Camphoric acid chiral cross-linking agent, wide temperature range visible light selective reflection cholesteric liquid crystal polymer and preparation method

Abstract

The application provides a camphoric acid chiral cross-linking agent, a wide-temperature-range visible light selective reflection cholesteric liquid crystal polymer and a preparation method, the chiral cross-linking agent is 4-(4-allyloxy) benzoyloxy-4'-hydroxy biphenyl camphoric acid bis ester; the chiral polymer dissolves monomers 4-undecylenoyloxy benzoic acid cholesteryl ester, cholesteryl acrylate, 4-allyloxy benzoic acid cholesteryl ester and the chiral cross-linking agent in toluene according to a certain molar ratio, after dissolution, a small amount of hexachloroplatinic acid complex catalyst is added under nitrogen protection and reaction is carried out. The chiral cross-linking agent of the application is a cholesteric liquid crystal; the liquid crystal elastomer series all appears obvious liquid crystal texture in the process of temperature rise and fall, is a cholesteric phase liquid crystal in the process of temperature rise, and a phase transition from a blue phase liquid crystal to a cholesteric phase liquid crystal appears in the process of temperature fall, and has a very wide blue phase and a blue phase-cholesteric phase coexistence interval. The liquid crystal polymer synthesized by the application has a wide blue phase interval, reaches dozens of DEG C, has a low Tg and a wide ΔT.

Description

Technical Field

[0001] This application belongs to the field of liquid crystal polymer technology, and particularly relates to a camphoric acid chiral crosslinking agent, a wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer, and its preparation method. Background Technology

[0002] The presence of asymmetric chiral centers gives chiral side-chain liquid crystal polymers a unique helical structure, which endows them with distinctive optical properties such as selective reflection, circular dichroism, high optical rotation, and optical dispersion. Chiral side-chain liquid crystal polymers can display different liquid crystal phases, including chiral smectic phases, cholesteric phases, and blue phases, each with different application areas. Among these, the selective reflection property of cholesteric and blue phase liquid crystals gives them enormous potential applications in nonlinear optical materials, color filters, polarizers, full-color liquid crystal displays, anti-counterfeiting printing, optics, information technology, color dyes, and military fields. They can also be used as color pigments, and their unique visual effects will bring innovative opportunities to fields such as painting, clothing, and advertising.

[0003] Chiral side-chain liquid crystal polymers combine the optical properties of small-molecule chiral liquid crystals with the ease of polymer processing, making them suitable materials for various novel optical devices. Currently, research on chiral side-chain liquid crystal polymers with cholesterol as the chiral center is becoming increasingly multifunctional, and continuous research and exploration are giving them greater practical and potential application value. For example, introducing molecules with different photochromic groups, such as spiropyran, spirophenoxazine, succinic anhydride, and azobenzene, into chiral liquid crystal polymers not only endows them with the optical properties of chiral liquid crystals but also gives them the special property of changing properties under light, thus broadening their application range in the optical field.

[0004] Currently, international research on chiral side-chain liquid crystal polymers is becoming increasingly in-depth, with numerous reports annually on fundamental and applied research on novel chiral side-chain liquid crystal polymers. For example, the research group of Zhang Baoyan at Northeastern University synthesized side-chain liquid crystal polymers containing different chiral units and conducted detailed research and discussions on the structure and properties of these liquid crystal polymers. The research group of Yang Huai et al. at Peking University has also conducted extensive research on side-chain chiral liquid crystal polymers, preparing chiral liquid crystal polymers with pitch gradients. These liquid crystal polymers exhibit broad-band selective reflection under temperature changes, making them valuable for applications in information storage, color filters, and smart switches. Furthermore, numerous studies have been conducted both domestically and internationally to control the optical properties of chiral liquid crystal polymers by varying temperature, electric field, pH value, organic solvent vapor, acidic gases, and ambient humidity. In summary, researchers hope to regulate the optical properties of chiral liquid crystals through changes in external conditions, enabling applications in optical fields such as information storage, displays, and optical sensors. Liquid crystal elastomers (LCEs) combine the orderliness of liquid crystals with the fluidity and elasticity of elastomers, thus possessing many unique properties. Compared to other non-crosslinked liquid crystal polymers, the most unique property of LCEs is their stress-orientation characteristics. Studies have shown that LCEs can achieve uniformly oriented liquid crystal domains with only 20% strain. In contrast, for non-liquid crystal elastomers, at least 1000% stress is required to obtain well-oriented samples under the same conditions. Furthermore, chiral smectic and cholesteric LCEs exhibit orientation stability, piezoelectricity, and ferroelectricity, properties that make them highly promising for applications in nonlinear optical materials, non-porous permeable membranes, and many other fields. Therefore, designing novel LCE molecules and studying the relationship between their structure and properties has become a current research focus. Current research directions for LCEs mainly focus on two aspects: theoretical research and practical applications in high-tech fields such as optical materials, medical materials, and solar cell materials.

[0005] However, there are still many issues in the research on liquid crystal elasticity that require further in-depth study. Designing and preparing novel liquid crystal elastomers will help develop truly practical and high-performance liquid crystal elastomer materials. Summary of the Invention

[0006] This application addresses the aforementioned issues and aims to provide a camphoric acid chiral crosslinking agent, a wide-temperature-range visible light selective reflective cholesteric liquid crystal polymer, and its preparation method. Camphoric acid, with its strong optical activity, is used as the chiral liquid crystal center to prepare the chiral crosslinking monomer. By adjusting the polymer composition and crosslinking ratio, liquid crystal polymers with different liquid crystal phases are obtained, such as: blue phase, blue phase and cholesteric coexistence, and cholesteric phase liquid crystal polymers. The liquid crystal polymer synthesized in this application has a wide blue phase range, reaching tens of °C, and the preparation of wide-temperature-range blue phase liquid crystal polymers has significant theoretical and applied value. The Tg of the synthesized polymer is relatively low. T is wider.

[0007] The first aspect of this application provides a camphoric acid chiral crosslinking agent, wherein the chiral crosslinking agent is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid diester, and its structural formula is: .

[0008] The second aspect of this application also provides a method for preparing a camphoric acid chiral crosslinking agent, comprising the following steps: dissolving 3.00 g (0.00900 mol) of 4-(4-allyloxy)benzoyloxy-4'-biphenyl in 30.0 mL of tetrahydrofuran and 5-10 drops of pyridine solution, and slowly adding the solution dropwise to 0.009 mol of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid monoester acyl chloride dissolved in 20.0 mL of tetrahydrofuran solution; reacting at room temperature for 1 h, and then heating under reflux at 60.0 °C for 36 h. After the reaction is completed, most of the solvent is distilled off under reduced pressure, the concentrated solution is poured into deionized water for soaking, filtered, and a brown powdery solid is obtained; the solid is then purified by ordinary silica gel chromatography to obtain the camphoric acid chiral crosslinking agent.

[0009] The specific synthetic routes include: (2.15) (2.16) (2.17) (2.18).

[0010] A third aspect of this application provides a wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer, wherein the polymer is a chiral liquid crystal elastomer with the following structural formula:

[0011] In the formula, 4-Undecyloxybenzoic acid cholesterol ester Cholesterol acrylate 4-Allyloxybenzoic acid cholesterol ester : 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester.

[0012] The fourth aspect of this application provides a method for preparing a wide-temperature-range visible light selective reflective cholesteric liquid crystal polymer, comprising the following steps: dissolving monomers, a chiral crosslinking agent, and tetramethylcyclotetrasiloxane (D4H) in toluene at a certain molar ratio; after complete dissolution, adding a small amount of hexachloroplatinic acid complexing catalyst under nitrogen protection, and reacting at 95.0℃ for 36 h; wherein the monomers are 4-undecyloxybenzoic acid cholesterol ester (M1), acrylate cholesterol ester (M2), and 4-allyloxybenzoic acid cholesterol ester (M3); the chiral crosslinking agent is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5); the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3=1:1:1, and M5 accounts for 0-20% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.57-8.4 mmol, thereby obtaining a chiral liquid crystal elastomer P2 system.

[0013] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0, and M5 accounts for 0% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 6.000 mmol, and chiral liquid crystal elastomer P is obtained. 2-1 .

[0014] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:1.3, and M5 accounts for 2.5% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.575 mmol, and chiral liquid crystal elastomer P is obtained. 2-2 .

[0015] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:1.5, and M5 accounts for 5% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.650 mmol, and chiral liquid crystal elastomer P is obtained. 2-3 .

[0016] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.3, and M5 accounts for 10% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 7.200 mmol, and chiral liquid crystal elastomer P is obtained. 2-4 .

[0017] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.5, and M5 accounts for 15% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.950 mmol, and chiral liquid crystal elastomer P is obtained. 2-5 .

[0018] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.6, and M5 accounts for 20% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 8.400 mmol, and chiral liquid crystal elastomer P is obtained. 2-6 .

[0019] The beneficial effects of this application are: This application synthesizes the liquid crystal monomers 4-undecyloxybenzoic acid cholesterol ester (M1), acrylate cholesterol ester (M2), 4-allyloxybenzoic acid cholesterol ester (M3), and the chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5). FT-IR and 1H-NMR analyses show that the liquid crystal monomers, the chiral crosslinking agent M5, and the series of side-chain liquid crystal elastomers P2 all conform to the molecular design.

[0020] POM analysis showed that monomers M1, M2, and M3, chiral crosslinker M5, and polymers in the P2 series all exhibited liquid crystal properties. Among them, monomers M1, M2, and M3, as well as chiral crosslinker M5, were all cholesteric liquid crystals. The P2 series elastomers all exhibited significant liquid crystal textures during heating and cooling processes. 2-1 ~P 2-6 All are cholesteric liquid crystal elastomers.

[0021] DSC analysis showed that the Tg values ​​of the P2 series liquid crystal polymers gradually increased with increasing chiral crosslinking agent M5 content. The Ti values ​​of all liquid crystal polymers decreased with increasing chiral crosslinking agent content. All three series of liquid crystal polymers exhibited a wide mesocrystalline range, which gradually decreased with increasing chiral crosslinking agent content.

[0022] This application innovatively utilizes camphor acid, which has strong optical activity, as a chiral liquid crystal center to prepare chiral crosslinking monomers. By adjusting the polymer composition and crosslinking ratio, liquid crystal polymers with different liquid crystal phases were obtained. The selective wavelength can be controlled by the ratio of crosslinking agents, such as: blue phase, blue phase and cholesteric coexistence, and cholesteric phase liquid crystal polymers. The liquid crystal polymers synthesized in this application have a wide blue phase range, reaching tens of degrees Celsius. The preparation of wide-temperature-range blue phase liquid crystal polymers has important theoretical and application value. The Tg synthesized in this application is low. T is wider.

[0023] By further optimizing the structure of the monomers and liquid crystal polymers, it is possible to achieve continuous variation of the reflection wavelength across the entire visible light region under the influence of temperature and electric field, and to exhibit a specific reflection wavelength at a particular temperature or voltage, thus adapting to different application requirements. These liquid crystal polymers require no energy and can develop color under visible light irradiation; they exhibit excellent adhesion to materials such as paper, plastics, metals, fabrics, and glass; and they possess good film-forming properties. Attached Figure Description

[0024] Figure 1 The infrared spectrum of 4-undecyloxybenzoic acid of this application; Figure 2 The infrared spectrum of 4-allyloxybenzoic acid in this application; Figure 3 The infrared spectrum of 4-(4-allyloxy)benzoyloxy-4′-hydroxybiphenyl of this application; Figure 4 The infrared spectrum of (+)-camphoric acid in this application; Figure 5 The infrared spectrum of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid monoester of this application; Figure 6 The infrared spectrum of 4-undecenoyloxybenzoic acid cholesterol ester of this application; Figure 7 The infrared spectrum of the cholesterol acrylate of this application; Figure 8 The infrared spectrum of 4-allyloxybenzoic acid cholesterol ester of this application; Figure 9 The infrared spectrum of the 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester of this application; Figure 10 The infrared spectrum of the tetramethylcyclotetrasiloxane of this application is shown. Figure 11 The infrared spectrum of the P2 series of liquid crystal elastomers of this application; Figure 12 The liquid crystal elastomer P of this application 2-4 Infrared spectrum; Figure 13 The NMR spectrum of the 4-(4-allyloxybenzoyloxy)-4'-hydroxybiphenyl camphorate diester of this application is shown. Figure 14 The NMR spectrum of D4H in this application; Figure 15 The NMR spectrum is for the P2 series of liquid crystal elastomers of this application; Figure 16These are polarized electron microscope images of the liquid crystal chiral crosslinking agent M5 of this application at different temperatures; Figure 17 The liquid crystal elastomer P of this application 2-1 Polarized electron microscope images at different temperatures; Figure 18 The liquid crystal elastomer P of this application 2-2 Polarized electron microscope images at different temperatures; Figure 19 The liquid crystal elastomer P of this application 2-3 Polarized electron microscope images at different temperatures; Figure 20 The liquid crystal elastomer P of this application 2-4 Polarized electron microscope images at different temperatures; Figure 21 The liquid crystal elastomer P of this application 2-5 Polarized electron microscope images at different temperatures; Figure 22 The liquid crystal elastomer P of this application 2-6 Polarized electron microscope images at different temperatures; Figure 23 The DSC curve of the chiral crosslinking agent M5 of this application; Figure 24 The liquid crystal elastomer P of this application 2-1 ~P 2-6 The trend of phase transition temperature with the content of monomer M5; Figure 25 The liquid crystal elastomer P of this application 2-1 ~P 2-6 The DSC curve; Figure 26 The POM diagram and maximum selectivity wavelength diagram of liquid crystal elastomers with different crosslinking agent contents of this application at the same temperature (28°C); Figure 27 The liquid crystal elastomer P of this application 2-2 POM plots and maximum selectivity wavelength plots at different temperatures. Detailed Implementation

[0025] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the camphoric acid chiral crosslinking agent, the wide-temperature-range visible light selective reflective cholesteric liquid crystal polymer, and the preparation method thereof. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0026] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 is listed for a specific parameter, it is expected that a range of 60-110 is also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 4 and 5, then the following ranges are all expected: 1-4, 1-5, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this application; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions; all technical features and optional technical features can be combined to form new technical solutions.

[0028] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0029] Chiral liquid crystal polymers possess a unique helical structure due to the presence of asymmetric chiral centers in their molecular structure. This helical structure endows them with many optical properties not found in conventional liquid crystal polymers, such as selective reflection and transmission, circular dichroism, high optical rotation, and optical dispersion. Chiral liquid crystal polymers can display different liquid crystal phases, including chiral smectic phases, cholesteric phases, and blue phases, each with different application ranges.

[0030] The selective reflection and transmission wavelengths of cholesteric and blue phase liquid crystals are determined by their pitch, which is influenced by polymer composition and external factors such as temperature, electric field, and magnetic field. Controlling the selective reflection wavelength through pitch variation is a challenge in the practical application of cholesteric and blue phase liquid crystal polymers and has become a research hotspot. Research on pitch regulation of cholesteric and blue phase liquid crystal polymers and exploring their potential applications mainly focuses on the following aspects.

[0031] I. The Influence of Liquid Crystal Polymer Structure and Composition on Pitch. Current research in this area mostly involves incorporating chiral liquid crystals into a nematic liquid crystal matrix, followed by polymerization in a prepolymer to prepare chiral liquid crystal polymers with different selective reflection wavelengths. These can be broadly categorized into polymer-dispersed liquid crystals and polymer-stabilized liquid crystals. This application investigates the influence of different comonomer compositions on polymer pitch. The study shows that selecting monomers with suitable structures and changing the proportion of comonomers can control the pitch.

[0032] II. The Influence of Temperature on the Pitch of Liquid Crystal Polymers. Currently, the study on the influence of temperature on pitch is the most extensive and comprehensive, and also the most likely to lead to practical applications.

[0033] III. The Influence of Light on the Reflection Wavelength of Chiral Liquid Crystal Polymers. This type of research primarily involves introducing azophenyl groups into liquid crystal polymers and using light to induce configurational changes in these groups, thereby controlling the selective reflection wavelength. These liquid crystal polymers show promise in information storage, optical devices, and medical materials. Other research modifies the helical direction of chiral liquid crystals through light, achieving control over the helical structure, which has potential applications in optical switching and other optical devices.

[0034] IV. Changing the pitch by applying an external electric field. This allows for control of the pitch of a digital liquid crystal display by varying external conditions, enabling applications in optical fields such as information storage, display, and optical sensors.

[0035] Significant progress has been made in the research on pitch and selective reflection wavelength control both domestically and internationally, laying the foundation for the application of cholesteric and blue phase liquid crystals. However, to truly realize the practical application of cholesteric and blue phase liquid crystal polymers and broaden their application range, the following properties still need further improvement.

[0036] First, ensuring that the selective reflection wavelength of cholesteric or blue phase liquid crystal polymers falls within the visible light region at room temperature or even lower—that is, displaying color at low or room temperature and maintaining color display over a wide temperature range—is both a key focus and a significant challenge in the research. Reports of chiral polymers achieving visible light reflection wavelengths at relatively high temperatures, with a narrow temperature range for visible light reflection, hinder practical applications. Currently, the only known reports of chiral liquid crystal polymers exhibiting room-temperature color development are from our research group and the Zhang Baoyan research group at Northeastern University. However, the types and number of polymers reported are very limited, the reflection wavelength coverage is narrow, and research on controlling the reflection wavelength has not been conducted, all of which severely restrict practical applications. Second, achieving the application of cholesteric or blue phase chiral liquid crystal polymers requires precise control of their selective reflection wavelength (pitch) through external conditions such as temperature, electric field, and light. Currently, research on controlling the selective reflection wavelength at room temperature and over a wide temperature range is limited. Furthermore, while there is considerable fundamental research on chiral liquid crystal polymers, related practical applications are still relatively few.

[0037] This study aims to prepare chiral liquid crystal monomers with different helical twisting forces and achiral liquid crystal monomers, and to introduce strongly polar groups, ionic groups, and photoluminescent groups such as azobenzene into the monomer molecular structure. Chiral liquid crystal compounds will be prepared by graft copolymerization of these monomers with hydrogen-containing polysiloxanes. These liquid crystal polymers are expected to possess the following characteristics.

[0038] Liquid crystal polymers possess a wide liquid crystal range and a low glass transition temperature, which are prerequisites for practical applications. Different liquid crystal monomers have been polymerized with polysiloxanes to prepare chiral liquid crystal polymers with low glass transition temperatures (-20℃) and wide liquid crystal ranges (above 100℃). If monomers with even better liquid crystal properties can be synthesized further and copolymerized with polysiloxanes in appropriate proportions, the liquid crystal range of the polymer will be further broadened.

[0039] The synthesized chiral liquid crystal polymers exhibit room-temperature color development, a color development range covering the entire visible light spectrum, and a wide color development temperature range. Studies have shown that liquid crystal polymers reflecting visible light at room temperature can be achieved by copolymerizing chiral and non-chiral monomers with different structures. The cholesteric and blue-phase liquid crystal polymers synthesized in this application exhibit selective reflection wavelengths between 359 and 654 nm at room temperature, and the color development temperature range of some polymers exceeds 150°C. Therefore, further research can be conducted to achieve selective wavelength coverage of the entire visible light spectrum at room temperature for liquid crystal polymers, while ensuring a wide color development temperature range to meet the needs of various applications.

[0040] The synthesized liquid crystal polymers can potentially achieve precise control over their pitch changes through temperature, light, and electric field intensity. The study demonstrated that the selective reflection wavelength of the liquid crystal polymers continuously varied between 503 and 405 nm from room temperature to 150 °C. Furthermore, the reflection wavelength of the prepared polymers varied between 900 and 600 nm under varying electric field intensity. Further optimization of the monomer and liquid crystal polymer structure holds promise for achieving continuous variation of the reflection wavelength across the entire visible light region under the influence of temperature and electric field, and for exhibiting specific reflection wavelengths at a particular temperature or voltage to meet diverse application requirements. Introducing photoisomerized azophenyl groups into the polymers holds promise for achieving photochromism. In addition to preparing liquid crystal polymers with temperature-dependent pitch, liquid crystal polymers with low pitch dependence on temperature were also prepared; the pitch of these polymers remained essentially unchanged from room temperature to 100 °C. Liquid crystal polymers with different pitch-temperature dependence have different application ranges.

[0041] The synthesized liquid crystal polymers exhibit excellent chemical and optical stability. All synthesized liquid crystal polymers demonstrate good thermal stability, with 5% weight loss occurring at temperatures above 290 °C. Experiments show that the liquid crystal polymers retain their original properties even after repeated heating and cooling. Some liquid crystal polymers show virtually no change in color after being stored at room temperature for more than 3 years, providing a guarantee for practical applications.

[0042] To obtain chiral liquid crystal elastomers with different liquid crystal phases, especially cholesteric and blue phases, this study investigates the relationship between the structure and properties of chiral liquid crystal elastomers, and examines the influence of monomer and chiral crosslinking agent composition on liquid crystal phase behavior and liquid crystal properties, laying a foundation for the application of chiral liquid crystal elastomers. This application synthesizes cholesteric liquid crystal monomers 4-undecyloxybenzoic acid cholesterol ester (M1), cholesteric acrylate (M2), and 4-allyloxybenzoic acid cholesterol ester (M3), and a novel chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5). The chiral crosslinking agent and different chiral liquid crystal monomers were graft copolymerized with tetramethylcyclotetrasiloxane (D4H) to prepare novel P2 series chiral liquid crystal elastomers.

[0043] 1. Synthesis methods of liquid crystal monomers, chiral crosslinking agents, and liquid crystal elastomers 1. Synthesis of liquid crystal monomers (1) Synthesis of 4-undecyloxybenzoic acid cholesterol ester (M1): 1) Synthesis of undecenoyl chloride 35.0 mL (0.170 mol) of undecenoic acid solution and 30.0 mL (0.390 mol) of thionyl chloride were added to a 100 mL round-bottom flask. 0.50 g of p-hydroxyanisole was added as a polymerization inhibitor. The mixture was stirred at room temperature for 1 h, then heated to 60.0 °C and refluxed for 5 h. After the reaction was complete, excess thionyl chloride was removed, and the fraction collected at 128.0–132.0 °C was collected by vacuum distillation, yielding 75.0%. Reaction formula: .

[0044] (2) Synthesis of 4-undecenoyloxybenzoic acid 36.0 g (0.260 mol) of p-hydroxybenzoic acid was added to a 250 mL round-bottom flask, along with 100 mL of tetrahydrofuran and a few drops of pyridine solution. Then, 40.0 g (0.200 mol) of undecenoic chloride was slowly added dropwise using a dropping funnel at room temperature. After the addition was complete, the mixture was allowed to react at room temperature for 2 hours, then heated to 60.0 °C and refluxed for 8 hours. After the reaction was complete, the mixture was cooled, and the reaction solution was poured into water. The pH was adjusted to approximately 4 with dilute hydrochloric acid. The mixture was filtered, washed several times with hot water, and then recrystallized from ethanol to obtain white flaky crystals with a melting point of 135.0–138.0 °C and a yield of 78.0%. Reaction formula: .

[0045] (3) Synthesis of 4-undecenoyloxybenzoyl chloride 20.0 g (0.0660 mol) of 4-undecyloxybenzoic acid was added to a 100 mL round-bottom flask, followed by 25.0 mL of thionyl chloride solution. The reaction was carried out at room temperature for 1 h, then refluxed at 60.0 °C for 4 h. After the reaction was complete, the remaining thionyl chloride was removed to obtain a deep red viscous liquid in 80.0% yield. Reaction formula: .

[0046] (4) Synthesis of 4-undecyloxybenzoic acid cholesterol ester (M1) 10.0 g (0.0260 mol) of cholesterol was added to a 100 mL round-bottom flask, along with 30.0 mL of chloroform and 4.30 mL of triethylamine. The mixture was stirred until dissolved, and then 10.0 g (0.0310 mol) of 4-undecenoyloxybenzoyl chloride solution was slowly added dropwise. After the addition was complete, the mixture was allowed to react at room temperature for 3 h, followed by reflux with stirring for 5 h. After the reaction was complete, the reaction solution was poured into ethanol to precipitate the solid. The precipitate was filtered, washed three times with hot ethanol, and then recrystallized from acetone to obtain a white powdery solid with a melting point of 112.0 °C and a yield of 63.0%. Reaction formula: .

[0047] (2) Synthesis of cholesterol acrylate (M2) 1) Synthesis of Acryloyl Chloride 22.0 mL of acrylic acid was added to a 100 mL round-bottom flask, followed by 22.0 mL of thionyl chloride. The mixture was reacted at room temperature for 2 hours, then heated to reflux at 60.0 °C for 3 hours. After the reaction was complete, excess thionyl chloride was removed, yielding 85.0%. Reaction formula: .

[0048] 2) Synthesis of cholesterol acrylate (M2) 35.0 g (0.0910 mol) of cholesterol was added to a 250 mL round-bottom flask, along with 100 mL of tetrahydrofuran and a few drops of pyridine solution. After dissolution, the above-mentioned acryloyl chloride solution was slowly added dropwise. The mixture was heated to reflux at 60.0 °C for 4 h. After the reaction was complete, the solvent was distilled off under reduced pressure, poured into water, filtered, and ethanol was added to the solid. The mixture was boiled, and the supernatant was filtered off. Ethanol was then added to the oily residue at the bottom, and the process was repeated 4-5 times. The solutions were combined, cooled, and white flaky crystals precipitated, with a yield of 82.0%. Reaction formula: .

[0049] (3) Synthesis of 4-allyloxybenzoic acid cholesterol ester (M3) 1) Synthesis of 4-allyloxybenzoic acid 42.0 g (0.300 mol) of p-hydroxybenzoic acid was added to a 250 mL round-bottom flask, dissolved in 75.0 mL of ethanol, and slowly added dropwise with stirring. A 50.0 mL aqueous solution prepared from 40.0 g of potassium hydroxide and 0.250 g of potassium iodide was added. After slightly cooling, 35.0 mL of bromopropene was slowly added dropwise. The reaction was carried out at room temperature for 1 h, and then refluxed at 65.0 °C for 15 h. After the reaction was complete, most of the solvent was distilled off under reduced pressure and poured into a beaker containing a large amount of water. The solution was acidified with 20% hydrochloric acid to a pH of 3-4. At this point, a large amount of white precipitate was formed in the beaker. The precipitate was filtered, washed twice with cold water and twice with hot water, dried, recrystallized from ethanol, filtered, and dried to obtain 34.0 g of white needle-like crystals, with a yield of 65.0%. Reaction formula: .

[0050] 2) Synthesis of 4-allyloxybenzoyl chloride 21.0 g (0.120 mol) of 4-allyloxybenzoic acid was added to a 100 mL round-bottom flask, followed by 35.0 mL of thionyl chloride solution. The mixture was stirred at room temperature for 1 h, then heated under reflux at 60.0 °C for another 6 h. After the reaction was complete, excess thionyl chloride was removed to obtain a pale yellow, transparent liquid in 80.0% yield. Reaction formula: .

[0051] 3) Synthesis of 4-allyloxybenzoic acid cholesterol ester (M3) 10.0 g (0.0260 mol) of cholesterol was added to a 100 mL round-bottom flask, followed by 30.0 mL of chloroform. The mixture was stirred until dissolved, and 5.00 g of anhydrous sodium carbonate was added as an acid remover. Then, 5.90 g (0.0300 mol) of 4-allyloxybenzoyl chloride was slowly added dropwise. The reaction was carried out at room temperature for 3 h, followed by reflux with stirring for 5 h. After the reaction was complete, most of the solvent was distilled off under reduced pressure. The concentrated solution was poured into water, filtered, and washed four times with hot ethanol to obtain 11.0 g of a white powdery solid. Melting point: 116~117℃, yield: 77.0%. Reaction formula: .

[0052] 2. Synthesis of chiral crosslinking agents (1) Synthesis of chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5) 1) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl 45.0 g (0.240 mol) of 4,4'-biphenyl was added to a 250 mL round-bottom flask, along with 150 mL of tetrahydrofuran and a few drops of pyridine solution. The mixture was stirred until dissolved, and then 7.60 g (0.0390 mol) of 4-allyloxybenzoyl chloride was slowly added dropwise. The reaction was carried out at room temperature for 2 h, followed by reflux at 60.0 °C for 36 h. After the reaction was complete, most of the solvent was distilled off under reduced pressure. The reaction solution was poured into water, filtered to obtain a solid, washed with 3% sodium hydroxide solution to remove excess biphenyl, then acidified with 2% hydrochloric acid, dried, and hot-filtered with ethanol. The filtrate was allowed to stand to precipitate, filtered, dried, recrystallized from ethanol, and dried again. The yield was 38.6%. Reaction formula: .

[0053] 2) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate monoester 4.00 g (0.0120 mol) of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl was added to a 100 mL round-bottom flask, along with 20.0 mL of tetrahydrofuran and a few drops of pyridine solution. 8.90 g of camphor anhydride dissolved in 20.0 mL of tetrahydrofuran solution was slowly added dropwise, followed by 0.180 g of DMAP and 1.19 g of DCC. The mixture was stirred at room temperature for 1 h and then reacted at 40.0 °C for 36 h. After the reaction was complete, the byproduct dicyclohexylurea (DCU) was removed by filtration, and the filtrate was retained. Most of the tetrahydrofuran solution was distilled off under reduced pressure. The concentrated solution was poured into deionized water, filtered, washed with hot water, recrystallized with a small amount of ethanol, dried, and stored for later use. The yield was 43.0%. Reaction formula: .

[0054] 3) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid monoester acyl chloride The above-mentioned monoester solid was added to a 100 mL round-bottom flask, followed by 25.0 mL of thionyl chloride solution. The reaction was carried out at room temperature for 1 h, then refluxed at 60.0 °C for 10 h. After the reaction was completed, excess thionyl chloride was removed by first distillation under normal pressure and then by distillation under reduced pressure, with a yield of 57.2%. Reaction formula: .

[0055] 4) Synthesis of chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5) 3.00 g (0.00900 mol) of 4-(4-allyloxy)benzoyloxy-4'-biphenol was dissolved in 30.0 mL of tetrahydrofuran and a few drops of pyridine solution. This solution was then slowly added dropwise to an acyl chloride solution dissolved in 20.0 mL of tetrahydrofuran. The reaction was carried out at room temperature for 1 h, followed by reflux at 60.0 °C for 36 h. After the reaction was complete, most of the solvent was distilled off under reduced pressure. The concentrated solution was poured into water, and a solid precipitated. The solid was filtered, washed thoroughly with plenty of water, dried, and purified by silica gel chromatography. The yield was 34.3%. Reaction formula: .

[0056] 3. Synthesis of Liquid Crystal Elastomer Series The monomer, chiral crosslinking agent, and tetramethylcyclotetrasiloxane (D4H) were dissolved in toluene according to the molar ratios in Table 1. After complete dissolution, a small amount of hexachloroplatinic acid complexing catalyst was added under nitrogen protection, and the reaction was carried out at 95.0℃ for 36 h. The reaction was monitored using an infrared spectroscopy instrument until the Si-H bonds (2166 cm⁻¹) in the reactants were detected. -1 The reaction was stopped when the stretching vibration peak of ) completely disappeared. Most of the solvent was distilled off under reduced pressure, and the remainder was poured into ethanol to precipitate a solid. The solid mixture was filtered, soaked in a methanol-chloroform mixture, allowed to stand overnight, filtered again to remove unreacted monomers, and then dried under vacuum at room temperature to obtain product P. 2-1 ~P 2-6 .

[0057] Table 1 Liquid Crystal Elastomer P 2~1 ~P 2~6 Feeding situation

[0058] Note: a: Molar percentage of chiral crosslinking agent M5 in (M1+M2+M3); M1: Cholesterol 4-undecyloxybenzoate; M2: Cholesterol acrylate; M3: Cholesterol 4-allyloxybenzoate; M5: 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester.

[0059] Liquid crystal elastomer P 2-1 ~P 2-6 Synthetic route (2.24) .

[0060] 2. Perform relevant performance tests on the obtained liquid crystal intermediate, monomer, chiral crosslinking agent, and liquid crystal elastomer: 1. Infrared analysis of liquid crystal intermediates (1) 4-Undecyloxybenzoic acid The main absorption peaks of 4-undecyloxybenzoic acid are assigned in Table 2, and its infrared spectrum is shown in [reference needed]. Figure 1 .

[0061] Figure 1 Middle, 3076cm -1 The peak corresponds to the stretching vibration of unsaturated hydrocarbons; 2925 cm⁻¹ -1 2855cm -1 This is the stretching vibration peak of saturated hydrocarbons; 2674 cm⁻¹ -1 2553cm -1 Peaks for stretching and deformation vibrations of the carboxyl hydroxyl group; 1685 cm⁻¹ -1 The absorption peak at 1604-1466 cm⁻¹ represents the stretching vibration of the carbonyl group in carboxylic acid. -1 The peak at 3378 cm⁻¹ represents the stretching vibration absorption of the benzene ring skeleton. The presence of these peaks indicates that the product possesses the characteristic peaks of the basic functional groups of the reactants. -1 The phenolic hydroxyl peaks on the left and right disappeared at 1755 cm⁻¹. -1 The peak at this point represents the stretching vibration of the ester carbonyl group. This peak is newly generated, indicating that an esterification reaction has occurred and the reaction is complete.

[0062] The above analysis shows that the compound is 4-undecyloxybenzoic acid, which is consistent with the molecular structure design.

[0063] Table 24 - Assignment of infrared absorption peaks of undecenoyloxybenzoic acid

[0064] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0065] (2) 4-Allyloxybenzoic acid The main absorption peaks of 4-allyloxybenzoic acid are assigned in Table 3, and its infrared spectrum is shown in [reference needed]. Figure 2 .

[0066] Figure 2 Medium, 3086~3032cm -1 The corresponding absorption peaks are for the stretching vibrations of the alkene bond and the unsaturated =CH on the benzene ring; 2668 cm⁻¹ -1 2560cm -1 Peaks for stretching and deformation vibrations of the carboxyl hydroxyl group; 1680 cm⁻¹ -1 The corresponding absorption peak for the carbonyl stretching vibration of aromatic carboxylic acids is 1607~1450 cm⁻¹. -1 Corresponding stretching vibration peak of the benzene ring skeleton; 815 cm⁻¹ -1 The absorption peak at 3378 cm⁻¹ is a characteristic absorption peak of para-substitution of the benzene ring. The presence of the above peaks indicates that the product possesses the characteristic peaks of the basic functional groups of the reactants. The reactant's 3378 cm⁻¹... -1 The disappearance of the phenolic hydroxyl peaks on the left and right indicates that the reaction is complete.

[0067] The above analysis shows that the compound is 4-allyloxybenzoic acid, which is consistent with the molecular structure design.

[0068] Table 34 - Assignment of infrared absorption peaks of allyloxybenzoic acid

[0069] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0070] (3) 4-(4-allyloxy)benzoyloxy-4′-hydroxybiphenyl The main absorption peak assignments for 4-(4-allyloxy)benzoyloxy-4′-hydroxybiphenyl are shown in Table 4, and their infrared spectra are shown in [reference needed]. Figure 3 .

[0071] Figure 3 Medium, 2980~2845cm -1 The absorption peak at 1648 cm⁻¹ is the stretching vibration absorption peak of saturated CH₄. -1 The absorption peak at 1605-1488 cm⁻¹ corresponds to the stretching vibration of an unsaturated carbon-carbon double bond. -1 The absorption peak corresponds to the stretching vibration of the aromatic ring skeleton; 1261 cm⁻¹ -1 The absorption peak is for the stretching vibration of the ether bond; 767 cm⁻¹ -1 The characteristic absorption peaks at the para-substitution of the benzene ring correspond to these peaks, indicating that the product possesses the characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of 4-allyloxybenzoic acid, the peak at 3449 cm⁻¹ is [not specified]. -1A stretching vibration peak of the phenolic hydroxyl group appeared at 2668 cm⁻¹. -1 2560cm -1 The absence of stretching and deformation vibration peaks of the carboxyl hydroxyl group at 1703 cm⁻¹ indicates that the carboxyl group has reacted; -1 The absorption peak corresponding to the stretching vibration of the ester carbonyl group is newly generated, indicating that an esterification reaction has occurred and the reaction is complete.

[0072] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4′-hydroxybiphenyl, which is consistent with the molecular structure design.

[0073] Table 44 - Assignment of infrared peaks for (4-allyloxy)benzoyloxy-4′-hydroxybiphenyl

[0074] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0075] (4) (+)-Camphoric acid The main absorption peaks of (+)-camphoric acid are assigned in Table 5, and their infrared spectra are shown in Table 5. Figure 4 .

[0076] Figure 4 In this process, influenced by the hydrogen bonding between the carboxyl groups on camphoric acid, the concentration at 3010 cm⁻¹ -1 Centered on, within 3326~2546cm -1 A broad and strong absorption peak appeared within the range; 2977 cm⁻¹ -1 2899cm -1 The peak corresponds to the stretching vibration of saturated hydrocarbons; 2755 cm⁻¹ -1 2681cm -1 This is the deformation vibration peak of the carboxylic acid hydroxyl group; 1688 cm⁻¹ -1 The stretching vibration peak corresponding to the carbonyl group of the carboxylic acid; 1459 cm⁻¹ -1 Corresponding peak for methylene stretching vibration; 1406 cm⁻¹ -1 1284cm -1 The corresponding peak corresponds to the methyl stretching vibration.

[0077] Based on the above analysis, the compound is (+)-camphoric acid. Table 5. Infrared spectra of (+)-camphoric acid

[0078] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0079] (5) 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate monoester The main absorption peak assignments of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate monoester are shown in Table 6, and its infrared spectrum is shown in [reference needed]. Figure 5 .

[0080] Figure 5 Middle, 2973~2922cm -1 The range is the stretching vibration peak of saturated hydrocarbons; 1806 cm⁻¹ -1 The peak at 1606-1525 cm⁻¹ represents the stretching vibration of the ester carbonyl group. -1 The absorption peak at 1492 cm⁻¹ represents the stretching vibration of the benzene ring skeleton CS. -1 The peak represents the stretching vibration of the methylene group; 1378 cm⁻¹ -1 The left and right peaks are the stretching vibration peaks of methyl groups; 1257 cm⁻¹ -1 The peak at 982 cm⁻¹ represents the stretching vibration of the ether bond. -1 These are characteristic absorption peaks for para-substitution of aromatic rings. The presence of these peaks indicates that the product possesses characteristic peaks of the basic functional groups of the reactants. (3024~2794 cm⁻¹) -1 The broad and strong absorption peak is caused by the presence of -COOH; 2851 cm⁻¹ -1 The small peaks around 1762 cm⁻¹ are the deformation vibration peaks of the hydroxyl group (-OH) in carboxylic acids. -1 The peak at 3449 cm⁻¹ represents the stretching vibration of the carboxyl carbonyl group. The presence of these peaks indicates that the product still contains a carboxyl group. Compared with the infrared spectrum of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl, the peak at 3449 cm⁻¹ is [missing information]. -1 The disappearance of the stretching vibration absorption peak of the phenolic hydroxyl group indicates that the phenolic hydroxyl group has undergone a reaction.

[0081] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate monoester, which is consistent with the molecular structure design.

[0082] Table 64 Infrared Peak Assignments of 4'-(4-allyloxy)benzoyloxy-4'-biphenol camphorate monoester

[0083] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0084] 2. Infrared analysis of liquid crystal monomers (1) Cholesterol 4-Undecyloxybenzoate The main absorption peak assignments of 4-undecyloxybenzoic acid cholesterol ester are shown in Table 7, and its infrared spectrum is shown in [reference needed]. Figure 6 .

[0085] Figure 6 Middle, 3069cm -1The peak corresponds to the stretching vibration of unsaturated hydrocarbons; 2924~2855 cm⁻¹ -1 The corresponding stretching vibration peak for saturated hydrocarbons is 1643 cm⁻¹. -1 The peak at 768 cm⁻¹ represents the C=C stretching vibration of the double bond. -1 These are characteristic absorption peaks for para-substitution of the benzene ring. The presence of these peaks indicates that the product possesses characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of cholesterol, 3437 cm⁻¹ is... -1 The disappearance of the hydroxyl peak at 2674 cm⁻¹ indicates that the hydroxyl group has undergone a reaction; compared with 4-undecenoyloxybenzoic acid, the peak at 2674 cm⁻¹ is... -1 2553cm -1 The absence of stretching and deformation vibration peaks of the carboxyl hydroxyl group at 1768 cm⁻¹ indicates that the carboxyl group underwent a reaction; -1 1716cm -1 The peak at this point represents the stretching vibration of the carbonyl group in the ester. This peak is newly generated, indicating that an esterification reaction has occurred and the reaction is complete.

[0086] The above analysis shows that the compound is 4-undecenoyloxybenzoic acid cholesterol ester, which is consistent with the molecular structure design.

[0087] Table 74 - Assignment of infrared peaks for undecenoyloxybenzoate cholesterol ester

[0088] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0089] (2) Cholesterol acrylate The main absorption peak assignments of cholesterol acrylate are shown in Table 8, and its infrared spectrum is shown in [reference needed]. Figure 7 .

[0090] Figure 7 Middle, 3031cm -1 The peak corresponds to the stretching vibration of carbon and hydrogen on the alkene bond; 2941 cm⁻¹ -1 2850cm -1 The peak represents the stretching vibration of saturated hydrocarbons; 1635 cm⁻¹ -1 The peak at 3437 cm⁻¹ represents the carbon-carbon stretching vibration absorption peak of the alkene bond. The presence of these peaks indicates that the product possesses characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of cholesterol, the peak at 3437 cm⁻¹ is... -1 The disappearance of the hydroxyl peak at 1710 cm⁻¹ indicates that the hydroxyl group has undergone a reaction; -1 The peak at this point represents the stretching vibration of the carbonyl group in the ester. This peak is newly generated, indicating that an esterification reaction has occurred and the reaction is complete.

[0091] The above analysis shows that the compound is cholesterol acrylate, which is consistent with the molecular structure design.

[0092] Table 8. Infrared peak assignments of cholesterol acrylate.

[0093] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0094] (3) 4-Allyloxybenzoic acid cholesterol ester The main absorption peak assignments of 4-allyloxybenzoic acid cholesterol ester are shown in Table 9, and its infrared spectrum is shown in [reference needed]. Figure 8 .

[0095] Figure 8 Middle, 3056cm -1 The peak corresponds to the stretching vibration of unsaturated hydrocarbons; 2961~2850 cm⁻¹ -1 The peaks correspond to the stretching vibrations of saturated hydrocarbons; the presence of these peaks indicates that the product possesses characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of cholesterol, 3437 cm⁻¹... -1 The disappearance of the hydroxyl peak at 2668 cm⁻¹ indicates that the hydroxyl group underwent a reaction; compared with the infrared spectrum of 4-allyloxybenzoic acid, the peak at 2668 cm⁻¹... -1 2560cm -1 The absence of stretching and deformation vibration peaks of the carboxyl hydroxyl group at 1705 cm⁻¹ indicates that the carboxyl group has reacted; -1 The peak at this point represents the stretching vibration of the carbonyl group in the ester. This peak is newly generated, indicating that an esterification reaction has occurred and the reaction is complete.

[0096] The above analysis shows that the compound is 4-allyloxybenzoic acid cholesterol ester, which is consistent with the molecular structure design.

[0097] Table 94 - Infrared Peak Assignments of Cholesterol Allyloxybenzoate

[0098] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0099] 3. Infrared analysis of chiral crosslinking agents (1) 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester The main absorption peak assignments of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester are shown in Table 10, and its infrared spectrum is shown in [reference needed]. Figure 9 .

[0100] Figure 9 Middle, 3078cm -1 The peak represents the stretching vibration of unsaturated hydrocarbons; 2970~2862 cm⁻¹ -1 This is the stretching vibration peak of saturated hydrocarbons; 1709 cm⁻¹ -1The peak represents the carbonyl stretching vibration of the ester group; 1577~1495 cm⁻¹ -1 This is the stretching vibration peak of the benzene ring skeleton; 1363 cm⁻¹ -1 The peak represents the stretching vibration of methyl groups; 804 cm⁻¹ -1 These are characteristic absorption peaks for para-substitution of the aromatic ring, and the presence of these peaks indicates that the product possesses characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl, 3449 cm⁻¹ is [not specified]. -1 The disappearance of the stretching vibration absorption peak of the phenolic hydroxyl group indicates that the phenolic hydroxyl group has reacted; compared with the infrared spectrum of camphoric acid, the peak at 2681 cm⁻¹ is [missing information]. -1 2755cm -1 The disappearance of the stretching and deformation vibration peaks of the carboxyl hydroxyl group indicates that the carboxyl group has undergone a reaction and the reaction is complete.

[0101] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester, which is consistent with the molecular structure design.

[0102] Table 104 Infrared Peak Assignments for 4-(4-allyloxy)benzoyloxy-4'-biphenol camphorate diester

[0103] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0104] 4. Infrared analysis and spectra of liquid crystal elastomers (1) Infrared analysis of D4H The main absorption peaks of D4H are assigned in Table 11, and their infrared spectra are shown in Table 11. Figure 10 .

[0105] Figure 10 Middle, 2168cm -1 The peak at 1251 cm⁻¹ represents the stretching vibration of a silicon-hydrogen bond. -1 The peaks represent the symmetrical deformation vibrations of methyl groups bonded to silicon; 1131~1023 cm⁻¹ -1 The stretching absorption peaks of silicon-oxygen-silicon (Si-O-Si) are observed in the range of 951–803 cm⁻¹. -1 The peaks at these locations represent the bending vibrations of silicon-hydrogen bonds, and these peaks are all characteristic absorption peaks of D4H.

[0106] Based on the above analysis, the compound can be identified as D4H, which is consistent with the molecular structure design.

[0107] Table 11. Infrared peak assignments for tetramethylcyclotetrasiloxane.

[0108] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0109] (2) Infrared analysis of P2 series liquid crystal elastomers The infrared spectra of the P2 series of liquid crystal elastomers are almost identical, so P was selected. 2-1 P 2-3 P 2-4 For example, see the infrared spectrum. Figure 11 Using liquid crystal elastomer P 2-4 Taking this as an example for analysis, its infrared spectrum is shown below. Figure 12 The assignments of its main absorption peaks are shown in Table 12.

[0110] Compare Figure 12 Liquid crystal elastomers and Figure 10 The infrared spectrum of D4H shows that at 2166 cm⁻¹... -1 The stretching vibration absorption peak of the silicon-hydrogen bond almost disappears, indicating that the hydrogen atoms in the silicon-hydrogen bond of D4H are replaced by other groups; 1640 cm⁻¹ -1 The carbon-carbon stretching vibration peaks of the olefin bonds at the left and right positions have essentially disappeared, indicating that the olefin bonds in both the monomer and the chiral crosslinking agent have reacted, and the graft copolymerization reaction is complete; in the polymer, the peaks at 2951~2865 cm⁻¹... -1 The range corresponds to the stretching vibration absorption peak of saturated alkyl hydrocarbons; 1709 cm⁻¹ -1 The absorption peak at this point is the carbonyl stretching vibration of the ester; 1607~1374 cm⁻¹ -1 The range corresponds to the stretching vibration absorption peak of the carbon skeleton in the benzene ring; 1263 cm⁻¹ -1 The peak at 1137-1023 cm⁻¹ is the vibrational peak of the methyl group bonded to silicon. -1 The broad and strong absorption peak appearing within the range is caused by the stretching vibration absorption of silicon-oxygen-silicon; 786 cm⁻¹ -1 The peak at position 1 is a characteristic absorption peak for para-substitution of the aromatic ring. Compared with the monomer and D4H, the peak positions and intensities of the above groups show almost no change, indicating that the polymer backbone is still tetramethylcyclotetrasiloxane, and the characteristic absorption peaks of each monomer are still retained. The above analysis confirms that the monomer, chiral crosslinking agent, and D4H underwent a hydrosilylation reaction.

[0111] The above analysis shows that the P2 series of liquid crystal elastomers conforms to the molecular structure design.

[0112] Table 12 Liquid Crystal Elastomer P 2-4 Infrared peak attribution

[0113] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0114] 4. NMR analysis of chiral crosslinking agents and liquid crystal elastomers (1) NMR analysis of 4-(4-allyloxybenzoyloxy)-4'-hydroxybiphenyl camphorate diester (M5) The major chemical shifts of 4-(4-allyloxy)-benzoyloxy-4'-hydroxybiphenyl camphorate diester are shown in Table 13, and the NMR spectrum is shown in [reference needed]. Figure 13 .

[0115] Depend on Figure 13 As shown in Table 13, the characteristic peaks of the monomer NMR spectrum are consistent with the molecular structure, and the integral area ratio of each hydrogen atom is consistent with the number ratio of hydrogen atoms, indicating that the chiral crosslinking agent M5 conforms to the molecular structure design.

[0116] Table 134 Chemical Shift Assignments of 4-(4-allyloxybenzoyloxy)-4'-hydroxybiphenyl camphorate diester

[0117] Note: s: singlet; d: doublet; t: triplet; m: multiplet.

[0118] .

[0119] 4-(4-Allyloxybenzoyloxy)-4'-hydroxybiphenyl camphorate diester (2) NMR analysis of D4H The NMR spectrum of D4H is shown below. Figure 14 As can be seen from the NMR spectrum, the singlet near chemical shift 4.71 is the hydrogen proton peak in Si-H, and the peak around 0.23 is the methyl hydrogen proton peak in Si-CH3.

[0120] The above analysis shows that the compound is tetramethylcyclotetrasiloxane (D4H).

[0121] (3) Nuclear magnetic resonance analysis of P2 series liquid crystal elastomers The NMR peak positions of the P2 series of liquid crystal elastomers are roughly the same, so polymer P was selected. 2-3 For example, see the NMR spectrum. Figure 15 .

[0122] Nuclear magnetic resonance spectrum Figure 15In the liquid crystal elastomer, the absorption peaks at δ = 8.17~6.87 are those of the benzene ring; the multiplet at around δ = 5.37 is the absorption peak of the olefin bond on the cholesterol in the cholesterol liquid crystal monomer; the multiplet at δ = 4.78~4.64 is the absorption peak of the hydrogen bond to the carbonyl group of the cholesterol; the absorption peak at δ = 4.58 is the absorption peak of the methylene group bonded to oxygen; the absorption peaks in the range of δ = 2.36~0.88 are the absorption peaks of the hydrogen in the camphor acid five-membered ring and the methyl methylene group on the cholesterol; the peak at around δ = 0.05 is the methyl hydrogen proton peak in Si-CH3. These data indicate that the characteristic absorption peaks of each monomer are still retained after the reaction, and the backbone of the liquid crystal elastomer remains polysiloxane. Compared with the monomer, chiral crosslinking agent, and D4H, the multiplet at the chemical shift δ = 6.07 for the =CH- hydrogen proton disappears; the dd peaks of the protons of the original terminal olefin at δ = 5.42 and δ = 5.28 disappear; δ = The singlet peak of Si-H bond strength at 4.71 has almost completely disappeared; the absorption peak of newly generated Si-CH2- is at δ = 0.68. The above data indicate that the terminal olefin bond has reacted with the silane-hydrogen bond, and the graft copolymerization reaction is complete.

[0123] The above analysis shows that the P2 series of liquid crystal elastomers conforms to molecular design.

[0124] 5. Polarizing microscopy analysis Polarizing microscopy (POM) is an important tool for characterizing liquid crystal states. POM testing and analysis can yield information related to liquid crystal states. Using POM, the softening temperature, melting point, clearing point, transition temperatures between different liquid crystal phases, and liquid crystal texture can be observed. Liquid crystal texture typically refers to the image of a liquid crystal film (10–100 μm thick) observed under a parallel light system using a crossed polarizing microscope (POM), including the presence of extinction points and other forms of extinction structures, as well as color differences. Liquid crystal texture is an important method for determining the type of liquid crystal phase. Common textures of nematic liquid crystals include filamentous texture, globular texture, and schlieren texture. Common textures of smectic liquid crystals include focal conic texture, fan-shaped texture, schlieren texture, and layered texture. Common textures of cholesteric liquid crystals include planar texture, oily filamentous texture, focal conic texture, Grandjean texture, and fingerprint texture. Therefore, the type of liquid crystal phase can be determined by the differences in liquid crystal texture. Furthermore, the texture morphology and changes of liquid crystals are closely related to the heating and cooling rates; slower heating and cooling rates are conducive to the formation of textures and phase states. Different textures correspond to different liquid crystal state types, but generally, the same liquid crystal state type can exhibit one or even multiple textures, and one texture can appear in different liquid crystal state types.

[0125] (1) Texture analysis of liquid crystal monomers, chiral crosslinking agents and polymers The liquid crystal sample was placed in a glass slide and then placed in the sample cell of the hot stage of a polarizing microscope. The heating rate was 5℃ / min and the cooling rate was 2℃ / min. Nitrogen was used as the protective gas. The texture and changes of the sample were observed using reflected light. At the same time, the phase transitions of the sample and the corresponding temperatures could also be observed.

[0126] 1) Texture analysis of chiral crosslinking agent M5 Under a polarizing microscope, the chiral crosslinking agent M5, when heated to 204℃, showed a change in field of view from dark to bright, indicating that the sample began to flow against a gray-green background; when heated to 237℃, fingerprint-like textures appeared in the field of view. Figure 16 (a)); as the temperature increases, the fingerprint texture becomes more and more obvious ( Figure 16 (b)); Upon further heating to 240℃, the texture color changed to a mixture of purple, yellow, and green, and the texture transformed from a fingerprint texture to a cholesteric oily silk texture. Figure 16 (c) When the temperature is raised to 243°C, the texture disappears and the sample enters an isotropic liquid state.

[0127] When the temperature was lowered from a point above the clearing point to 222°C, cholesteric liquid crystal oil filament texture appeared in the field of view. Figure 16 (d) As the temperature continues to decrease, the oil-fiber texture forms a cholesteric liquid crystal fingerprint texture. Figure 16 (e) With continued cooling, the fingerprint texture remained largely unchanged; at 158℃, crystal nuclei appeared in some areas. As the temperature continued to decrease, the crystal nuclei gradually grew and expanded to cover the entire field of view, and the sample entered a crystalline state. Figure 16 (f)).

[0128] Textural analysis revealed that the chiral crosslinking agent M5 is a thermo-induced tautomer cholesteric liquid crystal.

[0129] 2) Texture analysis of polymer P2 series Polymer P 2-1 Grandjean texture of cholesteric liquid crystals appears at room temperature, and its color is dark gray. Figure 17 (a) As the temperature increases, the sample flow accelerates, and an oily filament texture of cholesteric liquid crystals appears. Figure 17 (b) The temperature was increased further until the oil-woven fabric reached 146°C, at which point the texture disappeared and the field of vision darkened.

[0130] As the temperature drops above the clearing point, a Grandjean texture similar to that observed during the warming process appears. Figure 17 (c) ), the texture morphology did not change much as the temperature continued to drop.

[0131] From the texture analysis, polymer P 2-1 It is a cholesteric liquid crystal polymer.

[0132] Liquid crystal elastomer P2-2 Grandjean texture of cholesteric liquid crystals appears at room temperature; as the temperature increases, the texture color gradually changes from dark red to pink, then to yellow, and finally to green. Figure 18 (a) and (b)), but the morphology of the texture remained basically unchanged; when the temperature was raised to 74℃, the texture flow accelerated, and an oily texture appeared in the texture. At this time, the background was green, and it remained unchanged as the temperature increased. Figure 18 (c)); when heated to 112℃, the field of view turns light blue; with further heating, the entire field of view becomes spheroidal texture ( Figure 18 (d) When the temperature is gradually increased to 136℃, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0133] When the temperature is lowered from a point above the clearing point to 136°C, a liquid crystal phase begins to appear in the field of view and rapidly forms a focal cone texture. Figure 18 (e)); As the temperature decreases, the coke cone texture gradually grows and becomes denser. Under the action of external shear force, the coke cone texture transforms into an oil-fiber texture, at which point the background is blue ( Figure 18 (f)); During the cooling process, the background gradually changes from blue to green to yellow. Figure 18 (g)); A rich variety of colors appear at 58℃ ( Figure 18 (h)), at 55℃, the entire field of view turned almost pink. During the cooling process, the reflected wavelength redshifted, which, according to Bragg's equation, indicates that the pitch of the sample increased during the cooling process.

[0134] Texture analysis reveals that the liquid crystal elastomer P... 2-2 It is a thermo-induced tautomerism cholesteric liquid crystal.

[0135] Liquid crystal elastomer P 2-3 When the temperature rises to 30°C, a black Grandjean texture appears throughout the field of view. Figure 19 (a)); As the temperature rises, the field of vision begins to brighten, and a flowing oil-silk texture appears, with the oil silk flowing faster as the temperature increases ( Figure 19 (b) When the temperature is gradually increased to 132°C, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0136] As the temperature drops from a point above the clearing point, a focal cone texture appears during the cooling process. Figure 19 (c) Under the action of external shear force, an indistinct oil-silk texture appears in the field of vision. Figure 19 (d)); as the temperature continues to drop, the texture and color remain largely unchanged.

[0137] Texture analysis reveals that the liquid crystal elastomer P... 2-3 It is a thermo-induced tautomerism cholesteric liquid crystal.

[0138] Liquid crystal elastomer P 2-4 When the temperature rises to 35°C, a yellow Grandjean texture appears in the field of vision. Figure 20 (a)); As the temperature increases, the texture morphology does not change much, but the texture background color changes ( Figure 20 (b) indicates that the pitch of the sample has changed; when the temperature is gradually increased to 125°C, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0139] As the temperature drops from above the clearing point, bright spots appear in the field of view during the cooling process, gradually coalescing into a Grandjean texture similar to the warming texture; during the cooling process, the background of the texture gradually changes from dark blue to blue. Figure 20 (c)) to a color mixture of red and blue ( Figure 20 (d) Changes.

[0140] Texture analysis reveals that the liquid crystal elastomer P... 2-4 It is a thermo-induced tautomerism cholesteric liquid crystal.

[0141] Liquid crystal elastomer P 2-5 Oily silk texture appears during the heating process ( Figure 21 (a) Continuing to raise the temperature, the texture morphology does not change much; when the temperature is gradually raised to 117℃, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0142] Starting from a point higher than the clearing point, the temperature was lowered, and fine coke cone texture appeared during the cooling process. Figure 21 (b) As the temperature continues to drop, the small coke cones gradually aggregate to form a large, fan-shaped coke cone texture. Figure 21 (c) Under the action of external shear force, the coke cone texture transforms into an oil-fiber texture. Figure 21 (d)).

[0143] Texture analysis reveals that the liquid crystal elastomer P... 2-5 It is a thermo-induced tautomerism cholesteric liquid crystal.

[0144] Liquid crystal elastomer P 2-6 During the heating process, a blue planar texture appears in the field of view. Figure 22 (a)), and the field of vision brightens as the temperature increases ( Figure 22 (b) When the temperature is raised to the clearing point of 107°C, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0145] As the temperature drops from a point above the clearing point to 107°C, a blue planar texture similar to that observed during the temperature rise appears. Figure 22 (c) ) The texture and color do not change much during the continued cooling process.

[0146] Texture analysis reveals that the liquid crystal elastomer P...2-6 It is a thermo-induced tautomerism cholesteric liquid crystal.

[0147] 6. DSC Analysis (1) Thermal analysis of chiral crosslinking agent M5 The DSC curve of chiral crosslinking agent M5 is shown in the figure. Figure 23 As can be seen from the figure, the DSC curve of chiral crosslinking agent M5 is similar to that of chiral crosslinking agent M4. It only has a melting point endothermic peak (252℃) and no clearing point endothermic peak. However, under POM, it can be observed that the clearing point of M5 is around 243℃.

[0148] (2) Thermal analysis of liquid crystal elastomers The temperature at which a liquid crystal polymer transitions from a glassy state to a rubbery state or vice versa (i.e., the critical state of freezing and thawing of the movement of one part of the polymer chain relative to other parts) is called the glass transition temperature (T0). g The influence of the glass transition temperature (T) of the side-chain liquid crystal elastomer. g There are many factors that affect the glass transition temperature (T). Generally speaking, the better the flexibility of the side chain, the higher its glass transition temperature (T). g The lower the glass transition temperature (Tg), the more likely the liquid crystal side chain contains rigid groups, which will restrict the movement of chain segments, thus lowering the glass transition temperature (Tg). g The glass transition temperature (T0) increases; chemical cross-linking, on the one hand, hinders the movement of molecular chains, leading to an increase in the glass transition temperature (T0). g On the one hand, the introduction of some flexible chiral crosslinking agents has a plasticizing effect similar to that of plasticizers, leading to an increase in the glass transition temperature (T). g The glass transition temperature (T) decreases. g Whether it increases or decreases depends on which of these factors is dominant.

[0149] Clear highlights (T) i The temperature at which a polymer transitions from a liquid crystal state to an isotropic liquid state is called the clearing point (T0). Chemical cross-linking hinders the movement and orientation of mesocrystalline molecules, making it difficult for molecules to form a mesocrystalline orientation order within the liquid crystal elastomer, thus reducing the clearing point (T0). i On the one hand, the degree of crosslinking decreases; on the other hand, as the degree of crosslinking increases, additional energy is required to complete the transition from the liquid crystal state to the isotropic liquid state, thus reducing the clearing point (T). i The temperature of the cleaning point will increase or decrease depending on which of these factors is dominant.

[0150] To eliminate the influence of thermal history, DSC curves of all liquid crystal polymers were obtained after two temperature increases.

[0151] The glass transition temperature and clearing point of the P2 series liquid crystal polymers are shown in Table 14, and their DSC curves are shown in Table 14. Figure 25 The DSC temperature curve of the polymer shows that the liquid crystal elastomer P...2-1 ~P 2-6 The plateau-like transition to liquid crystal elastomer at low temperature for each sample is the glass transition temperature T. g The high-temperature region corresponds to the endothermic peak where the liquid crystal elastomer transitions from the liquid crystal phase to an isotropic state, i.e., the clearing point T. i .

[0152] Compared with liquid crystal polymer P without chiral crosslinking agent 1-1 and P 2-1 It can be observed that polymer P 2-1 The Tg is lower than that of polymer P 1-1 This is because the monomer cholesterol undecanoate benzoate has a long, flexible alkyl chain, and its addition makes the molecular chain movement of the liquid crystal polymer easier, thus lowering its glass transition temperature; P 2-1 The clear spot Ti and mesocrystalline region are higher than polymer P 1-1 This may be due to the interaction between long alkyl chains, which makes the mesocrystalline molecules more regularly and orderly arranged, thus improving the clearing point of the liquid crystal polymer and the temperature range of the mesocrystalline phase.

[0153] Figure 24 The effect of the chiral crosslinking agent M5 content on the phase transition temperature of polymers in the P2 series is presented. Figure 24 As can be seen from the data, for the P2 series polymers, as the content of chiral crosslinking agent M5 in the system increases, the T of the polymer... g The crosslinking effect gradually increases; considering only the molecular structure, since the chiral crosslinking agent M5 contains the rigid structure of phenyl ester biphenyl, its ability to restrict the movement of molecular chain segments may be comparable to that of the cholesteric group in a large molecule; on the other hand, the increase of the chiral crosslinking agent gradually increases the crosslinking effect, which restricts the movement of polymer chain segments and hinders their free rotation, thus increasing T. g Increase; therefore, as the content of chiral crosslinking agent M5 increases, the T of polymer P2 series increases. g Gradually increasing.

[0154] from Figure 24 As can be seen from P 2-2 ~P 2-4 T i The trend is downward because as the content of chiral crosslinking agent M5 increases, the proportions of M1, M2, and M3 in the polymer decrease relatively. Since the liquid crystal range of chiral crosslinking agent M5 is low, as the content of chiral crosslinking agent M5 increases, the Tc of the polymer decreases. i The degree of crosslinking decreases; furthermore, the increase of chiral crosslinking agents enhances the crosslinking effect, hindering the movement and orientation of mesocrystalline molecules. High crosslinking levels disrupt the ordered structure of the liquid crystal, leading to a decrease in Tc. i Decrease. For polymer P 2-6It is difficult to observe the clearing point on DSC; the clearing point is determined by observation using POM.

[0155] Table 14 Liquid Crystal Elastomer P 2-1 ~P 2-6 Thermal analysis results

[0156] Note: T g Glass transition temperature; T i Clear the highlights; T a Mesocrystalline temperature range (T) i -T g ).

[0157] Through infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) 1 The structure, liquid crystal behavior, and thermal properties of the monomers, chiral crosslinkers, and polymers were tested and characterized using IR-NMR, polarized optical microscopy (POM), and differential scanning calorimetry (DSC). The relationship between the structure and properties of the liquid crystal elastomer was also explored. IR and NMR analysis results showed that the structures of the synthesized liquid crystal monomers and liquid crystal elastomers conformed to the molecular design. POM analysis indicated that both the liquid crystal monomers and chiral crosslinkers were cholesteric liquid crystals.

[0158] DSC analysis showed that as the content of chiral crosslinking agent in the system increased, the Tt of the P2 series liquid crystal polymers increased. g The value first decreases and then increases; the T value of liquid crystal polymers i The values ​​all decreased with increasing chiral crosslinking agent content in the system. Liquid crystal polymers exhibit a wide mesocrystalline range, and this mesocrystalline range gradually decreases with increasing chiral crosslinking agent content.

[0159] Figure 26 This indicates that the selective wavelength can be controlled by adjusting the amount of crosslinking agent used. Figure 27 The maximum selectivity wavelength of a single liquid crystal at different temperatures indicates a large color change range.

[0160] This application prepared chiral liquid crystal elastomers with different liquid crystal phases by controlling the monomer structure and composition in the polymerization system, especially a blue phase liquid crystal elastomer with a wide temperature range.

[0161] This application synthesizes liquid crystal monomers 4-undecyloxybenzoic acid cholesterol ester (M1), cholesterol acrylate (M2), 4-allyloxybenzoic acid cholesterol ester (M3), and the chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5). Monomers M1, M2, and M3 are graft copolymerized with chiral crosslinking agent M5 and tetramethylcyclotetrasiloxane (D4H) to obtain the P2 series of side-chain liquid crystal elastomers. FT-IR and 1 H-NMR analysis showed that the liquid crystal monomer, the chiral crosslinking agent M5, and the series of side-chain liquid crystal elastomers P2 all conformed to the molecular design.

[0162] POM analysis showed that monomers M1, M2, and M3, chiral crosslinker M5, and the P2 series polymers all exhibited liquid crystal properties. Among them, monomers M1, M2, M3, and chiral crosslinker M5 were all cholesteric liquid crystals. The P2 series liquid crystal elastomers all exhibited significant liquid crystal textures during heating and cooling processes. 2-1 ~P 2-6 All are cholesteric liquid crystal elastomers.

[0163] DSC analysis showed that the T of the P2 series liquid crystal polymers g The T value gradually increases with increasing content of chiral crosslinking agent M5 in the system. The T value of the liquid crystal polymer... i The values ​​all decreased with increasing chiral crosslinking agent content in the system. All three series of liquid crystal polymers exhibited a wide mesocrystalline range, which gradually decreased with increasing chiral crosslinking agent content.

[0164] This application innovatively utilizes camphor acid, which has strong optical rotation, as a chiral liquid crystal center to prepare chiral crosslinking monomers. By adjusting the composition and crosslinking ratio of the polymer, liquid crystal polymers with different liquid crystal phases were obtained, such as: blue phase, blue phase and cholesteric coexistence, and cholesteric phase liquid crystal polymers. The liquid crystal polymers synthesized in this application have a wide blue phase range, reaching tens of °C. The preparation of wide-temperature-range blue phase liquid crystal polymers has important theoretical and application value. The T... g The lower the value, the wider the △T.

[0165] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A camphoric acid chiral crosslinking agent, characterized in that, The chiral crosslinking agent is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester, and its structural formula is: 。 2. A method for preparing a camphoric acid chiral crosslinking agent, characterized in that, The process includes the following steps: 3.00 g (0.00900 mol) of 4-(4-allyloxy)benzoyloxy-4'-biphenylphenol was dissolved in 30.0 mL of tetrahydrofuran and 5-10 drops of pyridine solution, and then slowly added dropwise to 0.009 mol of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid monoester acyl chloride dissolved in 20.0 mL of tetrahydrofuran solution. The reaction was carried out at room temperature for 1 h, and then heated under reflux at 60.0 °C for 36 h. After the reaction was completed, most of the solvent was distilled off under reduced pressure, and the concentrated solution was poured into deionized water for soaking. The solution was filtered to obtain a brown powdery solid, which was then purified by ordinary silica gel chromatography to obtain a camphoric acid chiral crosslinking agent.

3. A wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer, characterized in that, The polymer is a chiral liquid crystal elastomer with the following structural formula: In the formula, 4-Undecyloxybenzoic acid cholesterol ester Cholesterol acrylate 4-Allyloxybenzoic acid cholesterol ester : 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester.

4. A method for preparing a wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer, characterized in that, Includes the following steps: Monomers, chiral crosslinking agents, and tetramethylcyclotetrasiloxane (D4H) were dissolved in toluene at a certain molar ratio. After complete dissolution, a small amount of hexachloroplatinic acid complexing catalyst was added under nitrogen protection, and the reaction was carried out at 95.0℃ for 36 h. The monomers were 4-undecyloxybenzoic acid cholesterol ester (M1), acrylate cholesterol ester (M2), and 4-allyloxybenzoic acid cholesterol ester (M3). The chiral crosslinking agent was 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate diester (M5). The molar ratio of monomers to chiral crosslinking agents was M1:M2:M3=1:1:1, and M5 accounted for 0-20% of the total molar amount of monomers. The amount of D4H was 1.57-8.4 mmol, and the chiral liquid crystal elastomer P2 system was obtained.

5. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0, and M5 accounts for 0% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 6.000 mmol, and chiral liquid crystal elastomer P is obtained. 2-1 .

6. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:1.3, and M5 accounts for 2.5% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.575 mmol, resulting in chiral liquid crystal elastomer P. 2-2 .

7. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:1.5, and M5 accounts for 5% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.650 mmol, and chiral liquid crystal elastomer P is obtained. 2-3 .

8. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.3, and M5 accounts for 10% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 7.200 mmol, and chiral liquid crystal elastomer P is obtained. 2-4 .

9. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.5, and M5 accounts for 15% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 1.950 mmol, and chiral liquid crystal elastomer P is obtained. 2-5 .

10. The method for preparing the wide-temperature-range visible light selectively reflective cholesteric liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M1:M2:M3:M5 = 1:1:1:1:0.6, and M5 accounts for 20% of the total molar amount of monomers M1, M2, M3, and M5; the amount of D4H is 8.400 mmol, and chiral liquid crystal elastomer P is obtained. 2-6 .

Images