Optically driven cholesteric liquid crystal elastomer composite film, and preparation method and application thereof

Abstract

The application provides a light-driven cholesteric liquid crystal elastomer composite film and a preparation method and application thereof. The light-driven cholesteric liquid crystal elastomer composite film comprises a cholesteric liquid crystal elastomer color layer and a light-driven liquid crystal elastomer matrix layer which are arranged in a stack; the cholesteric liquid crystal elastomer color layer is arranged on the upper surface of the light-driven liquid crystal elastomer matrix layer and then subjected to heat pressing treatment, and the light-driven cholesteric liquid crystal elastomer composite film is obtained. The light-driven cholesteric liquid crystal elastomer composite film has a force-induced color change performance and a light-induced shrinkage performance, has excellent external stimulus response characteristics, and can stably maintain the color effect after deformation, thereby expanding the application of cholesteric liquid crystal elastomers in the fields of information storage and photonic crystals.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal materials technology, and in particular to a light-driven cholesteric phase liquid crystal elastomer composite film, its preparation method, and its application. Background Technology

[0002] Liquid crystal elastomers are smart materials that possess the anisotropy of liquid crystals and the elasticity of polymer networks, while also exhibiting external responsiveness and optical nonlinearity. Among them, cholesteric liquid crystal elastomers, due to their unique helical structure, excellent mechanochromic properties, superior color controllability, and excellent mechanical properties, have wide applications in sensing, anti-counterfeiting, and information storage. Currently, traditional cholesteric liquid crystal elastomers are typically composed of cholesteric liquid crystal molecules and an elastic matrix. The cholesteric liquid crystal molecules are fixed in the elastic matrix through a cross-linking reaction, and the cholesteric liquid crystal molecules spontaneously arrange themselves into a helical structure. The periodic changes in the helix cause the material to change color under specific conditions.

[0003] However, traditional cholesteric liquid crystal elastomers have some problems: (1) The deformation of traditional cholesteric liquid crystal elastomers depends entirely on the deformation under the action of external force (such as mechanical stretching), and cannot respond to external stimuli such as light and heat, and cannot use external stimuli such as light and heat to adjust its deformation; (2) The color produced by traditional cholesteric liquid crystal elastomers after deformation is usually instantaneous, and the color is not easy to maintain, making it difficult to stably maintain the color effect after deformation.

[0004] Therefore, developing a cholesteric liquid crystal elastomer that has responsive characteristics to external stimuli and can stably maintain the color effect after deformation is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a light-driven cholesteric liquid crystal elastomer composite film, which simultaneously possesses mechanochromic and photo-shrinkable properties, exhibits excellent response characteristics to external stimuli, and can stably maintain the color effect after deformation.

[0006] This invention also provides a method for preparing a light-driven cholesteric liquid crystal elastomer composite film, which can produce a light-driven cholesteric liquid crystal elastomer composite film with both mechanochromic and photo-shrinkage properties. This preparation method is simple and can be widely applied.

[0007] The present invention also provides an application of a light-driven cholesteric liquid crystal elastomer composite film in the preparation of optical drivers, displays, and sensors. Since the prepared optical drivers, displays, or sensors include a light-driven cholesteric liquid crystal elastomer composite film, the prepared optical drivers, displays, or sensors have mechanochromic properties and photo-shrinkage properties.

[0008] A first aspect of the present invention provides a light-driven cholesteric liquid crystal elastomer composite film, comprising a cholesteric liquid crystal elastomer color layer and a light-driven liquid crystal elastomer substrate layer stacked together;

[0009] The cholesteric phase liquid crystal elastomer color layer is prepared from a first raw material system comprising a first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, an acrylate chiral agent, a dithiol, a first acrylate dynamic bond molecule, a first photoinitiator, and a first thermal initiator.

[0010] The light-driven liquid crystal elastomer matrix layer is prepared from a second raw material system comprising a second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator;

[0011] The cholesteric phase liquid crystal elastomer color layer is disposed on the upper surface of the light-driven liquid crystal elastomer substrate layer and then subjected to hot pressing to obtain the light-driven cholesteric phase liquid crystal elastomer composite film.

[0012] In the light-driven cholesteric liquid crystal elastomer composite film described above, the photothermal filler in the second raw material system is at least one of carbon nanotubes, carbon fibers, graphene, carbon black, and polydopamine.

[0013] In the light-driven cholesteric liquid crystal elastomer composite film described above, the photothermal filler in the second raw material system has a mass percentage content of 0.1wt% to 2.0wt%.

[0014] In the light-driven cholesteric liquid crystal elastomer composite film as described above, in the second raw material system, the mass percentage of the second acrylate liquid crystal monomer is 50wt% to 60wt%, the mass percentage of the dithiol chain extender is 10wt% to 20wt%, the mass percentage of the polythiol crosslinking agent is 1wt% to 5wt%, the mass percentage of the second acrylate dynamic bond molecule is 1wt% to 10wt%, the mass percentage of the second photoinitiator is 0.5wt% to 1wt%, and the mass percentage of the second thermal initiator is 15wt% to 20wt%.

[0015] In the light-driven cholesteric liquid crystal elastomer composite film as described above, in the first raw material system, the mass ratio of the first acrylate liquid crystal monomer to the vinyl ether liquid crystal monomer is 10:(5-10); the mass of the acrylate chiral agent accounts for 1%-10% of the total mass of the first acrylate liquid crystal monomer and the vinyl ether liquid crystal monomer; the mass of the first acrylate dynamic bond molecule accounts for 5%-10% of the total mass of the first acrylate liquid crystal monomer, the vinyl ether liquid crystal monomer, and the acrylate chiral agent; the molar mass of the dithiol accounts for 80%-90% of the total molar mass of the first acrylate liquid crystal monomer, the acrylate chiral agent, the first acrylate dynamic bond molecule, and the vinyl ether liquid crystal monomer; the mass of the first photoinitiator accounts for 1%-5% of the total mass of the first raw material system; and the mass of the first thermal initiator accounts for 0.5%-1% of the total mass of the first raw material system.

[0016] In the light-driven cholesteric phase liquid crystal elastomer composite film described above, the dynamic bond molecule in the first acrylate dynamic bond molecule or the second acrylate dynamic bond molecule is any one of disulfide bond molecule, diselenide bond molecule, borate ester bond molecule, or boron oxide hexacyclic molecule;

[0017] And / or, the hot pressing treatment is performed at a pressure of 50N to 500N, a temperature of 40℃ to 100℃, and a time of 4h to 24h.

[0018] A second aspect of the present invention provides a method for preparing the aforementioned light-driven cholesteric liquid crystal elastomer composite film, comprising the following steps:

[0019] A first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, and an acrylate chiral agent are subjected to a first thermal mixing treatment to obtain a first mixture; dithiol, a first acrylate dynamic bond molecule, and a first photoinitiator are added to the first mixture for a second thermal mixing treatment to obtain a second mixture; the first thermal initiator is mixed with dichloromethane to obtain a first thermal initiator solution; the first thermal initiator solution is mixed with the second mixture to obtain a first precursor; the first precursor is coated onto a substrate and then subjected to a first thermal polymerization treatment and a first photopolymerization treatment in sequence to obtain a cholesteric phase liquid crystal elastomer color layer;

[0020] A second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator are added to an organic solvent for a third thermal mixing treatment to obtain a precursor liquid. The precursor liquid is poured into a mold, and after evaporation of the organic solvent, a second thermal polymerization treatment is performed to obtain a second precursor. The second precursor is stretched and then subjected to a second photopolymerization treatment to obtain a photodriven liquid crystal elastomer matrix layer.

[0021] The cholesteric phase liquid crystal elastomer color layer is disposed on the upper surface of the light-driven liquid crystal elastomer substrate layer and then subjected to hot pressing to obtain the light-driven cholesteric phase liquid crystal elastomer composite film.

[0022] In the method for preparing the light-driven cholesteric liquid crystal elastomer composite film as described above, the temperature of the first thermal polymerization treatment is 40℃~60℃;

[0023] And / or, the tensile strain during the stretching treatment is 200%.

[0024] In the method for preparing the light-driven cholesteric phase liquid crystal elastomer composite film as described above, the first acrylate liquid crystal monomer or the second acrylate liquid crystal monomer is at least one of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2-methyl-1,4-phenylenebis(4-(4-(acryloyloxy)butoxy)benzoate, 2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, (4-(((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoic acid 2-methyl-1,4-diphenol ester, and 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate;

[0025] And / or, the acrylate chiral agent includes reactive liquid crystal DK756;

[0026] And / or, the dithiol or the dithiol chain extender is at least one of ethylene glycol dithioacetate, di(mercaptoacetic acid)-1,4-butanediol, 2,2'-(1,2-ethylenedioxy)bis(ethylene ethyl mercaptan), 2-methyl-1,4-phenylenebis(4-(4-mercaptobutoxy)benzoate), and ethylene dithiol;

[0027] And / or, the first photoinitiator or the second photoinitiator is at least one of benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-methylphenylpropane-1-one, bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone;

[0028] And / or, the first thermal initiator or the second thermal initiator is at least one of alkoxides, basic amines, metal hydrides, and amine lithium;

[0029] And / or, the vinyl ether liquid crystal monomers include 4-[4-(ethoxy)butoxy]-,1,1'-(2-methyl-1,4-phenylene)benzoate;

[0030] And / or, the polythiol crosslinking agent is at least one of pentaerythritol tetra-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetra(3-mercaptopropionic acid) ester.

[0031] A third aspect of the present invention provides the application of the aforementioned light-driven cholesteric liquid crystal elastomer composite film in the preparation of optical drivers, displays, and sensors.

[0032] Compared with the prior art, the beneficial technical effects of the present invention include at least the following:

[0033] The light-driven cholesteric liquid crystal elastomer composite film provided by this invention has a bilayer structure, comprising a cholesteric liquid crystal elastomer color layer and a light-driven liquid crystal elastomer substrate layer stacked together. The cholesteric liquid crystal elastomer color layer is disposed on the upper surface of the light-driven liquid crystal elastomer substrate layer and then subjected to hot pressing. This process ensures a tight bond between the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer, resulting in a light-driven cholesteric liquid crystal elastomer composite film that simultaneously possesses photoinduced shrinkage and mechanochromic properties, exhibiting excellent external stimulus response characteristics. Furthermore, this light-driven cholesteric liquid crystal elastomer composite film can stably maintain its color effect after deformation, expanding the application of cholesteric liquid crystal elastomers in fields such as information storage and photonic crystals. Attached Figure Description

[0034] 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.

[0035] Figure 1 This is a schematic diagram of the preparation process of the light-driven cholesteric liquid crystal elastomer composite film of the present invention; wherein, process (1) is a schematic diagram of the preparation process of the light-driven liquid crystal elastomer substrate layer in this embodiment; process (2) is a schematic diagram of the preparation process of the cholesteric liquid crystal elastomer color layer in this embodiment; process (3) is a schematic diagram of the preparation process of the light-driven cholesteric liquid crystal elastomer composite film in this embodiment. Figure 1(4) is a conceptual diagram of the dynamic bond exchange reaction of micro-molecules when the cholesteric liquid crystal elastomer color layer is placed on the upper surface of the light-driven liquid crystal elastomer matrix layer and then subjected to hot pressing. The elements are as follows: red ellipse - liquid crystal unit fragments in the cholesteric liquid crystal elastomer color layer, black ellipse - liquid crystal unit fragments in the light-driven liquid crystal elastomer matrix layer, yellow ellipse - diselenylene bond molecules, and blue line - flexible chain segment; where (i) is a micro-molecule simulation diagram before the dynamic bond exchange reaction occurs, (ii) is a micro-molecule simulation diagram when the dynamic bond exchange reaction is occurring, and (iii) is a micro-molecule simulation diagram after the dynamic bond exchange reaction occurs.

[0036] Figure 2 These are photographs of the cholesteric liquid crystal elastomer color layer in Example 1 of the present invention before and after tensile strain; wherein, Figure 2 'a' is a photograph taken with a camera of the cholesteric phase liquid crystal elastomer color layer in Example 1; Figure 2 b is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 45%; Figure 2 c is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after 60% tensile strain; Figure 2 d is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after 90% tensile strain; Figure 2 e is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 135%;

[0037] Figure 3 These are photographs of the cholesteric liquid crystal elastomer color layer in Example 1 of the present invention before and after a 45% tensile strain; wherein, Figure 3 A is a photograph taken with a camera of the cholesteric phase liquid crystal elastomer color layer in Example 1; Figure 3 B is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 45%.

[0038] Figure 4 This is a reflection spectrum of the cholesteric phase liquid crystal elastomer color layer in Example 1 of the present invention, showing the change of the reflection peak with tensile strain.

[0039] Figure 5 These are photographs of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 and Example 1 of the present invention; wherein, Figure 5 Photo A is a photograph of the light-driven liquid crystal elastomer matrix layer in Comparative Example 1; Figure 5 Photograph B is of the light-driven liquid crystal elastomer substrate layer in Example 1;

[0040] Figure 6These are photographs of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 and Example 1 of the present invention before and after irradiation with infrared light; wherein, Figure 6 A is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 before and after being irradiated with infrared light. The infrared light intensity is 6.2W and the irradiation time is 30s. Among them, a is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1, and b is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 after being irradiated with infrared light. Figure 6 B is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1 before and after infrared light irradiation. The infrared light intensity is 6.2W and the irradiation time is 30s. C is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1, and d is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1 after infrared light irradiation.

[0041] Figure 7 The results of photothermal performance testing of the light-driven liquid crystal elastomer substrate layer in Examples 1-3 and Comparative Example 1 of the present invention are shown in the figure.

[0042] Figure 8 To take a photograph of the light-driven cholesteric phase liquid crystal elastomer composite film in Embodiment 4 of the present invention using a camera;

[0043] Figure 9 These are photographs of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 of the present invention before and after tensile strain; wherein, Figure 9 a is a photograph taken with a camera of the light-driven cholesteric phase liquid crystal elastomer composite film in Example 4; Figure 9 b is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after 83% tensile strain. Figure 9 c is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after 150% tensile strain.

[0044] Figure 10 These are photographs of the light-driven cholesteric phase liquid crystal elastomer composite film of the present invention before and after infrared light irradiation. The infrared light intensity was 6.2 W, and the irradiation time was 30 s. Figure 10 A is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after a tensile strain of 150%. Figure 9 B is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film after 150% tensile strain and irradiation with infrared light; the color descriptions in the photographs in this invention are based on the colors under natural light. Detailed Implementation

[0045] 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.

[0046] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available; and the processes used are conventional processes in the art.

[0047] It should be noted that the descriptions involving "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as limiting the invention.

[0048] The term "light-driven" refers to the change in configuration, polarity, or temperature of microscopic molecules under infrared light irradiation, which in turn causes a change in the shape of the macroscopic material (the light-driven cholesteric liquid crystal elastomer composite film of the present invention). Light-driven has the characteristics of remote, non-contact driving and does not cause damage to the material.

[0049] A first aspect of the present invention provides a light-driven cholesteric liquid crystal elastomer composite film, comprising a cholesteric liquid crystal elastomer color layer and a light-driven liquid crystal elastomer substrate layer stacked together;

[0050] The cholesteric phase liquid crystal elastomer color layer is prepared from a first raw material system comprising a first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, an acrylate chiral agent, a dithiol, a first acrylate dynamic bond molecule, a first photoinitiator, and a first thermal initiator.

[0051] The light-driven liquid crystal elastomer matrix layer is prepared from a second raw material system comprising a second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator;

[0052] After the cholesteric liquid crystal elastomer color layer is placed on the upper surface of the light-driven liquid crystal elastomer substrate layer, it is subjected to hot pressing to obtain the light-driven cholesteric liquid crystal elastomer composite film.

[0053] The present invention does not impose a particular limitation on the specific shape of the cholesteric liquid crystal elastomer color layer, which can be selected according to actual needs. In some embodiments, the cholesteric liquid crystal elastomer color layer can be patterned to obtain a patterned cholesteric liquid crystal elastomer color layer.

[0054] Specifically, the photo-driven cholesteric liquid crystal elastomer composite film of the present invention has a bilayer structure, comprising a cholesteric liquid crystal elastomer color layer and a photo-driven liquid crystal elastomer substrate layer stacked together. The cholesteric liquid crystal elastomer color layer exhibits mechanochromic color change upon stretching, while the photo-driven liquid crystal elastomer substrate layer exhibits photo-shrinkage upon exposure to infrared light. The present invention involves hot-pressing the cholesteric liquid crystal elastomer color layer onto the upper surface of the photo-driven liquid crystal elastomer substrate layer, thereby achieving a tight bond between the cholesteric liquid crystal elastomer color layer and the photo-driven liquid crystal elastomer substrate layer. This results in a photo-driven cholesteric liquid crystal elastomer composite film that possesses both mechanochromic and photo-shrinkage properties, exhibiting excellent external stimulus response characteristics. The inventors analyzed the phenomenon and believe the reason may lie in the fact that both the cholesteric liquid crystal elastomer (CCL) color layer and the photo-driven CCL matrix layer contain dynamic bond molecules. During hot pressing, these dynamic bond molecules undergo dynamic bond exchange reactions, leading to bond exchange at the small molecule level, chain entanglement at the polymer level, and adhesion between macroscopic interfaces. This results in a tight connection between the CCL and CCL matrix layers through the self-healing of dynamic bonds, achieving coordinated movement between them. This coordinated movement enables the prepared photo-driven CCL composite film to simultaneously possess photo-shrinkage and mechanochromic properties. Furthermore, the photo-driven CCL composite film can stably maintain its color effect after deformation.

[0055] In one specific embodiment, in the above-mentioned second raw material system, the photothermal filler is at least one of carbon nanotubes, carbon fibers, graphene, carbon black, and polydopamine.

[0056] When the above-mentioned materials are used as photothermal fillers, a photo-driven liquid crystal elastomer matrix layer with excellent photothermal properties is prepared, which is beneficial to improving the external stimulus response characteristics of the photo-driven cholesteric phase liquid crystal elastomer composite film.

[0057] In one specific embodiment, the mass percentage of the photothermal filler in the second raw material system is 0.1 wt% to 2.0 wt%.

[0058] When the mass percentage of photothermal filler in the second raw material system is within the above range, a light-driven liquid crystal elastomer matrix layer with superior photothermal properties can be prepared, further improving the external stimulus response characteristics of the light-driven cholesteric liquid crystal elastomer composite film, thereby preparing a light-driven cholesteric liquid crystal elastomer composite film with mechanochromic and photo-shrinkage properties.

[0059] For example, in the second raw material system, the mass percentage of the photothermal filler can be any one of 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, or 2.0wt%, or any combination thereof.

[0060] In one specific embodiment, in the above-mentioned second raw material system, the mass percentage of the second acrylate liquid crystal monomer is 50wt% to 60wt%, the mass percentage of the dithiol chain extender is 10wt% to 20wt%, the mass percentage of the polythiol crosslinking agent is 1wt% to 5wt%, the mass percentage of the second acrylate dynamic bond molecule is 1wt% to 10wt%, the mass percentage of the second photoinitiator is 0.5wt% to 1wt%, and the mass percentage of the second thermal initiator is 15wt% to 20wt%.

[0061] When the mass percentages of the second acrylate liquid crystal monomer, dithiol chain extender, polythiol crosslinking agent, second acrylate dynamic bond molecule, second photoinitiator, and second thermal initiator in the second raw material system are within the above-mentioned range, the second acrylate liquid crystal monomer, dithiol chain extender, polythiol crosslinking agent, second acrylate dynamic bond molecule, second photoinitiator, and second thermal initiator in the second raw material system can be better matched with the photothermal filler, thereby preparing a light-driven liquid crystal elastomer matrix layer with excellent photothermal properties, which is beneficial for preparing a light-driven cholesteric phase liquid crystal elastomer composite film with mechanochromic and photoshrinkage properties.

[0062] In one specific embodiment, in the first raw material system, the mass ratio of the first acrylate liquid crystal monomer to the vinyl ether liquid crystal monomer is 10:(5-10); the mass of the acrylate chiral agent accounts for 1%-10% of the total mass of the first acrylate liquid crystal monomer and the vinyl ether liquid crystal monomer; the mass of the first acrylate dynamic bond molecule accounts for 5%-10% of the total mass of the first acrylate liquid crystal monomer, the vinyl ether liquid crystal monomer, and the acrylate chiral agent; the molar mass of the dithiol accounts for 80%-90% of the total molar mass of the first acrylate liquid crystal monomer, the acrylate chiral agent, the first acrylate dynamic bond molecule, and the vinyl ether liquid crystal monomer; the mass of the first photoinitiator accounts for 1%-5% of the total mass of the first raw material system; and the mass of the first thermal initiator accounts for 0.5%-1% of the total mass of the first raw material system.

[0063] When the mass of the first acrylate liquid crystal monomer, vinyl ether liquid crystal monomer, acrylate chiral agent, dithiol, first acrylate dynamic bond molecule, first photoinitiator, and first thermal initiator in the first raw material system are within the above range, the first acrylate liquid crystal monomer, vinyl ether liquid crystal monomer, acrylate chiral agent, dithiol, first acrylate dynamic bond molecule, first photoinitiator, and first thermal initiator in the first raw material system can be better matched, and a cholesteric phase liquid crystal elastomer color layer with excellent mechanochromic properties can be prepared, which is beneficial to preparing a light-driven cholesteric phase liquid crystal elastomer composite film with mechanochromic properties and photo-shrinkage properties.

[0064] In one specific embodiment, the dynamic bond molecule in the first acrylate dynamic bond molecule or the second acrylate dynamic bond molecule is any one of disulfide bond molecule, diselenide bond molecule, borate ester bond molecule, or boron-oxygen hexacyclic molecule.

[0065] When the dynamic bond molecules in the first acrylate dynamic bond molecule or the second acrylate dynamic bond molecule are the aforementioned dynamic bond molecules, the dynamic bond molecules in the cholesteric liquid crystal elastomer color layer can undergo a sufficient dynamic bond exchange reaction with the dynamic bond molecules in the photodriven liquid crystal elastomer matrix layer, thereby preparing a photodriven cholesteric liquid crystal elastomer composite film with photo-induced shrinkage and mechanochromic properties.

[0066] In one specific embodiment, the pressure of the above-mentioned hot pressing treatment is 50N to 500N, the temperature is 40℃ to 100℃, and the time is 4h to 24h.

[0067] When the pressure, temperature, and time parameters of the hot-pressing process are within the above range, the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer matrix layer are more tightly connected, thereby giving the prepared light-driven cholesteric liquid crystal elastomer composite film superior mechanochromic and photo-shrinkage properties, as well as excellent external stimulus response characteristics.

[0068] A second aspect of the present invention provides a method for preparing a light-driven cholesteric liquid crystal elastomer composite film, comprising the following steps:

[0069] A first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, and an acrylate chiral agent are subjected to a first thermal mixing treatment to obtain a first mixture; dithiol, a first acrylate dynamic bond molecule, and a first photoinitiator are added to the first mixture for a second thermal mixing treatment to obtain a second mixture; the first thermal initiator is mixed with dichloromethane to obtain a first thermal initiator solution; the first thermal initiator solution is mixed with the second mixture to obtain a first precursor; the first precursor is coated onto a substrate and then subjected to a first thermal polymerization treatment and a first photopolymerization treatment in sequence to obtain a cholesteric phase liquid crystal elastomer color layer;

[0070] A second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator are added to an organic solvent for a third thermal mixing treatment to obtain a precursor liquid. The precursor liquid is poured into a mold, evaporated in an organic solvent, and then subjected to a second thermal polymerization treatment to obtain a second precursor. The second precursor is stretched and then subjected to a second photopolymerization treatment to obtain a photodriven liquid crystal elastomer matrix layer.

[0071] After the cholesteric liquid crystal elastomer color layer is placed on the upper surface of the light-driven liquid crystal elastomer substrate layer, it is subjected to hot pressing to obtain the light-driven cholesteric liquid crystal elastomer composite film.

[0072] The present invention does not impose any particular limitation on the specific sources of raw materials and reagents used in the preparation of light-driven cholesteric phase liquid crystal elastomer composite films. They can be obtained through commercial channels or prepared by methods well known in the art.

[0073] This invention does not impose a particular limitation on the specific type of organic solvent used, and it can be selected according to specific needs. In some embodiments, the organic solvent can be any one of tetrahydrofuran, dichloromethane, and toluene, preferably tetrahydrofuran. This invention also does not impose a particular limitation on the specific amount of organic solvent used, and it can be selected according to specific needs.

[0074] This invention does not impose any particular limitation on the specific material of the mold used, and the material can be selected according to specific needs. In some embodiments, the mold can be a polytetrahydrofuran mold.

[0075] In this invention, "first thermal mixing treatment", "second thermal mixing treatment" or "third thermal mixing treatment" should be understood as temperature-conditional mixing, which can be stirring and mixing under certain temperature conditions to ensure the uniformity of the mixture.

[0076] It is understood that the present invention mixes a first thermal initiator with dichloromethane to obtain a first thermal initiator solution, which is a first thermal initiator diluted with dichloromethane. For example, dichloromethane can be used to dilute it 10 times by mass. Using the first thermal initiator is beneficial to promote the thermal initiation process while preventing it from rapidly agglomerating.

[0077] The present invention performs a stretching process on the above-mentioned second precursor, which is beneficial to obtaining a well-oriented light-driven liquid crystal elastomer matrix layer.

[0078] The present invention prepares a light-driven cholesteric liquid crystal elastomer composite film by hot-pressing a cholesteric liquid crystal elastomer color layer on the upper surface of a light-driven liquid crystal elastomer substrate layer using the above preparation method. This results in a tight connection between the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer.

[0079] In one specific embodiment, the temperature of the first thermal polymerization treatment is 40°C to 60°C.

[0080] When the temperature parameters of the first thermal polymerization treatment are within the above range, the first thermal polymerization reaction can proceed smoothly, which is conducive to obtaining a stable cholesteric liquid crystal elastomer color layer, and thus conducive to preparing a light-driven cholesteric liquid crystal elastomer composite film with photo-induced shrinkage and mechanochromic properties.

[0081] In one specific embodiment, the tensile strain during the above-described tensile treatment is 200%.

[0082] When the tensile strain parameters during the stretching process are within the above range, it is beneficial to prepare a light-driven liquid crystal elastomer matrix layer with excellent photo-shrinkage properties.

[0083] In one specific embodiment, the first acrylate liquid crystal monomer or the second acrylate liquid crystal monomer is at least one of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2-methyl-1,4-phenylenebis(4-(4-(acryloyloxy)butoxy)benzoate, 2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, (4-(((4-((acryloyloxy)butoxy)carbonyl)oxy)benzoic acid 2-methyl-1,4-diphenol ester, and 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate.

[0084] When the above-mentioned substances are used as the first acrylate liquid crystal monomers, they act as liquid crystal building blocks, which impart anisotropy and orientation to the cholesteric liquid crystal elastomer color layer.

[0085] When the above-mentioned substance is used as the second acrylate liquid crystal monomer, it acts as a liquid crystal unit, which imparts anisotropy and orientation to the liquid crystal in the light-driven liquid crystal elastomer matrix layer.

[0086] In one specific embodiment, the dithiol or dithiol chain extender is at least one of ethylene glycol dithioacetate, di(mercaptoacetic acid)-1,4-butanediol, 2,2'-(1,2-ethylenedioxy)bis(ethylene ethyl mercaptan), 2-methyl-1,4-phenylenebis(4-(4-mercaptobutoxy)benzoate), and ethylene dithiol.

[0087] When the above-mentioned substances are dithiols or dithiols chain extenders, the distance between liquid crystal units can be reduced, the crosslinking density of the cholesteric phase liquid crystal elastomer color layer or the light-driven liquid crystal elastomer matrix layer can be reduced, and the elasticity can be improved.

[0088] In one specific embodiment, the first or second photoinitiator is at least one of benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-methylphenylpropane-1-one, bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone.

[0089] Using the above-mentioned substance as the first photoinitiator is beneficial to the first photopolymerization process.

[0090] Using the above-mentioned substances as the first photoinitiator is beneficial to the second photopolymerization process.

[0091] In one specific embodiment, the first thermal initiator or the second thermal initiator is at least one of alkoxides, basic amines, metal hydrides, and amine lithium.

[0092] When the above-mentioned substances are used as the first thermal initiator, it is beneficial to carry out the first thermal polymerization process.

[0093] When the above-mentioned substances are used as the second thermal initiator, it is beneficial to carry out the second thermal polymerization process.

[0094] In one specific embodiment, the above-mentioned vinyl ether liquid crystal monomer includes 4-[4-(ethoxy)butoxy]-,1,1'-(2-methyl-1,4-phenylene)benzoate.

[0095] When the above-mentioned substances are used as vinyl ether liquid crystal monomers, the possibility of self-polymerization of acrylate groups is reduced while providing liquid crystal properties.

[0096] In one specific embodiment, the aforementioned polythiol crosslinking agent is at least one of pentaerythritol tetra-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetra(3-mercaptopropionic acid) ester.

[0097] When the above-mentioned substances are used as polythiol crosslinking agents, the crosslinking density is increased.

[0098] A third aspect of the present invention provides the application of the above-described photo-driven cholesteric liquid crystal elastomer composite film in the fabrication of optical drivers, displays, and sensors. Since the fabricated optical drivers, displays, or sensors include the photo-driven cholesteric liquid crystal elastomer composite film, the fabricated optical drivers, displays, or sensors possess mechanochromic properties and photo-shrinkage properties.

[0099] The present invention will be further described below through specific embodiments.

[0100] Example 1

[0101] Please see Figure 1 , Figure 1 This is a schematic diagram of the preparation process of the light-driven cholesteric liquid crystal elastomer composite film of the present invention; wherein, process (1) is a schematic diagram of the preparation process of the light-driven liquid crystal elastomer substrate layer in this embodiment; process (2) is a schematic diagram of the preparation process of the cholesteric liquid crystal elastomer color layer in this embodiment; process (3) is a schematic diagram of the preparation process of the light-driven cholesteric liquid crystal elastomer composite film in this embodiment. Figure 1 (4) is a conceptual diagram of the dynamic bond exchange reaction of micro-molecules during hot pressing after the cholesteric liquid crystal elastomer color layer is set on the upper surface of the light-driven liquid crystal elastomer matrix layer. Figure 1 As shown, the light-driven cholesteric liquid crystal elastomer composite film of this embodiment is prepared by a method including the following steps:

[0102] 1. Preparation of color layer of cholesteric phase liquid crystal elastomer

[0103] 1) 0.13 g of 2-methyl-1,4-phenylene bis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, 0.13 g of 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate, 0.087 g of 4-[4-(ethenyloxy)butoxy]-,1,1'-(2-methyl-1,4-phenylene)ester (CAS No.: 172258-53-6) and 0.0215 g of reactive liquid crystal DK756 (CAS No.: 223572-88-1) were subjected to a first heat-mixing treatment under the condition of blowing with a blower, and then allowed to stand to obtain a first mixture;

[0104] 2) Add 0.0328g of 2,2'-(1,2-ethylenedioxy)bis(ethanethiol) and 0.0810g of 2-methyl-1,4-phenylenebis(4-(4-mercaptobutoxy)benzoate) (molecular formula: C 29H 32 O6S2 (Reaxys ID: 57446835), 0.0417 g of diselanediylbis(ethane-2,1-diyl)diacrylate (Reaxys ID: 31368792) and 0.007 g of benzoin dimethyl ether were added to the first mixture and subjected to a second heat-mixing treatment, followed by standing to obtain the second mixture;

[0105] 3) Mix 0.1g of dipropylamine with 1g of dichloromethane to obtain a thermal initiator solution. Mix the thermal initiator solution with the second mixture to obtain the first precursor.

[0106] 4) The first precursor is poured onto a glass substrate and coated with a scraper. The first thermal polymerization treatment is carried out at a temperature of 40°C for 24 hours to obtain the first prepolymer.

[0107] 5) The first prepolymer is subjected to a first photopolymerization treatment under ultraviolet light with a wavelength of 365nm for 10min to obtain a cholesteric phase liquid crystal elastomer color layer.

[0108] 2. Preparation of light-driven liquid crystal elastomer matrix layer

[0109] 1) 3.27 g of 2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, 0.93 g of 2,2'-(1,2-ethylenedioxy)diethylthiol, 0.065 g of pentaerythritol tetrakis(3-mercaptopropionic acid), 0.28 g of diselanediylbis(ethane-2,1-diyl)diacrylate (Reaxys ID: 31368792), 0.056 g of carbon nanotubes, 1 g of dipropylamine, and 0.05 g of benzoin dimethyl ether were added to tetrahydrofuran for a third thermal mixing treatment to obtain the precursor solution;

[0110] 2) Pour the precursor liquid into a polytetrahydrofuran mold, evaporate the organic solvent at 25°C, and then perform a second thermal polymerization treatment at 25°C for 24 hours to obtain the second precursor;

[0111] 3) The second precursor is subjected to a stretching treatment with a tensile strain of 200% to obtain the second prepolymer in a stretched state.

[0112] 4) The second prepolymer in the stretched state is subjected to a second photopolymerization treatment under ultraviolet light with a wavelength of 365nm for 10 minutes to obtain a light-driven liquid crystal elastomer matrix layer.

[0113] 3. Preparation of light-driven cholesteric liquid crystal elastomer composite films

[0114] After the cholesteric liquid crystal elastomer color layer is placed on the upper surface of the light-driven liquid crystal elastomer substrate layer, it is subjected to hot pressing to obtain the light-driven cholesteric liquid crystal elastomer composite film.

[0115] Example 2

[0116] The preparation of the light-driven cholesteric phase liquid crystal elastomer composite film provided in this embodiment is basically the same as that in Example 1, except that:

[0117] 2. Preparation of light-driven liquid crystal elastomer matrix layer

[0118] 1) The amount of photothermal filler added is 0.086g.

[0119] The preparation of the light-driven cholesteric liquid crystal elastomer composite film in this embodiment is basically the same as that in Example 1, except that the light-driven cholesteric liquid crystal elastomer composite film is prepared using the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer in this embodiment.

[0120] Example 3

[0121] The preparation of the light-driven cholesteric phase liquid crystal elastomer composite film provided in this embodiment is basically the same as that in Example 1, except that:

[0122] 2. Preparation of light-driven liquid crystal elastomer matrix layer

[0123] 1) The amount of photothermal filler added is 0.121g.

[0124] The preparation of the light-driven cholesteric liquid crystal elastomer composite film in this embodiment is basically the same as that in Example 1, except that the light-driven cholesteric liquid crystal elastomer composite film is prepared using the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer in this embodiment.

[0125] Example 4

[0126] The preparation of the light-driven cholesteric phase liquid crystal elastomer composite film provided in this embodiment is basically the same as that in Example 1, except that:

[0127] 3. Preparation of light-driven cholesteric liquid crystal elastomer composite films

[0128] The cholesteric liquid crystal elastomer color layer in this embodiment is patterned to obtain a cholesteric liquid crystal elastomer color layer with a firefly pattern; the cholesteric liquid crystal elastomer color layer with the firefly pattern is then placed on the upper surface of the light-driven liquid crystal elastomer substrate layer and subjected to hot pressing to obtain the desired result. Figure 8 The light-driven cholesteric phase liquid crystal elastomer composite film shown.

[0129] Comparative Example 1

[0130] The preparation of the light-driven cholesteric liquid crystal elastomer composite film provided in this comparative example is basically the same as that in Example 1, except that:

[0131] 1. Preparation of light-driven liquid crystal elastomer matrix layer

[0132] 1) The amount of photothermal filler added is 0g.

[0133] The preparation of the light-driven cholesteric liquid crystal elastomer composite film in this comparative example is basically the same as that in Example 1, except that the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer in this comparative example are used to prepare the light-driven cholesteric liquid crystal elastomer composite film.

[0134] Comparative Example 2

[0135] The preparation of the light-driven cholesteric liquid crystal elastomer composite film provided in this comparative example is basically the same as that in Example 1, except that:

[0136] 1. Preparation of color layer of cholesteric phase liquid crystal elastomer

[0137] 4) The temperature of the first thermal polymerization treatment is 25℃.

[0138] The preparation of the light-driven cholesteric liquid crystal elastomer composite film in this comparative example is basically the same as that in Example 1, except that the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer in this comparative example are used to prepare the light-driven cholesteric liquid crystal elastomer composite film.

[0139] During the preparation of the cholesteric liquid crystal elastomer color layer in this comparative example, the inventors discovered that a cholesteric liquid crystal elastomer color layer with good color could not be formed. The inventors analyzed the situation and believe the reason may be that the temperature during the first thermal polymerization process was too low, causing the acrylate components (2-methyl-1,4-phenylenebis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate, reactive liquid crystal DK756, (diselenodimethylbis(ethane-2,1-diyl))bis(4,1-phenylene)diacrylate) and the thiol components (2,2'-(1,2-ethylenedioxy)bis(ethanethiol, 2-methyl-1,4-phenylenebis(4-(4-mercaptobutoxy)benzoate)) to separate into phases and fail to polymerize effectively within the same system. Therefore, a well-colored cholesteric phase liquid crystal elastomer color layer cannot be formed, thus affecting the formation of the final light-driven cholesteric phase liquid crystal elastomer composite film.

[0140] Comparative Example 3

[0141] The preparation of the light-driven cholesteric liquid crystal elastomer composite film provided in this comparative example is basically the same as that in Example 1, except that:

[0142] 1. Preparation of color layer of cholesteric phase liquid crystal elastomer

[0143] 4) The temperature of the first thermal polymerization treatment is 80℃.

[0144] The preparation of the light-driven cholesteric liquid crystal elastomer composite film in this comparative example is basically the same as that in Example 1, except that the cholesteric liquid crystal elastomer color layer and the light-driven liquid crystal elastomer substrate layer in this comparative example are used to prepare the light-driven cholesteric liquid crystal elastomer composite film.

[0145] During the preparation of the cholesteric liquid crystal elastomer color layer in this comparative example, the inventors discovered that a cholesteric liquid crystal elastomer color layer with good color could not be formed. The inventors analyzed this and believe the reason may be that the temperature during the first thermal polymerization treatment was too high, which may have caused excessive decomposition of benzoin dimethyl ether, resulting in excessive free radicals. This led to an overly rapid thermal polymerization reaction, uncontrolled reaction system, and inability to form a stable cholesteric liquid crystal elastomer color layer, thus affecting the formation of the final light-driven cholesteric liquid crystal elastomer composite film.

[0146] Performance testing

[0147] 1. Testing of the color layer of cholesteric liquid crystal elastomer

[0148] 1) Apparent color

[0149] Figure 2 These are photographs of the cholesteric liquid crystal elastomer color layer in Example 1 of the present invention before and after tensile strain; wherein, Figure 2 'a' is a photograph taken with a camera of the cholesteric phase liquid crystal elastomer color layer in Example 1; Figure 2 b is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 45%; Figure 2 c is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after 60% tensile strain; Figure 2 d is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after 90% tensile strain; Figure 2 The 'e' is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 135%; the description of the colors in the photographs in this invention is based on the colors under natural light.

[0150] Depend on Figure 2It is known that the prepared cholesteric liquid crystal elastomer color layer is red (it appears red under natural light, but the photograph taken with a camera appears orange-yellow, and the actual color cannot be fully reflected in the photograph; the present invention uses the color under natural light as the standard). Under tensile strain, the cholesteric liquid crystal elastomer color layer changes from red to blue.

[0151] Figure 3 These are photographs of the cholesteric liquid crystal elastomer color layer in Example 1 of the present invention before and after a 45% tensile strain; wherein, Figure 3 A is a photograph taken with a camera of the cholesteric phase liquid crystal elastomer color layer in Example 1; Figure 3 B is a photograph taken with a camera of the cholesteric liquid crystal elastomer color layer in Example 1 after a tensile strain of 45%; the description of the colors in the photographs in this invention is based on the colors under natural light.

[0152] Depend on Figure 3 It can be seen that under 45% tensile strain, the cholesteric liquid crystal elastomer color layer changes from red to green. After relaxing the tensile strain, the cholesteric liquid crystal elastomer color layer can return to its initial shape and color, exhibiting reversible color-changing properties.

[0153] 2) Mechanochromic performance test

[0154] Figure 4 This is a reflection spectrum of the cholesteric phase liquid crystal elastomer color layer in Example 1 of the present invention, showing the change of the reflection peak with tensile strain.

[0155] Depend on Figure 4 It is known that the maximum tensile strain of the cholesteric liquid crystal elastomer color layer in Example 1 is 135%. During the stretching process, the reflection peak of the cholesteric liquid crystal elastomer color layer shifts from 680nm to 420nm, indicating that the cholesteric liquid crystal elastomer color layer has excellent mechanochromic ability.

[0156] In summary, the cholesteric liquid crystal elastomer color layer provided by the present invention has excellent mechanochromic properties.

[0157] 2. Testing of the light-driven liquid crystal elastomer matrix layer

[0158] 1) Apparent color

[0159] Figure 5 These are photographs of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 and Example 1 of the present invention; wherein, Figure 5 Photo A is a photograph of the light-driven liquid crystal elastomer matrix layer in Comparative Example 1; Figure 5 Photograph B is of the light-driven liquid crystal elastomer matrix layer in Example 1.

[0160] Depend on Figure 5It can be seen that the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 is white overall, while the light-driven liquid crystal elastomer substrate layer in Example 1 is black overall, indicating that the light-driven liquid crystal elastomer substrate layer provided by the present invention has good heat absorption capacity.

[0161] 2) Photoinduced shrinkage performance test

[0162] Figure 6 These are photographs of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 and Example 1 of the present invention before and after irradiation with infrared light; wherein, Figure 6 A is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 before and after being irradiated with infrared light. The infrared light intensity is 6.2W and the irradiation time is 30s. Among them, a is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1, and b is a photograph of the light-driven liquid crystal elastomer substrate layer in Comparative Example 1 after being irradiated with infrared light. Figure 6 B is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1 before and after infrared light irradiation. The infrared light intensity is 6.2W and the irradiation time is 30s. C is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1, and d is a photograph of the light-driven liquid crystal elastomer substrate layer in Example 1 after infrared light irradiation.

[0163] Depend on Figure 6 It can be seen that, compared with the light-driven liquid crystal elastomer substrate layer in Comparative Example 1, the liquid crystal elastomer in Embodiment 1 of the present invention has obvious photo-induced shrinkage capability.

[0164] 3) Photothermal performance testing

[0165] The photothermal performance of the light-driven liquid crystal elastomer substrate layers in Examples 1-3 and Comparative Example 1 was tested by irradiating them with infrared light, and the results are as follows: Figure 7 As shown.

[0166] Depend on Figure 7 It is known that when different amounts of photothermal filler are added, the photo-driven liquid crystal elastomer matrix layer has different photothermal properties. As the content of photothermal filler increases, the photothermal properties of the photo-driven liquid crystal elastomer matrix layer increase accordingly, and the temperature can reach up to 95°C after 30s of irradiation. This shows that the photo-driven liquid crystal elastomer matrix layer provided by the present invention has excellent photothermal properties.

[0167] 3. Testing of light-driven cholesteric liquid crystal elastomer composite films

[0168] Figure 9 These are photographs of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 of the present invention before and after tensile strain; wherein, Figure 9 a is a photograph taken with a camera of the light-driven cholesteric phase liquid crystal elastomer composite film in Example 4; Figure 9b is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after 83% tensile strain. Figure 9 c is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after 150% tensile strain; the color descriptions in the photographs in this invention are based on the colors under natural light.

[0169] Figure 10 These are photographs of the light-driven cholesteric phase liquid crystal elastomer composite film of the present invention before and after infrared light irradiation. The infrared light intensity was 6.2 W, and the irradiation time was 30 s. Figure 10 A is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film in Example 4 after a tensile strain of 150%. Figure 9 B is a photograph taken with a camera of the light-driven cholesteric liquid crystal elastomer composite film after 150% tensile strain and irradiation with infrared light; the color descriptions in the photographs in this invention are based on the colors under natural light.

[0170] Depend on Figures 8-9 It is known that in the light-driven cholesteric liquid crystal elastomer composite film, the cholesteric liquid crystal elastomer color layer exhibits color change characteristics when stretched, and can stably maintain the color effect after deformation. This may be because after the light-driven liquid crystal elastomer matrix layer is stretched, the liquid crystal network inside it is reoriented and can be stabilized, so that the color of the cholesteric liquid crystal elastomer color layer changes synergistically and can be maintained.

[0171] Depend on Figure 10 It is known that after being stimulated by infrared light, the matrix layer of the photodriven liquid crystal elastomer exhibits photo-induced shrinkage, while the color of the cholesteric liquid crystal elastomer color layer recovers to its initial color. This may be because after being stimulated by infrared light, the liquid crystal network in the matrix layer of the photodriven liquid crystal elastomer changes from parallel orientation to isotropic orientation, which macroscopically causes the shrinkage and deformation of the photodriven cholesteric liquid crystal elastomer composite film, thereby restoring the color of the cholesteric liquid crystal elastomer color layer to its initial color.

[0172] Depend on Figures 8-10It is known that the photo-driven cholesteric liquid crystal elastomer composite film provided in Example 4 of this invention possesses both mechanochromic and photo-shrinkable properties, exhibiting excellent external stimulus response characteristics. The inventors analyzed this and believe the reason may be that both the cholesteric liquid crystal elastomer color layer and the photo-driven liquid crystal elastomer matrix layer contain dynamic bond molecules. During hot pressing, the dynamic bond molecules in the cholesteric liquid crystal elastomer color layer and the photo-driven liquid crystal elastomer matrix layer undergo dynamic bond exchange reactions, leading to bond exchange at the small molecule level, chain entanglement at the polymer level, and adhesion between macroscopic interfaces. This allows the cholesteric liquid crystal elastomer color layer and the photo-driven liquid crystal elastomer matrix layer to achieve a tight connection through the self-healing of dynamic bonds, thereby realizing the coordinated movement of the cholesteric liquid crystal elastomer color layer and the photo-driven liquid crystal elastomer matrix layer. This coordinated movement enables the prepared photo-driven cholesteric liquid crystal elastomer composite film to simultaneously possess photo-shrinkable and mechanochromic properties. Figure 1 (4)).

[0173] In summary, the light-driven cholesteric liquid crystal elastomer composite film prepared by this invention possesses both mechanochromic and photo-shrinkable properties, exhibits excellent photothermal properties and external stimulus response characteristics, and can stably maintain the color effect after deformation. It can be applied to fields such as information storage and photonic crystals.

[0174] 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 light-driven cholesteric phase liquid crystal elastomer composite film, characterized in that, It includes a cholesteric liquid crystal elastomer color layer and a light-driven liquid crystal elastomer matrix layer stacked together; The cholesteric phase liquid crystal elastomer color layer is prepared from a first raw material system comprising a first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, an acrylate chiral agent, a dithiol, a first acrylate dynamic bond molecule, a first photoinitiator, and a first thermal initiator. The light-driven liquid crystal elastomer matrix layer is prepared from a second raw material system comprising a second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator; The cholesteric phase liquid crystal elastomer color layer is disposed on the upper surface of the light-driven liquid crystal elastomer substrate layer and then subjected to hot pressing to obtain the light-driven cholesteric phase liquid crystal elastomer composite film.

2. The light-driven cholesteric liquid crystal elastomer composite film according to claim 1, characterized in that, In the second raw material system, the photothermal filler is at least one of carbon nanotubes, carbon fibers, graphene, carbon black, and polydopamine.

3. The light-driven cholesteric liquid crystal elastomer composite film according to claim 2, characterized in that, In the second raw material system, the mass percentage of the photothermal filler is 0.1wt% to 2.0wt%.

4. The light-driven cholesteric liquid crystal elastomer composite film according to claim 3, characterized in that, In the second raw material system, the mass percentage of the second acrylate liquid crystal monomer is 50wt% to 60wt%, the mass percentage of the dithiol chain extender is 10wt% to 20wt%, the mass percentage of the polythiol crosslinking agent is 1wt% to 5wt%, the mass percentage of the second acrylate dynamic bond molecule is 1wt% to 10wt%, the mass percentage of the second photoinitiator is 0.5wt% to 1wt%, and the mass percentage of the second thermal initiator is 15wt% to 20wt%.

5. The light-driven cholesteric liquid crystal elastomer composite film according to claim 1, characterized in that, In the first raw material system, the mass ratio of the first acrylate liquid crystal monomer to the vinyl ether liquid crystal monomer is 10:(5-10); the mass of the acrylate chiral agent accounts for 1%-10% of the total mass of the first acrylate liquid crystal monomer and the vinyl ether liquid crystal monomer; the mass of the first acrylate dynamic bond molecule accounts for 5%-10% of the total mass of the first acrylate liquid crystal monomer, the vinyl ether liquid crystal monomer, and the acrylate chiral agent; the molar mass of the dithiol accounts for 80%-90% of the total molar mass of the first acrylate liquid crystal monomer, the acrylate chiral agent, the first acrylate dynamic bond molecule, and the vinyl ether liquid crystal monomer; the mass of the first photoinitiator accounts for 1%-5% of the total mass of the first raw material system; and the mass of the first thermal initiator accounts for 0.5%-1% of the total mass of the first raw material system.

6. The light-driven cholesteric liquid crystal elastomer composite film according to claim 1, characterized in that, In the first acrylate dynamic bond molecule or the second acrylate dynamic bond molecule, the dynamic bond molecule is any one of disulfide bond molecule, diselenide bond molecule, borate ester bond molecule, and boron-oxygen hexacyclic molecule; And / or, the hot pressing treatment is performed at a pressure of 50N to 500N, a temperature of 40℃ to 100℃, and a time of 4h to 24h.

7. A method for preparing a light-driven cholesteric phase liquid crystal elastomer composite film according to any one of claims 1 to 6, characterized in that, Includes the following steps: A first acrylate liquid crystal monomer, a vinyl ether liquid crystal monomer, and an acrylate chiral agent are subjected to a first thermal mixing treatment to obtain a first mixture; dithiol, a first acrylate dynamic bond molecule, and a first photoinitiator are added to the first mixture for a second thermal mixing treatment to obtain a second mixture; the first thermal initiator is mixed with dichloromethane to obtain a first thermal initiator solution; the first thermal initiator solution is mixed with the second mixture to obtain a first precursor; the first precursor is coated onto a substrate and then subjected to a first thermal polymerization treatment and a first photopolymerization treatment in sequence to obtain a cholesteric phase liquid crystal elastomer color layer; A second acrylate liquid crystal monomer, a dithiol chain extender, a polythiol crosslinking agent, a second acrylate dynamic bond molecule, a photothermal filler, a second thermal initiator, and a second photoinitiator are added to an organic solvent for a third thermal mixing treatment to obtain a precursor liquid. The precursor liquid is poured into a mold, and after evaporation of the organic solvent, a second thermal polymerization treatment is performed to obtain a second precursor. The second precursor is stretched and then subjected to a second photopolymerization treatment to obtain a photodriven liquid crystal elastomer matrix layer. The cholesteric phase liquid crystal elastomer color layer is disposed on the upper surface of the light-driven liquid crystal elastomer substrate layer and then subjected to hot pressing to obtain the light-driven cholesteric phase liquid crystal elastomer composite film.

8. The method for preparing the light-driven cholesteric liquid crystal elastomer composite film according to claim 7, characterized in that, The temperature of the first thermal polymerization treatment is 40℃~60℃; And / or, the tensile strain during the stretching treatment is 200%.

9. The method for preparing the light-driven cholesteric phase liquid crystal elastomer composite film according to claim 7, characterized in that, The first acrylate liquid crystal monomer or the second acrylate liquid crystal monomer is at least one of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, 2-methyl-1,4-phenylene bis(4-(4-(acryloyloxy)butoxy)benzoate, 2-methyl-1,4-phenylene bis(4-((6-(acryloyloxy)hexyl)oxy)benzoate, (4-(((4-((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoic acid 2-methyl-1,4-diphenol ester, and 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate; And / or, the acrylate chiral agent includes reactive liquid crystal DK756; And / or, the dithiol or the dithiol chain extender is at least one of ethylene glycol dithioacetate, di(mercaptoacetic acid)-1,4-butanediol, 2,2'-(1,2-ethylenedioxy)bis(ethylene ethyl mercaptan), 2-methyl-1,4-phenylenebis(4-(4-mercaptobutoxy)benzoate), and ethylene dithiol; And / or, the first photoinitiator or the second photoinitiator is at least one of benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-methylphenylpropane-1-one, bis(2,6-difluoro-3-pyrrolephenyldicyclopentadiene), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone; And / or, the first thermal initiator or the second thermal initiator is at least one of alkoxides, basic amines, metal hydrides, and amine lithium; And / or, the vinyl ether liquid crystal monomers include 4-[4-(ethoxy)butoxy]-,1,1'-(2-methyl-1,4-phenylene)benzoate; And / or, the polythiol crosslinking agent is at least one of pentaerythritol tetra-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), and pentaerythritol tetra(3-mercaptopropionic acid) ester.

10. The application of the light-driven cholesteric liquid crystal elastomer composite film according to any one of claims 1 to 6 in the preparation of optical drivers, displays, and sensors.

Images