WO2024011411A1 - Chiral phenyl ester polymer crosslinked film, and preparation method therefor and use thereof - Google Patents

Abstract

Disclosed in the present invention are a chiral phenyl ester polymer crosslinked film, and a preparation method therefor and the use thereof. The preparation method is a chiral construction and fixation method for a side-chain-type polymer. In the present invention, limonene steam is utilized to induce a polymer at a high temperature to make same obtain chirality, and then a 365 nm ultraviolet light source is utilized to irradiate the resulting polymer film to enable cinnamic acid groups therein to undergo a cycloaddition reaction, so as to achieve crosslinking; and the difference in the stability of the supermolecule chirality of the polymer film toward heat and a solvent before and after crosslinking is investigated. Different from a traditional chiral crosslinked film, the chirality disclosed in the present invention is a dynamic structure, a decrosslinking process can be achieved under 254 nm ultraviolet light control conditions, and the defect of the structure of a traditional crosslinked material being unable to be changed once the traditional crosslinked material is crosslinked is overcome. The crosslinked film prepared in the present invention has a good chiral performance, good heat resistance, solvent resistance and a chiral self-repairing function, and can realize reversible processes of crosslinking and decrosslinking of the structure multiple times, making material application more flexible.

Description

A chiral phenyl ester polymer cross-linked film and its preparation method and application Technical field

The invention belongs to the technical field of supramolecular chiral fixation, relates to supramolecular chirality induction and cross-linking fixation of achiral side chain phenyl ester random copolymers, and specifically relates to chiral phenyl ester polymer cross-linked films and their preparation. Methods and Applications.

Background technique

In recent years, chiral polymers have attracted widespread attention from researchers due to their promising application prospects in the fields of chiral recognition, photoinduced polarization fluorescence, and chiral catalysis. However, most chiral polymers obtained directly through organic synthesis methods use expensive chiral reagents, and the types of synthesized chiral polymers are also very limited, which greatly restricts the development of chiral polymers. Therefore, if supramolecular chirality can be constructed in achiral polymer systems through some induction method, it will not only avoid the use of expensive chiral reagents and cumbersome synthesis processes, but also expand the structure of chiral polymers. scope is of great significance.

In the existing technology, supramolecular chiral self-assembly is based on supramolecular weak forces such as hydrogen bonding, π-π stacking, acid-base interaction, metal-coordination interaction, host-guest interaction, etc., to construct chiral assemblies, regardless of the construction base. Elements are chiral small molecules or polymers whose driving force is reversible non-covalent weak interaction. This non-covalent weak interaction force is due to its weak energy (generally less than 10 KJ/mol), poor stability, the chiral supramolecular ordered structure is easily susceptible to external stimulation (light, heat, pH, solvent, metal ions, etc.) and responds to a certain extent, or even dissociates irreversibly, thus Destroying the formed chiral supramolecular structure greatly limits the application of supramolecular chiral materials.

The use of covalent bond cross-linking is currently one of the most commonly used methods to fix the structure of an assembly. However, the traditional covalent bond structure is fixed once cross-linked and cannot be changed. The solidified structure limits the use of chiral functional materials. Application scope.

Technical solutions

In view of the above situation, the present invention first synthesizes a phenyl ester random copolymer with a cinnamic acid group at the end of the side chain through a series of organic synthesis reactions and RAFT polymerization, and uses characterization methods such as nuclear magnetism, GPC, DSC, POM and XRD to characterize the polymer. The molecular weight and liquid crystal properties of Irradiation for 4 hours under a 365 nm ultraviolet light source allowed for cross-linking reaction, achieving the fixation of supramolecular chirality and overcoming the shortcomings of traditional assemblies that are unstable and easy to dissociate. In addition, the de-crosslinking process can be realized by 254 nm ultraviolet irradiation for 0.5 h, which overcomes the shortcomings of structural solidification after traditional covalent bond cross-linking. The dynamic cross-linking process can realize the switch of chiral memory and chiral self-healing functions. The specific technical solution is as follows: a method for preparing a chiral phenyl ester polymer cross-linked film. The side chain phenyl ester polymer is prepared into a film and then induced by a chiral reagent to obtain a chiral phenyl ester polymer film; The groups are cross-linked to obtain a chiral phenyl ester polymer cross-linked film; the side chain phenyl ester polymer has the following chemical structural formula: .

Among them, x:y=1:(0-5), preferably 1:(0.2-4), more preferably 1:(0.3-2), most preferably 1:(0.3-1).

In the present invention, a side chain phenyl ester polymer is obtained by polymerizing monomers, RAFT reagents, and initiators, with a number average molecular weight of 9,000 to 15,000; preferably, the polymerization temperature is 70 to 80°C and the time is 6 to 8 hours. ; The polymerization reaction is carried out in an anhydrous and oxygen-free environment; the molar ratio of monomers, RAFT reagents, and initiators is 50 to 500:3:1, preferably 100:3:1, and the monomer refers to the amount of all monomers; The above monomers are PeCA with cross-linking groups and Pe without cross-linking groups; the chemical structure of Pe is as follows: .

The chemical structure of PeCA is as follows: .

beneficial effects

In the present invention, the side chain phenyl ester polymer is prepared into a film by a solution spin coating method. Preferably, the spin coating is low speed spin coating followed by high speed spin coating; chiral limonene is used for thermal induction to obtain a chiral phenyl ester polymer film. ; Use cinnamic acid group for cross-linking to obtain a chiral phenyl ester polymer cross-linked film. Preferably, the cinnamic acid group is cross-linked at 365 nm UV illumination for 4 hours. Preferably, the cross-linked cinnamic acid group is at 254 The cross-linking is desolvated after 0.5h of nm ultraviolet irradiation, realizing a dynamic chiral memory functional material; the dynamic process can be repeated many times.

The invention discloses the application of the above-mentioned chiral phenyl ester polymer cross-linked film or chiral phenyl ester polymer film in the preparation of chiral cross-linked membrane materials. Preferably, the chiral cross-linked membrane material has heat resistance, solvent resistance, Chiral self-healing function.

The present invention solves the problem that the assembly formed by the existing method cannot exist stably by introducing cross-linkable active groups into the phenyl ester polymer structure and cross-linking to fix the supramolecular chiral structure under specific conditions.

Existing methods that use covalent bonds to fix the original structure of the assembly are similar to the acetal reaction cross-linking method, DA reaction cross-linking method, etc. However, the above methods usually use complex cross-linking conditions, such as cross-linking at a specific pH value. Or cross-linking by heating. These conditions greatly increase the difficulty of constructing supramolecular chirality and the difficulty of constructing cross-linking conditions. The present invention discloses for the first time the structure of a phenyl ester polymer with cinnamic acid at the end of the side chain and performs chiral induction. It utilizes mild conditions and convenient cross-linking methods to improve the stability of supramolecular chirality, and in the polymer system Achieve supramolecular chiral self-healing function; after cross-linking reaction, it can not only maintain the one-dimensional characteristics of the polymer main chain, but also enable the polymer chain to maintain its orientation when used in solvents or heated at high temperatures, with It has the advantages of simplicity and high efficiency; and in phenyl ester polymers, it can effectively avoid the structural damage caused by certain polymers such as azobenzene polymers to ultraviolet light of specific wavelengths.

Different from traditional covalent bond cross-linking, the present invention adopts a dynamic cross-linking process, which can realize the reversible process of cross-linking and de-cross-linking through simple illumination, solves the problem of structural solidification in the existing method, and can realize Photoswitch with chiral memory and self-healing function.

Description of drawings

Figure 1 is a schematic diagram of the preparation of the chiral phenyl ester polymer cross-linked film of the present invention.

Figure 2 shows the NMR images of achiral monomers Pe and PeCA.

Figure 3 shows the NMR images and GPC efflux curves of different polymers.

Figure 4 shows the polarizing microscope (POM) photos of different polymers, (ag) are expressed as: PPe, PPe ₁ -r -PeCA _0.2 , PPe ₁ -r -PeCA _0.3 , PPe ₁ -r -PeCA _{0 .6} , PPe ₁ -r -PeCA ₁ , PPe ₁ -r -PeCA ₃ , PPeCA.

Figure 5 shows the small-angle X-ray scattering and wide-angle X-ray diffraction patterns of the copolymer.

Figure 6 shows the CD spectrum and UV spectrum of the polymer film before and after induction.

Figure 7 shows the NMR and UV spectra of the film before and after cross-linking.

Figure 8 shows the solvent resistance of the copolymer PPe ₁ -r-PeCA ₃ chiral film before and after cross-linking.

Figure 9 shows the heat resistance of the copolymer PPe ₁ -r-PeCA ₃ chiral film before and after cross-linking.

Figure 10 shows that the cross-linked polymer film has chiral memory and self-healing functions.

Figure 11 shows the chiral memory switch achieved by dynamic cross-linking of a chiral phenyl ester polymer cross-linked film.

Figure 12 shows the chiral signal recovery status of different polymers.

Embodiments of the invention

The present invention obtains a side chain phenyl ester polymer by polymerizing monomers, RAFT reagents and initiators. The side chain phenyl ester polymer is prepared into a film and then induced by a chiral reagent to obtain a chiral phenyl ester polymer film; The groups are cross-linked to obtain a chiral phenyl ester polymer cross-linked film. Specific: 1) Synthesis of achiral methoxyphenyl ester monomer Pe: Add 6-bromo-n-hexanol to dry tetrahydrofuran, stir under argon, and add methacryloyl chloride dropwise under constant temperature conditions in an ice-salt bath. After the addition was completed, the reaction was maintained at room temperature overnight. After the reaction, the solid was removed by suction filtration. The filtrate was collected and the solvent was spun dry, redissolved in ethyl acetate, washed with saturated sodium bicarbonate water several times and then washed with saturated brine. The organic phase was dried over anhydrous sodium sulfate. The solvent was spun dry, and compound 1 was obtained as a light green liquid through column chromatography separation. Add paradiphenol, p-methoxybenzoic acid and the solvent methylene chloride into the round-bottomed flask. After stirring, add EDCI and DMAP and react at room temperature. After the reaction is completed, wash with saturated sodium bicarbonate water several times and then with saturated brine. The organic phase is dried with anhydrous sodium sulfate, the solvent is spin-dried, and a white solid compound 2 is obtained by column chromatography. Add the above-mentioned compound 2, potassium carbonate, potassium iodide and the solvent DMF into a three-neck flask, conduct a reflux reaction, and then add the DMF solution of compound 1 dropwise. After the reaction overnight, cool to room temperature, remove the excess solid by suction filtration, and extract with ethyl acetate. Wash away excess DMF with saturated ammonium chloride, water, and saturated salt water. Rotary evaporation and recrystallization from methanol gave compound 3 as a white solid.

2) Synthesis of phenyl ester monomer PeCA with terminal cinnamic acid group: Add p-diphenol, p-methoxycinnamic acid and solvent dichloromethane into a round-bottomed flask, then add EDCI and DMAP, and react at room temperature. After the reaction was completed, the mixture was washed several times with saturated sodium bicarbonate water and then with saturated brine, and the organic phase was dried over anhydrous sodium sulfate. The solvent was spun dry and compound 4 was obtained as a white solid by column chromatography. Add methyl paraben, potassium carbonate, potassium iodide and the solvent acetone into a three-neck flask, reflux the reaction, then add dropwise the acetone solution of 6-bromo-n-hexanol, react overnight and then cool to room temperature, remove the excess solid by suction filtration, and swirl Evaporate the solution to obtain a yellow oily crude product. Put the product into a mixed solution of methanol and water in a round-bottomed flask and heat it under reflux. Add KOH aqueous solution. After the reaction overnight, cool to room temperature and rotary evaporate. The remaining solution is acidified with dilute HCl. There is a large amount of A white solid precipitated, and the white solid was washed with ultrapure water after suction filtration. Put the obtained white solid, triethylamine, and DMAP into a round-bottomed flask, then add methylene chloride to dissolve it. Add methacrylic anhydride dropwise under ice bath conditions. After the reaction, pour the reaction solution into dilute hydrochloric acid, and use anhydrous sulfuric acid for the organic layer. After drying over sodium, it was evaporated and separated by column chromatography to obtain compound 2 as a white solid. Recrystallization gave the target product compound 5 as a white solid. Compound 4 and compound 5 were added to the round-bottomed flask, and after stirring, EDCI and DMAP were added and the reaction was carried out at room temperature. After the reaction was completed, the mixture was washed several times with saturated sodium bicarbonate water and then with saturated brine, and the organic phase was dried over anhydrous sodium sulfate. The solvent was spun off and recrystallized from methanol to obtain compound 6 as a white solid.

3) Synthesize achiral side-chain phenyl ester homopolymers and random copolymers: combine the monomer Pe obtained in step 1) and/or the monomer PeCA obtained in step 2) and the RAFT reagent α-dithionaphthoic acid Isobutyronitrile ester (CPDN), initiator azobisisobutyronitrile (AIBN), and solvent anisole are added to the reaction vessel, deoxygenated with inert gas, heated and polymerized to obtain achiral side chain ester benzene polymerization material (PPex-rPeCAy); wherein, the total molar amount of the two monomers, the molar ratio of the RAFT reagent and the initiator is 50 ~ 500:3:1, preferably 100:3:1; when one monomer is selected, it is Homopolymer.

See Figure 1 for the above reaction.

4) Preparation of achiral phenyl ester polymer film and chiral steam induction: The side chain ester benzene polymer is dissolved in an organic solvent to form a polymer solution. Take a clean thin quartz sheet, place it in the spin coater and fix it by suction. Use a pipette to suck up the polymer solution, add it dropwise to the surface of the quartz sheet, and then start the spin coater to start coating. The conditions for coating film are low-speed glue uniformity followed by high-speed glue uniformity, for example, low-speed glue uniformity for 6 s and a rotation speed of 0.5 kr/min, and high-speed glue uniformity for 20 s and a rotation speed of 1.9 kr/min. After the spin coating is completed, suspend the polymer film in a sealed cuvette, add a chiral solvent and place it at the bottom of the cuvette. Heat and then cool down to obtain a chiral phenyl ester polymer film. Take out the dried residual solvent and place it in the Wait for testing in a dark place; the chiral solvent is selected from one of chiral limonene, chiral carvone, chiral sec-butanol, and chiral sec-octanol, with chiral limonene being preferred.

5) Cross-linking of supramolecular chiral films: Suspend the chiral phenyl ester polymer film in a sealed cuvette, and irradiate the polymer film with a 365 nm ultraviolet light source in a dark environment for 4 h. A cross-linked film of chiral phenyl ester polymer was obtained. Place in a dark place to wait for testing.

The raw materials involved in the present invention are all existing products, and unless otherwise specified, the preparation is carried out under conventional conditions; the specific operating methods and testing methods involved are all existing technologies. The present invention will be further described below with reference to specific embodiments and drawings.

Chemical reagent: 6-bromo-n-hexanol, 95%, Acros.

Methacryloyl chloride, 95%, Aladdin.

Paramethoxybenzoic acid, 95%, Aladdin.

Paradiphenol, 97%, Aladdin.

Methylparaben, 97%, Aladdin.

p-Methoxycinnamic acid, 97%, Macklin.

Methacrylic anhydride, 95%, Aladdin.

1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI), 98%, Aladdin.

4-Dimethylaminopyridine (DMAP), 99%, Adamas.

Azobisisobutyronitrile (AIBN), chemically pure, Shanghai Reagent Factory No. 4.

Alpha-dithionaphthoic acid isobutyronitrile (CPDN), 99%, Bailingwei.

Anisole, 99.5%, Shanghai Chemical Reagent Company.

( S )-(+)-limonene, [α] 24 589 =99 .62°, TCI.

( R )-(-)-limonene, [α] 24 589 =97 .72°, TCI.

Potassium iodide, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Triethylamine, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Dichloromethane, 99.5%, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Anhydrous sodium sulfate, 98%, Sinopharm Chemical Reagent Co., Ltd.

Ethyl acetate, 99.5%, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Potassium carbonate, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Potassium hydroxide, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Petroleum ether, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Tetrahydrofuran, 99.5%, Nanjing Chemical Reagent Co., Ltd.

Ammonium chloride, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

TLC silica gel, CP, Qingdao Ocean Chemical Co., Ltd.

Concentrated hydrochloric acid, analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

Test instruments and conditions: CD spectrometer: J-1500 model of Japan JASCO Company, the test temperature is 25 ^o C, a quartz cuvette with a diameter of 10 mm is used, the scanning range is 200~600 nm, the scanning rate is 2000 nm/min, The bandwidth is 2 nm, the response time is 2 s, and the measurement optical path is 1 nm.

Proton nuclear magnetic resonance spectrum ( ¹ H-NMR): Use a Bruker 300MHz nuclear magnetic instrument, CDCl ₃ and DMSO- d ₆ as solvents, TMS as the internal standard, and measure at room temperature.

Ultraviolet-visible absorption spectrum: Use the UV-2600 ultraviolet-visible absorption spectrometer produced by Japan Tsushima Company to measure the ultraviolet absorption signal, with a scanning range of 200 ~ 600nm.

Differential Scanning Calorimeter (DSC): Using TA DSC 250, the first heating and cooling rate is 20 ^o C/min, and the second heating and cooling rate is 10 ^o C/min.

Polarized light microscope (POM): A CNOPTEC BK-POL polarized light microscope equipped with a (Linkam THMS600) hot stage was used for testing.

Example 1: Synthesis of achiral monomer methyl methacrylate phenyl ester (Pe).

Add 6-bromo-n-hexanol (10.46 mL, 80 mmol) to dry tetrahydrofuran (100 mL), stir under argon, and add methacryloyl chloride (11.52) dropwise in an ice-salt bath at constant temperature. mL, 120 mmol) diluted in THF. After the addition was completed, the reaction was maintained at room temperature overnight. After the reaction, the solid was removed by suction filtration. The filtrate was collected and the solvent was spun dry, redissolved in ethyl acetate, washed with saturated sodium bicarbonate water five times and then washed with saturated brine. The organic phase was dried over anhydrous sodium sulfate. The solvent was spin-dried and column chromatography separated to obtain light green liquid compound 1 (12.5 g).

Add p-diphenol (8.25 g, 75 mmol), p-methoxybenzoic acid (9.12 g, 60 mmol) and solvent dichloromethane (350 mL) into a 500 mL dry round-bottom flask, stir for 10 min, and add EDCI ( 17.2 g, 90 mmol), DMAP (3.65 g, 30 mmol). React at room temperature for 8 hours. After the reaction was completed, the mixture was washed 5 times with saturated sodium bicarbonate water and then with saturated brine, and the organic phase was dried over anhydrous sodium sulfate. The solvent was spin-dried and column chromatography was performed to obtain compound 2 (4.3 g) as a white solid.

Add the above compound 2 (2.1 g, 8.4 mmol), potassium carbonate (1.68 g, 12 mmol), potassium iodide (0.1g) and solvent DMF (40 mL) into a 100 mL dry three-neck flask, and reflux the reaction at 80 ^° C. 12 h, then the DMF dilution of compound 1 (2.44 g, 10 mmol) was added dropwise. After the reaction was overnight, it was cooled to room temperature. The excess solid was removed by suction filtration, extracted with ethyl acetate, washed with saturated ammonium chloride to remove excess DMF, and washed with water. , wash with saturated salt water. Rotary evaporation and recrystallization from methanol gave pure Pe monomer (1.72 g).

Figure 2 shows the NMR image of the above-mentioned achiral monomer Pe. The NMR peaks correspond to the monomer and there are no impurity peaks, indicating that the monomer is relatively pure.

Example 2: Synthesis of phenyl ester monomer PeCA with terminal cinnamic acid group.

Add p-diphenol (8.25 g, 75 mmol), p-methoxycinnamic acid (10.5 g, 60 mmol) and solvent dichloromethane (350 mL) into a 500 mL dry round-bottom flask, stir for 10 min, and add EDCI ( 17.2 g, 90 mmol), DMAP (3.65 g, 30 mmol). React at room temperature for 8 hours. After the reaction was completed, the mixture was washed 5 times with saturated sodium bicarbonate water and then with saturated brine, and the organic phase was dried over anhydrous sodium sulfate. The solvent was spin-dried and column chromatography performed column chromatography to obtain compound 4 (3.3 g) as a white solid.

Add methylparaben (15.2 g, 100 mmol), potassium carbonate (13.9 g, 98 mmol), potassium iodide (0.1g) and solvent acetone (250 mL) into a 500 mL dry three-neck flask, at 80 ^o C The reaction was refluxed for 12 h, and then the acetone dilution of 6-bromo-n-hexanol (13.07 mL, 100 mmol) was added dropwise. After the reaction for 20 h, it was cooled to room temperature, the excess solid was removed by suction filtration, and the solution was rotary evaporated to obtain a yellow oily crude product ( 25.2g). In a 500 mL dry round-bottomed flask, put 25.2 g of the yellow oily crude product obtained in the previous step into a 5:1 methanol and water mixed solution (480 mL), heat to reflux at 100 ^° C for 48 h, and then add KOH (22.4 g, 40 mmol) aqueous solution, reacted overnight, cooled to room temperature, and rotary evaporated. The remaining solution was acidified with dilute HCl. A large amount of white solid precipitated. After suction filtration, the white solid was washed with ultrapure water to finally obtain the white solid product (21.5 g). Put the obtained white solid (5.1 g, 22 mmol), 4 mL of triethylamine, and DMAP (288 mg, 2.2 mmol) into a 250 mL round-bottomed flask, then add methylene chloride (120 mL) to dissolve, and add dropwise under ice bath conditions. Methacrylic anhydride (3.92 mL, 26 mmol). After reacting for 5 hours, the reaction solution was poured into 10% dilute hydrochloric acid (250 mL) and shaken. The organic layer was dried with anhydrous sodium sulfate and then evaporated. The white color was obtained by column chromatography separation. Solid compound 5 (3.2 g).

Add compound 4 (1.7 g, 10 mmol) and compound 5 (2 g, 10 mmol) into a 500 mL dry round-bottomed flask, stir for 10 min until the solution is clear and transparent, add EDCI (1.6 g, 15 mmol), DMAP (386 mg, 5 mmol). React at room temperature for 3 hours. After the reaction was completed, the mixture was washed several times with saturated sodium bicarbonate water and then with saturated brine, and the organic phase was dried over anhydrous sodium sulfate. The solvent was spun off and recrystallized from methanol to obtain pure PeCA monomer (3.4 g).

Figure 2 shows the NMR image of the above-mentioned achiral monomer PeCA. The NMR peaks correspond to the monomer and there are no impurity peaks, indicating that the monomer is relatively pure.

Example 3: Synthesis of achiral side chain phenyl ester homopolymer and random copolymer.

Combine monomer Pe and/or monomer PeCA, RAFT reagent α-isobutyronitrile dithionaphthoate (CPDN) (8.08 mg, 0.029 mmol), and initiator azobisisobutyronitrile (AIBN). (1.64 mg, 0.010 mmol) and solvent anisole (1.5 mL) were added to a five-ml ampoule. The ratio of the total molar amount of monomer to RAFT reagent and initiator was 100:3:1. . After adding the sample, use a double-row tube to perform three cycles of freezing-pumping-inflating-thawing to remove oxygen. After completion, seal the bottle mouth and heat and stir for 6 hours at 80°C. Stop the reaction, dilute the reaction solution with 2 mL of THF, precipitate twice in methanol, collect the solid, and obtain an achiral side chain phenyl ester polymer (PPe _y -r-PeCA _x ).

Depending on the molar feeding ratio of monomer Pe and monomer PeCA, homopolymer (a monomer) and copolymer in different proportions can be obtained.

Figure 3 shows the NMR spectra and GPC elution curves of different polymers. By comparing the peaks of the cinnamic acid double bond and the hydrogen on the benzene ring in the NMR spectrum, the ratio of the two monomers in the copolymer (x:y) can be obtained. Figure 4 shows polarizing microscope (POM) photos of different polymers. The polymer solid powder is heated to exceed the clearing point transition temperature, and then cooled to the liquid crystal phase temperature range for testing. (ag) is expressed as: PPe, PPe ₁ -r -PeCA _0.2 , PPe ₁ -r-PeCA _0.3 , PPe ₁ -r-PeCA _0.6 , PPe ₁ -r-PeCA ₁ , PPe ₁ -r-PeCA ₃ , PPeCA. Figure 5 shows the small-angle X-ray scattering pattern and wide-angle X-ray diffraction pattern of the copolymer. The sample preparation conditions are the same as those of POM. The nematic liquid crystal structure of the polymer is determined through Figures 4 and 5.

Example 4: Preparation of achiral phenyl ester polymer film and chiral limonene steam induction to prepare chiral phenyl ester polymer film.

Weigh the side chain phenyl ester polymer and dissolve it in CHCl ₃ to prepare a 12 mg/mL polymer solution (clear solution). Take a clean thin quartz sheet, place it in the rotary coating machine and fix it by sucking the sheet, and adjust the speed and time of low-speed and high-speed glue uniformity. Use a pipette gun to absorb 100 uL of the polymer solution and drop it onto the surface of the quartz sheet. Then start the spin coater to start coating. Apply the glue at a low speed for 6 s at a rotation speed of 0.5 kr/min, then apply it at a high speed for 20 s at a rotation speed of 0.5 kr/min. is 1.9 kr/min; after the spin coating is completed, the film is placed in a vacuum oven and heated at 110°C for 12 hours for annealing treatment. After completion, take it out and place it in a dark place, waiting for testing. Suspend the annealed polymer film in a sealed cuvette, add chiral limonene and place it at the bottom of the cuvette (not touching the film), heat to 80°C and then cool down naturally to obtain a chiral phenyl ester polymer film. Dry at 40°C to remove residual chiral solvent and place in a dark place to wait for testing. After S-chiral limonene and R-chiral limonene are treated, S-chiral phenyl ester polymer film and R-chiral phenyl ester polymer film are obtained respectively.

Figure 6 shows the corresponding CD spectra and UV spectra of polymer (PPe ₁ -r-PeCA ₃ ) films at different temperatures in limonene vapor. It can be seen from the mirror CD signal that: the supramolecular chiral film induced by 1 S limonene vapor exhibits a positive Condon effect; the supramolecular chiral film induced by 1 R limonene vapor exhibits a negative Condon effect.

Example 5: Cross-linking of supramolecular chiral films to prepare chiral phenyl ester polymer cross-linked films.

The prepared chiral phenyl ester polymer film was irradiated under a 365 nm ultraviolet light source (15 W) for 4 h to cause the [2 + 2] cycloaddition reaction of the cinnamic acid group to produce a chiral cross-linked film.

The occurrence of the cross-linking reaction can be judged by the NMR and UV spectra of the film before and after cross-linking. As shown in Figure 7, taking PPe ₁ -r-PeCA ₃ as an example, it can be observed from the figure that as the irradiation time increases, the cinnamic acid bis The disappearance of bonds and the decrease of the corresponding UV absorption peak at 330 nm indicate that the cross-linking reaction is complete after 4 hours of illumination.

Figure 8 shows the investigation of the solvent resistance of the copolymer PPe ₁ -r-PeCA ₃ chiral film before and after cross-linking. THF, a good solvent of the polymer before cross-linking, was selected as the investigation object. It can be seen that the solubility of the membrane before and after cross-linking has changed substantially. The polymer membrane before cross-linking is easily soluble in THF, and the solution cannot show a CD signal, while the chiral film after cross-linking is easily soluble in THF. It showed significant solvent resistance. It was soaked in THF for 5 minutes and then taken out to test the change of chiral signal in the solvent. The CD spectrum shows that the chirality signal of the cross-linked polymer does not decrease in the solvent, which shows that the cross-linking has perfectly fixed the chirality; the present invention further extends the soaking time to 2 h, and the internal helix of the polymer film The structure still exists. After taking out the film, test the chiral signal. It will drop slightly. Then perform a simple temperature rising and cooling process (heat the film to 100°C and then lower it to room temperature for 20 seconds). Then test the chiral signal again and return to the initial state. This can be achieved. Chiral self-healing. The chiral azobenzene polymer cross-linked film (CN2020113259861) previously disclosed by the applicant had an obvious swelling effect when soaked in THF for 30 minutes. After the film was taken out and tested, the chiral signal dropped and could only be restored by heating and cooling; out Unexpectedly, when the chiral phenyl ester polymer cross-linked film of the present invention was soaked in THF for 30 minutes and the film was taken out and tested, the chiral signal did not decrease.

Figure 9 shows the investigation of the heat resistance of the copolymer PPe ₁ -r-PeCA ₃ chiral film before and after cross-linking. It can be seen from the figure that the CD signal stability of the films before and after cross-linking shows obvious differences at 100°C. The CD signal of the uncross-linked film disappears when heated to 100°C. Even if it returns to room temperature, the chiral signal does not change. reply. The corresponding cross-linked film has obvious thermal stability at high temperatures, and the chiral signal does not significantly decrease at high temperatures.

Figure 10 shows that the cross-linked polymer film has chiral memory and self-healing functions. Its chiral signal is eliminated by heating to a high temperature above the clearing point. However, after annealing for 12 h in the liquid crystal phase temperature range, the chiral signal returns to initial state.

Example 6: Dynamic cross-linking of chiral phenyl ester polymer cross-linked films to achieve chiral memory switching.

The cross-linked film was exposed to a 254 nm ultraviolet light source (1.5 W) for 0.5 h to cause de-cross-linking. The occurrence of the de-cross-linking reaction was judged by the UV spectrum, as shown in Figure 11 a. After 0.5 h of illumination, at 330 nm The UV absorption peak rises, indicating that the carbon-carbon double bond reappears at this time, and a decrosslinking reaction occurs. When irradiated with 365 nm ultraviolet light again, the corresponding absorption peak decreases again. This cycle can achieve dynamic reversibility of crosslinking and decrosslinking. process, and this process can be repeated multiple times (Figure 11 b). To explore the chiral fixation and self-healing properties of the cross-linked polymer film, the CD signal dropped significantly during the heating process, and the chirality recovery effect was also very poor after cooling, and it did not have a self-healing function (Figure 11 c). After being irradiated with a 365 nm UV light source for 4 h again, the second cross-linking process occurred, and the thermal stability test of the polymer was performed. The results showed that the polymer once again obtained the chiral memory function and had a self-healing function (Figure 11 d). The chiral azobenzene polymer cross-linked film (CN2020113259861) previously disclosed by the applicant does not have a dynamic cross-linking process (regardless of heating or light stimulation), and still maintains a self-healing function. There is no evidence in the existing technology that the chiral memory function can be eliminated. /Report on the development of chiral thin films.

Example 7: Chiral self-healing of homopolymers and copolymers in different proportions.

The chiral signal is eliminated by heating to a high temperature above the clearing point. After annealing for 12 hours in the liquid crystal phase temperature range, the recovery status of the chiral signal of different polymers is shown in Figure 12. The plus and minus signs on the ordinate in the figure represent the helical direction, and the absolute value is the ratio of the gCD value after chiral self-healing to the initial state. When the cross-linking group content is too low (less than 20%), the film (PPe ₁ -r-PeCA _0.2 ) does not have the chiral self-healing function. When the cross-linking component exceeds 20%, the polymer film begins to have Chiral self-healing function, PPe ₁ -r-PeCA ₁ and PPe ₁ -r-PeCA ₃ can achieve complete chiral self-healing; however, the chirality of PPeCA homopolymer (crosslinking group content 100%) cannot be repaired to the initial state.

The invention polymerizes new monomers, RAFT reagents, and initiators to obtain side chain phenyl ester polymers. The side chain phenyl ester polymers are prepared into films and then induced by chiral reagents to obtain chiral phenyl ester polymer films; After further group cross-linking, a chiral phenyl ester polymer cross-linked film is obtained. The present invention discloses for the first time the structure of a phenyl ester polymer with cinnamic acid at the end of the side chain and performs chiral induction. It utilizes mild conditions and convenient cross-linking methods to improve the stability of supramolecular chirality, and in the polymer system Achieve supramolecular chiral self-healing function; after cross-linking reaction, it can not only maintain the one-dimensional characteristics of the polymer main chain, but also enable the polymer chain to maintain its orientation when used in solvents or heated at high temperatures, with It has the advantages of simplicity and high efficiency; and in phenyl ester polymers, it can effectively avoid the structural damage caused by certain polymers such as azobenzene polymers to ultraviolet light of specific wavelengths. In particular, unlike the existing covalent bond cross-linking, the present invention adopts a dynamic cross-linking process, which can realize the reversible process of cross-linking and de-cross-linking through simple illumination, and solves the problem of structural solidification in the existing method. , and can realize optical switches with chiral memory and self-healing functions.

Claims (10)

A method for preparing a chiral phenyl ester polymer cross-linked film, which is characterized in that the side chain phenyl ester polymer is prepared into a film and then induced by a chiral reagent to obtain a chiral phenyl ester polymer film; and then cross-linked , to obtain a chiral phenyl ester polymer cross-linked film; the side chain phenyl ester polymer has the following chemical structural formula: ​ Among them, x:y=1: (0～5). The method for preparing a chiral phenyl ester polymer cross-linked film according to claim 1, characterized in that the side chain phenyl ester polymer is prepared into a film by a solution spin coating method; and 365 nm ultraviolet light is used for cross-linking to obtain Chiral phenyl ester polymer cross-linked film. The preparation method of chiral phenyl ester polymer cross-linked film according to claim 1, characterized in that the side chain phenyl ester polymer is obtained by polymerizing monomers, RAFT reagents and initiators; monomers, RAFT reagents and initiators The molar ratio is 50~500:3:1. The method for preparing a chiral phenyl ester polymer cross-linked film according to claim 3, wherein the monomers are PeCA and Pe; the chemical structure of Pe is as follows: The chemical structure of PeCA is as follows: . The method for preparing a chiral phenyl ester polymer cross-linked film according to claim 1, characterized in that the polymerization temperature is 70-80°C and the time is 6-8 hours; the polymerization reaction is carried out in an anhydrous and oxygen-free environment. A method for preparing a chiral phenyl ester polymer film, which is characterized in that a side chain phenyl ester polymer is prepared into a film and then induced by a chiral reagent to obtain a chiral phenyl ester polymer film. A chiral phenyl ester polymer cross-linked film or a chiral phenyl ester polymer film prepared according to the preparation method of claim 1 or 6. The chiral phenyl ester polymer cross-linked film according to claim 7, wherein the chiral phenyl ester polymer cross-linked film can achieve de-crosslinking under 254 nm ultraviolet light. The application of the chiral phenyl ester polymer cross-linked film or the chiral phenyl ester polymer film described in claim 7 in the preparation of chiral cross-linked membrane materials. The application according to claim 9, characterized in that the chiral cross-linked membrane material has heat resistance, solvent resistance, and chiral self-healing functions.