A side chain azobenzene polymer gel and its preparation method and construction of chiral photoswitch

Abstract

The present invention discloses a side chain azobenzene polymer gel and a preparation method thereof and the construction of a chiral optical switch, belonging to the technical field of high molecular polymer chirality induction and regulation. The present invention provides a side chain azobenzene polymer, which is made into a side chain azobenzene polymer gel, and its chirality is induced and regulated by circularly polarized light, so as to construct a series of chiral optical switches. The present invention first prepares the side chain azobenzene polymer into a gel film by supramolecular assembly technology, and then uses circularly polarized light to induce and regulate the chirality of the side chain azobenzene polymer gel. At the same time, the chirality can be erased and restored by ultraviolet light and heating and cooling treatment, so as to realize the construction of a chiral optical switch, and realize the visual identification of enantiomeric molecules by gel-sol transformation, which provides a new strategy for expanding the preparation of side chain azobenzene polymers and the construction of chiral optical switches.

Description

Technical Field

[0001] The invention relates to a side chain azobenzene polymer gel and a preparation method thereof and the construction of a chiral optical switch, belonging to the technical field of high molecular polymer chirality induction and regulation. Background Art

[0002] Chirality is a fundamental feature of nature, manifesting itself at all levels from molecules to supramolecular structures. The construction of multi-stimulus responsive materials and the precise control of their chiral optical properties show great potential for application in various fields such as chiral switches, information storage, and optical displays.

[0003] Azobenzene groups can change their polarity, shape and size under external light and heat stimulation, thereby realizing cis-trans isomerization. They are a typical type of light-controlled material. Introducing chiral groups into azobenzene polymers provides more options for the preparation of light-responsive chiral materials, which is of great significance for the controllable synthesis and regulation of azobenzene polymer chiral materials. There are many methods for imparting chirality to molecules, which can be roughly divided into the following categories: (1) polarized light irradiation method; (2) biochemical method; (3) chiral solvent and chiral catalysis method; (4) reactant chiral center induction method. Among them, the circularly polarized light (CPL) induction method has the advantages of wide optical properties, no angular dependence, safety, pollution-free, remote controllability, convenience, high efficiency and high adjustability. It is often used in the preparation of chiral photoresponsive polymers. However, there are few studies on the construction of azobenzene polymer chiral photoswitches in gel systems and the design of chiral recognition enantiomer molecular probes under gels. Therefore, it is of great significance to construct side chain azobenzene gel polymers with chiral arrangement structures and give them precise control of chiral photoswitches, while constructing chiral recognition probes. Summary of the invention

[0004] The invention prepares a side chain azobenzene polymer, makes it into a side chain azobenzene polymer gel, uses circularly polarized light to induce its chirality, constructs a series of chiral light switches, and designs a chiral enantiomer recognition probe based on gel-sol transition.

[0005] The technical solution of the present invention:

[0006] One of the purposes of the present invention is to provide a side chain azobenzene polymer gel, wherein the polymer gel is composed of a side chain azobenzene polymer gel, wherein the structural formula of Azo-PM is as follows:

[0007]

[0008] Further defined, specifically, Azo-PM is dissolved in a solvent, ultrasonically heated to the boiling point of the solvent, and kept warm for 30 minutes, taken out and naturally cooled to room temperature to obtain a side chain azobenzene polymer gel.

[0009] In a further embodiment, the solvent is benzene, toluene, ethylene dichloride, dioxane, cyclopentanone, ethyl acetate or triethylamine.

[0010] The second object of the present invention is to provide a method for preparing the above-mentioned side chain azobenzene polymer gel. The specific operation process of the method is: dissolving Azo-PM in a solvent, ultrasonically heating it to the boiling point of the solvent, and keeping it warm for 30 minutes, taking it out and naturally cooling it to room temperature to obtain the side chain azobenzene polymer gel.

[0011] The third object of the present invention is to provide a method for preparing the above-mentioned side chain azobenzene polymer gel Azo-PM, the specific operation process of the method is as follows:

[0012] S1, preparation of monomer Azo-M;

[0013] S2, using monomer Azo-M as raw material, azobisisobutyronitrile (AIBN) as initiator, and utilizing the principle of free radical polymerization to prepare azobenzene polymer Azo-PM.

[0014] Further defined, the structural formula of Azo-M is as follows:

[0015]

[0016] Further defined, the operation process of S1 is:

[0017] (1) Carboxy azobenzene, cholesterol and DMAP are added to dichloromethane, and ultrasonic treatment is performed. Then, a dichloromethane solution of DCC is added dropwise to the system at 30° C. and the reaction is continued for 72 hours. After the reaction is completed, the mixture is filtered and washed with dilute hydrochloric acid, sodium bicarbonate solution and distilled water in sequence. The organic phase is retained and dried by adding anhydrous magnesium sulfate. The crude product is passed through a column with an eluent, and the collected orange-yellow liquid is rotary evaporated and dried to obtain a brown-red solid Azo-1;

[0018] (2) Potassium carbonate, potassium iodide and Azo-1 were added to DMF and mixed evenly. Then, 6-chloro-1-hexanol was added dropwise under stirring, and the mixture was reacted at 120° C. for 72 h. Distilled water was added, the mixture was filtered and dried under vacuum. The product was filtered through a column with an eluent to obtain an orange solid Azo-2.

[0019] (3) DMAP, Azo-2 and methacrylic acid were dissolved in dichloromethane, and then a mixture of DCC and dichloromethane was added dropwise. The mixture was reacted at 30° C. for 72 h. After the reaction was completed, the mixture was filtered and washed with dilute hydrochloric acid, sodium bicarbonate solution and distilled water in sequence. The organic phase was retained and dried by adding anhydrous magnesium sulfate. The crude product was passed through a column with an eluent, and the collected orange-yellow liquid was rotary evaporated and dried to obtain an orange solid Azo-M.

[0020] It is further defined that the operation process of S2 is: Azo-M and AIBN are added into a polymerization tube, and then DMF is added. After three cycles of freezing, vacuuming, and filling with nitrogen, the reaction is carried out at 70°C for 72 hours. After the reaction is completed, the reaction solution is added dropwise into methanol for precipitation to obtain a brown-red solid Azo-PM.

[0021] It is further defined that the molar ratio of Azo-M to AIBN is 20:1, and the mass concentration of Azo-M in the reaction system is 10%.

[0022] The third object of the present invention is to provide an application of the above-mentioned side chain azobenzene polymer gel, specifically for constructing a chiral optical switch.

[0023] It is further defined that when the side chain azobenzene polymer gel is irradiated with 450nm left-handed circularly polarized light for 30 minutes, a left-handed helical structure is observed in the circular dichroism spectrum; then when it is irradiated with 450nm right-handed circularly polarized light for 40 minutes, a right-handed helical structure is observed in the circular dichroism spectrum, and multiple reversible cycles can be performed.

[0024] It is further defined that the side chain azobenzene polymer gel is irradiated with 450nm circularly polarized light for 30 minutes to induce a chiral structure, and then irradiated with 365nm ultraviolet light to transform it into a gel-sol to erase the chiral structure; then the side chain azobenzene liquid crystal polymer gel is obtained by heating and cooling to restore the chiral structure, and multiple reversible cycles can be performed.

[0025] A fourth object of the present invention is to provide an application of the above-mentioned side chain azobenzene polymer gel, specifically for constructing a chiral molecule recognition probe.

[0026] The present invention first prepares a gel by assembling side chain azobenzene polymer supramolecularly, uses circularly polarized light to induce and regulate the chirality of the side chain azobenzene polymer gel, uses ultraviolet light to erase its chirality, and restores its chirality by heating and cooling, thereby realizing the construction of a chiral optical switch. At the same time, based on the chiral structure azobenzene gel system, a chiral enantiomer molecular recognition probe is constructed. Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention realizes the construction of azobenzene polymer chiral photoswitch in gel system and chiral enantiomer recognition molecular probe under gel, which provides a new strategy for the preparation of extended side chain azobenzene polymer gel and the construction of enantiomer recognition probe;

[0028] (2) The side chain azobenzene polymer gel prepared by the present invention adopts circularly polarized light induction technology to induce its chirality, and has the advantages of wide range of optical properties, no angle dependence, safety, pollution-free, remote controllability, etc., and the wavelength, polarization state and intensity of light can be precisely controlled. In addition, the construction and regulation of chiral optical switches are realized through simple operations of light and heat. It can be used to construct reversible chiral optical switches and rewritable chiral optical data storage materials, providing additional value for the construction of multiple stimulus responsive materials.

[0029] (3) The side chain azobenzene polymer gel provided by the present invention can be used to construct chiral recognition probes and can be applied in the fields of biomedicine, fine chemicals, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The synthetic route of Azo-1 is shown below;

[0031] Figure 2 The synthetic route of Azo-2 is shown below;

[0032] Figure 3 The synthetic route of Azo-M is shown below;

[0033] Figure 4 is the structural formula of Azo-PM;

[0034] Figure 5 is the H NMR spectrum of Azo-M;

[0035] Figure 6 is the H NMR spectrum of Azo-PM;

[0036] Figure 7 This is the chiral photoswitching mechanism diagram of Azo-PM gel under 450nm L / R-CPL irradiation;

[0037] Figure 8 The chiral photo-switching mechanism diagram of Azo-PM gel after 450nm CPL irradiation under UV light and heating and cooling;

[0038] Fig. 9 Diagram of the chiral enantiomer recognition probe mechanism of Azo-PM gel after 450nm CPL irradiation. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0042] Example 1

[0043] The method for preparing the side chain azobenzene polymer gel in this embodiment is as follows:

[0044] (I) Preparation of Azo-M, the synthetic route is as follows Figure 1-Figure 3 As shown:

[0045] In a 250 ml single-mouth round-bottom flask, 0.11 g of carboxyazobenzene, 0.20 g of cholesterol and 0.005 g of DMAP were added, and then an appropriate amount of dichloromethane was added to dissolve it. The solution was ultrasonically shaken to obtain an orange-yellow transparent solution. A dichloromethane solution prepared by 0.18 g of DCC was added dropwise to the solution at 30°C, and the reaction was continued for 72 hours. After the reaction was completed, the solution was filtered and washed with dilute hydrochloric acid, 5 wt% sodium bicarbonate solution and distilled water in turn. The retained organic phase was dried by adding anhydrous magnesium sulfate. The crude product was passed through a column with an eluent, and the collected orange-yellow liquid was rotary evaporated and dried to obtain a brown-red solid (Azo-1).

[0046] In a 250ml three-necked round-bottom flask, 0.11g potassium carbonate, 0.002g potassium iodide and 0.50g Azo-1 were added in sequence, and then 100ml DMF was added as a solvent. 0.13g 6-chloro-1-hexanol was added dropwise to the round-bottom flask under stirring, and the mixture was reacted at 120°C for 72h. After the reaction, the mixture was added to 200ml distilled water to obtain a large amount of orange precipitate, which was finally filtered and vacuum dried. The product was passed through a column with an eluent to obtain an orange solid (Azo-2).

[0047] In a 250ml single-mouth round-bottom flask, 0.03g DMAP, 0.20g Azo-2, 100ml dichloromethane and 0.02g methacrylic acid were added in sequence, and the mixture was completely dissolved by stirring. Then, 0.06g DCC was dissolved in dichloromethane to prepare a solution, which was added dropwise to the round-bottom flask, and the mixture was reacted at 30°C for 72h. After the reaction was completed, the mixture was filtered, and the filtrate was washed with dilute hydrochloric acid, 5% sodium bicarbonate solution and distilled water in sequence. The organic phase was retained and dried by adding anhydrous magnesium sulfate. The crude product was then passed through a column using methanol: dichloromethane in a volume ratio of 1:25 as an eluent. The collected orange-yellow liquid was rotary evaporated and dried to obtain an orange solid (Azo-M).

[0048] The structure of Azo-M was characterized by H NMR spectrum. Figure 5 As shown, the peaks of δ at 8.24ppm, 8.02ppm, and 7.07ppm are the proton peaks on the benzene ring, the peaks of δ at 6.48ppm and 6.40ppm are the proton peaks of the methylene group on the C=C double bond connected to the benzene ring, and δ=2.01ppm is the proton peak of the methyl group on the C=C double bond connected to the benzene ring. The integrated area ratios of a, b, c, d, e, f, g, h, i, j, and k are 2:3:1:2:1:33:10:1:6:3:1, indicating that the structure is successfully synthesized. Figure 3 Azo-M shown.

[0049] (II) Preparation of Azo-PM, the synthetic route is as follows Figure 4 As shown:

[0050] A certain amount of Azo-M and AIBN were weighed and added to a polymerization tube, and then refined DMF was added, wherein the molar ratio of Azo-M to AIBN was 20:1, and the mass concentration of Azo-M was 10%. After three cycles of freezing-vacuuming-nitrogen filling, the reaction was carried out at 70°C for 72 hours. After the reaction was completed, the reaction solution was added dropwise to 50 ml of methanol for precipitation to obtain a brown-red solid (Azo-PM).

[0051] The structure of the obtained Azo-PM was characterized by H NMR spectrum. Figure 6 As shown in the H NMR spectrum, the two hydrogen peaks on the C=C double bond at 6.48ppm and 6.40ppm in the original monomer of Azo-PD2 disappeared, indicating that the monomer was polymerized, and the obtained structure was as follows: Figure 4 Azo-PM shown.

[0052] (III) Preparation of side chain azobenzene polymer gel:

[0053] Take 25 mg of Azo-PM in a transparent ultra-thin cuvette, then inject it into 1 mL of ethyl acetate, ultrasonically heat it to the boiling point of the solvent, and keep it warm for 30 minutes, then take it out and cool it naturally to room temperature. It was observed by the inversion method that a gel had been formed, and the color of the gel was uniform and the transparency was good.

[0054] Example 2

[0055] The construction process of the side chain azobenzene polymer gel chiral light switch obtained in Example 1 under the action of circularly polarized light is as follows:

[0056] When the azobenzene liquid crystal polymer gel is irradiated with 450nm L-CPL for 30min, an obvious left-handed helical structure can be observed in the circular dichroism spectrum; then the azobenzene liquid crystal polymer gel is irradiated with 450nm R-CPL for 30min, the left-handed helical structure formed previously is erased and a right-handed helical structure appears, and this phenomenon can be repeated for many times. The mechanism diagram is shown in the figure below. Figure 7 shown.

[0057] Example 3

[0058] The construction process of the side chain azobenzene polymer gel chiral light switch obtained in Example 1 under the action of circularly polarized light is as follows:

[0059] The azobenzene liquid crystal polymer gel was irradiated with 450nm left-handed and right-handed circularly polarized light for 30 minutes, and obvious CD signals were observed in the circular dichroism spectrum, and azobenzene gel polymer with a specific helix was prepared. By irradiating with 365nm ultraviolet light, its CD signal can be erased and the gel-to-sol transition can be achieved; reheating and cooling the gel can restore its original chiral structure. The construction mechanism of its chiral control switch is as follows Figure 8 As shown, its chirality can be reversibly changed in multiple cycles.

[0060] Example 4

[0061] The side chain azobenzene polymer gel chiral recognition probe obtained in Example 1 was constructed, and the construction process was as follows:

[0062] Azobenzene liquid crystal polymer gel was irradiated with 450nm CPL for 30 minutes, and obvious CD signals were observed in the circular dichroism spectrum. Using the ordered spiral structure produced by azobenzene polymer gel, a variety of enantiomeric organic small molecules with functional groups such as carboxyl or amino groups were selected. Due to the influence of steric hindrance and stereoselectivity, enantiomeric molecules with the same chirality will change the chiral gel structure, and then the gel will collapse and turn into a sol. Enantiomeric molecules with opposite chirality cannot destroy the chiral structure of the gel, and the system continues to maintain a gel state, achieving the purpose of chiral recognition of enantiomers. The chiral probe construction mechanism is as follows: Fig. 9 shown.

[0063] Although the present invention has been disclosed as above in the form of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A side chain azobenzene polymer gel, characterized in that: It is prepared by supramolecular assembly of azobenzene polymer Azo-PM in a solvent, wherein the structural formula of Azo-PM is as follows: The Azo-PM preparation method comprises: S1, preparation of monomer Azo-M; S2, using monomer Azo-M as raw material, azobisisobutyronitrile (AIBN) as initiator, and using the principle of free radical polymerization to prepare azobenzene polymer Azo-PM; The operation process of S2 is as follows: Azo-M and AIBN are added into a polymerization tube, and then DMF is added. After three cycles of freezing, vacuuming, and nitrogen filling, the reaction is carried out at 70°C for 72 hours. After the reaction is completed, the reaction solution is added dropwise into methanol for precipitation to obtain a brown-red solid Azo-PM. The molar ratio of Azo-M to AIBN is 20:1, and the mass concentration of Azo-M in the reaction system is 10%.

2. The side chain azobenzene polymer gel according to claim 1, characterized in that: The structural formula of Azo-M is as follows:

3. The side chain azobenzene polymer gel according to claim 1, characterized in that: The operation process of S1 is: (1) Carboxy azobenzene, cholesterol and DMAP are added to dichloromethane, and ultrasonic treatment is performed. Then, a dichloromethane solution of DCC is added dropwise to the system at 30° C. and the reaction is continued for 72 hours. After the reaction is completed, the mixture is filtered and washed with dilute hydrochloric acid, sodium bicarbonate solution and distilled water in sequence. The organic phase is retained and dried by adding anhydrous magnesium sulfate. The crude product is passed through a column with an eluent, and the collected orange-yellow liquid is rotary evaporated and dried to obtain a brown-red solid Azo-1; (2) Potassium carbonate, potassium iodide and Azo-1 were added to DMF and mixed evenly. Then, 6-chloro-1-hexanol was added dropwise under stirring, and the mixture was reacted at 120° C. for 72 h. Distilled water was added, the mixture was filtered and dried under vacuum. The product was filtered through a column with an eluent to obtain an orange solid Azo-2. (3) DMAP, Azo-2 and methacrylic acid were dissolved in dichloromethane, and then a mixture of DCC and dichloromethane was added dropwise. The mixture was reacted at 30° C. for 72 h. After the reaction was completed, the mixture was filtered and washed with dilute hydrochloric acid, sodium bicarbonate solution and distilled water in sequence. The organic phase was retained and dried by adding anhydrous magnesium sulfate. The crude product was passed through a column with an eluent, and the collected orange-yellow liquid was rotary evaporated and dried to obtain an orange solid Azo-M.

4. A method for preparing the side chain azobenzene polymer gel according to claim 1, characterized in that: Azo-PM was dissolved in a solvent, ultrasonically heated to the boiling point of the solvent, and kept warm for 30 minutes, then taken out and naturally cooled to room temperature to obtain a side chain azobenzene polymer gel.

5. An application of the side chain azobenzene polymer gel according to claim 1, characterized in that: Used to construct a chiral optical switch, specifically, the side chain azobenzene polymer gel is irradiated with 450nm left-handed circularly polarized light for 30 minutes, and a left-handed helical structure is observed in the circular dichroism spectrum; then it is irradiated with 450nm right-handed circularly polarized light for 40 minutes, and a right-handed helical structure is observed in the circular dichroism spectrum, and multiple reversible cycles can be performed.

6. An application of the side chain azobenzene polymer gel according to claim 1, characterized in that: Used to construct a chiral optical switch, specifically, 450nm circularly polarized light is used to irradiate the side chain azobenzene polymer gel for 30 minutes to induce a chiral structure, and then 365nm ultraviolet light is used to erase the chiral structure; then the side chain azobenzene liquid crystal polymer gel is obtained by heating and cooling to restore the chiral structure, and multiple reversible cycles can be performed.

7. An application of the side chain azobenzene polymer gel according to claim 1, characterized in that: Used to construct chiral molecule recognition probes.

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