown in 3a. This material exhibits high-contrast color switching behavior under external stimulation. This behavior is attributed to the structural transition induced by the protonation-deprotonation of the imine group in IPVA under alkaline and acidic conditions, respectively ( Figure 3 b) The UV-visible and fluorescence spectra of ITAD in alkaline solution showed negative intensity peaks at 299 nm and positive intensity peaks at 328 nm, confirming that Na + After adding NaOt-Bu, the fluorescence intensity decreased significantly due to the formation of "point-surface" cation-π interaction ( Figure 4 );

[0061] IPVA shows great potential in information encryption by utilizing its excellent stimulus-responsive color-changing properties. In order to verify the color-changing mechanism of IPVA under acid-base stimulation, Gaussian software was used to calculate the optimized energy of IPVA model compounds in nitrogen anions and the changes in HOMO and LUMO energy levels ( Figure 4 ). The results show that the energy gap between HOMO and LUMO decreases, resulting in reduced energy absorption and emission of photons. This finding provides strong evidence for the stimulus-induced color change mechanism of IPVA. When ITAD is dissolved in DMF and then an equal amount of NaOt-Bu is added, the solution quickly changes from light yellow to bright green ( Figure 3 b) Add CF 3 COOH can reverse this and quickly restore the color. Figure 3 c shows that the ITAD-doped IPVA film appears yellow under visible light. After adding an equal amount of NaOt-Bu, the IPVA+NaOt-Bu film clearly changes from yellow to green. It is worth noting that even with only 1% ITAD, the IPVA film shows a clear color transition. The color change of the IPVA film to alkaline and acidic conditions highlights its rapid response ability, and the reaction may be faster with increasing ITAD dosage. Mechanical properties are critical to evaluating the effect of ITAD doping on the properties of the polymer matrix. Stress-strain curve results of IPVA+NaOt-Bu film ( Figure 3 d) shows that it significantly improves the elongation at break of the film while causing a slight decrease in strength. This improvement is attributed to the formation of cation-π interactions between indole groups, thereby providing micro-crosslinks within the matrix.

Claims

1. A method for preparing a stimulus-responsive color-changing material, characterized in that: The following steps are involved: (1) soaking the cross-linked indole polyvinyl alcohol polymer in an Escherichia coli solution and collecting the solid insoluble matter; (2) The solid insoluble matter is dissolved in a polar solvent, and then an indole reagent is added thereto. The mixture is mechanically stirred and mixed, and then dried to obtain the product.

2. The method for preparing a stimulus-responsive color-changing material according to claim 1, wherein: The cross-linked indole polyvinyl alcohol polymer in step (1) is prepared by the following method: S1: Under an inert atmosphere, IPDI is dissolved in dichloromethane to obtain an IPDI solution; Tryp and DBTDL are dissolved in dichloromethane to obtain a mixed solution, the mixed solution is added dropwise to the IPDI solution, and then heated to complete the reaction, purified, and dried to obtain ITr; S2: Under an inert atmosphere, PVA is dissolved in DMSO to prepare a PVA solution, ITr and DBTDL are added thereto, and stirred until dissolved in dichloromethane, the mixture is heated to react, and after the reaction is completed, the mixture is poured into dichloromethane, the solid polymer is collected and impurities are removed to prepare PIVA; S3: PIVA is dissolved in DMSO, MDI-TAD is dissolved in DMAc, and the MDI-TAD solution is poured into the PIVA solution under high-speed stirring to prepare a cross-linked indole polyvinyl alcohol polymer.

3. The method for preparing a stimulus-responsive color-changing material according to claim 1, wherein: The soaking time in step (1) is 50-100 days.

4. The method for preparing a stimulus-responsive color-changing material according to claim 2, wherein: Step S1: the mass ratio of IPDI:Tryp:DBTDL in the mixture solution is 10-30:10-30:1; the mass concentration of the IPDI solution is 100-200 g / L; the mass concentration of Tryp in the mixture solution is 100-200 g / L; the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

5. The method for preparing a stimulus-responsive color-changing material according to claim 2, wherein: In the reaction solution of step S2, the mass concentration of PVA is 40-200 g / L, the mass concentration of ITr is 190-770 g / L, and the mass concentration of DBTDL is 6-12 g / L; the heating reaction temperature is 40-50° C., and the reaction time is 3-5 h.

6. The method for preparing a stimulus-responsive color-changing material according to claim 2, wherein: In step S3, the mass ratio of PIVA to MDI-TAD is 1000:1-75, and the reaction temperature is 0-25°C.

7. The method for preparing a stimulus-responsive color-changing material according to claim 1, wherein: In step (2), the solvent is dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

8. The method for preparing a stimulus-responsive color-changing material according to claim 1, wherein: The amount of the indole reagent added is 0.1-20% of the amount of the solid insoluble matter.

9. A stimulus-responsive color-changing material, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. Use of the stimulus-responsive color-changing material according to claim 9 in the preparation of anti-counterfeiting labels.

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