Polymerizable chiral agents and methods of making and using the same

Abstract

The application discloses a polymerizable chiral agent and a preparation method and application thereof, and the polymerizable chiral agent has a structure as shown in the following general formula I-1 or I-2: (formula I-1) and (formula I-2); wherein at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl, and n is a positive integer in 1-6. The polymerizable chiral agent disclosed by the application has a larger conjugated system and chiral structure, a higher birefringence, a polymerizable methacrylate group or acrylate group, and when used in a liquid crystal composition, the polymerizable chiral agent has good compatibility with other components and is convenient to blend.

Description

Technical Field

[0001] This invention relates to the field of optical materials, and more particularly to polymerizable chiral agents, their preparation methods, and applications. Background Technology

[0002] High birefringence liquid crystal materials, as key functional materials in the field of modern optical engineering, play an important role in core technology scenarios such as phase delayers, laser detectors, 3D displays and optical communications.

[0003] Existing liquid crystal materials, such as phenyl ester liquid crystals, generally have a birefringence (Δn) below 0.27, while acrylate liquid crystals generally have a Δn below 0.2, which cannot meet the requirements of high-precision optics and limits their application in high-density gratings. Furthermore, existing birefringence liquid crystal materials lack chiral units themselves, requiring the addition of chiral agents to induce the formation of a cholesteric phase in nematic liquid crystals. The poor compatibility of chiral agents with other components and the unstable properties of the prepared liquid crystal films make them unsuitable for the preparation of polymeric liquid crystals. Summary of the Invention

[0004] In view of this, the present invention proposes a polymerizable chiral agent, its preparation method and application, aiming to achieve the following: it can be used as a chiral agent and can also carry out polymerization reactions, has a high birefringence, and is stable in properties when used in the preparation of polymeric liquid crystals.

[0005] The polymerizable chiral agent proposed in the first aspect of this invention has the following general structural formula: Formula I-1 or Formula I-2: (Equation I-1), and, (Formula I-2); In this group, at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl, and n is a positive integer from 1 to 6.

[0006] As can be seen from the above technical solution, the polymerizable chiral agent proposed in the first aspect of this invention has a main skeleton containing a chiral binaphthalene, and the binaphthalene has a conjugated π system. The binaphthalene is connected to a benzene ring through a carbon-carbon triple bond, and the benzene ring has at least one electron-withdrawing group. These groups can be further combined with a conjugated system to achieve a larger conjugated system. At the same time, the two side chains formed by the two sets of carbon-carbon triple bonds, the benzene ring, and the electron-withdrawing group can also form a certain steric hindrance, so that the skeleton with the above-mentioned larger conjugated system can maintain a certain chiral structure and effectively prevent racemization. Since the main skeleton itself has a chiral structure, it acts as a chiral agent. The main skeleton is also connected with (meth)acrylate groups, or the main skeleton is connected with acrylate groups through alkyl groups of a specific chain length. The acrylate groups can provide better polymerization performance in the subsequent polymerization process, improve the polymerizability of the entire polymerizable chiral agent, and when used in liquid crystal compositions, it has good compatibility with other components, is easy to blend, and remains relatively stable after mixing, making it convenient for storage and use. The use of alkyl groups of a specific chain length can adjust the solubility of the polymerizable chiral agent and also adjust its own viscosity.

[0007] The second aspect of this invention provides a method for preparing a polymerizable chiral agent, comprising the following steps: reacting a bromofatty alcohol with a first compound via an acylation reaction to generate a polymerizable chiral agent with the general structural formula I-1. The first product; the first compound is methacryloyl chloride or acryloyl chloride, wherein the bromo fatty alcohol has 1 to 6 carbon atoms; the first product is subjected to a nucleophilic substitution reaction with a halo-naphthol to produce a compound with the general structural formula [structure omitted]. The second product, R4, is selected from H or methyl; the second product is coupled with a terminal acetylenoid compound to produce a compound with the general structural formula [structure omitted]. A polymerizable chiral agent wherein at least one of R1, R2, and R3 is an electron-withdrawing group, and the remainder are H; or, the preparation of a polymerizable chiral agent with the general structural formula I-2 comprises the following steps: subjecting a first compound to an oxyacylation reaction with a halo-binaphthol to generate a compound with the general structural formula I-2. The fourth product is obtained, wherein the first compound is methacryloyl chloride or acryloyl chloride; the fourth product is coupled with a terminal acetylenoid compound to produce a compound with the general structural formula [structure omitted]. A polymerizable chiral agent in which at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H.

[0008] As can be seen from the above technical solutions, the method for preparing polymerizable chiral agents proposed in the second aspect of the present invention, through multi-step synthesis, can introduce a chiral, highly conjugated structure with a binaphthyl backbone and formed by carbon-carbon triple bonds, benzene rings and electron-withdrawing groups into the polymerizable chiral agent as the backbone; it can also introduce side chains of the required chain length and reactive functional groups (meth)acrylates into the polymerizable chiral agent, thereby obtaining a polymerizable chiral agent with high birefringence, high polymerizability, and good compatibility, which can be further applied in liquid crystal mixtures.

[0009] The liquid crystal composition proposed in the third aspect of the present invention includes at least the aforementioned polymerizable chiral agent or the polymerizable chiral agent prepared by the aforementioned method for preparing the polymerizable chiral agent; and further includes reactive liquid crystal, nematic liquid crystal, and initiator.

[0010] As can be seen from the above technical solutions, the liquid crystal composition proposed in the third aspect of this invention, by applying a polymerizable chiral agent to the liquid crystal composition, allows the polymerizable chiral agent to polymerize under induction conditions, and it itself forms a helical structure with a certain chirality. The reactive liquid crystal, under the action of an initiator, can construct a polymer backbone along the chiral helical structure during polymerization to stabilize or lock the orientation of the liquid crystal. The nematic liquid crystal, under the action of the polymerizable chiral agent, can form a cholesteric liquid crystal with a helical structure from a non-chiral structure, enabling the system to acquire optical properties such as selective reflection of circularly polarized light. Thus, without the need for additional chiral agents, the components in the liquid crystal composition can be polymerized to form a stable polymer film with a specific helical structure. It also has a high birefringence and can adjust the liquid crystal properties.

[0011] The optical device according to the fourth aspect of the present invention includes a structure made using the aforementioned liquid crystal composition; and / or, the optical device includes a polarizer holographic grating, the polarizer holographic grating including a thin film made using the aforementioned liquid crystal composition.

[0012] As can be seen from the above technical solutions, the optical device proposed in the fourth aspect of this application has relatively stable liquid crystal properties and wide-temperature-range nematic / cholesterol properties, making it suitable for optical devices in extreme environments. The fabricated polarizing holographic grating has a birefringence greater than or equal to 0.27 and a diffraction efficiency greater than 75%.

[0013] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the embodiments of the present invention. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the general structural formula of the polymerizable chiral agent proposed in some embodiments of the present invention; Figure 2This is a schematic diagram of the general structural formula of the polymerizable chiral agent proposed in other embodiments of the present invention; Figure 3 This is a schematic diagram of the molecular structure of a nematic liquid crystal LC1057 provided in some embodiments of this application; Figure 4 This is a schematic diagram of the molecular structure of a nematic liquid crystal PLC051 provided in some embodiments of this application; Figure 5 This is a schematic diagram of the molecular structure of the initiator Irgacure 651 provided in some embodiments of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0016] High birefringence liquid crystal materials are key functional materials in the field of modern optical engineering and have important applications in phase delayers, laser detectors, 3D displays and optical communications.

[0017] Traditional liquid crystal materials, such as nematic liquid crystals, have low birefringence (Δn) (typically <0.2), making it difficult to meet the requirements of high-precision optical devices for fast response and low power consumption. For example, acrylate liquid crystals have polymerizable properties, but their birefringence is generally lower than 0.2; phenyl ester liquid crystals, for instance, typically have Δn below 0.27, which cannot meet the requirements of high-precision optics.

[0018] Existing birefringence liquid crystal materials do not possess chirality themselves and require the addition of chiral agents to induce the formation of a cholesteric phase in the helical structure of nematic liquid crystals or other liquid crystals. The added chiral agents have poor compatibility with other components, and the prepared liquid crystal polymer films are unstable, making them difficult to use for the preparation of polymeric liquid crystals.

[0019] In view of this, this application proposes a polymerizable chiral agent and its preparation method, a method for preparing a polymerizable chiral agent, a liquid crystal composition, and an optical device, aiming to improve the Δn of the polymerizable chiral agent and enhance its polymerizability. When the polymerizable chiral agent is applied to the liquid crystal composition, it can polymerize better, has good compatibility with other components, and can provide chiral induction for other liquid crystal components, effectively improving the liquid crystal properties of the optical device prepared by the liquid crystal composition. When applied to a polarizing holographic grating, it can achieve a birefringence greater than or equal to 0.27 and a diffraction efficiency >75%.

[0020] The following describes, by way of example, a method for preparing a polymerizable chiral agent according to an embodiment of this application.

[0021] Combination Figure 1 and Figure 2 As shown in the embodiments of this application, a polymerizable chiral agent has the following general structural formula: Formula I-1 or Formula I-2: (Equation I-1), and, (Formula I-2); In this group, at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl, and n is a positive integer from 1 to 6, for example, n is 1, 2, 3, 4, 5, 6.

[0022] It should be noted that in the polymerizable chiral agents of Formulas I-1 and I-2 mentioned above in the embodiments of this application, the chirality of the naphthalene part can be R or S, as long as it can induce the chirality of other liquid crystal components in a certain direction.

[0023] As can be seen from the above, the polymerizable chiral agent proposed in this application has a binaphthalene with a certain degree of chirality in its main skeleton. Since the main skeleton itself has a chiral structure, it has the function of a chiral agent. When used in liquid crystal compositions, it can utilize its own chiral helical structure to induce other liquid crystal components to form a cholesteric phase during the polymerization process, so that no additional chiral agent needs to be added during application.

[0024] Binaphthyl, a polymerizable chiral agent, possesses a conjugated π-system. Binaphthyl connects to a benzene ring via a carbon-carbon triple bond, and the benzene ring has at least one electron-withdrawing group. The interaction between these groups can further enhance the conjugated system, achieving a larger conjugated structure. The long π-conjugated system of the two naphthalene rings can improve the optical anisotropy of the molecule, laying the structural foundation for high birefringence. Simultaneously, the two side chains formed by the two sets of carbon-carbon triple bonds, the benzene ring, and the electron-withdrawing group can also create steric hindrance, allowing the skeleton with the aforementioned large conjugated system to maintain a certain chiral structure and effectively preventing racemization. The acetylidene group can maintain the extension of the conjugated direction of its corresponding naphthalene ring. The two side chains formed by the two acetylidene groups and the electron-withdrawing group connected to the acetylidene group can form conjugated structures in different directions with their respective connected naphthalene rings, which is beneficial for binaphthyl to further maintain its chirality. The two chiral structural parts can maintain a high degree of molecular order and have different polarizabilities along the long and short axes of their respective naphthalene rings, exhibiting high optical anisotropy and providing the necessary structural basis for the high birefringence of the entire compound.

[0025] The main skeleton of the polymerizable chiral agent is also connected with (meth)acrylate groups, or with acrylate groups connected through alkyl groups of a specific chain length. The acrylate groups can provide better polymerization performance in the subsequent polymerization process, and improve the polymerizability of the entire polymerizable chiral agent. When used in liquid crystal compositions, since other components usually also have polymerizable acrylate groups, the polymerizable chiral agent has good compatibility with other components, is easy to blend, and can remain relatively stable after mixing, making it convenient to store and use.

[0026] Based on this, the chiral binaphthyl host in the polymerizable chiral agent is further fused with the two acrylate side chains, which reduces the difficulty of synthesizing high refractive index segments and achieves good compatibility of the polymerizable chiral agent with other liquid crystal components, which is beneficial for preparing uniform polymer films.

[0027] For polymerizable chiral agents containing alkyl groups of a specific chain length, both the solubility of the polymerizable chiral agent and its viscosity can be adjusted.

[0028] As can be seen from the above, the polymerizable chiral agent of the present invention can combine chiral units and polymerizable acrylate groups into one, achieving a balance between chiral polymerizability and high birefringence characteristics.

[0029] In some embodiments, the electron-withdrawing group may be selected from at least one of -F, -CN, -NCS, -NCO, and -CHO. Exemplarily, -CN (i.e., cyano), -NCS (i.e., isothiocyanate group), and -NCO (i.e., isocyanate) can achieve strong electron-withdrawing properties, which is beneficial for improving the mobility of the electron cloud within the entire conjugated framework and increasing the polarizability of the molecule. Exemplarily, -F (i.e., fluorine) has a certain inductive effect and can achieve p-π conjugation with the π electron cloud of the benzene ring through its lone pair electrons, thereby achieving certain electron-withdrawing properties and adjusting the solubility and stability of the entire polymerizable chiral agent.

[0030] In some embodiments, n can be a positive integer from 2 to 6. For example, n can be 2, 3, 4, 5, 6, or within the range formed by any two of the aforementioned specific values. By further limiting the number of alkyl groups in the side chain to the above range, the solubility of the polymerizable chiral agent can be further improved, thereby enabling better miscibility with other components during application.

[0031] In some embodiments, the polymerizable chiral agent may be selected from compounds having the following structural formulas, denoted as A6-1, A6-2, A6-3, A6-4, A6-5, A6-6, A6-7, and A6-8, respectively.

[0032] The structural formula of A6-1 is: Each benzoynyl group here is attached to an electron-withdrawing group, and the electron-withdrawing group is selected from -CN. The remaining benzoynyl groups are all attached to H. R4 here is selected from H, and n is 3.

[0033] The structural formula of A6-2 is: Each benzoynyl group here is connected to an electron-withdrawing group, and the electron-withdrawing group is selected from -CN. The remaining benzoynyl groups are all connected to H. R4 here is selected from H, and the naphthalene is directly connected to the acrylate group, and n is 0.

[0034] The structural formula of A6-3 is: Each benzoynyl group here is connected to two electron-withdrawing groups, namely -CN and -F, and the remaining benzoynyl groups are connected to H; R4 here is selected from H, and n is 3.

[0035] The structural formula of A6-4 is: Each benzoynyl group here is connected to three electron-withdrawing groups, and the electron-withdrawing groups are -CN and two -F groups respectively; R4 is selected from H, and n is 3.

[0036] The structural formula of A6-5 is: Each benzoynyl group here is connected to an electron-withdrawing group, and the electron-withdrawing group is -NCS. The remaining benzoynyl groups are all connected to H. R4 here is selected from H, and n is 3.

[0037] The structural formula of A6-6 is: Each benzoynyl group here is connected to an electron-withdrawing group, and the electron-withdrawing group is -NCO. The remaining benzoynyl groups are all connected to H. R4 here is selected from H, and n is 3.

[0038] The structural formula for A6-7 is: Each benzoynyl group here is connected to an electron-withdrawing group, and the electron-withdrawing group is -CN. The remaining benzoynyl groups are connected to H. R4 is selected from H, and n is 3.

[0039] The structural formula of A6-8 is: Each benzoynyl group here is connected to an electron-withdrawing group, and the electron-withdrawing group is -CN. The remaining benzoynyl groups are all connected to H. R4 here is selected from H, and n is 3.

[0040] The compounds with specific structural formulas given above are all illustrative examples. Those skilled in the art will understand that the electron-withdrawing groups can be other combinations, R4 can be methyl, and n can be 1, 2, 4, 5, or 6.

[0041] The preparation method of the polymerizable chiral agent used in the foregoing embodiments is described below by way of example.

[0042] The embodiments of this application propose a method for preparing a polymerizable chiral agent for the foregoing embodiments. The preparation of a polymerizable chiral agent with the general structural formula I-1 includes steps S110, S210, and S310.

[0043] Step S110: The bromo fatty alcohol is acylated with the first compound to produce a compound with the general structural formula: The first product; the first compound can be methacryloyl chloride or acryloyl chloride, and the number of carbon atoms in the bromofatty alcohol can be 1 to 6. In this step, the hydroxyl group of the bromofatty alcohol acts as a nucleophile, attacking the carbonyl carbon attached to Cl in methacryloyl chloride or acryloyl chloride, eliminating the chlorine atom and regenerating a carbonyl group, thereby introducing acrylate onto the bromofatty chain to form a (meth)acrylate attached to a carbon chain of a certain length, while the -Br at the end of the carbon chain facilitates subsequent reactions.

[0044] In some embodiments, the bromo fatty alcohol may be selected from at least one of methanol bromide, 2-bromoethanol, 3-bromo-1-propanol, 4-bromo-1-butanol, 5-bromo-1-pentanol, and 6-bromo-n-hexanol. These bromo fatty alcohols can respectively bring carbon chains with n=1, 2, 3, 4, 5, and 6 to the first product, thereby enabling the (meth)acrylate to be linked to the reactive functional group -Br through a carbon chain of a certain length, providing a structural basis for subsequent further linkage to binaphthylene and the formation of the required carbon chain length and the required polymerizable functional group.

[0045] In some embodiments, the first compound may be acryloyl chloride. Acryloyl chloride reacts more rapidly in step S110, exists in the form of acrylate after the reaction, and ultimately serves as the polymerizable reactive functional group of the polymerizable chiral agent. It causes less disturbance to binaphthyl during polymerization and can polymerize more quickly, which is beneficial for the polymerizable chiral agent to maintain high order, specific helical characteristics, and chirality during polymerization. In other embodiments, the first compound may be methacryl chloride. Methacryl chloride, after participating in the polymerization reaction in step S110, can form a harder polymeric structure and a polymeric structure with higher thermal stability.

[0046] In some embodiments, the acylation reaction of a bromofatty alcohol with a first compound may include: dissolving the bromofatty alcohol in a first organic solvent, adding an acid-binding agent, adding the first compound in an ice-water bath, and completing the reaction at room temperature, followed by post-treatment to obtain the first product. Adding the first compound in an ice-water bath effectively prevents the polymerization of (meth)acryloyl chloride, making the reactants more stable and reducing byproducts.

[0047] The first organic solvent can make the reaction system more homogeneous. For example, the first organic solvent is selected from at least one of dichloromethane, trichloromethane, tetrahydrofuran and ethyl acetate. For example, when dichloromethane is used, it also has the advantages of low boiling point and easy post-processing.

[0048] The acid-binding agent neutralizes the hydrogen chloride produced in the reaction, thus promoting the reaction in the forward direction. For example, the acid-binding agent is selected from at least one of triethylamine and N,N-diisopropylethylamine.

[0049] Adding (meth)acryloyl chloride as the first compound under ice-water bath conditions can effectively prevent the polymerization of acryloyl chloride, making the properties of each reactant more stable and reducing byproducts.

[0050] The reaction is easier to perform at room temperature, which is exemplarily defined as room temperature. For example, the reaction time at room temperature is 2 to 8 hours. Room temperature is easier to operate; for instance, room temperature reaction times include values ​​such as 2h, 2.1h, 2.2h, 2.3h, 2.5h, 2.8h, 3h, 3.4h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, 4.2h, 4.5h, 5h, 5.3h, 5.8h, 6h, 6.4h, 6.6h, 7h, 7.2h, 7.5h, and 8h, as well as ranges between any two of the above specific values, thereby enabling a more complete acylation reaction.

[0051] For example, the molar ratio of bromofatty alcohol to (meth)acryloyl chloride can be 1:1.1 to 2.5, such as molar ratios including 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.58, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, and ranges including any two of the above specific values. An excess of (meth)acryloyl chloride can ensure that all hydroxyl groups on the bromofatty alcohol react fully with (meth)acryloyl chloride, thereby increasing the yield of the polymerizable chiral agent.

[0052] In some embodiments, step S110 may further include the following post-processing steps: Exemplarily, the reaction solution is extracted with dichloromethane. Exemplarily, the solvent can be removed by vacuum distillation, for example, by rotary evaporation. Exemplarily, the product can be purified by silica gel column chromatography, for example, using silica gel column chromatography with dichloromethane / petroleum ether (1:1) as the eluent.

[0053] The chemical reaction equation for step S110 is listed below, in which the bromo fatty alcohol (denoted as A1) undergoes an acylation reaction with the first compound to give the first product (denoted as A2).

[0054] Wherein, R4 is selected from H or methyl, and n is a positive integer from 1 to 6, for example, n is 1, 2, 3, 4, 5, or 6.

[0055] Step S210: The general structural formula is The first product undergoes a nucleophilic substitution reaction with a halo-naphthol to produce a product with the general structural formula [structure omitted]. The second product, R4, is selected from H or methyl. In step S210, the hydroxyl group on the halo-naphthol undergoes a nucleophilic substitution reaction with the Br of the first product to form two side chains with carbon chains of a certain length and (meth)acrylate, which can retain the original chiral configuration of the halo-naphthol and retain the reactive group X on the halo-naphthol.

[0056] In some embodiments, the general structural formula of halo-binaphthol can be: For example, the halo-binaphthols can be selected from at least one of (R)-3,3'-diiodo-1,1'-binaphthol, (R)-6,6'-dibromo-1,1'-bis-2-naphthol, and 4,4'-dibromo-[1,1'-binaphthyl]-2,2'-diol. In these embodiments, each halo-binaphthol has a chiral unit that can provide the required chiral unit for the synthesized second product in step S210. The chiral configuration of the halo-binaphthol remains unchanged after the reaction, providing the required structural basis for the final synthesis of a polymerizable chiral agent. The position of the hydroxyl groups in these halo-binaphthols determines the position of the added carbon chain, and each molecule of these three halo-binaphthols has two hydroxyl groups, which can form two side chains. The position of the halogen groups in these halo-binaphthols determines the position where the terminal acetylenoid compound can be added in the subsequent step S310, and the number of halogen groups determines the position of the terminal acetylenoid compound that can be added. The halogen group of 3,3'-diiodo-1,1'-binaphthol can be I, while the halogen group of (R)-6,6'-dibromo-1,1'-bis-2-naphthol and 4,4'-dibromo-[1,1'-binaphthol]-2,2'-diol can be Br.

[0057] In some embodiments, the molar ratio of the first product to the halo-binaphthol can be 2 to 5:1, for example, the molar ratio includes values ​​such as 2:1, 2.069:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.2:1, 3.6:1, 4:1, 4.3:1, 4.6:1, 5:1, and the range of values ​​including any two of the above specific values. By making the first product slightly excessive, the halo-binaphthol can be completely converted, so that the two hydroxyl groups in the halo-binaphthol in each molecule can be connected to (meth)acrylates with a certain carbon chain length and reactive functional groups, so that the hydroxyl groups react completely.

[0058] In some embodiments, the nucleophilic substitution reaction of the first product with halo-naphthol comprises: dissolving the first product, halo-naphthol, and a basic auxiliary agent in a second organic solvent, refluxing and stirring at 60°C to 80°C for 5 to 7 hours, and then obtaining the second product after post-treatment. The refluxing and stirring at 60°C to 80°C for 5 to 7 hours includes values ​​of 60°C, 65°C, 70°C, 75°C, 80°C, and any range between any two of these values; the reaction time includes values ​​of 5 hours, 5.5 hours, 5.8 hours, 6 hours, 6.4 hours, 6.6 hours, 7 hours, and any range between any two of these values. Within the above reaction temperature and time, the halo-naphthol reaction is promoted, the hydroxyl group conversion is more complete, the nucleophilic substitution reaction has a certain rate, and double substitution can be achieved.

[0059] For example, the basic auxiliary can be selected from potassium carbonate, sodium carbonate, cesium carbonate, potassium fluoride, and sodium hydroxide. During the nucleophilic substitution process, the basic auxiliary abstracts a hydrogen proton from the hydroxyl group of naphthol, enhancing the nucleophilicity of the oxygen atom of the halo-naphthol, thereby facilitating the attack on the carbon bonded to Br in the first product and realizing the nucleophilic substitution reaction. It can also neutralize the generated HBr during the reaction process, keeping the reaction system in an alkaline environment so that the reaction can continue.

[0060] For example, the second organic solvent can be selected from at least one of acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and 1,4-dioxane. When multiple solvents are selected, the ratio can be chosen to ensure that each solvent is miscible and can dissolve the first product, halonaphthol, basic auxiliaries, etc. These second organic solvents will not form hydrogen bonds with the phenoxy anion of halonaphthol, thus ensuring the normal progress of the nucleophilic substitution reaction.

[0061] For example, the post-processing step to obtain the second product can be: filtration and dichloromethane extraction, which can dissolve the second product in dichloromethane as much as possible, separate it from other unreacted water-soluble salts, and separate it into layers. This facilitates the removal of unreacted alkaline auxiliaries such as potassium carbonate during filtration. For example, in the crude product obtained by column chromatography, some byproducts are removed to improve the purity of the second product. For example, recrystallization of the crude product with petroleum ether and methanol forms a second product with extremely high purity, uniform crystallinity, and regular arrangement, facilitating further steps in step S310.

[0062] The chemical reaction equation for step S210 is listed below, in which the first product (denoted as A2) undergoes a nucleophilic substitution reaction with halo-naphthol (denoted as A3) to generate the second product (denoted as A4).

[0063]

[0064] Wherein, R4 is selected from H or methyl, n is a positive integer from 1 to 6, for example, n is 1, 2, 3, 4, 5, 6; X is selected from Br or I.

[0065] Step S310: The second product is coupled with a terminal acetylenoid compound to generate a compound with the general structural formula: A polymerizable chiral agent (denoted as I-1) wherein at least one of R1, R2, and R3 is an electron-withdrawing group, and the rest are H. In step S310, a polymerizable chiral agent is generated by coupling the X of the second product with the carbon-carbon triple bond of the terminal acetylenoid compound. This agent not only retains the chiral configuration, a certain length of carbon chain, and reactive functional groups of the second product, but also retains the acetylinyl group, benzene ring, and electron-withdrawing group of the terminal acetylenoid compound.

[0066] In some embodiments, the general structural formula of the terminal acetylenoid compound is as follows: For example, the terminal acetylenoid compound can be selected from at least one of 4-acetylenol-benzonitrile, 4-acetylenol-3-fluorobenzonitrile, 4-acetylenol-3,5-difluorobenzonitrile, 1-acetylenol-4-isothiocyanate phenylene, 1-acetylenol-4-isocyanate phenylene, 4-acetylenol-2,3-difluorobenzaldehyde, and 1-acetylenol-2,4,5-trifluorobenzene. The position and type of the electron-withdrawing group differ in these reactants. 4-acetylenol-benzonitrile can provide -CN as an electron-withdrawing group, and 4-acetylenol-3-fluorobenzene... Formonitrile can provide -CN and -F as electron-withdrawing groups; 4-ethynyl-3,5-difluorobenzonitrile can provide -CN and -F as electron-withdrawing groups; 1-ethynyl-4-isothiocyanate phenylene can provide -NCS as an electron-withdrawing group; 1-ethynyl-4-isocyanate phenylene can provide -NCO as an electron-withdrawing group; 4-ethynyl-2,3-difluorobenzaldehyde can provide -CHO and two -F as electron-withdrawing groups; 1-ethynyl-2,4,5-trifluorobenzene can provide three electron-withdrawing groups, all of which are -F.

[0067] In some embodiments, the molar ratio of the second product to the terminal alkynylbenzene compound can be 1:2 to 6. An excess of the terminal alkynylbenzene compound promotes the complete reaction of halogen groups at various sites in the second product, achieving two coupling reactions per molecule of the second product. For example, molar ratios include values ​​such as 1:2, 1.2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.5, 1:4, 1:4.4, 1:4.8, 1:5, 1:5.2, 1:5.5, and 1:6, as well as ranges consisting of any two of the above specific values.

[0068] In some embodiments, the coupling reaction of the second product with the terminal alkynylbenzene compound may include: dissolving the second product, the terminal alkynylbenzene compound, the palladium source, the co-catalyst, and the ligand in a third organic solvent under nitrogen or an inert gas atmosphere, refluxing and stirring at 60°C to 110°C for 6 h to 28 h, and then obtaining the polymerizable chiral agent of formula I-1 after post-treatment. For example, the reaction temperature includes values ​​such as 60℃, 63℃, 65℃, 68℃, 70℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 88℃, 90℃, 92℃, 95℃, 97℃, 100℃, 101℃, 104℃, 107℃, and 110℃, as well as ranges between any two of the above specific values. This provides the activation energy required for the second product during the reaction, making it easier for palladium sources, such as palladium atoms, to insert into the CX bond, facilitating the oxidative addition between the palladium catalyst and the second product containing X. Subsequently, after substitution with terminal alkyne benzene compounds and ligands, and reduction and elimination, a polymerizable chiral agent is obtained; making the reaction process more controllable. For example, the reflux reaction time includes values ​​such as 6h, 10h, 15h, 20h, 21h, 23h, 24h, 25h, 26h, 27h, and 28h, as well as a range of values ​​between any two of the above specific values. By controlling the reaction time of the coupling reaction in step S310, the coupling reaction is made more complete and thorough, and the reaction time is controlled within a reasonable range to prevent the coupling reaction from being insufficient due to a short reaction time and to avoid the byproducts that may be generated due to a long reaction time.

[0069] In the presence of nitrogen or an inert gas, the oxygen in the reaction environment is removed, providing an oxygen-free reaction system. This promotes a more stable reaction environment, maintains the activity of the palladium source and co-catalyst, ensures effective catalysis of the substrate, and reduces side reactions. For example, argon can be used as the inert gas.

[0070] For example, the palladium source can be selected from one of bis(triphenylphosphine)palladium dichloride, tetra(triphenylphosphine)palladium, and palladium acetate. The palladium source can rapidly activate the second product to form a complex containing a binaphthyl skeleton, a reactive functional group side chain connected to a carbon chain of a certain length, Pd, and X, which is beneficial for the catalytic reaction.

[0071] For example, the cocatalyst can be selected from cuprous iodide and cuprous bromide. Under the action of the cocatalyst and an alkaline third organic solvent, the terminal alkynylbenzene compound is activated and forms a complex with copper. Then, the alkynyl group is transferred to coordinate with Pd, and further reductive elimination is carried out to obtain a polymerizable chiral agent with the desired structure.

[0072] For example, the ligand can be selected from triphenylphosphine. The ligand is able to stabilize Pd during the Sonogashira coupling catalytic cycle reaction. 0 This prevents palladium deactivation and promotes the catalytic cycle reaction.

[0073] For example, the third organic solvent can be selected from triethylamine, or a mixed solution of triethylamine and other organic solvents, wherein the other organic solvents can be selected from at least one of toluene, tetrahydrofuran, acetone, and N,N-dimethylformamide. For example, the volume ratio of toluene and triethylamine can be a 1:1 mixed solution. Triethylamine not only makes the substances in the system more homogeneous, providing a more uniform reaction system, but it can also neutralize some of the HX generated in the reaction, which is beneficial to the efficient progress of the main reaction; triethylamine also facilitates the deprotonation of terminal alkyne compounds. By using a mixed solution of triethylamine and other organic solvents, a more homogeneous reaction system can be formed, which is beneficial to improving the reaction rate and reproducibility of the coupling reaction.

[0074] For example, the post-processing steps for obtaining the polymerizable chiral agent of formula I-1 include: filtration, vacuum distillation to obtain a crude product, and recrystallization with a mixed solvent of petroleum ether and ethanol to obtain a polymerizable chiral agent with higher purity.

[0075] The chemical reaction equation for step S310 is listed below, in which the second product (denoted as A4) undergoes a coupling reaction with a terminal acetylenoid compound (denoted as A5) to obtain a polymerizable chiral agent (denoted as A6).

[0076] In this group, at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl, and n is a positive integer from 1 to 6.

[0077] The following describes the steps for preparing a polymerizable chiral agent with the general structural formula I-2.

[0078] In some embodiments, the preparation of a polymerizable chiral agent with the general structural formula I-2 may include the following steps: step S220 and step S320.

[0079] Step S220: The first compound is subjected to an oxyacylation reaction with a halo-binaphthol to generate a compound with the general structural formula: The fourth product (denoted as A7) is a first compound that is methacryloyl chloride or acryloyl chloride. In step S220, an oxyacylation reaction is achieved between the hydroxyl group on the halo-naphthol and Cl in the first compound to form two side chains with (meth)acrylate, which can retain the original chiral configuration of the halo-naphthol and retain the reactive group X on the halo-naphthol.

[0080] In some embodiments, when preparing the polymerizable chiral agent with the above-mentioned general structural formula I-2, the molar ratio of the first compound to the halo-binaphthol in step S220 can be 2 to 3:1. For example, the molar ratio can include values ​​such as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, and a range of values ​​including any two of the above specific values. By slightly exceeding the amount of the first compound, the halo-binaphthol can be completely converted, so that both hydroxyl groups in the halo-binaphthol in each molecule can be linked to (meth)acrylates with reactive functional groups.

[0081] In some embodiments, the general structural formula of halo-binaphthol can be: For example, the halo-binaphthols can be selected from at least one of (R)-3,3'-diiodo-1,1'-binaphthol, (R)-6,6'-dibromo-1,1'-bis-2-naphthol, and 4,4'-dibromo-[1,1'-binaphthyl]-2,2'-diol. In these embodiments, each halo-binaphthol has a chiral unit that provides the required chiral unit for the synthesized fourth product in step S220. The chiral configuration of the halo-binaphthol remains unchanged after the reaction, providing the required structural basis for the final synthesis of a polymerizable chiral agent. The position of the hydroxyl groups in these halo-binaphthols determines the position where the (meth)acrylate is added, and each of the three halo-binaphthols has two hydroxyl groups, thus forming two side chains. The position of the halogen groups in these halo-binaphthols determines the position where the terminal acetylenoid compound can be added in the subsequent step S320, and the number of halogen groups determines the position of the terminal acetylenoid compound that can be added. The halogen group of 3,3'-diiodo-1,1'-binaphthol can be I, while the halogen group of (R)-6,6'-dibromo-1,1'-bis-2-naphthol and 4,4'-dibromo-[1,1'-binaphthol]-2,2'-diol can be Br.

[0082] In some embodiments, the oxyacylation reaction of the first compound with halo-naphthol may include: dissolving the halo-naphthol in a fourth organic solvent, adding an auxiliary agent, adding the first compound in an ice-water bath, and completing the reaction at room temperature, followed by post-treatment to obtain the fourth product. Adding (meth)acryloyl chloride as the first compound under ice-water bath conditions can effectively prevent the polymerization of acryloyl chloride, making the properties of the reactants more stable and reducing byproducts. Completing the reaction at room temperature makes it easier to operate; exemplarily, room temperature is room temperature. For example, the reaction time at room temperature is 2h to 7h. Room temperature is easier to operate. For example, the room temperature reaction time can include values ​​such as 2h, 2.1h, 2.2h, 2.3h, 2.5h, 2.8h, 3h, 3.4h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, 4.2h, 4.5h, 5h, 5.4h, 5.8h, 6h, 6.3h, 6.6h, and 7h, as well as ranges consisting of any two of the above specific values, thereby making the oxyacylation reaction more complete.

[0083] For example, the fourth organic solvent can be at least one of dichloromethane, chloroform, and tetrahydrofuran. When multiple solvents are used, the ratio is chosen to ensure that each solvent is miscible and can dissolve the first compound, halonaphthol, and auxiliaries. The fourth organic solvent does not react with halonaphthol or the first compound, allowing the reactants to be miscible and form a homogeneous reaction system, which is beneficial for efficient reaction.

[0084] For example, the auxiliary agent may be selected from at least one of triethylamine and N,N-diisopropylethylamine, which can neutralize the HCl produced in the reaction and activate the substrate to enable the reaction to proceed efficiently.

[0085] The chemical reaction equation for step S220 is listed below, in which halo-naphthol (denoted as A3) undergoes an oxyacylation reaction with the first compound to give the fourth product (denoted as A7).

[0086] In this context, R4 is selected from H or methyl, and X is selected from I or Br.

[0087] Step S320: The fourth product is coupled with a terminal acetylenoid compound to generate a compound with the general structural formula: The polymerizable chiral agent has at least one electron-withdrawing group among R1, R2, and R3, and the rest are H. In step S320, the polymerizable chiral agent is generated by coupling the X of the fourth product with the carbon-carbon triple bond of the terminal acetylenoid compound. This process not only retains the chiral configuration and reactive functional group of the fourth product, but also retains the acetylinyl group, benzene ring, and electron-withdrawing group of the terminal acetylenoid compound.

[0088] In some embodiments, the general structural formula and specific optional substances of the terminal acetylenoid compound can be referred to the foregoing embodiments, and will not be repeated here.

[0089] In some embodiments, the molar ratio of the fourth product to the terminal alkynylbenzene compound can be 1:2 to 3, with an excess of the terminal alkynylbenzene compound, which is beneficial for the complete reaction of the halogen group in the second product, achieving a complete reaction of the two halogen molecules. For example, the molar ratio can include values ​​such as 1:2, 1.2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, and a range of values ​​including any two of the above specific values.

[0090] In some embodiments, the coupling reaction of the fourth product with the terminal alkynylbenzene compound may include: dissolving the fourth product, the terminal alkynylbenzene compound, the palladium source, the co-catalyst, and the ligand in a fourth organic solvent under nitrogen or an inert gas atmosphere, refluxing and stirring at 60°C to 110°C for 6 h to 28 h, and then obtaining the polymerizable chiral agent of formula I-2 after post-treatment. For example, the reaction temperature can include values ​​such as 60℃, 61℃, 62℃, 63℃, 65℃, 68℃, 70℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 88℃, 90℃, 92℃, 95℃, 97℃, 100℃, 101℃, 104℃, 107℃, and 110℃, as well as ranges between any two of the above specific values. This provides the activation energy required for the fourth product during the reaction, making it easier for palladium sources, such as palladium atoms, to insert into the CX bond, facilitating the oxidative addition between the palladium catalyst and the fourth product containing X. Subsequently, after substitution with terminal alkyne benzene compounds and ligands, and reduction and elimination, a polymerizable chiral agent is obtained; making the reaction process more controllable. For example, the reflux reaction time includes values ​​such as 6h, 8h, 10h, 13h, 15h, 18h, 20h, 21h, 23h, 24h, 25h, 26h, 27h, and 28h, as well as a range of values ​​between any two of the above specific values. By controlling the reaction time of the coupling reaction in step S320, the coupling reaction is made more complete and thorough, and the reaction time is controlled within a reasonable range to prevent the coupling reaction from being insufficient due to an excessively short reaction time, and to avoid the byproducts that may be generated due to an excessively long reaction time. The selection and function of the inert gas, palladium source, co-catalyst, and ligands are as described in step S310 of the aforementioned embodiments, and will not be repeated here. The fourth organic solvent is as described in step S310 of the aforementioned embodiments, and will not be repeated here.

[0091] The chemical reaction equation for step S320 is listed below, in which the fourth product (denoted as A7) undergoes a coupling reaction with a terminal acetylenoid compound (denoted as A5) to obtain a polymerizable chiral agent of formula I-2 (denoted as A6).

[0092] Among them, at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl.

[0093] As can be seen from the above, the preparation method of the polymerizable chiral agent proposed in the embodiments of this application adopts a multi-step synthesis, wherein the polymerizable chiral agent of formula I-1 requires three-step synthesis and the polymerizable chiral agent of formula I-2 requires two-step synthesis. It can introduce a chiral, highly conjugated structure with a binaphthalene backbone and formed by carbon-carbon triple bonds, benzene rings and electron-withdrawing groups into the polymerizable chiral agent as the backbone; it can also introduce side chains of the required chain length and reactive functional groups (meth)acrylates into the polymerizable chiral agent, thereby obtaining a polymerizable chiral agent with high birefringence, high polymerizability, and good compatibility, which can be further applied in liquid crystal mixtures.

[0094] In related technologies, existing liquid crystal compositions induce liquid crystal molecules to form helical structures by adding chiral agents, thereby preparing cholesteric liquid crystals with selective Bragg reflection properties. These materials have shown good application potential in optical components such as brightness enhancement films and polarizing holographic gratings. However, inducing helical structures to form cholesteric liquid crystals by adding additional chiral dopants presents technical challenges such as poor compatibility and easy yellowing, shortening their service life. Some cyano-containing liquid crystal materials have high viscosity, affecting the processing performance of liquid crystal cells or liquid crystal films. Some liquid crystal materials have poor thermal stability, such as a narrow nematic phase temperature range, making them difficult to use in the preparation of polymeric liquid crystals and adaptable to wide temperature environments.

[0095] The technical solutions of liquid crystal compositions formed based on the polymerizable chiral agents in the foregoing embodiments are described below by way of example.

[0096] The embodiments of this application provide a liquid crystal composition comprising at least the polymerizable chiral agent of any of the foregoing embodiments or a polymerizable chiral agent prepared by a method comprising at least the polymerizable chiral agent of any of the foregoing embodiments; and further comprising a reactive liquid crystal, a nematic liquid crystal, and an initiator.

[0097] As can be seen from the above, the liquid crystal composition proposed in this application, by applying a polymerizable chiral agent to the liquid crystal composition, allows the polymerizable chiral agent to polymerize under induction conditions, and it itself forms a helical structure with a certain chirality. The reactive liquid crystal, under the action of the initiator, can build a polymer backbone along the chiral helical structure during polymerization to stabilize or lock the orientation of the liquid crystal. The nematic liquid crystal, under the action of the polymerizable chiral agent, can form a cholesteric liquid crystal with a helical structure from a non-chiral structure, enabling the system to acquire optical properties such as selective reflection of circularly polarized light. Thus, without adding other chiral agents, the components in the liquid crystal composition can be polymerized to form a stable polymer film with a specific helical structure. It has a high birefringence, which can adjust the liquid crystal properties, and the compatibility of the polymerizable chiral agent with other components is improved. Using a liquid crystal compound with a high birefringence can reduce film thickness, reduce material usage, simplify process conditions, and thus reduce production costs. By selecting an appropriate polymerizable chiral agent, the viscosity of the polymerizable chiral agent can be reduced and its solubility improved. By employing polymerizable chiral agents with large conjugated structures, π-π interactions enhance the stability of the liquid crystal phase, resulting in a significant increase in the clearing point (i.e., the transition temperature from nematic phase to isotropic liquid), thus broadening the operating temperature range.

[0098] In some embodiments, the mass percentages of each component may be 0.5% to 10% polymerizable chiral agent, 1% to 97% reactive liquid crystal, 2% to 98% nematic liquid crystal, and 0.1% to 2% initiator, respectively; and / or, the reactive liquid crystal includes RM257, whose structural formula is [insert structural formula here]. It is a bifunctional reactive liquid crystal, with each molecule containing two polymerizable acrylate groups and three benzene ring groups, and the acrylate groups are linked by a carbon chain containing three -CH2- groups. (Reference) Figure 3 and Figure 4Nematic liquid crystals include LC1057 and PLC051. Each molecule of LC1057 has one polymerizable acrylate group at each end, and the main chain also has multiple naphthalene rings, benzene rings, and other groups, which helps to improve birefringence. The entire monomer has a certain rigidity and length, which can adjust the flexibility, crosslinking degree, viscosity, and other properties of the polymer network. PLC051 (Jiangsu Xinshuo New Materials Co., Ltd.) has two benzene rings in its main chain, which are connected by carbon-carbon triple bonds. The main chain has a certain rigidity and a large conjugated structure, and dielectric anisotropy, which helps to improve birefringence. Each molecule of PLC051 has one acrylate group at one end that can participate in the polymerization reaction. Since the benzene ring and the acrylate group are connected by four -CH2- carbon chains, PLC051 can crosslink with other components during polymerization, adjusting the toughness of the entire polymer network. The initiator includes Irgacure 651. Irgacure 651 (CAS No.: 24650-42-8, 2,2-dimethoxy-phenylacetophenone) is a photosensitizer. Under specific ultraviolet light irradiation, Irgacure 651 absorbs light and cleaves to form free radicals. These free radicals initiate the opening of double bonds with reactive acrylate functional groups, leading to subsequent cross-linking reactions. After the polymerization of each component and continuous cross-linking, a solid polymer film is formed. By simultaneously employing a polymerizable chiral agent, reactive liquid crystal, nematic liquid crystal, and an initiator, where the initiator is a photosensitizer, a polymer network structure with a periodic helical structure (chiral) can be prepared under light irradiation, achieving higher diffraction efficiency. The polymerizable chiral agent can both polymerize and function as a chiral agent, eliminating the need for additional chiral agents. Since the polymerizable chiral agents, RM257, LC1057, and PLC051 in the above components all have acrylate groups, or the polymerizable chiral agents have methacrylate groups, based on the principle of like dissolves like, each component has good solubility. Under conditions where the initiator is not activated, the components can maintain good miscibility and are not prone to precipitation. After the initiator is activated, the polymerization of each component is induced, and a relatively stable liquid crystal polymer structure can be formed. Because the polymerizable chiral agents, RM257, LC1057, and PLC051 in the above components contain different types and lengths of large conjugated structures, different numbers of polymerizable groups, different lengths of flexible chains, and different other functional groups, the polymerization rates of each component are different. Each component can polymerize at an appropriate rate, so that each component can polymerize as completely as possible, which is beneficial to a more stable polymer network structure after polymerization. By employing the above-described liquid crystal composition, the polymerizable chiral agent possesses a highly birefringent aromatic yne structure, a chiral binaphthyl structure, and polymerizable acrylate groups. During photocuring, it can undergo polymerization reactions with other blended liquid crystal components, thereby obtaining a uniform blended liquid crystal film. This enables simpler preparation of uniform films.By using the above-mentioned liquid crystal composition, the blended high birefringence material exhibits excellent thermal stability and durability, improves the problem of yellowing, and has a longer service life.

[0099] For example, the mass percentage of the polymerizable chiral agent accounts for 0.5% to 10% of the mass of the liquid crystal composition. For example, the mass percentage includes specific values ​​such as 0.5%, 0.7%, 0.9%, 1%, 2%, 3%, 4%, 4.5%, 4.8%, 5%, 5.5%, 5.8%, 6%, 7%, 8%, 9%, and 10%, as well as ranges consisting of any two of the above specific values. Thus, under inducing conditions, the polymerizable chiral agent can not only polymerize to form a network structure, but also, due to its own chiral structure, form a helical structure with a certain chirality during the polymerization process, achieving a specific optical rotation direction. This can induce other components, such as nematic liquid crystals, to undergo phase transitions, changing from a nematic phase to a cholesteric phase or a chiral nematic phase.

[0100] For example, the reactive liquid crystal accounts for 1% to 97% of the mass of the liquid crystal composition. For example, the mass percentage includes specific values ​​such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 33%, 35%, 36%, 38%, 39%, 40%, 43%, 45%, 47%, 49%, 50%, 52%, 55%, 57%, 60%, 63%, 66%, 69%, 70%, 75%, 80%, 84%, 86%, 90%, 93%, 95%, and 97%, as well as ranges of values ​​between any two of the above specific values, thereby providing the desired highly ordered polymer network, ensuring a certain level of crosslinking density and mechanical strength of the polymer network.

[0101] For example, the mass percentage of the nematic liquid crystal accounts for 2% to 98% of the mass of the liquid crystal composition. For example, the mass percentage includes specific values ​​such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 30%, 33%, 35%, 36%, 38%, 39%, 40%, 43%, 45%, 47%, 49%, 50%, 52%, 55%, 57%, 60%, 63%, 65%, 66%, 69%, 70%, 75%, 80%, 84%, 86%, 90%, 93%, 95%, 97%, and 98%, as well as range values ​​including any two of the above specific values. This allows for the adjustment of the flexibility and cross-linking degree of the entire polymer network, thereby improving the toughness of the final polymer material. For example, the mass percentage of PLC051 to LC1057 is 0.5 to 1.2:1, such as specific values ​​of 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.02:1, 1.04:1, 1.06:1, 1.09:1, 1.1:1, 1.11:1, 1.13:1, 1.15:1, 1.17:1, 1.2:1, etc., as well as ranges of any two of the above specific values. This allows adjustment of the polymerization rate, the degree of crosslinking of the network structure, and the toughness. When the proportion of LC1057 is larger, the toughness of the polymer network is greater; when the proportion of PLC051 is larger, it is beneficial to further improve the high birefringence of the polymer network structure or improve the clearing point.

[0102] For example, the initiator accounts for 0.1% to 2% of the mass of the liquid crystal composition. For example, the mass percentage includes specific values ​​such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.9%, 1%, and 2%, as well as ranges consisting of any two of the above specific values. This enables the initiator to initiate polymerization reactions of the components with reactive functional groups under initiation conditions, thereby producing a periodically oriented cholesteric liquid crystal film. For example, it can initiate the RM257 reaction with acrylate groups, the LC1057 reaction, the PLC051 reaction, and the reaction of polymerizable chiral agents.

[0103] It should be noted that the aforementioned percentage of each component in the liquid crystal composition by mass can also be replaced by the percentage of each component by weight in the liquid crystal composition.

[0104] In some specific embodiments, the mass percentages of each component of the liquid crystal composition are as follows: polymerizable chiral agent (5%), RM257 (29%), PLC051 (35%), LC1057 (30%), and Irgacure (1%).

[0105] In other embodiments, the components of the liquid crystal composition may also be any combination of specific values ​​within the range of mass percentages shown for the aforementioned components, which will not be elaborated here.

[0106] The optical device prepared based on the liquid crystal composition of the foregoing embodiments will now be described by way of example.

[0107] Embodiments of this application provide an optical device comprising a structure made using the aforementioned liquid crystal composition; and / or, the optical device comprises a polarizer holographic grating comprising a thin film made using the liquid crystal composition of the aforementioned embodiments.

[0108] As can be seen from the above, the optical device proposed in this application uses a polymerizable chiral agent as a component of the liquid crystal composition. The components of the liquid crystal composition have good compatibility. During the polymerization process, the large conjugated structures and flexible chain lengths contained in each component are different. This allows for stepwise polymerization with a certain polymerization rate difference. After polymerization, the rigid polymer network can be softened by the components with flexible chains, reducing the stress of the polymer network structure formed after the polymerization of each component. This makes the liquid crystal properties more stable and has nematic / cholesterol properties over a wide temperature range, making it suitable for optical devices in extreme environments.

[0109] When the optical device of this application includes a polarizing holographic grating, the fabricated polarizing holographic grating has a birefringence greater than or equal to 0.27 and a diffraction efficiency greater than 75%.

[0110] For example, optical devices include near-eye display waveguides, cholesteric displays, spatial light modulators, etc. Devices made from polarization-responsive polarimetric holographic gratings as described in the foregoing embodiments can be integrated into the subsequent fabrication of near-eye display waveguides, cholesteric displays, spatial light modulators, etc. In near-eye display waveguides, because the birefringence of the polarimetric holographic grating is greater than or equal to 0.27, its diffraction efficiency is >75%, resulting in extremely high single-pass diffraction efficiency. This reduces light loss during transmission, leading to higher brightness at the eye; it also allows for a wider range of transmitted light angles and a broader field of view. In cholesteric displays, because the birefringence of the polarimetric holographic grating is greater than or equal to 0.27, the cholesteric display can broaden the reflection spectrum, covering the entire visible light band; it can improve display quality, increase contrast, and reduce device thickness. In spatial light modulators, the birefringence of the polarimetric holographic grating is greater than or equal to 0.27, resulting in lower driving voltage, high precision in optical phase / amplitude control, fast response speed, clear beam deflection, and clear holographic imaging effects.

[0111] The following describes an exemplary method for fabricating a polarizing holographic grating.

[0112] In related technologies, liquid crystal devices based on polarizer holographic gratings often rely on multilayer coating or complex photolithography processes, which are costly and inefficient.

[0113] Therefore, there is an urgent need to develop liquid crystal materials that combine chirality, high birefringence, low viscosity, and wide temperature range—specifically, the polymerizable chiral agents described in the aforementioned embodiments—and combine them with an efficient polarization volume grating (PVG) preparation method.

[0114] First, a photoalignment material is selected and coated onto the substrate. For example, the photoalignment material can be a commercially available material such as Nissan PI, Brilliant Yellow, or SD-1, the substrate can be a glass, resin, silicon carbide, or other substrates, and the coating method can be spin coating, inkjet printing, blade coating, or other methods.

[0115] Next, the coated photo-alignment material is placed under a light field pattern for exposure. At this time, the molecular orientation of the photo-alignment material is patterned to form an alignment layer. For example, the exposure method of the light field can be linear polarized light exposure or polarization interference exposure.

[0116] Again, the aforementioned liquid crystal composition is selected as the blending component, and blending formulations with different mass fractions are prepared according to the required reflection wavelength. The liquid crystal layer is then coated onto the alignment layer by spin coating or inkjet printing. Exemplarily, the coating thickness ranges from nanometers to micrometers.

[0117] Finally, the liquid crystal layer is irradiated with 365 nm wavelength UV light for a specific time, causing the internal polymerizable liquid crystal components to react and form a polymer network of a specific wavelength. The resulting film is a volume holographic grating device with polarization response, which can be integrated into subsequent near-eye display waveguides, cholesteric displays, spatial light modulators, etc. For example, the irradiation intensity ranges from 0.5 mW / cm². 2 ~200 mW / cm 2 For example, 0.5mW / cm 2 1.5mW / cm 2 2mW / cm 2 3.5mW / cm 2 5mW / cm 2 10mW / cm 2 20mW / cm 2 22mW / cm 2 30mW / cm 2 37mW / cm 2 40mW / cm 2 49mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 88mW / cm 2 94mW / cm 2 103mW / cm 2 111mW / cm 2 119mW / cm 2 123mW / cm 2 137mW / cm 2 144mW / cm 2 155mW / cm 2 160mW / cm 2 176mW / cm 2 188mW / cm 2 190mW / cm 2 196mW / cm 2 200 mW / cm 2The specific values, including any two of the above specific values, can be adjusted to regulate the rate at which the photoinitiator generates free radicals and indirectly regulate the polymerization rate, thereby controlling the changes in the cholesteric helical structure. It can also regulate the orderliness and pitch of the network structure. The irradiation time ranges from 1 min to 60 min, including specific values ​​such as 1 min, 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min, as well as any two of the above specific values. This allows for the maximum polymerization of each polymerizable monomer, forming a stable cross-linked network, reducing yellowing, and controlling the degree of cross-linking in the network structure.

[0118] Therefore, by adopting the above-mentioned method for preparing polarizing holographic gratings, and through the two-layer coating technology, the preparation cost of polarizing holographic gratings can be controlled within a reasonable range, while improving production efficiency and process stability. This will enhance the large-scale application and industrialization of liquid crystal devices with polarizing holographic gratings, and facilitate technological upgrades in the application of liquid crystal devices. In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," and "fourth" may explicitly or implicitly include one or more of the stated features.

[0119] In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically defined.

[0120] Unless otherwise specified, the first compound, second compound, halo-naphthol, bromo-fatty alcohol, terminal acetylenoid compound, first organic solvent, second organic solvent, third organic solvent, fourth organic solvent, acid binder, basic auxiliary agent, palladium source, co-catalyst, ligand, reactive liquid crystal, nematic liquid crystal, and initiator in the embodiments of this application can all be obtained from conventional commercial sources.

[0121] The polymerizable chiral agent of the present invention, its preparation method, and its application are described below with reference to specific embodiments.

[0122] Example 1 The structures of the polymerizable chiral agents in this embodiment are shown in Table 1 below. The structures of R1, R2, R3 or R4 of each polymerizable chiral agent can be the same or different, and the number of n can be the same or different.

[0123] Table 1 Polymerizable chiral agents

[0124] The following example, using the preparation method of polymerizable chiral agent A6-1, illustrates the preparation method of polymerizable chiral agents with n being 1-6 in Example 1.

[0125] Step S111, Preparation of the first product A2-1: 84.65 mmol of 3-bromo-1-propanol (denoted as A1-1) was dissolved in 100 mL of dichloromethane and stirred at room temperature. After complete dissolution, 22 g of triethylamine (30.3 mL) was added dropwise. After stirring for 3 min, the solution was placed in an ice-water bath. Subsequently, 19.15 g (211.62 mmol) of the first compound, acryloyl chloride, was added dropwise. The molar ratio of 3-bromo-1-propanol to acryloyl chloride was approximately 1:2.5. The reaction temperature was maintained at approximately 0 °C during the dropwise addition. After the addition was complete, the reaction was carried out at room temperature for 3 h. The product was then extracted with dichloromethane, and the resulting product was obtained by rotary evaporation followed by column chromatography. The first product (denoted as A2-1).

[0126] Step 211, Preparation of the second product A4-1: Weigh 45.01 mmol of the first product A2-1, 21.75 mmol of the halonaphthol (R)-3,3'-diiodo-[1,1'-binaphthyl]-2,2'-diol (denoted as A3-1), and dissolve 61.34 mmol of potassium carbonate in 100 mL of acetonitrile. The molar ratio of the first product to the halonaphthol is 2.069:1, and the molar ratio of potassium carbonate to the halonaphthol is 2.82:1. After stirring under reflux at 60°C for 6 hours, filter and extract with dichloromethane. Obtain the crude product by column chromatography. Recrystallize from petroleum ether and methanol to obtain the product with the following structural formula: The second product is denoted as A4-1.

[0127] Step S311, Preparation of polymerizable chiral agent A6-1: Under nitrogen protection, weigh 0.05 mol of A4-1 and weigh 0.15 mol of [the following is a structural formula] A terminal-terminated acetylenoid compound (denoted as A5-1) was obtained by weighing 1% mol of cuprous iodide, 1% mol of bis(triphenylphosphine)palladium dichloride, and 2% mol of triphenylphosphine. These substances were added to a three-necked flask, and the mixture was stirred magnetically and refluxed at 80°C for 24 hours using 50 mL of toluene and 50 mL of triethylamine as a mixed solvent. After cooling, the mixture was filtered and distilled under reduced pressure to obtain the crude product. Recrystallization with a petroleum ether / ethanol mixed solvent yielded the pure product A6-1, with the structural formula [insert structural formula here]. The molar ratio of the second product A4-1 to the terminal acetylenoid compound A5-1 is 1:3.

[0128] The following is a list of the chemical reaction steps involved in the synthesis of A6-1: .

[0129] The synthesis of A6-3 is largely the same as that of A6-1, except that the terminal acetylenoid compound in step S311 is replaced with 4-ethynyl-3-fluorobenzonitrile. The amount used is adjusted according to the substance used, which will not be elaborated here.

[0130] The synthesis of A6-4 is largely the same as that of A6-1, except that the terminal acetylenoid compound in step S311 is replaced with 4-ethynyl-3,5-difluorobenzonitrile. The amount used is adjusted according to the substance used, which will not be elaborated here.

[0131] The synthesis of A6-5 is largely the same as that of A6-1, except that the terminal acetylenoid compound in step S311 is replaced with 1-ethynyl-4-isothiocyanate phenylene. The amount used is adjusted according to the substance used, which will not be elaborated here.

[0132] The synthesis of A6-6 is largely the same as that of A6-1, except that the terminal acetylenoid compound in step S311 is replaced with 1-ethynyl-4-isocyanate phenylene. The amount used is adjusted according to the substance used, which will not be elaborated here.

[0133] The synthesis of A6-7 is largely the same as that of A6-1, except that the halo-naphthol in step S211 is replaced with 4,4'-dibromo-[1,1'-binaphthol]-2,2'-diol. The amount used is adjusted according to the substance used, which will not be elaborated here.

[0134] The synthesis of A6-8 is largely the same as that of A6-1, except that the halo-naphthol in step S211 is replaced with (R)-6,6'-dibromo-1,1'-bis-2-naphthol. The amount of halo-naphthol is adjusted according to the substance used, which will not be elaborated here.

[0135] The synthesis of A6-9 is largely the same as that of A6-1, except that the bromo-fatty alcohol in step S111 is replaced with 6-bromo-n-hexanol, and the terminal acetylenoid compound in step S311 is replaced with 4-ethynyl-2,3-difluorobenzaldehyde. The amounts used are adjusted according to the substances used, which will not be elaborated here.

[0136] The synthesis of A6-10 is largely the same as that of A6-1, except that the bromo fatty alcohol in step S111 is replaced with 2-bromoethanol and acryloyl chloride is replaced with methacryloyl chloride, and the terminal acetylenoid compound in step S311 is replaced with 1-ethynyl-2,4,5-trifluorobenzene. The amounts are adjusted according to the substances used, which will not be elaborated here.

[0137] The synthesis of A6-11 is roughly the same as that of A6-1, except that the bromo fatty alcohol in step S111 is replaced with methanol bromine and acryloyl chloride is replaced with methacryloyl chloride. The amounts are adjusted according to the substances used, which will not be elaborated here.

[0138] The synthesis of A6-2 is carried out using the following steps: Step S221, Preparation of the fourth product A7-1: 84.65 mmol of halo-naphthol (R)-3,3'-diiodo-[1,1'-binaphthyl]-2,2'-diol (denoted as A3-1) was dissolved in 100 mL of dichloromethane. The solution was stirred at room temperature until completely dissolved. 22 g of triethylamine (30.3 mL) was added dropwise, and the mixture was stirred for 3 min. The solution was then placed in an ice-water bath. Subsequently, 19.15 g (211.62 mmol) of the first compound, acryloyl chloride, was added dropwise. The molar ratio of halo-naphthol to acryloyl chloride was approximately 1:2.5. The reaction temperature was maintained at approximately 0 °C during the dropwise addition. After the addition was complete, the reaction was carried out at room temperature for 3 h. The mixture was then extracted with dichloromethane, and the resulting product was obtained by rotary evaporation followed by column chromatography. The fourth product (denoted as A7-1).

[0139] Step S321, Preparation of polymerizable chiral agent A6-2: Under nitrogen protection, weigh 0.05 mol of A7-1 and 0.15 mol of [the following is a structural formula] A terminal-terminated acetylenoid compound (denoted as A5-1) was obtained by weighing 1% mol of cuprous iodide, 1% mol of bis(triphenylphosphine)palladium dichloride, and 2% mol of triphenylphosphine. These substances were added to a three-necked flask, and the mixture was stirred magnetically and refluxed at 80°C for 24 hours using 50 mL of toluene and 50 mL of triethylamine as a mixed solvent. After cooling, the mixture was filtered and distilled under reduced pressure to obtain the crude product. Recrystallization with a petroleum ether / ethanol mixed solvent yielded the pure product A6-2, with the structural formula [insert structural formula here]. The molar ratio of the fourth product A7-1 to the terminal acetylenoid compound A5-1 is 1:3.

[0140] The following is a list of the chemical reaction steps involved in the synthesis of A6-2:

[0141] .

[0142] Example 2 Using photoalignment material SD-1, an alignment layer solution with a mass fraction of 1.5 wt% was prepared with DMF as solvent. After cleaning the glass substrate with ultraviolet ozone, the alignment layer SD-1 solution was spin-coated onto the substrate at a rotation speed of 3000 r / s to obtain the coated photoalignment material.

[0143] Exposure was performed under a polarization interference light field with a period of 1 μm, and the exposure dose was 2 J / cm². 2 This yields a periodically oriented SD-1 thin film layer.

[0144] A liquid crystal composition was selected, and the components and their mass ratios in the liquid crystal composition were as follows: 5% polymerizable chiral agent, 29 parts liquid crystal RM257, 35 parts liquid crystal PLC051, 30 parts LC1057, and 1 part Irgacure 651. A liquid crystal blend solution with a mass concentration of 15 wt% was prepared using toluene as a solvent. The liquid crystal blend solution was coated onto the alignment layer using a spin coating method to form a liquid crystal layer with a coating thickness of 500 nm.

[0145] Irradiated under a UV-LED lamp at a temperature of 30℃ and an intensity of 10 mW / cm². 2 The irradiation time was 3 minutes, and a polarizing holographic grating with a thickness of 500 nm was obtained.

[0146] The polymerizable chiral agents are A6-1 to A6-11 as described in Example 1. Polarizing holographic gratings 1 to 11 are obtained sequentially, denoted as PVG1 to PVG11.

[0147] Comparative Example 1 R5011 (CAS: 944537-61-5), a common chiral agent, has no polymerizable (meth)acrylate groups.

[0148] Following the steps of Example 2, the polymerizable chiral agent was replaced with the ordinary chiral agent of Comparative Example 1, and a polarizing holographic grating was obtained, denoted as PVG Comparative 1.

[0149] Comparative Example 2 R811 (CAS: 133676-09-2), a common chiral agent, has no polymerizable (meth)acrylate groups.

[0150] Following the steps of Example 2, the polymerizable chiral agent was replaced with the ordinary chiral agent of Comparative Example 2, and a polarizing holographic grating was obtained, denoted as PVG Comparative 2.

[0151] Test Example 1 The birefringence, haze, and diffraction rate of the thin films of polarizing holographic gratings prepared in the aforementioned embodiments and comparative examples were measured. The test methods are as follows, and the test results are shown in Table 2.

[0152] 1) Test method for birefringence (Δn): Abbe refractometer The liquid crystal material is uniformly coated on a clean glass slide (approximately 10-20 μm thick), ensuring no air bubbles are present. A rub-oriented polyimide film is used to induce the molecules to align in a specific direction.

[0153] Use a standard glass block or pure water to calibrate the refractometer to ensure measurement accuracy.

[0154] Rotate the analyzer to two orthogonal positions (0° and 90°), corresponding to parallel (ne) and perpendicular (no) measurements, respectively.

[0155] Place the sample on the refractometer prism and add a small amount of contact liquid (such as bromonaphthalene, refractive index ≈ 1.66) to eliminate interfacial reflection. Record the refractive index values ​​parallel (ne) and perpendicular (no) to the molecular orientation, respectively. Calculate birefringence: Δn = |ne - no|.

[0156] 2) Haze and yellowness: HZ-V3 haze meter Calibration: Perform 0% and 100% calibration using a standard haze sheet (such as an NPL traceability board) to ensure light source stability.

[0157] Sample placement: Lay the thin film sample flat at the opening of the integrating sphere to avoid air bubbles or wrinkles interfering with the optical path.

[0158] Light source selection: Select a light source (such as D65 to simulate natural light) based on the light transmission characteristics of the thin film, and adjust the incident angle to vertical or 45°.

[0159] Data acquisition: The instrument automatically measures the total transmitted light flux (TP) and the scattered light flux (TD) and calculates the haze value.

[0160] 3) Diffraction efficiency: Thorlabs HG10 holographic grating spectrometer Optical path setup: Use a polarizing beam splitter to separate S / P polarized light and incident them onto the grating respectively. Adjust the incident angle to the Bragg angle (controlled by an electric rotary displacement stage).

[0161] Light source configuration: Select a light source whose wavelength matches the grating design: He For Ne lasers, if polarization-sensitive testing is required, add a λ / 4 waveplate to adjust the polarization state.

[0162] Data acquisition: The intensity of transmitted and diffracted light is recorded using a spectrometer, and the diffraction efficiency is calculated.

[0163] Table 2 Test parameters for each substance in the examples and comparative examples

[0164] Analysis of Table 2 shows that the PVG1 to PVG11 prepared by adding a polymerizable chiral agent to the liquid crystal composition in the embodiments of this application have a birefringence greater than or equal to 0.27, a refractive index modulation corresponding to the birefringence greater than or equal to 0.27, a diffraction efficiency greater than or equal to 75.9%, and a haze between 0.47 and 2.10. Therefore, compared to PVG Comparison 1 and PVG Comparison 2 prepared by R5011 and R811 in the comparative examples, the PVG1 to PVG11 of this application have higher birefringence, greater diffraction efficiency, and lower haze, or are comparable to the comparative examples.

[0165] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A polymerizable chiral agent, characterized in that, Its general structural formula is shown in Equation I-1 or Equation I-2 below: (Equation I-1), and, (Formula I-2); In this group, at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H; R4 is selected from H or methyl, and n is a positive integer from 1 to 6.

2. The polymerizable chiral agent as described in claim 1, characterized in that, The electron-withdrawing group is selected from at least one of -F, -CN, -NCS, -NCO, and -CHO; n is a positive integer from 2 to 6.

3. The polymerizable chiral agent as described in claim 1, characterized in that, The polymerizable chiral agent is selected from compounds having the following structural formula: , , , , , , or .

4. A method for preparing a polymerizable chiral agent according to any one of claims 1 to 3, characterized in that, The preparation of polymerizable chiral agents with the general structural formula I-1 includes the following steps: The acylation reaction of the bromo fatty alcohol with the first compound yields the compound with the general structural formula [structure omitted]. The first product; the first compound is methacryloyl chloride or acryloyl chloride, wherein the bromo fatty alcohol has 1 to 6 carbon atoms; The first product was subjected to a nucleophilic substitution reaction with a halo-naphthol to produce the product with the general structural formula [structure omitted]. The second product, R4 is selected from H or methyl; The second product was coupled with a terminal acetylenic phenyl compound to produce a compound with the general structural formula [structure omitted]. A polymerizable chiral agent wherein at least one of R1, R2, and R3 is an electron-withdrawing group, and the remainder are H; or, The preparation of polymerizable chiral agents with the general structural formula I-2 includes the following steps: The first compound was subjected to an oxyacylation reaction with a halo-binaphthol to produce a compound with the general structural formula [structure omitted]. The fourth product, wherein the first compound is methacryloyl chloride or acryloyl chloride; The fourth product was coupled with a terminal acetylenic phenyl compound to produce a compound with the general structural formula [structure omitted]. A polymerizable chiral agent in which at least one of R1, R2 and R3 is an electron-withdrawing group, and the rest are H.

5. The method for preparing a polymerizable chiral agent as described in claim 4, characterized in that, The bromo fatty alcohol is selected from at least one of methanol bromide, 2-bromoethanol, 3-bromo-1-propanol, 4-bromo-1-butanol, 5-bromo-1-pentanol, and 6-bromo-n-hexanol; the first compound is acryloyl chloride.

6. The method for preparing a polymerizable chiral agent as described in claim 4, characterized in that, The general structural formula of the halo-binaphthol is: The molar ratio of the first product to the halo-binaphthol is 2-5:1; or, when preparing a polymerizable chiral agent with the general structural formula I-2, the molar ratio of the first compound to the halo-binaphthol is 2-3:

1.

7. The method for preparing a polymerizable chiral agent as described in claim 6, characterized in that, The halo-naphthol is selected from at least one of (R)-3,3'-diiodo-1,1'-naphthol, (R)-6,6'-dibromo-1,1'-bis-2-naphthol, and 4,4'-dibromo-[1,1'-binaphthol]-2,2'-diol.

8. The method for preparing a polymerizable chiral agent as described in claim 4, characterized in that, The general structural formula of the terminal acetylenoid compound is as follows: The molar ratio of the second product to the terminal alkynylbenzene compound is 1:2 to 6, or the molar ratio of the fourth product to the terminal alkynylbenzene compound is 1:2 to 3.

9. The method for preparing a polymerizable chiral agent as described in claim 8, characterized in that, The terminal acetylenoid compound is selected from at least one of 4-ethynyl-benzonitrile, 4-ethynyl-3-fluorobenzonitrile, 4-ethynyl-3,5-difluorobenzonitrile, 1-ethynyl-4-isothiocyanate phenylene, 1-ethynyl-4-isocyanate phenylene, 4-ethynyl-2,3-difluorobenzaldehyde, and 1-ethynyl-2,4,5-trifluorobenzene.

10. The method for preparing a polymerizable chiral agent as described in claim 4, characterized in that, The acylation reaction of the bromo fatty alcohol with the first compound includes: dissolving the bromo fatty alcohol in a first organic solvent, adding an acid-binding agent, adding the first compound in an ice-water bath, and completing the reaction at room temperature, followed by post-treatment to obtain the first product; The nucleophilic substitution reaction of the first product with halo-naphthol includes: dissolving the first product, halo-naphthol, and basic auxiliary agent in a second organic solvent, refluxing and stirring at 60℃~80℃ for 5h~7h, and obtaining the second product after post-treatment; The coupling reaction of the second product with the terminal alkynylbenzene compound includes: dissolving the second product, the terminal alkynylbenzene compound, the palladium source, the co-catalyst, and the ligand in a third organic solvent under nitrogen or an inert gas atmosphere, refluxing and stirring at 60°C to 110°C for 20 to 28 hours, and obtaining the polymerizable chiral agent of formula I-1 after post-treatment.

11. The method for preparing a polymerizable chiral agent as described in claim 4, characterized in that, The oxyacylation reaction of the first compound with halo-binaphthol includes: dissolving halo-binaphthol in a fourth organic solvent under nitrogen or inert gas protection, adding an auxiliary agent, adding the first compound in an ice-water bath, and completing the reaction at room temperature, followed by post-treatment to obtain the fourth product; The coupling reaction between the fourth product and the terminal alkynylbenzene compound includes: dissolving the fourth product, the terminal alkynylbenzene compound, the palladium source, the co-catalyst, and the ligand in a fourth organic solvent under nitrogen or an inert gas atmosphere, refluxing and stirring at 60°C to 110°C for 20 to 28 hours, and obtaining the polymerizable chiral agent of formula I-2 after post-treatment.

12. A liquid crystal composition, characterized in that, It includes reactive liquid crystals, nematic liquid crystals, initiators, and polymerizable chiral agents prepared by any one of claims 1 to 3 or any one of claims 4 to 11.

13. The liquid crystal composition according to claim 12, characterized in that, The mass percentages of each component are 0.5%~10% polymerizable chiral agent, 1%~97% reactive liquid crystal, 2%~98% nematic liquid crystal, and 0.1%~2% initiator.

14. The liquid crystal composition according to claim 12, characterized in that, The reactive liquid crystal includes RM257; the nematic liquid crystal includes LC1057 and PLC051, wherein the mass ratio of LC1057 to PLC051 is 0.5~1.2:1; the initiator includes Irgacure 651.

15. An optical device, characterized in that, The optical device includes a structure made using the liquid crystal composition as described in any one of claims 12 to 14; and / or, the optical device includes a polarizer holographic grating, the polarizer holographic grating comprising a thin film made using the liquid crystal composition as described in any one of claims 12 to 14.

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