Method for preparing large-area side-chain cholesteric liquid crystal elastomer film based on blade coating method and application of large-area side-chain cholesteric liquid crystal elastomer film

Abstract

The invention provides a method for preparing a large-area side-chain cholesteric liquid crystal elastomer thin film based on a blade coating method and application of the large-area side-chain cholesteric liquid crystal elastomer thin film. By controlling the content of sulfydryl functional groups in a system and accurately controlling key process parameters such as the blade coating rate and the blade coating temperature in the blade coating process, simple and controllable preparation of a one-pot method is achieved, and the prepared large-area side-chain cholesteric liquid crystal elastomer film has the force-induced discoloration and thermochromism dual response characteristics and is suitable for large-scale production. Wide application prospects are shown in the fields of color-changing materials, strain sensing, intelligent anti-counterfeiting, soft robots and the like, a new thought is provided for controllable preparation of high-performance intelligent response materials, and a new technical route is opened up for manufacturing of large-area customizable functional films.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal material preparation technology, and in particular to a method and application for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on a blade coating method. Background Technology

[0002] Liquid crystal elastomers (LCEs) have attracted significant attention in the field of smart responses due to their combination of the anisotropy of liquid crystals and the elasticity of polymer networks. Among them, cholesteric liquid crystal elastomers (CLCEs) possess a self-organized helical structure, enabling Bragg reflection of circularly polarized light at specific wavelengths. The reflected wavelength λ = n·P (where n is the average refractive index and P is the helical pitch) exhibits structural color within the visible light range, requiring no dyes for coloring. Among various CLCE types, side-chain CLCEs, compared to main-chain CLCEs, have mesocrystalline units suspended from the polymer backbone as side chains, exhibiting higher molecular freedom of movement. This results in significant advantages in response sensitivity, rate of response to external stimuli (such as force and heat), and amplitude of optical changes, demonstrating important application value in strain sensing, adaptive optics systems, intelligent anti-counterfeiting, and soft robotics.

[0003] Currently, traditional methods for preparing cholesteric liquid crystal elastomer (CLCE) films mainly include solvent evaporation and cell-based alignment techniques. Solvent evaporation relies on a slow, spontaneous evaporation process to induce cholesteric phase alignment, which is too time-consuming and fails to meet the efficiency requirements of practical applications. While cell-based alignment techniques can control alignment, they require the precursor to be evaporated and concentrated before being poured into the cell. The fabrication area is limited by the cell size, and the process is cumbersome, hindering large-area continuous production and severely restricting its industrial transformation potential.

[0004] Therefore, developing a novel process that enables rapid orientation and large-area preparation of side-chain cholesteric phase liquid crystal elastomer films is an urgent problem to be solved in this field. Summary of the Invention

[0005] This invention provides a method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films using a blade coating method. The large-area side-chain cholesteric phase liquid crystal elastomer films prepared by this method exhibit both mechanochromic and thermochromic response characteristics. This preparation method is simple and can be widely applied.

[0006] The present invention also provides a large-area side-chain cholesteric phase liquid crystal elastomer film prepared by the above preparation method, which has both mechanochromic and thermochromic response characteristics.

[0007] The present invention also provides an application of a large-area side-chain type cholesteric phase liquid crystal elastomer film prepared by the above preparation method as an anti-counterfeiting label.

[0008] The present invention also provides the application of a large-area side-chain cholesteric phase liquid crystal elastomer film prepared by the above preparation method in the preparation of thermochromic materials and / or mechanochromic materials.

[0009] The first aspect of the present invention provides a method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on a blade coating method, comprising the following steps:

[0010] A mixed solution was obtained by thermally mixing a raw material system comprising liquid crystal molecules with double-ended acrylate groups, nematic liquid crystal molecules with single-ended acrylate groups, a chiral dopant, a photoinitiator, a thiol molecule, and a solvent.

[0011] The mixed solution was heated to evaporate the solvent, yielding a cholesteric phase liquid crystal elastomer oligomer precursor.

[0012] The cholesteric liquid crystal elastomer oligomer precursor was directly coated onto the substrate surface using a blade coating method to obtain a cholesteric liquid crystal elastomer oligomer film with an oriented structure.

[0013] The cholesteric phase liquid crystal elastomer oligomer film is crosslinked and cured under light to obtain a large-area side-chain cholesteric phase liquid crystal elastomer film.

[0014] In the method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method described above, the liquid crystal molecule with double-ended acrylate groups is liquid crystal monomer RM82, the nematic liquid crystal molecule with single-ended acrylate groups is liquid crystal monomer RM105, the chiral dopant is LC756, the photoinitiator is IRG651, and the thiol molecule is 1,6-hexanedithiol.

[0015] In the method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method as described above, the mass ratio of the double-terminated acrylate liquid crystal molecules, the single-terminated acrylate nematic liquid crystal molecules, the chiral dopant, the photoinitiator, and the thiol molecules is 0.36:5.34:(0.21-0.4):0.1:1.

[0016] In the method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method described above, the heat treatment temperature is 90-110℃ and the time is 2-4h.

[0017] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method described above includes the following process parameters:

[0018] The coating speed is 1-10 mm / s, the coating temperature is 30-60℃, and the coating thickness is 100-250 μm.

[0019] In the method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method as described above, the crosslinking and curing temperature is 30-60℃ and the time is 5-10 min.

[0020] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method described above, wherein the illumination conditions are: wavelength of 365 nm and power of 6-10 mW / cm². 2 Ultraviolet light.

[0021] A second aspect of the present invention provides a large-area side-chain type cholesteric phase liquid crystal elastomer film, which is prepared by the aforementioned preparation method.

[0022] A third aspect of the present invention provides an application of the large-area side-chain type cholesteric phase liquid crystal elastomer film as an anti-counterfeiting label.

[0023] A fourth aspect of the present invention provides the application of the large-area side-chain cholesteric phase liquid crystal elastomer film described above in the preparation of thermochromic materials and / or mechanochromic materials.

[0024] Compared with the prior art, the beneficial technical effects of the present invention include at least the following:

[0025] This invention provides a method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films using a blade coating method. By precisely controlling key process parameters such as coating rate and temperature, the method directly induces cholesteric phase orientation, effectively optimizing the molecular arrangement order of the side-chain cholesteric phase liquid crystal elastomer film and achieving large-area, high-efficiency preparation. This method overcomes the size limitations of traditional liquid crystal cells, avoids prolonged solvent evaporation, and significantly improves preparation efficiency. The "one-pot" method simplifies the process and reduces costs, showing broad application prospects in color-changing materials, strain sensing, intelligent anti-counterfeiting, and soft robotics, and possesses good potential for large-scale production. Furthermore, the large-area side-chain cholesteric phase liquid crystal elastomer films prepared using this method exhibit both mechanochromic and thermochromic response characteristics, high response sensitivity, and excellent optical properties. This provides a new approach for the controllable preparation of high-performance intelligent response materials and opens up a new technical route for the manufacture of large-area, customizable functional films. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1The experimental procedure for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films according to the present invention is as follows: Figure 1 Figure a is a schematic diagram of the preparation of a large-area side-chain cholesteric phase liquid crystal elastomer film; Figure 1 b is a schematic diagram showing the state of liquid crystal cells changing from chaotic and disordered to orderly and neat during the coating process.

[0028] Figure 2 This is a photograph of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Embodiment 1 of the present invention.

[0029] Figure 3 This is a photograph of the cholesteric phase liquid crystal elastomer film in Comparative Example 1 of the present invention.

[0030] Figure 4 The apparent color of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Examples 1-4 of the present invention is shown in the figure. Figure 4 'a' represents the apparent color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1. Figure 4 b represents the apparent color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 2. Figure 4 c represents the apparent color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 3. Figure 4 d represents the apparent color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 4.

[0031] Figure 5 These are scanning electron microscope (SEM) images of the large-area side-chain type cholesteric phase liquid crystal elastomer films in Examples 1-4 of this invention, wherein... Figure 5 Image a is a SEM image of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1. Figure 5 b is a SEM image of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 2; Figure 5 c is the SEM image of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 3; Figure 5 d is the SEM image of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 4.

[0032] Figure 6 This is a side scanning electron microscope (SEM) image of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Example 3 of the present invention, wherein... Figure 6 Image a is a side-view SEM image of a large-area side-chain type cholesteric phase liquid crystal elastomer film. Figure 6 b is Figure 6 A magnified view of the selected area in region a;

[0033] Figure 7The stress-strain curves are for the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 1-4 of the present invention, where 30°C is Example 1, 40°C is Example 2, 50°C is Example 3, and 60°C is Example 4.

[0034] Figure 8 The stress-strain curves of the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 5-6 of the present invention are shown, where 1 mm / s is Example 5 and 5 mm / s is Example 6.

[0035] Figure 9 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of tensile strain.

[0036] Figure 10 The reflection spectrum of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of tensile strain.

[0037] Figure 11 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of temperature;

[0038] Figure 12 The reflection spectrum of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of temperature.

[0039] Figure 13 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention as a function of tensile strain.

[0040] Figure 14 The reflection spectrum of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention is shown as a function of tensile strain.

[0041] Figure 15 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention as a function of temperature;

[0042] Figure 16 The reflection spectrum of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention as a function of temperature.

[0043] Figure 17 The actual color of the cholesteric liquid crystal elastomer film in Comparative Example 1 of the present invention as a function of tensile strain.

[0044] Figure 18 The actual color of the cholesteric phase liquid crystal elastomer film in Comparative Example 1 of the present invention as a function of temperature;

[0045] Figure 19This is a physical diagram of a device used in the encryption application of the thin film of this invention.

[0046] Figure 20 This is a physical image showing the temperature variation of a device in the information encryption application of the thin film of this invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this art or in accordance with the product instructions. Reagents or instruments used without specified manufacturers are all conventional products that can be obtained commercially.

[0048] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, 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 the embodiments of the present invention.

[0049] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to 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 the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0050] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0051] Figure 1 The experimental procedure for preparing large-area side-chain cholesteric phase liquid crystal elastomer films according to the present invention is as follows: Figure 1 As shown, the first aspect of the present invention provides a method for preparing a large-area side-chain type cholesteric phase liquid crystal elastomer film based on a blade coating method, comprising the following steps:

[0052] A mixed solution was obtained by thermally mixing a raw material system comprising liquid crystal molecules with double-ended acrylate groups, nematic liquid crystal molecules with single-ended acrylate groups, a chiral dopant, a photoinitiator, a thiol molecule, and a solvent.

[0053] The mixed solution was heated to evaporate the solvent, yielding a cholesteric phase liquid crystal elastomer oligomer precursor.

[0054] The cholesteric liquid crystal elastomer oligomer precursor was directly coated onto the substrate surface using a blade coating method to obtain a cholesteric liquid crystal elastomer oligomer film with an oriented structure.

[0055] The cholesteric phase liquid crystal elastomer oligomer film is crosslinked and cured under light to obtain a large-area side-chain cholesteric phase liquid crystal elastomer film.

[0056] In this invention, "thermal mixing" should be understood as temperature-conditional mixing, which can be stirring and mixing under certain temperature conditions to ensure uniform mixing. In some embodiments, the conditions for thermal mixing are: heating from room temperature to 95-105°C at a rate of 1-3°C / min and holding at that temperature for 5-20 minutes.

[0057] The present invention does not impose a specific limit on the amount of solvent used, which can be selected according to specific needs.

[0058] In this invention, the solvent is acetone.

[0059] The present invention does not impose any particular limitation on the shape, size, or thickness of the substrate; the substrate can be selected according to actual needs.

[0060] The present invention does not impose any particular limitation on the specific material of the substrate, and any conventional material is acceptable. For example, the substrate may be a glass plate.

[0061] Specifically, this invention first involves thermally mixing a raw material system comprising double-terminated acrylate liquid crystal molecules, single-terminated acrylate nematic liquid crystal molecules, a chiral dopant, a photoinitiator, thiol molecules, and a solvent to obtain a mixed solution. The double-terminated acrylate liquid crystal molecules act as crosslinking agents, the single-terminated acrylate nematic liquid crystal molecules act as side groups, the chiral dopant is used to induce periodic stacking of polymer chains, and the thiol molecules act as chain extenders. To ensure a uniform, stable, and defect-free cholesteric phase liquid crystal elastomer structure, the mixed solution is heated. The solvent is evaporated to obtain a cholesteric phase liquid crystal elastomer oligomer precursor. Then, the cholesteric phase liquid crystal elastomer oligomer precursor is directly coated onto the substrate surface using a blade coating method. The directional shearing force of the blade induces the liquid crystal molecules to align along the coating direction, resulting in a cholesteric phase liquid crystal elastomer oligomer film with an oriented structure. Finally, the cholesteric phase liquid crystal elastomer oligomer film is cross-linked and cured under light through a polymerization reaction, "locking" the oriented structure within the cross-linked network, ultimately obtaining a large-area side-chain type cholesteric phase liquid crystal elastomer film.

[0062] The principle of preparing large-area side-chain cholesteric phase liquid crystal elastomer films according to the present invention is explained as follows: (1) During the coating process, the directional shear force of the doctor blade is used to overcome the random orientation of the liquid crystal molecules, so that they can achieve directional arrangement along the shear force direction during the flow process, and the orientation structure is fixed by subsequent cross-linking and curing; (2) Two types of chemical reactions are involved in the cross-linking and curing process: one is the "click chemistry" reaction based on mercapto molecules (1,6-hexanedithiol in the present invention), liquid crystal molecules with double-terminated acrylate groups (liquid crystal monomer RM82 in the present invention), and nematic liquid crystal molecules with single-terminated acrylate groups (liquid crystal monomer RM105 in the present invention), which has the characteristics of high efficiency, fast speed and insensitivity to oxygen, and can be carried out in mild conditions. Under certain conditions, precise connection between liquid crystal building blocks and crosslinking agents is achieved, efficiently constructing a polymer network. Secondly, based on the free radicals generated by the photoinitiator (IRG651 in this embodiment), free radical polymerization reactions occur between liquid crystal molecules with double-ended acrylate groups and nematic liquid crystal molecules with single-ended acrylate groups, either on their own or between them. The chain growth is rapid, and the macroscopic orientation can be quickly fixed. These two types of chemical reactions are triggered under specific wavelength light irradiation, and the oriented liquid crystal molecules are crosslinked and solidified through covalent bonds, thereby permanently "fixing" the helical periodic structure of the cholesteric phase in the three-dimensional elastomer network, forming a structurally stable and stimuli-responsive cholesteric phase liquid crystal elastomer (CLCE) material, namely the large-area side-chain cholesteric phase liquid crystal elastomer film of this invention.

[0063] This invention provides a method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films using a blade coating method. By precisely controlling key process parameters such as coating rate and temperature, the method directly induces cholesteric phase orientation, effectively optimizing the molecular arrangement order of the side-chain cholesteric phase liquid crystal elastomer film and achieving large-area, high-efficiency preparation. This method overcomes the size limitations of traditional liquid crystal cells, avoids prolonged solvent evaporation, and significantly improves preparation efficiency. The "one-pot" method simplifies the process and reduces costs, showing broad application prospects in color-changing materials, strain sensing, intelligent anti-counterfeiting, and soft robotics, and possesses good potential for large-scale production. Furthermore, the large-area side-chain cholesteric phase liquid crystal elastomer films prepared using this method exhibit both mechanochromic and thermochromic response characteristics, high response sensitivity, and excellent optical properties. This provides a new approach for the controllable preparation of high-performance intelligent response materials and opens up a new technical route for the manufacture of large-area, customizable functional films.

[0064] In one specific embodiment, the liquid crystal molecule with double-ended acrylate groups is liquid crystal monomer RM82, the nematic liquid crystal molecule with single-ended acrylate groups is liquid crystal monomer RM105, the chiral dopant is LC756, the photoinitiator is IRG651, and the thiol molecule is 1,6-hexanedithiol.

[0065] In one specific embodiment, the mass ratio of the double-terminated acrylate liquid crystal molecule, the single-terminated acrylate nematic liquid crystal molecule, the chiral dopant, the photoinitiator, and the thiol molecule is 0.36:5.34:(0.21-0.4):0.1:1.

[0066] When the mass ratio of the above-mentioned double-terminated acrylate liquid crystal molecules, the single-terminated acrylate nematic liquid crystal molecules, the chiral dopant, the photoinitiator, and the thiol molecules meets the above conditions, this formulation system can achieve rapid and uniform network crosslinking through the synergistic effect of polymerization and thiol-ene click chemistry. It can precisely control the crosslinking density, liquid crystal phase behavior, and cholesteric phase pitch of the material, thereby efficiently "locking" the orientation structure induced by the coating process, and obtaining a structurally stable and stimuli-responsive cholesteric phase liquid crystal elastomer (CLCE) material, namely the large-area side-chain cholesteric phase liquid crystal elastomer film of the present invention.

[0067] In one specific embodiment, the heat treatment temperature is 90-110℃ and the time is 2-4 hours. This heat treatment process mainly serves as thermal annealing and pre-curing. When the temperature and time parameters of the above heat treatment meet the above conditions, it can eliminate component inhomogeneity and internal stress, promote the formation of a uniform helical periodic structure of cholesteric liquid crystal, and lay the foundation for subsequent cross-linking and curing.

[0068] In one specific embodiment, the process parameters of the blade coating method include: a blade coating rate of 1-10 mm / s, a blade coating temperature of 30-60℃, and a blade coating thickness of 100-250 μm.

[0069] In this invention, the coating temperature refers to the temperature of the substrate.

[0070] This invention achieves large-area, high-efficiency preparation by precisely controlling key process parameters such as coating rate and coating temperature during the coating process and directly inducing cholesteric phase orientation using the coating method.

[0071] In one specific embodiment, the cross-linking curing temperature is 30-60℃ and the time is 5-10 min.

[0072] When the temperature and time parameters of the polymerization reaction meet the above conditions, the high-fidelity, low-defect transformation of the liquid crystal orientation structure into an elastomer network can be achieved within the optimal thermodynamic window (cholesterol phase temperature range). This is a key process guarantee for achieving the goal of preparing "large-area side-chain type cholesterol phase liquid crystal elastomer films".

[0073] In one specific embodiment, the illumination conditions are: wavelength of 365nm and power of 6-10mW / cm². 2Ultraviolet light.

[0074] A second aspect of the present invention provides a large-area side-chain cholesteric liquid crystal elastomer film, which is prepared by the aforementioned preparation method; the large-area side-chain cholesteric liquid crystal elastomer film has both mechanochromic and thermochromic response characteristics.

[0075] A third aspect of the present invention provides an application of the aforementioned large-area side-chain cholesteric liquid crystal elastomer film as an anti-counterfeiting label. Research by the present invention shows that, based on the thermochromic properties of the large-area side-chain cholesteric liquid crystal elastomer film, pattern information can be covered, and subsequently, by controlling the temperature, the pattern information can be reproduced and erased.

[0076] A fourth aspect of the present invention provides the application of the large-area side-chain cholesteric phase liquid crystal elastomer film described above in the preparation of thermochromic materials and / or mechanochromic materials.

[0077] The present invention will be further described below through specific embodiments.

[0078] In the following examples, liquid crystal monomer RM82 was purchased from Aladdin, CAS number 125248-71-7; liquid crystal monomer RM105 was purchased from Aladdin, CAS number 82200-53-1; chiral dopant LC756 was purchased from Aladdin, CAS number 223572-88-1; photoinitiator IRG651 was purchased from Aladdin, CAS number 947-19-3; and 1,6-hexanedithiol was purchased from Aladdin, CAS number 1191-43-1.

[0079] Example 1

[0080] This embodiment provides a method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on a blade coating method, including the following steps:

[0081] (1) Dissolve 0.36g of liquid crystal monomer RM82, 5.34g of liquid crystal monomer RM105, 0.21g of chiral dopant LC756 and 0.1g of photoinitiator IRG651 in 5mL of acetone to obtain an initial mixed solution;

[0082] Dissolve 1 g of 1,6-hexanedithiol in 1 mL of acetone to prepare a solution containing mercapto molecules;

[0083] The solution containing thiol molecules was poured into the initial mixed solution, heated from room temperature to 100°C at a rate of 2°C / min and held for 10 min to allow all components to dissolve and mix thoroughly. After standing and cooling, the mixed solution was obtained.

[0084] (2) The mixed solution obtained in step (1) is heated at 80°C for 3 hours to evaporate the solvent in the mixed solution and obtain the precursor of cholesteric phase liquid crystal elastomer oligomer.

[0085] (3) Using a glass plate as a substrate, 250 μL of the cholesteric liquid crystal elastomer oligomer precursor obtained in step (2) is directly coated onto the substrate surface by a scraping method to obtain a red cholesteric liquid crystal elastomer oligomer with an oriented structure; wherein, the process parameters of the scraping method are set as follows: the scraping rate is 10 mm / s, the scraping temperature is 40℃, and the scraping thickness is 150 μm.

[0086] (4) The red cholesteric phase liquid crystal elastomer oligomer obtained in step (3) is subjected to a temperature of 40°C (i.e., the temperature of the glass plate is controlled at 40°C so that the red cholesteric phase liquid crystal elastomer oligomer is in the cholesteric phase) and a wavelength of 365nm and a power of 6mW / cm. 2 Crosslinking and curing under ultraviolet light for 10 minutes yields the following result: Figure 2 The large-area side-chain cholesteric phase liquid crystal elastomer film shown.

[0087] Example 2

[0088] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 1, except that:

[0089] In step (3), the coating temperature is 30℃.

[0090] In step (4), the temperature is 30°C.

[0091] Example 3

[0092] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 1, except that:

[0093] In step (3), the coating temperature is 50℃.

[0094] In step (4), the temperature is 50°C.

[0095] Example 4

[0096] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 1, except that:

[0097] In step (3), the coating temperature is 60℃.

[0098] In step (4), the temperature is 60°C.

[0099] Example 5

[0100] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 3, except that:

[0101] In step (3), the scraping rate is 1 mm / s.

[0102] Example 6

[0103] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 3, except that:

[0104] In step (3), the scraping rate is 5 mm / s.

[0105] Example 7

[0106] The method for preparing large-area side-chain cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this embodiment is basically the same as that in Example 1, except that:

[0107] In step (1), 0.21g of chiral dopant LC756 is replaced with 0.4g of chiral dopant LC756.

[0108] Comparative Example 1 (without added thiol molecules)

[0109] The method for preparing cholesteric phase liquid crystal elastomer films based on the blade coating method provided in this comparative example is basically the same as that in Example 1, except that 1,6-hexanedithiol is not added. Specifically, it includes the following steps:

[0110] (1) Dissolve 0.36g of liquid crystal monomer RM82, 5.34g of liquid crystal monomer RM105, 0.21g of chiral dopant LC756 and 0.1g of photoinitiator IRG651 in 5mL of acetone, heat from room temperature to 100℃ at a rate of 2℃ / min and keep warm for 10min to fully dissolve and mix the components. After standing and cooling, a mixed solution is obtained.

[0111] (2) The mixed solution obtained in step (1) is heated at 80°C for 3 hours to evaporate the solvent in the mixed solution and obtain the precursor of cholesteric phase liquid crystal elastomer oligomer.

[0112] (3) 250 μL of the cholesteric liquid crystal elastomer oligomer precursor obtained in step (2) was directly coated onto the surface of a glass plate by a scraping method to obtain a white cholesteric liquid crystal elastomer oligomer with an oriented structure; wherein, the process parameters of the scraping method were set as follows: the scraping rate was 10 mm / s, the scraping temperature was 40 °C, and the scraping thickness was 150 μm.

[0113] (4) The white cholesteric phase liquid crystal elastomer oligomer obtained in step (3) is subjected to a temperature of 40°C (i.e., the temperature of the glass plate is controlled at 40°C so that the white cholesteric phase liquid crystal elastomer oligomer is in the cholesteric phase) and a wavelength of 365nm and a power of 6mW / cm. 2 Crosslinking and curing under ultraviolet light for 10 minutes yields the following result: Figure 3 The cholesteric phase liquid crystal elastomer film shown.

[0114] Performance testing

[0115] 1. Morphological characterization of the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 1-4 of the present invention. Figure 4 The apparent color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Examples 1-4 of the present invention; Figure 5 These are scanning electron microscope (SEM) images of the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 1-4 of the present invention. Figure 6 This is a side scanning electron microscope (SEM) image of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 3 of the present invention.

[0116] Depend on Figure 4 It is known that the closer the film is to the cholesteric phase transition temperature, the brighter the color. The film color becomes lighter after 50°C, forming a multi-domain film.

[0117] Depend on Figure 5 It can be seen that the thin film surface is more uniform the closer it is to the cholesteric phase transition temperature.

[0118] Depend on Figure 6 It can be seen that the film forms a layer-by-layer spiral periodic structure, and the pitch of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 3 is 540 nm.

[0119] 2. The stress-strain curve of the large-area side-chain cholesteric phase liquid crystal elastomer film in Examples 1-6 of the present invention was tested by tensile test, and the elongation at break and modulus of the film were calculated according to the stress-strain curve. The calculation results are recorded in Table 1. Figure 7 The stress-strain curves of the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 1-4 of the present invention are shown. Figure 8 The stress-strain curves are for the large-area side-chain cholesteric phase liquid crystal elastomer films in Examples 5-6 of this invention.

[0120] Table 1 Test Results

[0121]

[0122] Depend on Figures 7-8As shown in Table 1, comparing Examples 1-4, it was found that as the coating temperature gradually increased from 30℃ to 50℃, the elongation at break of the film first increased and then decreased, while the modulus first decreased and then increased. When the temperature was increased to 60℃, both the elongation at break and the modulus of the film were unsatisfactory. Considering both elongation at break and modulus, the film quality was better when the coating temperature was 50℃. Comparing Examples 3, 5, and 6, it was found that the film had the lowest elongation at break and the highest modulus when the coating rate was 1 mm / s; the film had the highest elongation at break and the lowest modulus when the coating rate was 10 mm / s. Considering both elongation at break and modulus, the film quality was better when the coating rate was 5 mm / s.

[0123] 3. The mechanochromic and thermochromic properties of the large-area side-chain cholesteric liquid crystal elastomer films in Examples 1 and 7 of the present invention and the cholesteric liquid crystal elastomer film in Comparative Example 1 were tested respectively.

[0124] Figure 9 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of tensile strain. Figure 10 This is a reflection spectrum of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Example 1 of the present invention, showing the change of reflection peaks with tensile strain. Figures 8-9 It can be seen that as the tensile strain increases, the pitch of the film gradually decreases, and the reflection wavelength also gradually decreases, which is macroscopically manifested as a blue shift in color.

[0125] Figure 11 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 1 of the present invention as a function of temperature; Figure 12 This is a reflection spectrum of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Example 1 of the present invention, showing the reflection peak as a function of temperature. Figures 11-12 It can be seen that as the temperature rises, the pitch of the thin film gradually increases, and the reflection wavelength also gradually increases, which is macroscopically manifested as a red shift in color. When the temperature rises to 120℃, it exceeds the visible light region.

[0126] Figure 13 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention as a function of tensile strain. Figure 14 This is a reflection spectrum of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Example 7 of the present invention, showing the change of reflection peaks with tensile strain. Figures 13-14 It can be seen that as the tensile strain increases, the pitch of the film gradually decreases, and the reflection wavelength also gradually decreases, which is macroscopically manifested as a blue shift in color.

[0127] Figure 15 The actual color of the large-area side-chain cholesteric phase liquid crystal elastomer film in Example 7 of the present invention as a function of temperature; Figure 16This is a reflection spectrum of the large-area side-chain type cholesteric phase liquid crystal elastomer film in Example 7 of the present invention, showing the reflection peak as a function of temperature. Figures 15-16 As can be seen, as the temperature rises, the pitch of the thin film gradually increases, and the reflection wavelength also gradually increases, which macroscopically manifests as a red shift in color, achieving full spectrum coverage from blue to red.

[0128] Figure 17 The image shows the actual color of the cholesteric phase liquid crystal elastomer film in Comparative Example 1 of this invention as a function of tensile strain. Figure 17 It can be seen that the cholesteric phase liquid crystal elastomer film in Comparative Example 1 has no achromatic color-changing properties.

[0129] Figure 18 This is the actual color of the cholesteric phase liquid crystal elastomer film in Comparative Example 1 of the present invention as a function of temperature. Figure 18 It can be seen that the cholesteric liquid crystal elastomer film in Comparative Example 1 can achieve the transition between opaque and transparent states.

[0130] 4. Applications of thin film in information encryption

[0131] Using an aluminum sheet with a pattern printed on its surface as a substrate, a thin film is prepared on the patterned surface of the aluminum sheet according to the method in Example 4 to obtain the device. The specific steps include:

[0132] (1) Dissolve 0.36g of liquid crystal monomer RM82, 5.34g of liquid crystal monomer RM105, 0.21g of chiral dopant LC756 and 0.1g of photoinitiator IRG651 in 5mL of acetone to obtain an initial mixed solution;

[0133] Dissolve 1 g of 1,6-hexanedithiol in 1 mL of acetone to prepare a solution containing mercapto molecules;

[0134] The solution containing thiol molecules was poured into the initial mixed solution, heated from room temperature to 100°C at a rate of 2°C / min and held for 10 min to allow all components to dissolve and mix thoroughly. After standing and cooling, the mixed solution was obtained.

[0135] (2) The mixed solution obtained in step (1) is heated at 80°C for 3 hours to evaporate the solvent in the mixed solution and obtain the precursor of cholesteric phase liquid crystal elastomer oligomer.

[0136] (3) Using an aluminum sheet with a pattern printed on its surface as a substrate, 250 μL of the cholesteric liquid crystal elastomer oligomer precursor obtained in step (2) is directly coated onto the substrate surface (the surface of the aluminum sheet with the pattern printed on it) by a scraping method to obtain cholesteric liquid crystal elastomer oligomer; wherein, the process parameters of the scraping method are set as follows: the scraping rate is 10 mm / s, the scraping temperature is 60℃, and the scraping thickness is 150 μm.

[0137] (4) The cholesteric phase liquid crystal elastomer oligomer obtained in step (3) is subjected to a temperature of 60°C and a wavelength of 365 nm and a power of 6 mW / cm. 2 Crosslinking and curing under ultraviolet light for 10 minutes yields the following result: Figure 19 The device shown.

[0138] Figure 20 This is a physical diagram showing the temperature variation of a device in the information encryption application of the thin film of this invention. Figure 20 It can be seen that as the temperature rises, the pattern information on the substrate surface can be revealed, and as the temperature falls, the pattern information on the substrate surface will be hidden.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on a blade coating method, characterized in that, Includes the following steps: A mixed solution was obtained by thermally mixing a raw material system comprising liquid crystal molecules with double-ended acrylate groups, nematic liquid crystal molecules with single-ended acrylate groups, a chiral dopant, a photoinitiator, a thiol molecule, and a solvent. The mixed solution was heated to evaporate the solvent, yielding a cholesteric phase liquid crystal elastomer oligomer precursor. The cholesteric liquid crystal elastomer oligomer precursor was directly coated onto the substrate surface using a blade coating method to obtain a cholesteric liquid crystal elastomer oligomer film with an oriented structure. The cholesteric phase liquid crystal elastomer oligomer film is crosslinked and cured under light to obtain a large-area side-chain cholesteric phase liquid crystal elastomer film.

2. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 1, characterized in that, The liquid crystal molecule with double-ended acrylate groups is liquid crystal monomer RM82, the nematic liquid crystal molecule with single-ended acrylate groups is liquid crystal monomer RM105, the chiral dopant is LC756, the photoinitiator is IRG651, and the thiol molecule is 1,6-hexanedithiol.

3. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 2, characterized in that, The mass ratio of the liquid crystal molecule with double-ended acrylate groups, the nematic liquid crystal molecule with single-ended acrylate groups, the chiral dopant, the photoinitiator, and the thiol molecule is 0.36:5.34:(0.21-0.4):0.1:

1.

4. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 1, characterized in that, The heat treatment is performed at a temperature of 90-110℃ for 2-4 hours.

5. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 1, characterized in that, The process parameters for the scraping method include: The coating speed is 1-10 mm / s, the coating temperature is 30-60℃, and the coating thickness is 100-250 μm.

6. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 1, characterized in that, The cross-linking curing temperature is 30-60℃ and the time is 5-10 min.

7. The method for preparing large-area side-chain type cholesteric phase liquid crystal elastomer films based on the blade coating method according to claim 1, characterized in that, The illumination conditions are: wavelength 365nm, power 6-10mW / cm². 2 Ultraviolet light.

8. A large-area side-chain type cholesteric phase liquid crystal elastomer film, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the large-area side-chain type cholesteric phase liquid crystal elastomer film as described in claim 8 as an anti-counterfeiting label.

10. The application of the large-area side-chain cholesteric phase liquid crystal elastomer film of claim 8 in the preparation of thermochromic materials and / or mechanochromic materials.

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