A pH-responsive cholesteric liquid crystal elastomer film, a preparation method and use thereof
Patent Information
- Application Number
- CN202611061139.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-16
- Publication Date
- 2026-10-23
AI Technical Summary
[0006]本发明的目的旨在克服现有技术的不足，提供一种基于pH响应的胆甾相液晶弹性体薄膜、其制备方法及用途，旨在解决现有信息存储材料功能单一、信息加密与防伪能力有限、难以实现可重复写入与擦除的技术问题
[0026]1.在酸的刺激下，TPE-1或TPE-2可以被质子化，同时荧光颜色发生红移，使荧光胆甾相液晶弹性体薄膜在酸处理前后具有高度差异的荧光颜色变化。这表明可以通过使用酸作为“墨水”将数据写入胆甾相液晶弹性体薄膜，实现荧光信息的写入。
Smart Images
Figure CN122958730A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to new materials and their preparation methods, and particularly to a thin film material for information storage, its preparation method, and its uses. Background Technology
[0002] Cholesteric liquid crystal elastomers (CLCEs) are smart materials that combine the optical anisotropy of liquid crystals with the flexibility of elastomers. Their unique internal helical superstructure selectively reflects circularly polarized light of specific wavelengths, thus exhibiting vibrant structural colors. The wavelength of these structural colors can be tuned by the pitch within the cholesteric liquid crystal elastomer, and this pitch is extremely sensitive to external stimuli (such as temperature, stress, and chemical environments). Therefore, CLCEs show broad application prospects in fields such as smart color-changing coatings, flexible sensors, optical anti-counterfeiting, and information storage.
[0003] Currently, there is considerable research on the control of reflective colors in liquid crystal crystals (CLCEs). For example, by adjusting the doping amount of chiral agents, the helical twisting force of the liquid crystal system can be changed, thereby achieving static control of basic reflective colors such as red, green, and blue. Furthermore, by mechanically stretching the film to change its thickness and molecular orientation, its reflective color can also be dynamically adjusted, allowing the film to exhibit different structural colors under different strain states. However, most existing CLCE-based materials can only achieve single-dimensional color changes or simple mechanical responses, making it difficult to meet the needs of multifunctional integration in complex scenarios, especially in the field of information security.
[0004] In information storage and encryption, traditional methods typically rely on luminescent materials such as fluorescent dyes or quantum dots. However, these materials often suffer from problems such as photobleaching, biotoxicity, or complex preparation processes. More importantly, most existing solutions can only achieve "writing" and "reading" of information, lacking effective "encryption" and "erasing" mechanisms, resulting in low information security and difficulty in achieving multiple recycling. Furthermore, how to simultaneously integrate structural color changes, fluorescence responses, and reversible chemical regulation within the same material system to achieve multiple encryption and anti-counterfeiting measures remains a major challenge for current technology.
[0005] Therefore, developing a multifunctional smart material with a simple preparation process, fast response speed, and the ability to simultaneously achieve dynamic control of structural color, writing and hiding of fluorescent information, and repeated erasure on the same material is of great significance for promoting the development of new information storage and anti-counterfeiting technologies. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pH-responsive cholesteric phase liquid crystal elastomer film, its preparation method and uses, in order to solve the technical problems of existing information storage materials having single function, limited information encryption and anti-counterfeiting capabilities, and difficulty in achieving rewritable and erasable properties.
[0007] Therefore, the technical solution of the present invention is as follows: a method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film, comprising the following steps:
[0008] (S1) Dissolve liquid crystal monomer RM257, chiral agent LC756, pH-responsive molecule, chain extender EDDET, crosslinking agent PETMP, alkaline catalyst DPA and photoinitiator I-651 in toluene and mix them evenly;
[0009] (S2) The mixed solution obtained in step (S1) is dropped onto a glass substrate and placed in a vacuum oven. It is kept at 26°C for 24 hours to carry out a prepolymerization reaction and form a prepolymerized film.
[0010] (S3) The prepolymerized film obtained in step (S2) is peeled off from the glass substrate and then subjected to ultraviolet light irradiation to complete the secondary crosslinking, thereby obtaining the cholesteric phase liquid crystal elastomer film.
[0011] A further improvement of the present invention is that the reflective color of the film in its initial state is controlled by adjusting the content of the chiral agent LC756. When the amount of chiral agent LC756 is 4.6 wt%, 5.8 wt%, and 7.1 wt% of the total mass of liquid crystal monomer RM257, the reflective colors of the cholesteric liquid crystal elastomer film in its initial state are red, green, and blue, respectively.
[0012] When the amount of chiral agent LC756 is 4.6 wt% of the total mass of liquid crystal monomer RM257, the reflected color of the film is red when the stretching length is 0%; yellow-green when the stretching length is 40%; and blue when the stretching length is 70%.
[0013] Further, the molar ratios of each component in step (S1) are as follows: liquid crystal monomer RM257 : chiral agent LC756 : pH-responsive molecule : chain extender EDDET : crosslinking agent PETMP : alkaline catalyst DPA : photoinitiator I-651 = 1.070 : 0.030 : 0.004 : 0.850 : 0.075 : 0.030 : 0.016.
[0014] The pH-responsive molecule is a compound having the following structural formula:
[0015] .
[0016] The preparation method of the pH-responsive molecule TPE-1 or TPE-2 includes the following steps:
[0017] (1) 5-bromo-2-thiophene acetonitrile or p-bromophenylacetonitrile, pyridine-4-boronic acid, potassium carbonate and catalyst Pd(PPh3)4 are heated under reflux in a mixed solvent of tetrahydrofuran and water under nitrogen protection, and the intermediate 2-(5-(pyridin-4-yl)thiophene-2-yl)acetonitrile or (4-(4-pyridinyl)phenylacetonitrile is obtained after separation and purification; wherein the molar ratio of 5-bromo-2-thiophene acetonitrile or p-bromophenylacetonitrile, pyridine-4-boronic acid, Pd(PPh3)4 and K2CO3 is 1 : 1 : 0.026 : 2.45;
[0018] (2) The intermediate obtained in step (1) is reacted with 1,1,2-triphenyl-2-(4-carboxyphenyl)ethylene under alkaline conditions, and then separated and purified to obtain the target product TPE-1 or TPE-2. Specifically, the target product TPE-1 is obtained from 5-bromo-2-thiophene acetonitrile, and the target product TPE-2 is obtained from p-bromophenylacetonitrile.
[0019] The present invention provides a pH-responsive cholesteric liquid crystal elastomer film, which can be applied in the fields of data storage and encryption. By utilizing the reversible changes in fluorescence color under acid and alkali stimulation and the reversible changes in structural color under mechanical stimulation of the pH-responsive cholesteric liquid crystal elastomer film material, information can be written, hidden, displayed, and erased.
[0020] When this pH-responsive cholesteric phase liquid crystal elastomer film is used in data storage and encryption, the following steps can be taken:
[0021] (a) Information writing: After stretching the information storage material, a specific area is treated with acid gas to change the fluorescent color of the area and form a pattern;
[0022] (b) Information encryption: Remove the tension to restore the material to its original state. Due to the removal of the tension, the fluorescent pattern is deformed and cannot be read. In addition, after the tension is removed, the structural color of the material will change from yellow-green to red, which has the function of anti-counterfeiting while encrypting information.
[0023] (c) Information decryption and anti-counterfeiting: The material is stretched again, the structural color changes, and the pattern reappears due to the difference in fluorescent color;
[0024] (d) Information erasure: The material is treated with alkaline gas to restore the fluorescent color to its initial state, thereby erasing the information.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. Under acid stimulation, TPE-1 or TPE-2 can be protonated, and the fluorescence color undergoes a red shift, resulting in a highly different fluorescence color change in the fluorescent cholesteric liquid crystal elastomer film before and after acid treatment. This indicates that data can be written into the cholesteric liquid crystal elastomer film using acid as "ink," thus achieving the writing of fluorescent information.
[0027] 2. Under the action of mechanical force, the pitch of the CLCE-TPE-1 film decreases as the strain increases, and the structural color of the film undergoes a blue shift, realizing the dynamic control of the structural color from red to blue.
[0028] 3. By synergistically controlling the structural and fluorescent colors of cholesteric liquid crystal elastomer films using force and acid-base interactions, dynamic writing and multiple encryption of information patterns were achieved. This technology can be applied to information storage and encryption fields.
[0029] This invention utilizes RM257 liquid crystal monomers combined with polymerizable chiral agent LC756 and photoinitiator I-651 to achieve low-temperature, rapid UV curing, forming a cholesteric liquid crystal optical film that is precipitation-free, optically stable, capable of wide-band color tuning, and possesses flexible color-changing properties. The film is easy to process, stable in storage, and has low overall cost. This provides new ideas and experimental basis for developing intelligent liquid crystal materials that integrate multiple stimulus responses, information storage, and anti-counterfeiting functions. Attached Figure Description
[0030] Figure 1 The structural color change and reflection spectrum (a) of the CLCE-TPE-1 film prepared in Example 2 under different stretching ratios are shown in Example 2.
[0031] Figure 2 The images show (a) UV-Vis absorption spectra and (b) fluorescence spectra of TPE-1 prepared in Example 2 in solutions at different pH values.
[0032] Figure 3 The water with different volume fractions (f) prepared in Example 2 w (a) UV-Vis absorption spectrum and (b) fluorescence spectrum of TPE-1 in an acetonitrile / water mixture.
[0033] Figure 4 This refers to the changes in structural color during the stretching of the CLCE-TPE-1 film in Example 2, and the appearance and disappearance of fluorescent encryption information under acid and alkali stimulation. Detailed Implementation
[0034] Example 1
[0035] The synthesis and preparation process of monomer TPE-1 and the specific steps are as follows:
[0036]
[0037] (1) 5-bromo-2-thiopheneacetonitrile (5.1832 g, 25.65 mmol), pyridine-4-boronic acid (3.1529 g, 25.65 mmol), Pd(PPh3)4 (0.7627 g, 0.66 mmol), 100 mL THF and 20 mL K2CO3 (8.7167 g, 63.07 mmol) aqueous solution were added to a 250 mL round-bottom flask. The mixture was heated under reflux for 24 h, and nitrogen protection was required throughout the reaction. After the reaction was completed, the solvent was removed under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 1 / 1 as eluent). The final intermediate 1 (2-(5-(pyridin-4-yl)thiophene-2-yl)acetonitrile) was a white solid (4.2122 g, yield 82%). 1 H NMR (600 MHz, CDCl3) δ 8.61 (d, J = 5.6 Hz, 2H), 7.47(d, J = 6.1 Hz, 2H), 7.41 (d, J = 3.7 Hz, 1H), 7.11 (d, J = 3.7 Hz, 1H), 3.96(s, 2H).
[0038] (2) Intermediate 1 (2-(5-(pyridin-4-yl)thiophen-2-yl)acetonitrile) (1.0313 g, 5.15 mmol), 1,1,2-triphenyl-2-(4-carboxyphenyl)ethylene (1.8563 g, 5.15 mmol), and ethanol (50 mL) were added to a 250 mL round-bottom flask. NaOH (0.2060 g, 5.15 mmol) was dissolved in 20 mL of ethanol, and the supernatant was added to the mixture. The mixture was stirred at room temperature for 6 h. After the reaction was completed, the solid was filtered off and recrystallized from ethanol to obtain a deep yellow solid TPE-1 (1.7328 g, yield 62%). 1 H NMR (600 MHz, DMSO) δ 8.62 (d, J = 6.0 Hz, 2H), 7.88 (d, J = 3.9Hz, 1H), 7.80 (s, 1H), 7.73 (d, J = 8.3 Hz, 2H), 7.68 (d, J = 6.1 Hz, 2H), 7.52 (d, J = 3.9 Hz, 1H), 7.16 (m, J = 26.5, 19.2, 7.5 Hz, 11H), 7.05 - 6.98 (m, 6H). 13C NMR (100 MHz, CDCl3) δ 150.66, 150.43, 146.97, 143.23, 143.06,142.56, 141.27, 140.91, 140.36, 139.88, 132.18, 131.92, 131.45, 131.40,131.19, 130.98, 128.91, 128.61, 128.02, 127.77, 127.53, 127.13, 126.93,126.80, 126.35, 126.00, 119.76, 119.40, 116.54, 116.51, 104.67.
[0039] Example 2
[0040] The preparation and performance verification of pH-responsive cholesteric phase liquid crystal elastomer films are as follows:
[0041] 1. Liquid crystal monomer RM257, chiral agent LC756, pH-responsive molecule TPE-1, chain extender EDDET, crosslinking agent PETMP, alkaline catalyst DPA, and photoinitiator I-651 were dissolved in toluene solution. The molar ratios of each component are as follows: Liquid crystal monomer RM257 : Chiral agent LC756 : pH-responsive molecule : Chain extender EDDET : Crosslinking agent PETMP : Alkaline catalyst DPA : Photoinitiator I-651 = 1.070 : 0.030 : 0.004 : 0.850 : 0.075 : 0.030 : 0.016. Liquid crystal monomer RM257, chiral agent LC756, chain extender EDDET, crosslinking agent PETMP, alkaline catalyst DPA, and photoinitiator I-651 are all commercially available. The structural formulas of the materials used are as follows:
[0042]
[0043] 2. After sonicating at room temperature for 1 min, drop the sample onto a glass plate and place it in a 26°C vacuum oven for 24 h to complete the prepolymerization stage.
[0044] 3. The prepolymerized film is scraped off the glass plate and then placed under ultraviolet light to complete the secondary crosslinking, thereby obtaining a pH-responsive cholesteric phase liquid crystal elastomer film, denoted as CLCE-TPE-1 film.
[0045] Schematic diagram and reflectance spectrum of structural color change of CLCE-TPE-1 film under different stretching ratios:
[0046] The prepared CLCE-TPE-1 film was stretched, as follows: Figure 1 As shown in Figure a, the structural color change of the CLCE-TPE-1 film under different stretching ratios can be observed, from the initial red to the blue at a stretching ratio of 70%, indicating that the structural color of the film undergoes a blue shift as the stretching ratio increases. Figure 1 b shows the reflection spectra of the CLCE-TPE-1 film at different stretching ratios. As the film progresses from its initial unstrained state to a strain of 70%, the reflection peak shifts from the 660 nm red region to the 420 nm blue region. Experimental results indicate that as the stretching ratio increases, the structural color of the film shifts from red to blue.
[0047] UV-Vis absorption and fluorescence spectra of TPE-1 in solutions at different pH values
[0048] A series of solutions with different pH values were prepared and analyzed by ultraviolet-visible absorption spectroscopy (UV-Vis). Figure 2 a) and fluorescence spectrum ( Figure 2 b) The pH-responsive behavior of TPE-1 was investigated. From Figure 2 As shown in b, with decreasing pH, the fluorescence emission peak shifts towards longer wavelengths and the fluorescence intensity gradually decreases. This indicates that TPE-1 can achieve high-contrast fluorescence signal conversion under acid-base stimulation.
[0049] Water with different volume fractions (f w UV-Vis absorption and fluorescence spectra of TPE-1 in an acetonitrile / water mixture:
[0050] Prepare a series of waters with different volume fractions (f w A TPE-1 solution of an acetonitrile / water mixture was analyzed by UV-Vis absorption spectroscopy. Figure 3 a) and fluorescence spectrum ( Figure 3 b) To investigate the AIE behavior of TPE-1. As can be seen from the figure, in f w In a TPE-1 solution with a water volume fraction of 0, the fluorescence intensity is minimum. As the water volume fraction increases, the fluorescence intensity continuously increases. This is because TPE-1 is insoluble in water and forms aggregates, while it dissolves in acetonitrile solution. Since the fluorescence intensity is related to the concentration of molecular aggregates, the fluorescence intensity increases with increasing water volume fraction. w The fluorescence intensity is highest in a 100% TPE-1 solution, which further demonstrates that TPE-1 has AIE properties.
[0051] Changes in structural color during stretching of CLCE-TPE-1 film and the manifestation and recovery of fluorescence encryption information under acid and alkali stimulation:
[0052] The prepared CLCE-TPE-1 film was stretched, as follows: Figure 4As shown in Figure a, the structural color change of the CLCE-TPE-1 film under stretching can be observed, from the initial red to the yellow-green at a stretching ratio of 40%, indicating that the structural color of the film undergoes a blue shift with increasing stretching ratio. Figure 4 As shown in b, the CLCE-TPE-1 film exhibits green fluorescence under 365nm ultraviolet light. After stretching the film by 40%, a perforated pentagram pattern was tightly bonded to the underlying layer. The sample was then treated with acetic acid gas, resulting in a yellow fluorescent pentagram pattern being imprinted on the back of the film, thus writing information. Upon removing the tension, the film returned to its original state, and the yellow fluorescent pentagram pattern was no longer clearly visible, indicating that the written information was hidden, achieving information encryption. Finally, the film was stretched, and the structural color changed from the initial red to yellow-green (anti-counterfeiting), and the yellow fluorescent pentagram pattern became visible, revealing the information. These results demonstrate that the material possesses both information encryption and anti-counterfeiting functions. More importantly, due to the differences between TPE-1 and TPE-1H... + There exists a reversible protonation / deprotonation dynamic equilibrium. The yellow fluorescent pattern can be completely erased after treatment with triethylamine gas for 90 minutes, and the film recovers to its initial green fluorescence. The writing and encryption process can be repeated, which proves that the material has excellent repeatability in the writing and erasing process.
[0053] Both TPE-1 and TPE-2 pH-responsive molecules exhibit a reversible protonation / deprotonation dynamic equilibrium process as follows:
[0054] .
[0055] Based on the experiments in Example 1 above, 5-bromo-2-thiophene acetonitrile was replaced with an equimolar amount of p-bromophenylacetonitrile to finally obtain the pH-responsive molecule of TPE-2. It was verified that the film prepared according to the steps of Example 2 has the same properties as the CLCE-TPE-1 film.
[0056] By further varying the dosage of chiral agent LC756, when the dosage of chiral agent LC756 was 4.6 wt%, 6.0 wt%, and 7.5 wt% of the total mass of liquid crystal monomer RM257, the initial reflection colors of the cholesteric phase liquid crystal elastomer film were red, green, and blue, respectively. Therefore, the initial reflection color of the film can be controlled by adjusting the content of chiral agent LC756. When the dosage of chiral agent LC756 was 4.6 wt% of the total mass of liquid crystal monomer RM257, the reflection color was red when the film's stretch length was 0%, yellowish-green when the stretch length was 40%, and blue when the stretch length was 70%.
[0057] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.
Claims
1. A method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film, characterized in that, Includes the following steps: (S1) Dissolve liquid crystal monomer RM257, chiral agent LC756, pH-responsive molecule, chain extender EDDET, crosslinking agent PETMP, alkaline catalyst DPA and photoinitiator I-651 in toluene and mix them evenly; (S2) The mixed solution obtained in step (S1) is dropped onto a glass substrate and placed in a vacuum oven. It is kept at 26°C for 24 hours to carry out a prepolymerization reaction and form a prepolymerized film. (S3) The prepolymerized film obtained in step (S2) is peeled off from the glass substrate and then subjected to ultraviolet light irradiation to complete the secondary crosslinking, thereby obtaining the cholesteric phase liquid crystal elastomer film.
2. The method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film according to claim 1, characterized in that, The reflective color of the film in its initial state was controlled by adjusting the content of the chiral agent LC756. When the amount of chiral agent LC756 was 4.6 wt%, 5.8 wt%, and 7.1 wt% of the total mass of liquid crystal monomer RM257, the reflective colors of the cholesteric liquid crystal elastomer film in its initial state were red, green, and blue, respectively.
3. The method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film according to claim 2, characterized in that, When the amount of chiral agent LC756 is 4.6 wt% of the total mass of liquid crystal monomer RM257, the reflected color of the film is red when the stretching length is 0%; yellow-green when the stretching length is 40%; and blue when the stretching length is 70%.
4. The method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film according to claim 3, characterized in that, The molar ratios of each component in step (S1) are as follows: Liquid crystal monomer RM257 : Chiral agent LC756 : pH-responsive molecule : Chain extender EDDET : Crosslinking agent PETMP : Alkali catalyst DPA : Photoinitiator I-651 = 1.070 : 0.030 : 0.004 : 0.850 : 0.075 : 0.030 : 0.
016.
5. The method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film according to claim 1, characterized in that, The pH-responsive molecule is a compound having the following structural formula: 。 6. The method for preparing a pH-responsive cholesteric phase liquid crystal elastomer film according to claim 5, characterized in that, The preparation method of the pH-responsive molecule TPE-1 or TPE-2 includes the following steps: (1) 5-bromo-2-thiophene acetonitrile or p-bromophenylacetonitrile, pyridine-4-boronic acid, potassium carbonate and catalyst Pd(PPh3)4 are heated under reflux in a mixed solvent of tetrahydrofuran and water under nitrogen protection, and the intermediate 2-(5-(pyridin-4-yl)thiophene-2-yl)acetonitrile or (4-(4-pyridinyl)phenylacetonitrile is obtained after separation and purification; wherein the molar ratio of 5-bromo-2-thiophene acetonitrile or p-bromophenylacetonitrile, pyridine-4-boronic acid, Pd(PPh3)4 and K2CO3 is 1 : 1 : 0.026 : 2.45; (2) The intermediate obtained in step (1) is reacted with 1,1,2-triphenyl-2-(4-carboxyphenyl)ethylene under alkaline conditions, and then separated and purified to obtain the target product TPE-1 or TPE-2. Specifically, the target product TPE-1 is obtained from 5-bromo-2-thiophene acetonitrile, and the target product TPE-2 is obtained from p-bromophenylacetonitrile.
7. A pH-responsive cholesteric phase liquid crystal elastomer film, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.
8. The use of a pH-responsive cholesteric phase liquid crystal elastomer film as described in claim 7, characterized in that: In the field of data storage and encryption, the reversible changes in fluorescence color under acid and alkali stimulation and the reversible changes in structural color under mechanical stimulation of the pH-responsive cholesteric phase liquid crystal elastomer film material are used to realize the writing, hiding, displaying and erasing of information.
9. The use of the pH-responsive cholesteric phase liquid crystal elastomer film according to claim 8, characterized in that, Includes the following steps: (a) Information writing: After stretching the information storage material, a specific area is treated with acid gas to change the fluorescent color of the area and form a pattern; (b) Information encryption: Remove the tension to restore the material to its original state. Due to the removal of the tension, the fluorescent pattern is deformed and cannot be read. In addition, after the tension is removed, the structural color of the material will change from yellow-green to red, which has the function of anti-counterfeiting while encrypting information. (c) Information decryption and anti-counterfeiting: The material is stretched again, the structural color changes, and the pattern reappears due to the difference in fluorescent color; (d) Information erasure: The material is treated with alkaline gas to restore the fluorescent color to its initial state, thereby erasing the information.