CN111499817B - Supermolecule chiral azobenzene assembly and in-situ construction method - Google Patents

Supermolecule chiral azobenzene assembly and in-situ construction method Download PDF

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CN111499817B
CN111499817B CN202010121548.7A CN202010121548A CN111499817B CN 111499817 B CN111499817 B CN 111499817B CN 202010121548 A CN202010121548 A CN 202010121548A CN 111499817 B CN111499817 B CN 111499817B
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assembly
azobenzene
chiral
chiral azobenzene
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CN111499817A (en
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张伟
程笑笑
缪腾飞
马浩天
周年琛
张正彪
朱秀林
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Suzhou University
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    • C07C245/08—Azo compounds, i.e. compounds having the free valencies of —N=N— groups attached to different atoms, e.g. diazohydroxides with nitrogen atoms of azo groups bound to carbon atoms of six-membered aromatic rings with the two nitrogen atoms of azo groups bound to carbon atoms of six-membered aromatic rings, e.g. azobenzene
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Abstract

The invention discloses a supermolecule chiral azobenzene assembly and an in-situ construction method. The method comprises the following steps: the method comprises the steps of mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator and an alcohol solvent, and carrying out polymerization reaction in an oxygen-free environment to obtain the supramolecular chiral azobenzene polymer.

Description

Supermolecule chiral azobenzene assembly and in-situ construction method
Technical Field
The invention belongs to the technical field of polymer synthesis, and particularly relates to synthesis of chiral azobenzene molecules and polymerization-induced chiral self-assembly.
Background
Chirality refers to the property of an object not coinciding with its mirror image. It is a basic attribute in nature and widely exists in nature, including micro-sized chiral small molecules, biomacromolecules, animal and plant helical structures on a macro scale, interstellar vortexes and the like. Scientists construct a precise and ordered chiral spiral structure by a supermolecule assembly method, simulate interesting phenomena in life, and prepare chiral materials, asymmetric catalytic materials, bionics materials and the like. After french scientist Lehn first proposed the concept of "supramolecules" in 1978, researchers have conducted extensive studies on supramolecular chirality. The supermolecule is an aggregate which is formed by combining two or more molecules together by virtue of intermolecular non-covalent bond interaction, has a complex ordered structure, keeps certain integrity and has a definite microstructure and macroscopic characteristics. The azobenzene compound and the derivative thereof are one of the common photoresponse materials in daily production and life, and the unique reversible photocis-trans isomerization performance of the azobenzene compound can generally cause the physical and chemical properties of the azobenzene compound to be obviously changed, so that the properties of the azobenzene compound are obviously changed. The azobenzene compound has N = N double bonds in the structure, lone pair electrons on the N = N double bonds can generate pi-pi and N-pi electron transition when being excited by light irradiation, and therefore cis-trans photoisomerization can be generated under the light irradiation condition. During the photo-isomerisation process, two isomeric forms are produced, a more stable trans isomer and a more active cis isomer. The relatively planar trans-isomer can be converted into a curved cis-structure under ultraviolet radiation, the cis-isomer is more active than the trans-isomer, the cis-isomer can be converted into the trans-isomer under relatively mild conditions, and the reversible conversion process can cause the structure and the performance of the material to be changed. In the prior art, a research group successfully realizes the construction of the supermolecule chirality of side-chain type and main-chain type achiral azobenzene polymers through chiral solvation induction, and the supermolecule chirality of the side-chain azobenzene polymers is derived from the supermolecule structure of a relatively planar trans-azobenzene unit in a polymer structure.
Disclosure of Invention
Aiming at the situation, the invention designs and utilizes thermal polymerization to synthesize a solvophilic macromolecular chain transfer agent, then utilizes the synthesized macromolecular chain transfer agent to successfully initiate a solvophobic chiral azobenzene monomer to carry out polymerization in ethanol through a thermal initiator, and carries out self-assembly in the polymerization process to construct a supermolecular chiral liquid crystal assembly containing azobenzene.
In order to achieve the purpose, the invention prepares the block copolymers with different polymerization degrees and the azobenzene supermolecule chiral liquid crystal assemblies with different morphologies in situ, and provides a new method which comprises the following steps: polymerization induces chiral self-assembly. The specific technical scheme is as follows:
the preparation method of the supermolecule chiral azobenzene assembly comprises the following steps of mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator and an alcohol solvent, carrying out polymerization reaction in an oxygen-free environment to obtain a supermolecule chiral azobenzene polymer, and carrying out in-situ preparation of an azobenzene block copolymer assembly.
In the invention, the chemical structural formula of the chiral azobenzene monomer is as follows:
Figure DEST_PATH_IMAGE001
Figure DEST_PATH_IMAGE002
the chiral azobenzene monomer isS-azobenzene monomer,RAn azobenzene monomer, a being 1 to 9 and b being 1 to 12.
In the invention, the alcohol solvent is any one of methanol, ethanol, propanol and butanol, and ethanol is preferred.
In the invention, the polymerization reaction is carried out at 60-80 ℃ for 12-18 hours, preferably at 70 ℃ for 15 hours.
According to the invention, the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent is 3-180: 1; preferably, the amount of free radical initiator is 20% of the molar amount of macromolecular chain transfer agent.
According to the method, methacryloyl chloride and an intermediate product 4 are used as raw materials, and reflux reaction is carried out under inert gas to prepare a chiral azobenzene monomer; intermediate 4 is as follows:
Figure DEST_PATH_IMAGE003
preferably, p-nitrophenol and chiral alcohol are used as raw materials to prepare an intermediate product 1; the intermediate product 1 is subjected to amination and diazotization in sequence and then reacts with phenol to obtain an intermediate product 3; intermediate 3 is reacted with a halogen alcohol to provide intermediate 4. To be provided withRThe reaction described above can be schematically illustrated as follows, taking an azobenzene monomer as an example:
Figure DEST_PATH_IMAGE005
specific reaction steps can be exemplified as follows:
to synthesizeRAzo-benzene monomers are examples. The raw materials of p-nitrophenol and chiral octanol (A), (B)S-octanol), diisopropyl azodicarboxylate and diethyl ether were added to a three-necked flask, and triphenylphosphine was added to the flask; reacting for 12 hours at room temperature; after the reaction is finished, carrying out suction filtration, then spin-drying the solvent, and then carrying out column chromatography purification and drying to obtain an intermediate product 1; adding the intermediate product 1 into a three-neck flask, adding tin dichloride, heating for reaction for 3 hours, adding into ice water after the reaction is finished, adjusting the pH value to 7-8, extracting with ethyl acetate, spin-drying the solvent, purifying by column chromatography, and drying to obtain an intermediate product 2; diluting hydrochloric acid with water, dropwise adding the diluted hydrochloric acid into the intermediate product 2 under stirring, and dropwise adding a sodium nitrite aqueous solution after the dropwise addition is finished, so as to obtain a diazonium salt solution of the intermediate product 2; dropwise adding the diazonium salt solution of the intermediate product 2 into a solution containing phenol, sodium hydroxide and sodium bicarbonate under the condition of mechanical stirring, reacting for 4 hours after dropwise adding is finished to obtain a yellowish-brown turbid liquid, and finally obtaining a yellow intermediate product 3 after carrying out suction filtration, extraction, drying, column chromatography purification and vacuum drying on the obtained turbid liquid; potassium carbonate, intermediate 3, potassium iodide and 6-chlorohexanol were mixed and heated to 85 deg.f o C, reacting for 4 hours, then cooling to room temperature, and extracting by ethyl acetate and water to obtainDrying the obtained oil phase by using anhydrous sodium sulfate, then purifying by column chromatography through rotary evaporation, and then drying to obtain an intermediate product 4; adding triethylamine, methacryloyl chloride and an intermediate product 4 into tetrahydrofuran, performing reflux reaction for 24 hours under argon, and adding ammonium chloride NH 4 Aqueous Cl solution, followed by extraction with dichloromethane, the combined organic extracts washed with water, dried over anhydrous sodium sulfate, and the crude product purified by flash chromatography to give a yellow solid after dryingR-an azobenzene monomer.S-a step of synthesis of azobenzene monomer andRthe azobenzene monomer is the same except in stepR-the use of octanol.
In the invention, a hydrophilic monomer and a micromolecular chain transfer agent are used as raw materials to prepare a macromolecular chain transfer agent; preferably, a hydrophilic monomer, a micromolecular chain transfer agent, a free radical initiator and ethanol are added into a reaction container, and then the mixture is stirred for 4-8 hours at the temperature of 70-80 ℃; stopping the reaction, then settling in n-hexane for 3 times, dialyzing in a dialysis bag for three days, settling in n-hexane after dialysis, and then drying to obtain the solvophilic macromolecular chain transfer agent; further preferably, the molar ratio of the hydrophilic monomer, the small molecule chain transfer agent and the radical initiator is 50 to 500: 1: 0.2, preferably 60: 1: 0.2. For example, the chemical structure of the macromolecular chain transfer agent is as follows:
Figure DEST_PATH_IMAGE006
further, the original reaction material chiral alcohol of the invention is selected from any one of chiral octanol, chiral hexanol and chiral butanol, preferably chiral octanol; the halogen alcohol is selected from any one of 6-chlorohexanol, 12-bromo-1-dodecanol, 8-bromo-1-heptanol, 4-bromobutanol and 2-bromoethanol, preferably 6-chlorohexanol; the catalyst used in the reaction of methacryloyl chloride and intermediate 4 is selected from any one of sodium hydroxide, triethylamine, sodium bicarbonate and potassium carbonate, preferably triethylamine; the solvent used in the reaction of methacryloyl chloride and intermediate 4 is selected from any one of tetrahydrofuran, acetone, dichloromethane and n-hexane, preferably Tetrahydrofuran (THF); the radical initiator is selected from any one of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate and 4,4 '-azo (4-cyanovaleric acid), preferably 4,4' -azo (4-cyanovaleric acid) (ACVA).
Further, the hydrophilic monomer of the present invention is selected from any one of methacrylic acid, acrylic acid, and N-isopropylacrylamide, preferably methacrylic acid (MAA); the small molecule chain transfer agent is selected from any one of 4-cyano-4- (thiobenzoyl) valeric acid, 2-methyl-2- (dodecyl trithiocarbonate) propionic acid, 4-cyano-4- ((((ethylthio) carbonylthio) thio) valeric acid, 4-cyano-4- [ [ (dodecylthio) thiolmethyl ] thio ] valeric acid, and preferably 4-cyano-4- (thiobenzoyl) valeric acid (CPADB).
In the invention, the oxygen-free environment is inert gas. The inert gas in the invention is selected from any one of argon, nitrogen, helium and neon, and argon is preferred.
In the preparation method disclosed in the present invention, after completion of each reaction step, purification steps such as chromatography, dissolution/precipitation separation, filtration and the like may be performed in order to obtain a product with higher purity.
Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:
the invention discloses an azobenzene supermolecule chiral liquid crystal assembly constructed by polymerization-induced chiral self-assembly for the first time. In recent years, azobenzene polymers play an important role in scientific research and industrial production due to structural particularity, and chiral azobenzene polymer materials have important roles in the research of chiral resolution, enantiomer crystallization and optical switch materials as a class of high polymer materials with special performance. The process of the invention is used as a strategy for constructing the controllable and various-appearance azobenzene polymer supermolecule chiral assembly by a one-step method, and the synthetic method of the chiral material is expanded.
Drawings
FIG. 1 is a nuclear magnetic diagram of a chiral monomer in example 1. The nuclear magnetic peak corresponds to the monomer, and no impurity peak indicates that the monomer is relatively pure.
FIG. 2 is a nuclear magnetic spectrum and GPC elution curve of the macromolecular chain transfer agent of example 2. Wherein FIG. 2A is a nuclear magnetic map of a macromolecular chain transfer agent post-modified benzyl for GPC testing. FIGS. 2B and 2C are post-modified nuclear magnetic maps and GPC outflow curves.
FIG. 3 is a TEM image, an AFM image and a corresponding height image of block copolymer assemblies of different polymerization degrees in example 3. Different polymerization degrees can be obtained by adjusting the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent. Random micelle, spherical, worm, flake and vesicle shapes can be obtained by different polymerization degrees.
FIG. 4 is PMAA 51 -S 49 And PMAA 51 -R 46 DSC chart, POM chart, SAXS chart and theoretical calculation chart of the block copolymer assembly; DSC chart shows that the two liquid crystal-isotropic transition temperatures are 72 o C, obtaining both liquid crystals by a POM diagram, obtaining both smectic phase liquid crystals by an SAXS diagram, and obtaining the interlayer spacing of the liquid crystals to be 5.88 nm by theoretical calculation.
FIG. 5 is a CD spectrum and a UV spectrum of a block copolymer assembly with different degrees of polymerization. The curves of the upper mirror image and the lower mirror image of the CD spectrogram show that the supermolecule chirality is successfully constructed in the azobenzene block copolymer. Wherein A, B, E, F is CD spectrogram and ultraviolet spectrogram of different chiral azobenzene block lengths.
FIG. 6 is a calculated CD sum for block copolymer assemblies of different degrees of polymerizationg CD Spectra. Graph A is the CD sum of the obtained whole chiral azobenzene block length intervalg CD Spectra. B is the CD sum of random micelle, spherical, worm, sheet and vesicle morphologiesg CD Spectra. And the figure C is an assembly schematic diagram of the worm. Whereing CD Is calculated by [ ellipticity/32,980]Absorbance. The size of the random micelle is 50-100 nm.
FIG. 7 is PMAA 51 -S 49 And PMAA 51 -R 46 Block copolymer assembly (A, B) photoisomerization, (C, D) reversible cycle diagram. Wherein graph A and B use 365 nm ultraviolet light for prolonging ultraviolet light irradiation time, PMAA 51 -S 49 And PMAA 51 -R 46 CD of (1) andg CD gradually decreasing; graph A and graph B were treated with 365 nm UV light and heat-cool, and CD andg CD disappearance, after heat-Cooling treatment, CD andg CD and then resume. And the disappearance-recovery process may be cycled at least 5 times.
FIG. 8 is PMAA 51 -S 49 And PMAA 51 -R 46 Block copolymer assembly thermal response CD plot. The CD values gradually decreased when graph A was heated, and increased when graph B was cooled.
Fig. 9 is a reaction schematic diagram of the supramolecular chiral azobenzene assembly and the morphology of the assembly in example 3, including random micelle, spherical, worm, sheet, and vesicle morphology.
Figure 10 is the GPC outflow graph of supramolecular chiral azobenzene assemblies prepared in example 3.
Detailed Description
The preparation method of the supermolecule chiral azobenzene assembly comprises the following steps of mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator and an alcohol solvent, carrying out polymerization reaction in an oxygen-free environment to obtain a supermolecule chiral azobenzene polymer, and carrying out in-situ preparation of an azobenzene block copolymer assembly.
The invention will be further described with reference to specific embodiments and drawings.
Chemical reagents:
4-cyano-4- (thiobenzoyl) pentanoic acid, 97%, aladin;
4,4' -azo (4-cyanovaleric acid), 98%, J & K Chemical; recrystallizing twice before use;
6-chlorohexanol, 95%, Acros;
95% of p-nitrophenol and Aladdin;
phenol, AR, aladin;
tin dichloride, 98%, Energy Chemical;
diisopropyl azodicarboxylate, 98%, 3A Chemicals;
triphenylphosphine, 99%, great;
99% of benzyl chloride, Macklin;
99% of methacrylic acid, and aladin;
chiral octanol (R-an octanol group,S-octanol), 99%, TCI;
tetrahydrofuran, 99.5%, Nanjing chemical reagents, Inc.;
ethanol, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
methacryloyl chloride, 95%, aladin;
hydrochloric acid, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium nitrite, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
potassium iodide, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
triethylamine, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
anhydrous sodium sulfate, 98%, national drug group chemical reagents ltd;
potassium carbonate; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium hydroxide; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium bicarbonate; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
ethyl acetate, 99.5%, Jiangsu Qiangsheng functional chemistry GmbH;
petroleum ether, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
diethyl ether, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
ammonium chloride, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
testing instruments and conditions:
gel Permeation Chromatography (GPC): molecular weight and molecular weight distribution A gel permeation chromatograph with TOSOH TSKgel SuperHM-M was used, which is an automatic feeding model, polymethyl methacrylate was used as a standard sample to calculate the molecular weight of the polymer, N, N-Dimethylformamide (DMF) was used as a mobile phase at a flow rate of 0.65 mL/min and a temperature of 0.65 mL/minIs 40 from o C。
Nuclear magnetic resonance hydrogen spectrum ( 1 H-NMR): using a Bruker 300MHz NMR spectrometer in CDCl 3 And DMSO-d 6 As solvent, TMS as internal standard, measured at room temperature.
Transmission Electron Microscope (TEM): the accelerating voltage was 120 kV using a HITACHI HT 7700 transmission electron microscope.
Atomic Force Microscope (AFM) A Bruker Multimode 8 atomic force microscope was used, and the imaging mode was tapping.
Circular Dichroism (CD): using a Japanese JASCO J-815 circular dichroism spectrometer, 25 o And C, measuring, wherein the scanning speed is 200 nm/min, the scanning range is 300-600 nm, and the bandwidth is 2 nm.
Ultraviolet visible spectrum (UV-vis): and (3) using a Shimadzu UV-2600 ultraviolet spectrometer, wherein the scanning range is 300-600 nm.
Differential Scanning Calorimeter (DSC): using TA DSC 250, the temperature ramp rate was 10 o C/min。
Small angle X-ray scattering (SAXS): an Anton Paar SAXSess MC2 diffractometer, Cu Ka radiation source, wavelength 0.154 nm was used.
Polarizing microscope (POM): a CNOPTEC BK-POL polarizing microscope was used.
Example 1: monosynthesized chiral azobenzene monomer (S-azobenzene andR-azobenzene)
To synthesizeSAzobenzene is an example. 13.9 g of p-nitrophenol serving as a raw material and 0.1 mol of the p-nitrophenol,ROctanol (13.0 g, 0.1 mol), diisopropyl azodicarboxylate (20 mL) and 300 mL diethyl ether were added to a three-necked flask, and triphenylphosphine (26.2 g, 0.1 mol) was dissolved in 50mL diethyl ether at 0 ℃ and then added to the flask. Reacting for 12 hours at room temperature; after the reaction is finished, suction filtration is carried out, then the solvent is dried in a spinning mode, and then column chromatography purification and drying are carried out. Intermediate 1 (21.2 g, 0.084 mol) was obtained.
Intermediate 1 (21.2 g, 0.084 mol) and 100 mL of ethanol were added to a three-necked flask, followed by addition of tin dichloride (31.8 g, 0.17 mol), and heating to 70 o And C, reacting for 3 hours. Reaction ofAfter completion, the mixture was poured directly into 600 mL of ice water, and potassium carbonate was added to adjust the pH to 7. Extracting with ethyl acetate, drying with anhydrous sodium sulfate, vacuum filtering, spin drying solvent, purifying by column chromatography, and drying. Intermediate 2 (16.2 g, 0.073 mol) was obtained.
At low temperature 0 o Under C, sodium nitrite (7.0 g, 0.11 mol) was dissolved in 100 mL of water, 30 mL of hydrochloric acid was diluted with 30 mL of water, and the diluted hydrochloric acid was added to intermediate 2 (16.2 g, 0.073 mol) with stirring for 30 minutes. After the above steps are completed, the aqueous solution of sodium nitrite is added dropwise (the dropwise adding time is 20 minutes) into the hydrochloride solution, and the temperature is always kept at 0 o C, thereby obtaining a diazonium salt solution of intermediate 2. C
Phenol (16.0 g) was dissolved in 400 mL of water at 0 deg.C, and sodium hydroxide NaOH (8.0 g) and sodium bicarbonate NaHCO were added 3 (8.4 g). The diazonium salt solution of intermediate 2 obtained previously was then added dropwise to the above-mentioned phenol solution under mechanical stirring, maintaining the conditions of 0 ℃ for 30 minutes. The solution gradually changed from colorless to yellow and finally to brown-yellow. After the dropwise addition, the reaction is carried out for 4 hours under the environment to obtain a yellowish turbid liquid, and the obtained turbid liquid is subjected to suction filtration, extraction, drying by anhydrous sodium sulfate, post column chromatography purification and vacuum drying for a series of treatments to finally obtain a yellow intermediate product 3 (14.3 g, 0.044 mol).
Into a 500 mL dry round bottom flask was added potassium carbonate (50.0 g, 0.36 mol), intermediate 3 (14.3 g, 0.044 mol), potassium iodide KI 1.0g and 6-chlorohexanol (12.0 g, 0.088 mol), and heated to 85 o C, adding 300 mL of tetrahydrofuran into the round-bottom flask, and stirring to completely dissolve the potassium carbonate. The round-bottom flask changed from milky to brown turbidity. After vigorous stirring for 4 h, cool to room temperature, extract with ethyl acetate, water, dry over anhydrous sodium sulfate, rotary evaporate the oil phase, then purify by column chromatography, then dry to give intermediate 4 (13.6 g, 0.032 mol).
Triethylamine (25 mL), methacryloyl chloride (5.0 g, 0.048 mol), intermediate 4 (13.6 g, 0.032)mol) was added to 300 mL of tetrahydrofuran solution and refluxed under argon. After 24 hours, 10wt% NH was added 4 20 mL of Cl aqueous solution. Then extracted with dichloromethane and the combined organic extracts washed with water and dried over anhydrous sodium sulfate. The crude product is then purified by flash chromatography and dried to give a yellow solidSAzobenzene monomer (12.8 g, 0.026 mol).
R-a step of synthesis of azobenzene monomer andSthe azobenzene monomer is the same except in stepR-octanol toSOctanol to yield 13.2 gR-an azobenzene monomer.
FIG. 1 is a nuclear magnetic diagram of the chiral azobenzene monomer, wherein a nuclear magnetic peak corresponds to the monomer, and no hetero peak exists, which indicates that the monomer is relatively pure.
The reaction process is schematically shown as follows:
Figure DEST_PATH_IMAGE008
example 2: synthesis process of solvent-philic macromolecular chain transfer agent
The starting material methacrylic acid (5.16 g, 60.0 mmol), the small molecule chain transfer agent 4-cyano-4- (thiobenzoyl) pentanoic acid (0.28 g, 1.0 mmol), 4' -azo (4-cyanovaleric acid) (56.1 mg, 0.2 mmol) and the solvent ethanol (10.32 g) were added to a reaction vessel, the reaction temperature was controlled at 70 ℃, and the reaction was stirred for 5 hours. The reaction was stopped, then diluted with 2 mL of ethanol, settled in 500 mL of n-hexane for 3 times, then placed in a dialysis bag, dialyzed in 1000 mL of ethanol for three days, settled in 500 mL of n-hexane after the end of dialysis, and then completely dried. A solvophilic macromolecular chain transfer agent (PMAA macro-CTA) was obtained (4.32 g, 84% yield). Wherein the molar weight of the monomer and the molar ratio of the micromolecule chain transfer agent to the initiator are as follows: 60: 1: 0.2. FIG. 2 is a nuclear magnetic diagram and GPC outflow curve of the macromolecular chain transfer agent described above. Wherein FIG. 2A is a nuclear magnetic map of a macromolecular chain transfer agent post-modified benzyl for GPC testing, as is conventional. FIGS. 2B and 2C are post-modified nuclear magnetic maps and GPC outflow curves.
Example 3: general procedure for polymerization induced chiral self-assembly (PICSA)
The chiral monomer obtained in example 1 (A)SAn azobenzene monomer andRazobenzene monomer), macromolecular chain transfer agent (93.3 mg, 0.02 mmol) obtained in example 2, 4' -azo (4-cyanovaleric acid) (1.16 mg, 0.004 mmol) and ethanol as solvent were added to a reaction vessel, deoxygenated with argon, 70.004 mmol o And C, polymerizing for 15 hours to obtain the supramolecular chiral azobenzene assembly. Wherein the solid content of the reaction system is 10 wt%; the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent to the 4' -azo (4-cyanovaleric acid) can be 3-180: 1: 0.2, products with different polymerization degrees can be obtained, for example, the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent is 49: 1 under extremely high conversion rate, and the obtained supramolecular chiral azobenzene assembly is PMAA 51 -S 49 The molar ratio of the block copolymer, such as chiral azobenzene monomer to macromolecular chain transfer agent is 46: 1, and the obtained supramolecular chiral azobenzene assembly is PMAA 51 -R 46 A block copolymer.
The chemical structural formula of the supramolecular chiral azobenzene assembly is as follows:
Figure DEST_PATH_IMAGE010
as in fig. 10, the GPC outflow curve indicates successful polymerization.
FIG. 3 is a TEM image, an AFM image and a corresponding height image of the block copolymer assemblies having different polymerization degrees. Different polymerization degrees can be obtained by adjusting the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent, random micelles, spheres, worms, sheets and vesicle-shaped appearances can be obtained by the different polymerization degrees, in a height diagram, the ordinate is height, the unit is nanometer, no abscissa exists, and the size of the random micelles is 50-100 nanometers.
FIG. 4 is PMAA 51 -S 49 And PMAA 51 -R 46 DSC, POM, SAXS and theoretical calculation of Block copolymer assemblies, DSC diagram gives two liquid crystal-isotropic transition temperatures of 72 o And C, obtaining both liquid crystals by using a POM diagram, obtaining both smectic phase liquid crystals by using an SAXS diagram, and obtaining the interlayer spacing of the liquid crystals by theoretical calculation of 5.88 nanometers.
FIG. 5 is a CD spectrum and a UV spectrum of a block copolymer assembly with different degrees of polymerization. The curves of the upper mirror image and the lower mirror image of the CD spectrogram show that the supermolecule chirality is successfully constructed in the azobenzene block copolymer. Wherein A, B, E, F is CD spectrogram and ultraviolet spectrogram of different chiral azobenzene block lengths.
FIG. 6 is a calculated CD sum for block copolymer assemblies of different degrees of polymerizationg CD Spectra. The CD values for random micelle, spherical, worm, platelet, and vesicle morphologies vary. Whereing CD Is calculated as [ ellipticity/32,980]Absorbance.
FIG. 7 is PMAA 51 -S 49 And PMAA 51 -R 46 Block copolymer assembly (A, B) photoisomerization, (C, D) reversible cycle diagram. Wherein graph A and B use 365 nm ultraviolet light for prolonging ultraviolet light irradiation time, PMAA 51 -S 49 And PMAA 51 -R 46 CD of (1) andg CD gradually decreasing; graph A and graph B were treated with 365 nm UV light and heat-cool, and CD andg CD disappearance, then heating (70 ℃) -cooling (room temperature) treatment, CD andg CD and again recovered, and the disappearance-recovery process may cycle at least 5 times.
FIG. 8 is PMAA 51 -S 49 And PMAA 51 -R 46 Block copolymer assembly thermal response CD plot. The CD values gradually decreased when graph A was heated, and increased when graph B was cooled.
Fig. 9 is a reaction schematic diagram of supramolecular chiral azobenzene assemblies and assembly morphologies, including random micelle, spherical, worm, platelet, and vesicle morphologies. If the ethanol in the preparation method is changed into N, N-dimethylformamide or tetrahydrofuran, and the rest is not changed, an assembly cannot be obtained, and the assembly is a dissolved polymer solution and cannot generate random micelle, spherical, worm, sheet and vesicle shapes.
In the product prepared by the invention, the supermolecule chirality combines the molecular chiral characteristics and the weak interaction force of supermolecule chemistry, and the chiral space structure formed by the non-covalent weak interaction force between chiral molecules or non-chiral molecules shows the chirality of the supermolecule ordered assembly body, but not the chirality of single molecules. In recent years, the rapid development of supramolecular science has led to the realization that optically active assemblies can be obtained by intermolecular non-covalent weak interactions in addition to intramolecular covalent bonds. Achiral molecules or chromophores can be induced to assemble into modules to form supramolecular aggregates with specific helical structures under the conditions of mechanical stirring, steric hindrance, circular polarized light and the like, so that chiral information can be amplified in a nonlinear mode; according to the invention, the azobenzene functional group is introduced as a photoresponse element so as to endow the material with remarkable optical properties. The polarity, shape and size of the azobenzene assembled unit can change rapidly under illumination, so that the ultraviolet visible spectrum (UV-vis) and Circular Dichroism (CD) spectrum of the azobenzene polymer can correspondingly show reversible changes. In the invention, as the polymerization is carried out, the solubility of a polymer chain in a solution is reduced, the extension degree of a core chain segment in an assembly, the surface tension of a core and a solvent of the assembly and the repulsive force between a shell layer of the assembly and the soluble chain segment drive the amphiphilic block polymer to self-assemble into a nano assembly, and the assembly of the block copolymer with different morphologies, such as spheres, worms, sheets and vesicle morphologies, can be quickly and conveniently constructed. Particularly, the invention introduces an azobenzene supermolecule structure into a polymer assembly, and constructs the supermolecule chiral liquid crystal polymer assembly containing azobenzene in situ through polymerization induction chiral self-assembly, thereby providing a strategy for effectively constructing the supermolecule chiral assembly of the azobenzene polymer with controllable and various shapes, and further functionalizing the material with controllable supermolecule chiral characteristics to expand the application range of the nano material containing azobenzene chiral.

Claims (8)

1. The preparation method of the supramolecular chiral azobenzene assembly is characterized by comprising the following steps of preparing a macromolecular chain transfer agent by using a hydrophilic monomer and a micromolecular chain transfer agent as raw materials; mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator and an alcohol solvent, and carrying out polymerization reaction in an oxygen-free environment to obtain a supermolecule chiral azobenzene polymer; the chemical structural formula of the chiral azobenzene monomer is one of the following chemical structural formulas:
Figure 836392DEST_PATH_IMAGE001
Figure 19111DEST_PATH_IMAGE002
wherein a is 1-9 and b is 1-12.
2. The supramolecular chiral azobenzene assembly as claimed in claim 1, wherein the alcohol solvent is any one of methanol, ethanol, propanol and butanol.
3. The supramolecular chiral azobenzene assembly as claimed in claim 1, wherein the polymerization reaction is carried out at 60-80 ℃ for 12-18 hours.
4. The supramolecular chiral azobenzene assembly as claimed in claim 1, wherein the molar ratio of chiral azobenzene monomer to macromolecular chain transfer agent is 3-180: 1.
5. The supramolecular chiral azobenzene assembly as claimed in claim 1, wherein methacryloyl chloride and intermediate product 4 are used as raw materials, and reflux reaction is carried out under inert gas to prepare chiral azobenzene monomer; the chemical structural formula of the intermediate product 4 is one of the following chemical structural formulas:
Figure 877477DEST_PATH_IMAGE003
。
6. the supramolecular chiral azobenzene assembly as claimed in claim 5, wherein intermediate 1 is prepared from p-nitrophenol and chiral alcohol; the intermediate product 1 is subjected to amination and diazotization in sequence and then reacts with phenol to obtain an intermediate product 3; intermediate 3 is reacted with a halogen alcohol to provide intermediate 4.
7. The supramolecular chiral azobenzene assembly as claimed in claim 1, wherein said supramolecular chiral azobenzene assembly is in micelle, spherical, worm, sheet or vesicle morphology.
8. Use of the supramolecular chiral azobenzene assembly as claimed in claim 1 for the preparation of chiral liquid crystal polymers.
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