Camphoric acid chiral cross-linking agent, liquid crystal polymer with wide temperature range blue phase and preparation method

Abstract

The application provides a camphoric acid chiral cross-linking agent, a wide-temperature-range blue-phase liquid crystal polymer and a preparation method. The chiral cross-linking agent is 4-(4-allyloxy) benzoyloxy-4'-hydroxy benzocamphoric acid bis ester; the chiral liquid crystal network dissolves monomer cholesteryl acrylate, cholesteryl 4-allyloxybenzoate and the chiral cross-linking agent in toluene according to a certain molar ratio, and after dissolution, a small amount of hexachloroplatinic acid complex catalyst is added under nitrogen protection for reaction. The chiral cross-linking agent is a cholesteric liquid crystal; the liquid crystal elastomer series all shows obvious liquid crystal texture in the heating and cooling process, is a cholesteric phase liquid crystal in the heating process, shows a phase transition from a blue-phase liquid crystal to a cholesteric phase liquid crystal in the cooling process, 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 DEGREEES, has a low Tg, a wide T, and the preparation of the wide-temperature-range blue-phase liquid crystal polymer has important theoretical and application values.

Description

Technical Field

[0001] This application belongs to the field of liquid crystal polymer technology, and particularly relates to a camphoric acid chiral central crosslinking agent, a chiral wide-temperature-range blue phase liquid crystal network 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 holds significant potential value in fields such as nonlinear optical materials, color filters, polarizers, full-color liquid crystal displays, anti-counterfeiting, color dyes, and military applications.

[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) are an emerging research branch in the field of liquid crystal polymers. 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 possess orientation stability, piezoelectricity, and ferroelectricity, properties that make them highly promising for applications in nonlinear optical materials, non-porous permeable membranes, and many other areas. 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 blue-phase liquid crystal polymer, and its preparation method. Camphoric acid, with its strong optical activity, serves as the chiral liquid crystal center, and chiral crosslinking monomers are prepared. 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 synthesized liquid crystal polymer has a low Tg. T is wider.

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

[0008] The second aspect of this application also provides a method for preparing a camphoric acid chiral crosslinking agent, comprising the following steps: dissolving 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene in 15.0 mL of tetrahydrofuran and 4.00 mL of pyridine solution, and slowly adding (about 1 drop / 3-5 seconds) dropwise to 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene 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; wherein the 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene and 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene camphoric acid monoester acyl chloride are in a molar ratio of 1:1 to 1:1.2. 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, which is then purified by ordinary silica gel chromatography. The specific synthetic route includes: (2.10) (2.11) (2.12) (2.13) (2.14).

[0009] A third aspect of this application provides a wide-temperature-range blue phase liquid crystal polymer, wherein the wide-temperature-range blue phase liquid crystal polymer is a chiral liquid crystal elastomer with the following structural formula:

[0010] in, Cholesterol acrylate 4-Allyloxybenzoic acid cholesterol ester : 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzyl camphorate diester.

[0011] The fourth aspect of this application provides a method for preparing a wide-temperature-range blue phase 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°C for 36 h; wherein the monomers are cholesterol acrylate (M2) and cholesterol 4-allyloxybenzoate (M3), and the chiral crosslinking agent is 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4); the molar ratio of the monomers to the chiral crosslinking agent is M2:M3 = 1.257 to 1:1, and M4 accounts for 0%-20% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.57 to 6.167 mmol, thereby obtaining a chiral liquid crystal elastomer P1 series.

[0012] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 1.429:1.136:0, and M4 accounts for 0% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.57 mmol, and chiral liquid crystal elastomer P is obtained. 1-1 .

[0013] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 15.36:12.21:1, and M4 accounts for 2.5% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.75 mmol, and chiral liquid crystal elastomer P is obtained. 1-2 .

[0014] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 9.591:7.624:1.0, and M4 accounts for 5% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.87 mmol, and chiral liquid crystal elastomer P is obtained. 1-3 .

[0015] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 4.786:3.807:1.0, and M4 accounts for 10% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 6.167 mmol, and chiral liquid crystal elastomer P is obtained. 1-4 .

[0016] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 2.833:2.833:1.0, and M4 accounts for 15% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.737 mmol, resulting in chiral liquid crystal elastomer P. 1-5 .

[0017] In any embodiment, the molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 2.376:1.890:1.0, and M4 accounts for 20% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.667 mmol, resulting in chiral liquid crystal elastomer P. 1-6 .

[0018]

[0019] The beneficial effects of this application are: In this application, a novel chiral crosslinking agent, 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4), was synthesized. Monomers M2 and M3 were then graft copolymerized with chiral crosslinking agent M4 and tetramethylcyclotetrasiloxane (D4H) to obtain the P1 series of side-chain liquid crystal elastomers. FT-IR and 1H-NMR analyses showed that the liquid crystal monomers, chiral crosslinking agent M4, and side-chain liquid crystal elastomers P1 all conformed to the molecular design.

[0020] POM analysis showed that both the chiral crosslinking agent M4 and the P1 series polymers exhibited liquid crystal properties. Specifically, the chiral crosslinking agent M4 was a cholesteric liquid crystal. The P1 series of liquid crystal elastomers all showed significant liquid crystal textures during heating and cooling processes. 1-2 P 1-3 During heating, it is a cholesteric liquid crystal; during cooling, a phase transition occurs from a blue phase liquid crystal to a cholesteric phase liquid crystal, exhibiting a wide range of blue phase and blue-cholesteric phase coexistence. 1-4 ~P 1-6 Both the temperature rise and fall are in the cholesteric phase.

[0021] DSC analysis showed that the Tg values ​​of the P1 series liquid crystal polymers first decreased and then increased with the increase of the chiral crosslinking agent M4 content in the system; the Ti values ​​of the liquid crystal polymers all decreased with the increase of the chiral crosslinking agent content in the system, and all had a wide mesocrystalline range, and the mesocrystalline range gradually decreased with the increase of the chiral crosslinking agent content.

[0022] 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 significant theoretical and applied value. The synthesized liquid crystal polymers have a low Tg. Its wide T-width gives it enormous potential applications in fields such as nonlinear optical materials, color filters, polarizers, full-color LCD displays, anti-counterfeiting, color dyes, and military applications. Attached Figure Description

[0023] Figure 1 The infrared spectrum of 4-allyloxybenzoic acid of this application; Figure 2 The infrared spectrum of 4-(4-allyloxy)benzoyloxy-4′-hydroxybenzene of this application; Figure 3 The infrared spectrum of (+)-camphoric acid in this application; Figure 4 The infrared spectrum of 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphoric acid monoester of this application; Figure 5 The infrared spectrum of the cholesterol acrylate of this application; Figure 6 The infrared spectrum of 4-allyloxybenzoic acid cholesterol ester of this application; Figure 7 The infrared spectrum of the 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester of this application is shown. Figure 8 The infrared spectrum of the tetramethylcyclotetrasiloxane of this application is shown. Figure 9 The infrared spectrum of the P1 series of liquid crystal elastomers of this application; Figure 10 The liquid crystal elastomer P of this application 1-4 Infrared spectrum; Figure 11 The NMR spectrum of the 4-(4-allyloxy)-benzoyloxy-4'-hydroxyphenylcamphorate diester of this application is shown. Figure 12 The NMR spectrum of D4H in this application; Figure 13 The NMR spectrum is for the P1 series of liquid crystal elastomers of this application; Figure 14 These are polarized light electron microscope images of the chiral crosslinking agent M4 of this application at different temperatures; Figure 15 The liquid crystal elastomer P of this application 1-1 Polarized electron microscope images at different temperatures; Figure 16 The liquid crystal elastomer P of this application 1-2 Polarized electron microscope images at different temperatures; Figure 17 The liquid crystal elastomer P of this application 1-3 Polarized electron microscope images at different temperatures; Figure 18 The liquid crystal elastomer P of this application 1-4 Polarized electron microscope images at different temperatures; Figure 19 The liquid crystal elastomer P of this application 1-5 Polarized electron microscope images at different temperatures; Figure 20 The liquid crystal elastomer P of this application 1-6 Polarized electron microscope images at different temperatures; Figure 21 The DSC curve of the chiral crosslinking agent M4 in this application; Figure 22 For the liquid crystal P of this application 1-1 ~P 1-6 A trend graph showing the phase transition temperature as a function of monomer M4 content; Figure 23 The liquid crystal elastomer P of this application 1-1 ~P 1-6 The DSC curve. Detailed Implementation

[0024] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of a camphoric acid chiral crosslinking agent, a wide-temperature-range blue phase liquid crystal polymer, and a preparation method thereof. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same 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.

[0025] 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 ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 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" indicates that all real numbers between "0-5" have been listed in the application; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥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.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

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

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] 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.

[0030] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0031] Chiral liquid crystal materials possess unique optical properties due to their special helical structure. They can display different liquid crystal phases, including chiral smectic phases, cholesteric phases, and blue phases, each with different application areas. Chiral liquid crystal elastomers organically combine the properties of chiral liquid crystal materials and liquid crystal elastomers. Besides possessing the optical and photoelectric properties of chiral liquid crystal materials, they also exhibit excellent mechanical properties, thermal stability, and chemical stability. Therefore, chiral liquid crystal elastomers have enormous potential application value in fields such as displays, optics, biomedicine, and energy.

[0032] 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 cholesterol acrylate (M2), cholesterol 4-allyloxybenzoate (M3), and a novel chiral crosslinking agent, 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4). The chiral crosslinking agent and different chiral liquid crystal monomers were graft copolymerized with tetramethylcyclotetrasiloxane (D4H) to prepare novel P1 series chiral liquid crystal elastomers.

[0033] 1. Synthesis methods of liquid crystal monomers, chiral crosslinking agents, and liquid crystal elastomers 1. Synthesis of liquid crystal monomers (1) 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 refluxed at 60.0 °C for 3 hours. After the reaction was complete, excess thionyl chloride was removed, yielding 85.0%. Reaction equation: .

[0034] 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, and 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, the supernatant was filtered off, and ethanol was added to the oily residue at the bottom. This process was repeated 4-5 times. The solutions were combined, cooled, and white flaky crystals precipitated, with a yield of 82.0%. Reaction formula: .

[0035] (2) 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. 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 heated to reflux at 65.0 °C for 15 h. After the reaction was completed, 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: .

[0036] 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, and then refluxed 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 with a yield of 80.0%. Reaction formula: .

[0037] 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: . 2. Synthesis of chiral crosslinking agents (1) Synthesis of chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4) 1) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene 50.0 g (0.450 mol) of hydroquinone was added to a 250 mL round-bottom flask, along with 75.0 mL of tetrahydrofuran and 10.0 mL of pyridine, and stirred until dissolved. Then, 13.1 g (0.067 mol) of 4-allyloxybenzoyl chloride was slowly added dropwise, and the mixture was stirred at room temperature for 1 h and refluxed at 60.0 °C for 10 h. After the reaction was complete, most of the solvent was evaporated under reduced pressure, and the bottom liquid was poured into water after slight cooling and allowed to stand overnight. The mixture was then filtered, and excess hydroquinone was removed by boiling in hot water several times. The filter cake was then hot-filtered with ethanol to remove the diester. The filtrate was allowed to stand, filtered, and dried to obtain 11.4 g of a pale yellow powder solid, with a yield of 57.4%. Reaction formula: .

[0038] 2) Synthesis of camphor anhydride 8 g (0.0400 mol) of camphoric acid was added to a 100 mL round-bottom flask, followed by 50.0 mL of thionyl chloride solution. The mixture was reacted at room temperature for 1 h, then refluxed at 60.0 °C for 5 h. After the reaction was complete, excess thionyl chloride was removed to obtain 8.10 g of product (85.0% yield). The product was sealed and stored for later use. Reaction formula: .

[0039] 3) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzyl camphorate monoester 5.00 g (0.0190 mol) of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene was dissolved in 20.0 mL of tetrahydrofuran and 7.00 mL of pyridine solution. This solution was slowly added dropwise to 8.10 g of camphor anhydride dissolved in 20.0 mL of tetrahydrofuran solution. 0.57 g of DMAP and 3.81 g of DCC were added. 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 and stirred. The solution was filtered, hot-filtered with a small amount of ethanol, and allowed to stand to precipitate. The precipitate was then filtered, dried, recrystallized from ethanol, dried again, and stored for later use. The yield was 70.0%. Reaction formula: .

[0040] 4) Synthesis of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzyl camphorate monoester acyl chloride The above-mentioned monoester solid was added to a 100 mL round-bottom flask, along with 20.0 mL of thionyl chloride. The mixture was heated to reflux at 60.0 °C overnight. After the reaction was complete, excess thionyl chloride was removed, and the product was reserved for later use. The yield was 85.2%. Reaction formula: .

[0041] 5) Synthesis of chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4) 2.00 g (0.0074 mol) of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene was dissolved in 15.0 mL of tetrahydrofuran and 4.00 mL of pyridine solution, and then slowly added dropwise to an acyl chloride dissolved in tetrahydrofuran solution. 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 completed, most of the solvent was distilled off under reduced pressure. The concentrated solution was poured into deionized water, filtered, and a brown powdery solid was obtained. The solid was purified by ordinary silica gel chromatography with a yield of 50.2%. Reaction formula: .

[0042] 3. Synthesis of Liquid Crystal Elastomer Series The monomers, chiral crosslinking agents, and tetramethylcyclotetrasiloxane (D4H) obtained above 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. -1The 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. 1-1 ~P 1-6 .

[0043] Table 1 Liquid Crystal Elastomer P 1~1 ~P 1~6 Feeding situation

[0044] Note: a: Molar percentage of chiral crosslinking agent M4 in (M2+M3+M4); M2: Cholesterol acrylate; M3: Cholesterol 4-allyloxybenzoate; M4: 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester.

[0045] (1) Liquid crystal elastomer P 1-1 ~P 1-6 Synthetic route

[0046] .

[0047] 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-Allyloxybenzoic acid The main absorption peaks of 4-allyloxybenzoic acid are assigned in Table 2, and its infrared spectrum is shown in [reference needed]. Figure 1 .

[0048] Figure 1 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.

[0049] The above analysis shows that the compound is 4-allyloxybenzoic acid, which is consistent with the molecular structure design.

[0050] Table 24 - Assignment of infrared absorption peaks of allyloxybenzoic acid

[0051] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0052] (2) 4-(4-allyloxy)benzoyloxy-4′-hydroxybenzene The main absorption peak assignments for 4-(4-allyloxy)benzoyloxy-4′-hydroxybenzene are shown in Table 3, and its infrared spectrum is shown in [reference needed]. Figure 2 .

[0053] Figure 2 Middle, 2912~2850cm -1 The absorption peak is the stretching vibration of saturated hydrocarbons; 1607~1518 cm⁻¹ -1 This is the stretching vibration peak of the benzene ring skeleton; 1255 cm⁻¹ -1 The corresponding vibrational absorption peaks at 3433 cm⁻¹ indicate that the product possesses characteristic peaks of the basic functional groups of the reactants. Compared with the infrared spectrum of 4-allyloxybenzoic acid, the peak at 3433 cm⁻¹ is... -1 An absorption peak for the stretching vibration 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 1708 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.

[0054] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4′-hydroxybenzene, which is consistent with the molecular structure design.

[0055] Table 34: Assignment of infrared absorption peaks for 4-(4-allyloxy)benzoyloxy-4′-hydroxybenzene

[0056] Note: s: strong absorption; ms: moderate absorption; w: weak absorption.

[0057] (3) (+)-Camphoric acid The main absorption peaks of (+)-camphoric acid are assigned in Table 4, and their infrared spectra are shown in Table 4. Figure 3 .

[0058] Figure 3 In this process, influenced by the hydrogen bonding between the carboxyl groups on camphoric acid, the concentration at 3010 cm⁻¹ -1Centered 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.

[0059] Based on the above analysis, the compound is (+)-camphoric acid. Table 4. Infrared spectra of (+)-camphoric acid

[0060] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0061] (4) 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 5, and its infrared spectrum is shown in [reference needed]. Figure 4 .

[0062] Figure 4 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. -1The 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.

[0063] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4'-hydroxybiphenyl camphorate monoester, which is consistent with the molecular structure design.

[0064] Table 54 Infrared Peak Assignments for 4'-(4-allyloxy)benzoyloxy-4'-biphenol camphorate monoester

[0065] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0066] 2. Infrared analysis of liquid crystal monomers (1) Cholesterol acrylate The main absorption peak assignments of cholesterol acrylate are shown in Table 6, and its infrared spectrum is shown in [reference needed]. Figure 5 .

[0067] Figure 5 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.

[0068] The above analysis shows that the compound is cholesterol acrylate, which is consistent with the molecular structure design.

[0069] Table 6. Infrared peak assignments of cholesterol acrylate.

[0070] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0071] (2) 4-Allyloxybenzoic acid cholesterol ester The main absorption peak assignments of 4-allyloxybenzoic acid cholesterol ester are shown in Table 7, and its infrared spectrum is shown in [reference needed]. Figure 6 .

[0072] Figure 6 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.

[0073] The above analysis shows that the compound is 4-allyloxybenzoic acid cholesterol ester, which is consistent with the molecular structure design.

[0074] Table 74 - Infrared Peak Assignments of Cholesterol Allyloxybenzoate

[0075] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0076] 3. Infrared analysis of chiral crosslinking agents (1) Chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester The main absorption peak assignments of the chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester are shown in Table 8, and its infrared spectrum is shown in [reference needed]. Figure 7 .

[0077] Figure 7 Middle, 3082cm -1 The peak represents the stretching vibration of unsaturated hydrocarbons; 2980~2888 cm⁻¹ -1 This is the stretching vibration peak of saturated hydrocarbons; 1712 cm⁻¹ -1 The stretching vibration peak of the carbonyl group in the ester group; 1603~1510 cm⁻¹ -1 This is the stretching vibration peak of the benzene ring skeleton; 1419 cm⁻¹ -1 The peak is the stretching vibration peak of the methyl group; 766 cm⁻¹ -1 These are characteristic absorption peaks for para-substitution of the aromatic 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 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene, 3433 cm⁻¹ is [missing value]. -1The disappearance of the stretching vibration absorption peak of the phenolic hydroxyl group indicates that the phenolic hydroxyl group has undergone a reaction; compared with the infrared spectrum of camphoric acid, the peak at 2681 cm⁻¹ is significantly higher. -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.

[0078] The above analysis shows that the compound is 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzylcamphorate diester, which is consistent with the molecular structure design.

[0079] Table 84 Infrared Peak Assignments of 4'-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester

[0080] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0081] 4. Infrared analysis and spectra of liquid crystal elastomers (1) Infrared analysis of D4H The main absorption peaks of D4H are assigned in Table 9, and their infrared spectra are shown in Table 9. Figure 8 .

[0082] Figure 8 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.

[0083] Based on the above analysis, the compound can be identified as D4H, which is consistent with the molecular structure design.

[0084] Table 9. Infrared Peak Assignments for Tetramethylcyclotetrasiloxane

[0085] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0086] (2) Infrared analysis of P1 series liquid crystal elastomers The infrared spectra of the P1 series of liquid crystal elastomers are almost identical, so P was selected. 1-1 P 1-3 P 1-4 For example, see the infrared spectrum. Figure 9 Using liquid crystal elastomer P 1-4 Taking this as an example for analysis, its infrared spectrum is shown below. Figure 10The main absorption peaks are assigned in Table 10.

[0087] Compare Figure 10 Liquid crystal elastomers and Figure 8 The infrared spectrum of D4H shows that at 2166 cm⁻¹... -1 The absence of the stretching vibration absorption peak of the silane-hydrogen bond indicates that the hydrogen atoms in the silane-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, 2953~2867 cm⁻¹ -1 The range corresponds to the stretching vibration absorption peak of saturated alkyl hydrocarbons; 1709 cm⁻¹ -1 The absorption peak at 1607-1372 cm⁻¹ corresponds to the carbonyl stretching vibration of the ester. -1 The range corresponds to the stretching vibration absorption peak of the carbon skeleton in the benzene ring; 1262 cm⁻¹ -1 The peak at 1137-1002 cm⁻¹ is the vibrational peak of the methyl group bonded to silicon; the stretching vibration absorption of silicon-oxygen silicon causes the peak at 1137-1002 cm⁻¹. -1 A broad and strong absorption peak within the range; 785 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.

[0088] The above analysis shows that the P1 series of liquid crystal elastomers conforms to the molecular structure design.

[0089] Table 10 Liquid Crystal Elastomer P 1-4 Infrared peak attribution

[0090] Note: s: strong absorption; ms: moderately strong absorption; w: weak absorption.

[0091] 5. NMR analysis of chiral crosslinking agents and liquid crystal elastomers (1) NMR analysis of 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4) The major chemical shifts of 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester are shown in Table 11, and the NMR spectrum is shown in [reference needed]. Figure 11 .

[0092] Depend on Figure 11 As shown in Table 11, 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 M4 conforms to the molecular structure design.

[0093] Table 114 Chemical Shift Assignments of 4'-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester

[0094] Note: s: singlet; d: doublet; t: triplet; m: multiplet.

[0095]

[0096] 4-(4-allyloxy)-benzoyloxy-4'-hydroxyphenylcamphorate diester (2) NMR analysis of D4H The NMR spectrum of D4H is shown below. Figure 12 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.

[0097] The above analysis shows that the compound is tetramethylcyclotetrasiloxane (D4H).

[0098] (3) Nuclear magnetic resonance analysis of P1 series liquid crystal elastomers The NMR peak positions of the P1 series of liquid crystal elastomers are roughly the same, so polymer P was selected. 1-2 For example, see the NMR spectrum. Figure 13 .

[0099] Nuclear magnetic resonance spectrum Figure 13 In the liquid crystal elastomer, the absorption peaks at δ = 8.13~6.83 are those of the benzene ring; the multiplet at around δ = 5.40 is the absorption peak of the olefin bond on the cholesterol in the cholesterol monomer; the multiplet at δ = 4.98~4.83 is the absorption peak of the hydrogen atom attached to the carbonyl group of the cholesterol; the absorption peak at δ = 4.56 is the absorption peak of the methylene group attached to oxygen; the absorption peaks at δ = 2.25~0.88 are the absorption peaks of the hydrogen atom of the camphor acid five-membered ring and the methyl methylene group on the cholesterol; and 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 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 δ = 6.07 for the =CH- hydrogen proton disappears in the liquid crystal elastomer; the dd peaks at δ = 5.44 and δ = 5.33 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.

[0100] The above analysis shows that the P1 series of liquid crystal elastomers conforms to molecular design.

[0101] 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.

[0102] (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.

[0103] (2) Texture analysis of chiral crosslinking agent M4 Under a polarizing microscope, the chiral crosslinking agent M4 showed that when the temperature was raised to 150°C, the sample began to melt; the field of view gradually brightened; with further heating, the sample flow accelerated, and a fingerprint-like texture appeared in the field of view, with a predominantly yellow background. Figure 14 (a)); As the temperature increases, a distinct fingerprint texture appears ( Figure 14 (b) The fingerprint texture is a unique texture of cholesteric liquid crystals. Theoretically, the pitch of cholesteric liquid crystals can be calculated from the fin spacing. The width of the fingerprint line is equal to half the pitch. With continued heating, the texture exhibits multiple colors, and the fingerprint gradually becomes blurred. Figure 14 (c) When the temperature rises to near the clearing point, some fingerprint texture disappears, and fingerprint texture and granular texture coexist. Figure 14 (d)); Gradually increase the temperature to 252℃, the entire field of view turns black, the liquid crystal phase disappears, and the sample enters an isotropic liquid state.

[0104] When the temperature drops from above the clear spot to around 250°C, fingerprint texture appears in the field of vision. Figure 14 (e)); As the temperature continues to drop, green appears against the yellow background of the texture, and the spacing between the fingerprints widens slightly. Figure 14 (f) indicates that the pitch of the monomer has become longer.

[0105] Textural analysis revealed that the chiral crosslinking agent M4 is a thermo-induced tautomer cholesteric liquid crystal.

[0106] (3) Texture analysis of the P1 series of compounds Liquid crystal elastomer P 1-1 At room temperature, a planar texture of blue cholesteric liquid crystals appears; with further heating, the texture morphology remains basically unchanged. Figure 15 (a) only the color changed to dark blue. Figure 15 (b)); thereafter the texture and color remained basically unchanged. At 137°C, the sample field of view turned black, the texture disappeared, and the sample entered an isotropic liquid state. As the temperature drops from above the clearing point to around 137°C, a blue planar texture similar to that observed during the warming phase appears in the field of vision. Figure 15 (c) As the temperature continued to drop, the texture remained unchanged; only the color of the texture gradually changed from dark blue to sky blue. Figure 15 (c)).

[0107] Liquid crystal elastomer P 1-2 The texture and P exhibited during the heating process 1-1 Similarly, a blue planar texture appears at room temperature, and the texture does not change significantly with further heating. Figure 16 (a)); As the temperature gradually increased, the sample flow accelerated significantly, and an oil-fiber texture appeared ( Figure 16 (b)); thereafter the oil-fiber texture was maintained, and when the temperature rose to 122°C, the sample field of view turned black, the texture disappeared, and the sample entered an isotropic liquid state.

[0108] As the temperature decreased from above the clearing point to 122°C, a blue hue appeared in the field of vision. Figure 16 (c) Continue cooling to maintain the blue phase texture, but the color of the texture gradually shifts from dark blue to longer wavelengths, that is, gradually becomes sky blue. Figure 16 (d)); When the temperature continued to drop to 74℃, the visibility in some areas became significantly brighter. Figure 16 (e) indicates the presence of a cholesteric phase, signifying the beginning of the cholesteric phase transition in the liquid crystal elastomer. This transition is relatively slow; as the temperature decreases, the cholesteric region increases, persisting until 68.3℃, where most of the field of view is cholesteric, but some areas still exhibit a blue phase texture. Further cooling to room temperature does not eliminate some of the blue phase texture. Figure 16 (f).

[0109] Texture analysis reveals that the liquid crystal elastomer P... 1-2 When heated, it is a cholesteric liquid crystal polymer. When cooled from the clearing point, a blue phase appears, and there is a phase transition from the blue phase to the cholesteric phase. The temperature range in which the blue phase and the blue phase and the cholesteric phase coexist is very wide.

[0110] Liquid crystal elastomer P 1-3 When the temperature is raised to 30°C, a light blue planar texture characteristic of cholesteric polymers appears in the field of view. Figure 17 (a)); as the temperature continued to rise to 70℃, the color and state of the texture did not change significantly; when the temperature rose to 92℃, the sample flow began to accelerate and the texture color gradually turned dark blue, with oil-like stripes appearing in the texture. Figure 17 (b)); Gradually increase the temperature to 118°C, the liquid crystal texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0111] The sample was cooled from a temperature higher than the clearing point. When the temperature dropped to around 118°C, a deep blue blue phase texture appeared. Figure 17 (c)); As the temperature continued to drop, the color of the texture gradually changed from dark blue to sky blue, with little change in the texture shape. Figure 17 (d), (e)); When the temperature drops to 64℃; the field of view becomes significantly brighter, indicating the appearance of the cholesteric phase, and the liquid crystal begins to change from the blue phase to the cholesteric phase; with continued cooling, it is in a state where the blue and cholesteric phases coexist; when the temperature drops to 40℃, P 1-3 The blue phase completely transforms into the cholesteric phase, and a blue planar texture appears, as shown in Figure (3.34(d)).

[0112] Texture analysis reveals that the liquid crystal elastomer P... 1-3 Upon heating, it exhibits a cholesteric phase liquid crystal, but upon cooling, it displays a wider temperature range exhibiting a blue phase transition, indicating a transition from the blue phase to the cholesteric phase. Compare this to polymer P. 1-2 With P 1-3 It can be seen that as the content of chiral crosslinking agent increases from 2.5% to 5%, the clearing point of the liquid crystal polymer decreases slightly, but the blue phase liquid crystal region increases significantly when the temperature drops.

[0113] Liquid crystal elastomer P 1-4 As the temperature gradually rises, pink cholesteric Grandjean texture appears in the field of vision. Figure 18 (a)); As the temperature rises, the Grandjean texture gradually changes from pink to yellow and then to green. Figure 18 (b) That is, the reflected wavelength undergoes a blue shift. According to the Bragg equation 2dsinθ=nλ, as the temperature increases, the reflected wavelength becomes shorter, that is, the pitch of the liquid crystal elastomer becomes smaller. When the temperature is gradually increased to 108℃, the texture disappears, the field of view becomes dark, and the sample enters an isotropic liquid state.

[0114] Starting from above the clearing point, as the temperature decreased to 107°C, cholesterol granules appeared in the field of view; with continued cooling, the cholesterol granules continued to aggregate. Figure 18 (c)); At 95°C, cholesteric granules merge and grow into a focal cone texture of cholesteric granules, which remains unchanged during subsequent cooling. Figure 18 (d)).

[0115] Texture analysis reveals that the liquid crystal elastomer P... 1-4 It is a thermo-induced tautomer cholesteric liquid crystal. When the chiral crosslinking agent increases to 10%, polymer P 1-4 The bright spots are further reduced; and the liquid crystal polymer P 1-4 It exhibits only the cholesteric phase during temperature rise and fall, without the appearance of the blue phase.

[0116] Liquid crystal elastomer P 1-5 It exhibits a cholesteric liquid crystal texture at room temperature. Upon increasing the temperature from room temperature, the texture turns a bright red (…). Figure 19 (a) As the temperature increases, the field of view gradually changes from red to yellow and then to green, indicating that as the temperature increases, the reflected wavelength becomes shorter and the pitch of the sample becomes smaller; when the temperature is raised to 73℃, an oily texture appears in the field of view, and the background is a coexistence of yellow, green and blue colors. Figure 19 (b) When the temperature is gradually increased to 102°C, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0117] When the temperature was lowered from a point above the clearing point to 102°C, cholesteric oil filaments appeared in the field of view; with further cooling, the texture remained unchanged. Figure 19 (c)), but the background color gradually turns yellow and then red, that is, the reflected wavelength redshifts, indicating that the sample pitch increases as the temperature decreases; at 48℃, the entire field of view becomes bright red ( Figure 19 (d)).

[0118] Texture analysis reveals that the liquid crystal elastomer P... 1-5 This is a thermo-induced tautomer cholesteric liquid crystal. As the content of the chiral crosslinking agent increases to 15%, the fluidity of the liquid crystal polymer deteriorates, and the amount of texture decreases significantly. (Polymer P...) 1-5 During the heating and cooling process, a Grandjean texture of cholesteric liquid crystal phase appeared. The texture was not as colorful as that of polymers with low chiral crosslinking agent content, and the color was significantly darker. This indicates that the increase of chiral crosslinking agent restricted the movement of liquid crystal molecules and the formation of liquid crystal phase.

[0119] Liquid crystal elastomer P 1-6 Grandjean texture of cholesteric liquid crystals appears at room temperature. Figure 20(a)), at this point the background is mainly gray; as the temperature continues to rise, at 49°C, the background color is a Grandjean texture with a mixture of blue, dark red and gray. Figure 20 (b)); When the temperature is raised to 72°C, the blue area turns reddish-yellow ( Figure 20 (c)); When heated to 87°C, the color begins to turn grayish-white. Figure 20 (d) When the temperature is raised to 92°C, the texture disappears, the field of view darkens, and the sample enters an isotropic liquid state.

[0120] As the temperature drops from above the point of clarity to around 92°C, bright spots begin to appear in the field of vision, gradually coalescing into a blue planar texture; with continued cooling, the texture change becomes less noticeable. Figure 20 (e)); As the temperature continued to decrease, cholesteric Grandjean texture appeared in the field of view, and the color of the Grandjean texture gradually darkened as the temperature decreased ( Figure 20 (f)).

[0121] From the texture analysis, polymer P 1-6 During the heating and cooling process, a cholesteric liquid crystal phase is observed. From the POM, it can be seen that the polymer P... 1-6 The texture, color, and morphology showed little change, the color darkened, and the liquid crystal texture became less distinct. This indicates that when the chiral crosslinking agent increased to a certain extent, it suppressed the formation of the polymer liquid crystal state.

[0122] The P1 series of liquid crystal elastomers all exhibited the characteristic texture of cholesteric liquid crystals during heating and cooling processes. This was particularly evident in samples with low chiral crosslinking agent content. 1-2 P 1-3 During the cooling process, a phase transition from the cholesteric phase to the blue phase occurred, exhibiting a relatively wide blue phase range; with the increase of chiral crosslinking agent, P 1-3 The blue phase region begins to shrink; the chiral crosslinking agent continues to increase, P 1-4 P 1-5 P 1-6 During the heating and cooling process, only the cholesteric liquid crystal texture appeared; there was no transition from the blue phase to the cholesteric phase. P 1-4 P 1-5 The textures all undergo Bragg reflection when heated, P 1-5 The texture of the liquid crystal elastomer P also exhibited Bragg reflection during cooling. The reflected wavelength showed a blue shift upon heating and a red shift upon cooling, indicating that the liquid crystal elastomer P 1-4 and P 1-5 Pitch is related to temperature; during the heating process, P 1-4 P 1-5 The pitch decreases, and P decreases during cooling. 1-5 The pitch increases.

[0123] 6. DSC Analysis (1) Thermal analysis of chiral crosslinking agent M4 The DSC curve of chiral crosslinking agent M4 is shown in the figure. Figure 21 As can be seen from the figure, an endothermic peak appears at 151℃ during the heating process of chiral crosslinking agent M4. This peak is the endothermic peak of the transition from solid to liquid crystal state. However, the endothermic peak of the transition from liquid crystal state to isotropic state is not shown. This may be because the energy required for monomer disorientation is relatively small, so no clearing point is observed on the DSC curve. However, the clearing point of chiral crosslinking agent M4 can be observed at around 252℃ using a polarizing microscope.

[0124] (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.

[0125] 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.

[0126] To eliminate the influence of thermal history, DSC curves of all liquid crystal polymers were obtained after two temperature increases.

[0127] (3) Thermal analysis of P1 series liquid crystal elastomers The glass transition temperature and clearing point of the liquid crystal elastomer are shown in Table 12, and its DSC curves are shown in Table 12. Figure 3 0.50. From Figure 3As can be seen from .50, sample P 1-1 ~P 1-5 The DSC heating curves all show two endothermic phase transitions, P 1-6 The phase transition at high temperatures is not significant. The plateau-like transition at low temperatures represents the glass transition of various liquid crystal elastomers, corresponding to the glass transition temperature T. g The endothermic peak at high temperature represents the transition of the liquid crystal elastomer from the liquid crystal phase to the isotropic state; the corresponding temperature is the clearing point T. i Liquid crystal elastomer P 1-1 ~P 1-6 The DSC test results are basically consistent with the POM test results.

[0128] As can be seen from Table 12, the T of the polymer g The values ​​are not high because the main chain of the polymer is polysiloxane, and the T of polysiloxane-based liquid crystal polymers is low. g Relatively low. Figure 22 The effect of the chiral crosslinking agent M4 content on the phase transition temperature (Tg) of polymers in the P1 series is presented. For liquid crystal elastomers, the effect on Tg is mainly twofold: firstly, crosslinking, where the degree of crosslinking restricts molecular movement, thus increasing Tg; secondly, the molecular structure. Larger or rigid groups in the molecule restrict chain movement, increasing Tg, while smaller groups or flexible chains decrease Tg. Figure 22 It can be seen that the liquid crystal polymer P 1-1 T g The highest, this is due to P 1-1 It is polymerized from cholesterol-containing liquid crystal monomers. Cholesterol has a large volume and strong intermolecular forces, which restrict the free movement of molecular chain segments, thus causing its T... g Higher. With increasing content of chiral crosslinking agent M4, the liquid crystal polymer P... 1-1 ~P 1-3 T g The temperature dropped rapidly from 15.2℃ to -3.3℃, ​​which is due to the polymer P 1-1 It is synthesized from two liquid crystal monomers containing cholesterol units. Cholesterol molecules are relatively large and have strong intermolecular forces, which restricts the chain movement of the liquid crystal molecules. g Relatively high. At low degrees of crosslinking, the effect of crosslinking on Tg is small because the added chiral crosslinking agent has a small molecular volume and a large free volume, thus its effect on Tg is relatively low. g The effect of T is greater than that of cross-linking. g The value shows a gradually decreasing trend. With continued increase in the chiral crosslinking agent, the liquid crystal polymer P... 1-4 ~P 1-6 T gValue relative to polymer P 1-3 The temperature gradually increased from -3.3℃ to 8.9℃. This indicates that when the chiral crosslinking agent content exceeds 10%, the crosslinking effect on T... g The influence of chiral crosslinking agents is dominant. Therefore, the Tg of P1 series polymers first decreases and then increases with the increase of chiral crosslinking agents.

[0129] from Figure 22 P can be seen from 1-1 ~P 1-6 T i The trend is downward. With the increase of chiral crosslinking agent content, the T of the liquid crystal polymer... i The temperature was gradually decreased from 135℃ to 92℃. This is because the increased content of the chiral crosslinking agent M4 increases the degree of polymer crosslinking. This increased crosslinking degree hinders the movement and orientation of mesocrystalline molecules, disrupting the ordered structure of the liquid crystal and leading to a decrease in T... i It gradually decreases. Table 12 also shows that P... 1-1 ~P 1-6 The mesocrystalline temperature range is relatively wide; and with the increase of chiral crosslinking agent content, P 1-1 ~P 1-6 The mesocrystalline temperature range gradually decreases.

[0130] Table 12 Liquid Crystal Elastomer P 1-1 ~P 1-6 Thermal analysis results

[0131] Note: T g Glass transition temperature; T i Clear the highlights; T a Mesocrystalline temperature range (T) i -T g ) 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 results indicated that both the liquid crystal monomers and chiral crosslinkers were cholesteric liquid crystals. The liquid crystal elastomer P... 1-2 and P 1-3 During the cooling process, a phase transition occurs from blue phase liquid crystal to cholesteric phase liquid crystal; and these liquid crystal elastomers exhibit a wide blue phase temperature range. Other liquid crystal polymers only exhibit the cholesteric phase during heating and cooling.

[0132] DSC analysis showed that as the content of chiral crosslinking agent in the system increased, the Tt of the P1 series liquid crystal polymers increased. g The value first decreases and then increases, T i The value decreases with the increase of the chiral crosslinking agent content in the system. The liquid crystal polymer has a wide mesocrystalline range, and the mesocrystalline phase range gradually decreases with the increase of the chiral crosslinking agent content.

[0133] The application describes the preparation of chiral liquid crystal elastomers with different liquid crystal phases by controlling the monomer structure and composition in the polymerization system, especially the preparation of a blue phase liquid crystal elastomer with a wide temperature range.

[0134] The applicant synthesizes the liquid crystal monomers cholesterol acrylate (M2), cholesterol 4-allyloxybenzoate (M3), and the chiral crosslinking agent 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4). Monomers M2 and M3 are graft copolymerized with the chiral crosslinking agent M4 and tetramethylcyclotetrasiloxane (D4H) to obtain the P1 series of side-chain liquid crystal elastomers.

[0135] FT-IR and 1 H-NMR analysis showed that the liquid crystal monomer, chiral crosslinker M4, and side-chain liquid crystal elastomer P1 all conformed to the molecular design.

[0136] POM analysis showed that monomers M2 and M3, chiral crosslinker M4, and polymers in the P1 series all exhibited liquid crystal properties. Among them, monomers M2 and M3, and chiral crosslinker M4 were all cholesteric liquid crystals. The P1 series of liquid crystal elastomers all exhibited significant liquid crystal textures during heating and cooling processes. 1-2 P 1-3 During heating, it is a cholesteric liquid crystal; during cooling, a phase transition occurs from a blue phase liquid crystal to a cholesteric phase liquid crystal, exhibiting a wide range of blue phase and blue-cholesteric phase coexistence. 1-4 ~P 1-6 Both the temperature rise and fall are in the cholesteric phase.

[0137] DSC analysis showed that the T of the P1 series liquid crystal polymers g The T value of the liquid crystal polymer initially decreases and then increases with increasing content of chiral crosslinking agent M4 in the system. i The values ​​all decreased with the increase of the chiral crosslinking agent content in the system. The liquid crystal polymers all had a wide mesocrystalline range, and the mesocrystalline range gradually decreased with the increase of the chiral crosslinking agent content.

[0138] The application innovatively utilizes camphor acid, which has strong optical activity, 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 synthesized liquid crystal polymers have a wide blue phase range, reaching tens of... ℃ The preparation of wide-temperature-range blue phase liquid crystal polymers has significant theoretical and applied value; the T synthesized... g Lower T is wider.

[0139] 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 crosslinking agent is a camphoric chiral center crosslinking agent of 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphoric acid 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: 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene is dissolved in 15.0 mL of tetrahydrofuran and 4.00 mL of pyridine solution, and slowly added dropwise (approximately 1 drop / 3-5 seconds) to 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene camphoric acid monoester chloride dissolved in 20.0 mL of tetrahydrofuran solution. The reaction is carried out at room temperature for 1 h, followed by reflux at 60.0 °C for 36 h. The molar ratio of 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene and 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzene camphoric acid monoester chloride is 1:1 to 1:1.

2. After the reaction is completed, most of the solvent is distilled off under reduced pressure, and the concentrated solution is soaked in deionized water, filtered, and a brown powdery solid is obtained. The solid is then purified by ordinary silica gel chromatography to obtain a camphoric acid chiral crosslinking agent.

3. A wide-temperature-range blue phase liquid crystal polymer, wherein the wide-temperature-range blue phase liquid crystal polymer is a chiral liquid crystal elastomer with the following structural formula: In the formula, Cholesterol acrylate 4-Allyloxybenzoic acid cholesterol ester : 4-(4-allyloxy)benzoyloxy-4'-hydroxybenzyl camphorate diester.

4. A method for preparing a wide-temperature-range blue phase liquid crystal polymer, comprising the following steps: A monomer, a chiral crosslinking agent, 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 cholesterol acrylate (M2) and cholesterol 4-allyloxybenzoate (M3), and the chiral crosslinking agent was 4-(4-allyloxy)benzoyloxy-4'-hydroxyphenylcamphorate diester (M4). The molar ratio of the monomers to the chiral crosslinking agent was M2:M3 = 1.257 to 1:1, and M4 accounted for 0%-20% of the total molar amount of monomers M2, M3, and M4. The amount of D4H was 2.57 to 6.167 mmol, and the chiral liquid crystal elastomer P1 series was obtained.

5. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 1.429:1.136:0, and M4 accounts for 0% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.57 mmol, and chiral liquid crystal elastomer P is obtained. 1-1 .

6. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 15.36:12.21:1, and M4 accounts for 2.5% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.75 mmol, resulting in chiral liquid crystal elastomer P. 1-2 .

7. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 9.591:7.624:1.0, and M4 accounts for 5% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.87 mmol, and chiral liquid crystal elastomer P is obtained. 1-3 .

8. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 4.786:3.807:1.0, and M4 accounts for 10% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 6.167 mmol, resulting in chiral liquid crystal elastomer P. 1-4 .

9. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 2.833:2.833:1.0, and M4 accounts for 15% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.737 mmol, resulting in chiral liquid crystal elastomer P. 1-5 .

10. The method for preparing a wide-temperature-range blue phase liquid crystal polymer according to claim 4, characterized in that, The molar ratio of the monomers and the chiral crosslinking agent is M2:M3:M4 = 2.376:1.890:1.0, and M4 accounts for 20% of the total molar amount of monomers M2, M3, and M4; the amount of D4H is 2.667 mmol, resulting in chiral liquid crystal elastomer P. 1-6 .

Images