CN109337671B - Layered photochromic film and preparation method thereof - Google Patents

Abstract

The invention discloses a layered photochromic film and a preparation method thereof. The layered photochromic film of the present invention contains montmorillonite as a host material, a cation represented by the following formula I, and a quaternary ammonium cation represented by the following formula II. The layered photochromic film of the present invention does not need to be polymerized, can be easily obtained, is stable, and is not prone to phase separation.

Description

Layered photochromic film and preparation method thereof

technical field

The invention relates to the field of photochromic, in particular to a photochromic film and a preparation method thereof.

Background technique

Photochromic molecules have the characteristics of light-induced reversible color changes, and have potential applications in the fields of optical information storage, optical switches, and chemical sensing. Spiropyran is a commonly used organic photochromic molecule, and light can cause reversible structural isomerization between the colorless ring-closed spiropyran and the colored ring-opened merocyanine. Generally, spiropyran molecules need to be dispersed in a host material to form a film for further application. For example, Patent Document 1 discloses a polymer film formed by dispersing spiropyran molecules in a polymer monomer and polymerizing the polymer. However, the preparation method of this photochromic film is cumbersome and the process is complicated. In addition, there is a shortcoming of low spiropyran molecular concentration that leads to weak photochromic luminous intensity, which limits its wide application. In addition, a polymer film obtained by directly dispersing spiropyran into a polymer material as a host material is also disclosed. Although such a preparation method is simple, because the spiropyran is not directly connected to the polymer material, therefore, such The obtained polymer film has disadvantages such as poor stability and easy phase separation.

Patent Document 1: CN107099282A

Contents of the invention

In order to solve at least some of the problems existing in the photochromic thin film materials in the prior art, and to obtain a stable photochromic thin film material that is not prone to phase separation, etc., the inventors conducted in-depth research and found that the layered photochromic thin film material of the present invention The photochromic thin film can solve at least one aspect of the aforementioned technical problems, thus completing the present invention.

The invention provides a layered photochromic film and a preparation method thereof. Specifically, the present invention includes the following contents.

The first aspect of the present invention provides a layered photochromic film, which contains montmorillonite as a host material, a cation represented by the following formula I, and a quaternary ammonium cation represented by the following formula II.

Another aspect of the present invention also provides a kind of preparation method of layered photochromic film, it comprises the following steps:

An ion exchange step in which the precursor of the cation represented by the following formula I and the precursor of the quaternary ammonium cation represented by the following formula II are ion-exchanged with montmorillonite.

The layered photochromic film of the present invention is obtained by ion-exchanging the precursor of the cation represented by formula I, the precursor of the quaternary ammonium cation represented by formula II, and montmorillonite. Preferably, the montmorillonite has a lamellar structure. In the present invention, montmorillonite is mixed with the precursor of the cation shown in formula I and the precursor of the quaternary ammonium cation shown in formula II, and the cations such as potassium, sodium and calcium in montmorillonite are mixed with the cation shown in formula I The cations and the quaternary ammonium cations shown in formula II carry out ion exchange and intercalation reaction occurs, so that the montmorillonite which is originally a sheet structure is peeled off and the cations shown in formula I are fixed on the surface, so that the cations shown in formula I can be used as the host material. A high concentration of photoluminescent material is dispersed in montmorillonite. Wherein, by containing the precursor of the quaternary ammonium cation shown in the formula II in the aforementioned mixing process, the concentration of the precursor of the cation shown in the formula I in the obtained layered photochromic film can be further improved, thereby increasing the montmorillonite The active site where the soil nanosheet interacts with the precursor of the cation shown in formula I.

The layered photochromic film of the present invention contains the cation shown in formula I, which exists in the form of a closed ring under visible light irradiation, and the layered photochromic film as a whole appears light yellow; under ultraviolet light or dark conditions, its It exists in the form of ring-opening body, and the layered photochromic film appears purple-red as a whole.

The layered photochromic film of the present invention does not need to go through polymer polymerization commonly used in the prior art, which can simplify the process flow. And because the cation shown in formula I is fixed on the surface of montmorillonite, compared with the photochromic film prepared by directly mixing the two without bonding, the layered photochromic film of the present invention has stable performance and will not Phase separation occurs.

Description of drawings

Figure 1: TEM image of the layered photochromic film obtained in Example 1.

Figure 2: AFM topography of the layered photochromic film obtained in Example 1.

Fig. 3: SEM surface and cross-sectional view of the layered photochromic film obtained in Example 1; wherein, Fig. 3 (A) is the SEM figure of the surface of the layered photochromic film obtained in Example 1 , FIG. 3(B) is a partially enlarged view of FIG. 3(A), and FIG. 3(C) is an SEM image of a cross-section of the layered photochromic film obtained in Example 1.

Figure 4: Photochromic performance of the layered photochromic film obtained in Example 1 and its corresponding UV reflection spectrum. Wherein, Fig. 4 (A) is the color state diagram (magenta) of the layered photochromic film 1 just prepared (the cation shown in formula I is an open ring structure), and Fig. 4 (B) is the layered photochromic film The color state diagram (light yellow) of film 1 (the cation shown in formula I is a closed-loop structure after visible light irradiation), and Fig. 4 (C) is the layered photochromic film 1 after visible light irradiation and then after ultraviolet light irradiation ( The cation shown in formula I is the color state diagram (magenta) of ring-opened structure). Fig. 4(D) is an ultraviolet reflectance spectrum diagram of the layered photochromic film 1 in a state corresponding to Fig. 4(A), Fig. 4(B) and Fig. 4(C). The uppermost curve in Fig. 4(D) is after visible light, the middle curve is after ultraviolet light, and the bottom curve is just after preparation.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention.

It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention. In addition, regarding the numerical ranges in the present invention, it should be understood that the upper and lower limits of the range and every intermediate value therebetween are specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control. "%" is a percentage by weight unless otherwise specified.

In the present invention, the "precursor of the cation shown in formula I" refers to a compound capable of producing or releasing the cation shown in formula I, and its example includes the cation shown in formula I as a cation with other anions (such as Br ⁻ , Cl ^- ) compound.

In the present invention, "the precursor of the quaternary ammonium-based cation shown in formula II" refers to a compound capable of producing or releasing a cation shown in formula II, and its example includes the cation shown in formula II as a cation with other anions (such as Br ⁻ , Cl ^- ) compound.

[Layered photochromic film]

The layered photochromic film of the present invention contains montmorillonite as a host material, a cation represented by the following formula I, and a quaternary ammonium cation represented by the following formula II.

The photochromic active molecule used in the layered photochromic film of the present invention contains the structure represented by the aforementioned formula I. As the precursor of the photochromic active molecule, a compound with Br ^- or Cl ^- as the anion and the structure shown in formula I as the cation can be mentioned. The compound having Br ^- as an anion may be referred to simply as "compound 1" in the present invention. The compound having Cl ^- as an anion may be referred to simply as "compound 2" in the present invention. One or a combination of the above two compounds can be used in the present invention.

In the layered photochromic film of the present invention, the effect of the quaternary ammonium cation shown in the aforementioned formula II is to improve the dispersion of montmorillonite nanosheets, thereby increasing the interaction between montmorillonite nanosheets and photochromic active molecules. active site. Examples of the anion contained in the precursor of the quaternary ammonium cation represented by formula II include Br ^- or Cl ^- . The compound with Br ^- as the anion and the structure shown in formula II as the cation may be simply referred to as "compound 3" in the present invention. The compound with Cl ^- as the anion and the structure shown in formula II as the cation may be simply referred to as "compound 4" in the present invention. One or a combination of two of the above compounds can be used in the present invention.

The montmorillonite as the host material contained in the layered photochromic film of the present invention preferably has a lamellar structure. In the present invention, the guest molecule of the structure represented by the formula I containing the quaternary ammonium group and the structure represented by the formula II containing the quaternary ammonium group are utilized. The shown cationic compound molecules are ion-exchanged with montmorillonite to immobilize photochromic active molecules on the surface of montmorillonite. As the montmorillonite used in the layered photochromic film of the present invention, it is preferred to use two-dimensional montmorillonite nano Sheets, the lateral dimensions of two-dimensional montmorillonite nanosheets are usually greater than 100 nm or up to several microns or even larger, for example, between 10 and 8000 nm, preferably between 15 and 1000 nm. Its thickness can be as thin as one or several atomic layers, for example, it can reach less than 5 nm, on the other hand it is greater than 0.01 nm, more preferably greater than 0.1 nm. Due to the super-high specific surface area of two-dimensional montmorillonite nanosheets, many spatial sites, and easy film formation, it is possible to obtain high photochromic intensity and excellent manufacturing process by using such two-dimensional montmorillonite nanosheets as the main material. Simple and highly stable layered photochromic film.

[Preparation method of layered photochromic film]

The preparation method of the layered photochromic film of the present invention comprises: the precursor with the structure shown in following formula I, the precursor with the quaternary ammonium cation shown in following formula II and montmorillonite carry out ion exchange The ion exchange step,

In the aforementioned ion exchange step, the quaternary ammonium group of the precursor with the structure shown in formula I and the quaternary ammonium group of the precursor with the structure shown in formula II undergo an ion exchange reaction with montmorillonite, thereby fixing the photochromic active molecules on the montmorillonite. Desoiled surface. The two precursor molecules can be in the form of a mixed solution dissolved in water first, and the aforementioned montmorillonite can be in the form of a suspension suspended in water in advance. Preferably, the reaction temperature in the ion exchange step is 50-90°C, preferably 60-80°C.

In the preparation method of the layered photochromic film of the present invention, at least one of the following steps can also be further included:

centrifuging the solution after the aforementioned ion exchange step at room temperature, removing the suspension to obtain the centrifuging step of the precipitate;

Washing the precipitate obtained in the aforementioned centrifugation step with, for example, a chloroform/methanol mixed solvent to clean the precipitate;

A dispersion step in which the precipitate that has undergone the aforementioned cleaning steps is fully stirred and dispersed in chloroform;

The step of suction-filtering the precipitate that has gone through the aforementioned dispersion step onto the filter membrane, and then peeling off the filter membrane to obtain the forming step of the layered photochromic film.

In the aforementioned centrifugal separation step, the product after the ion exchange reaction is subjected to centrifugal separation, and the suspension is removed to obtain a precipitate as a reaction product.

The aforementioned cleaning step washes the precipitate to improve the purity of the reaction product. The solvent used for washing is preferably a mixed solvent of chloroform/methanol. The ratio of chloroform and methanol in the mixed solvent of chloroform/methanol can be determined by those skilled in the art according to common knowledge in the field, for example, it can be 1:1. In order to obtain a layered photochromic film with less impurity content, the aforementioned cleaning steps can be repeated more than 2 times, but from the aspects of improving the efficiency of the preparation process and reducing the loss of reaction products, the aforementioned cleaning steps are preferably less than 5 times.

The aforementioned dispersing step is carried out in chloroform, and as the stirring time, as long as the precipitate is sufficiently dispersed in chloroform, it can be, for example, 2 to 72 hours. From the sufficient consideration of stirring, it is preferably more than 12 hours, more preferably more than 24 hours, From the viewpoint of stirring efficiency, it is preferably 48 hours or less.

In the aforementioned forming step, as the filter membrane used, a filter membrane made of polyethylene, nylon, or the like can be used. After the filter membrane is peeled off, a self-supporting layered photochromic film can be obtained.

In one embodiment of the preparation method of layered photochromic film of the present invention, comprise the steps:

(1) carry out ion exchange reaction with 0.02～0.4g compound 1, 0.02～0.4g compound 3 and 0.1～0.5g montmorillonite in 5-40mL water for 1～2 hours, set the reaction temperature to be 50～90 ℃, thereby will The montmorillonite is exfoliated into a nanosheet structure with photochromic active molecules fixed on the surface;

(2) Naturally cool the montmorillonite mixed solution after the ion exchange reaction to room temperature, and centrifuge the suspension at a speed of 2000 to 5000 rpm to obtain a light yellow precipitate;

(3) Washing the aforementioned light yellow precipitate with a mixed solvent of chloroform/methanol;

(4) Fully stir and disperse the light yellow precipitate in chloroform, and the stirring time is 24 to 48 hours;

(5) Vacuum filter the uniformly dispersed mixed solution through a nylon filter membrane, and then peel off the nylon filter membrane to obtain a layered photochromic film.

Example

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The specification and examples in this application are exemplary only.

Example 1

At room temperature, 0.4 g of montmorillonite was dissolved in 20 mL of deionized water to obtain a pale yellow montmorillonite suspension. Then 0.034 g of compound 1 and 0.306 g of compound 3 were dissolved in 10 mL of deionized water. Transfer to three-necked flasks respectively, and the two are mixed evenly. Adjust the temperature of the three-necked flask to 70° C., and heat and stir in an oil bath for one hour. After returning to room temperature, centrifuge the suspension at 2000 rpm for 5 min to obtain a light yellow precipitate. The precipitate was washed with chloroform/methanol at a volume ratio of 1:1 to clean the precipitate. The washed precipitate was stirred in 25 mL of chloroform for 48 hours. Soak the nylon filter membrane in chloroform solution to make it completely wet, lay it flat on the filter, and turn on the water pump. Take 5mL of the light yellow suspension and add it to the filter membrane along the wall of the vessel, and filter it with suction for 20 minutes to obtain a compact layered membrane, which is then peeled off from the filter membrane to obtain a self-supporting layered photochromic film 1 .

The obtained layered photochromic film 1 was characterized as follows.

(1) TME morphology characterization

Fig. 1 is the TEM topography figure of the layered photochromic film 1 obtained in embodiment 1, can clearly see the nanosheet structure of the layered photochromic film 1 from Fig. 1, and its size is in tens to several Between hundreds of nanometers, the larger ones can reach several microns.

(2) AFM characterization

Fig. 2 is the AFM diagram obtained by scanning the thickness of the prepared layered photochromic film 1 by AFM, it can be clearly seen from Fig. 2 that the dimension thickness of the layered photochromic film 1 peeling off the filter film thickness is 4.5 about nm.

(3) SEM morphology characterization

FIG. 3 is a diagram obtained by observing the microscopic morphology of the layered photochromic film 1 by SEM. It is found through cross-sectional observation that the prepared layered photochromic film 1 has a clear layered structure.

(4) Photochromic properties of layered photochromic films and corresponding UV reflection spectra

FIG. 4 is a characterization of the photochromic properties of the layered photochromic film 1 . Firstly, the layered photochromic film 1 is cut into pieces, and pasted on the ultraviolet spectrum integrating sphere with double-sided tape for observation. Figure 4 (A) is the color state diagram of the newly prepared layered photochromic film 1 (the photochromic active molecule is an open ring structure), and Figure 4 (B) is the color state of the layered photochromic film 1 after visible light The color state diagram (the photochromic active molecule is a closed-ring structure), and Figure 4 (C) is the color state diagram of the layered photochromic film 1 after visible light irradiation and then after ultraviolet light (the photochromic active molecule is an open ring structure). structure). The results show that the layered photochromic film 1 has clear photochromic properties, that is, after visible light fades, the color can be restored by ultraviolet light. Fig. 4(D) is an ultraviolet reflectance spectrum diagram of the layered photochromic film 1 in a state corresponding to Fig. 4(A), Fig. 4(B) and Fig. 4(C).

Example 2

At room temperature, 0.2 g of montmorillonite was dissolved in 10 mL of deionized water to obtain a pale yellow montmorillonite suspension. Then 0.051 g of compound 1 and 0.119 g of compound 3 were dissolved in 5 mL of deionized water. Transfer to three-necked flasks respectively, and the two are mixed evenly. Adjust the temperature of the three-necked flask to 70° C., and heat and stir in an oil bath for one hour. After natural cooling and returning to room temperature, centrifuge the suspension at 2000 rpm for 5 min to obtain a light yellow precipitate. The precipitate was washed with chloroform/methanol with a volume ratio of 1:1. The washed precipitate was stirred in 25 mL of chloroform for 48 hours. Soak the nylon filter membrane in chloroform solution to make it completely wet, lay it flat on the filter, and turn on the water pump. Take 5mL of the light yellow suspension and add it to the filter membrane along the wall of the device, and filter it with suction for 20 minutes to obtain a compact layered membrane, which is then peeled off from the filter membrane to obtain the photochromic membrane 2.

Example 3

At room temperature, 0.2 g of montmorillonite was dissolved in 10 mL of deionized water to obtain a pale yellow montmorillonite suspension. Then 0.085 g of compound 2 and 0.085 g of compound 3 were dissolved in 5 mL of deionized water. Transfer to three-necked flasks respectively, and the two are mixed evenly. Adjust the temperature of the three-necked flask to 70° C., and heat and stir in an oil bath for one hour. After natural cooling and returning to room temperature, centrifuge the suspension at 2000 rpm for 5 mins to obtain a light yellow precipitate. The precipitate was washed with chloroform/methanol with a volume ratio of 1:1. The washed precipitate was stirred in 25 mL of chloroform for 48 hours. Soak the nylon filter membrane in chloroform solution to make it completely wet, lay it flat on the filter, and turn on the water pump. Take 5mL of the light yellow suspension and add it to the filter membrane along the wall of the device, and filter with suction for 20 minutes to obtain a compact layered film, which is then peeled off from the filter membrane to obtain the photochromic film 3.

Example 4

At room temperature, 0.2 g of montmorillonite was dissolved in 10 mL of deionized water to obtain a pale yellow montmorillonite suspension. Then 0.119 g of compound 1 and 0.051 g of compound 4 were dissolved in 5 mL of deionized water. Transfer to three-necked flasks respectively, and the two are mixed evenly. Adjust the temperature of the three-necked flask to 70° C., and heat and stir in an oil bath for one hour. After natural cooling and returning to room temperature, the suspension was centrifuged at 2000 rpm for 5 min to obtain a reddish-brown precipitate. The precipitate was washed with chloroform/methanol with a volume ratio of 1:1. The washed precipitate was stirred in 25 mL of chloroform for 48 hours. Soak the nylon filter membrane in chloroform solution to make it completely wet, lay it flat on the filter, and turn on the water pump. Take 5mL of the light yellow suspension and add it to the filter membrane along the wall of the device, and filter it with suction for 20 minutes to obtain a compact layered film, which is then peeled off from the filter membrane to obtain the photochromic film 4.

Claims (9)

1. a layered photochromic film, which contains montmorillonite as host material, and the cation shown in the following formula I, the quaternary ammonium cation shown in the following formula II, its preparation method comprises making the quaternary ammonium cation shown in the formula I The precursor of the cation shown and the precursor of the quaternary ammonium cation shown in formula II carry out the step of ion exchange with the described montmorillonite, 2. The layered photochromic film according to claim 1, wherein the montmorillonite has a nanosheet structure, and the cation shown in the formula I is fixed on its surface. 3. The layered photochromic film according to claim 1, wherein the precursor of the cation represented by formula I contains Br ⁻ and/or Cl ⁻ as an anion. 4. The layered photochromic film according to claim 1, wherein the precursor of the quaternary ammonium cation represented by formula II contains Br ⁻ and/or Cl ⁻ as anion. 5. The layered photochromic film according to any one of claims 1 to 4, which is a self-supporting layered photochromic film. 6. A method for preparing the layered photochromic film according to any one of claims 1 to 5, comprising the following ion exchange step: the precursor of the cation shown in the following formula I, the following formula The precursor of the quaternary ammonium cation shown in II carries out ion exchange with montmorillonite in water, 7. The preparation method of layered photochromic film according to claim 6, it also comprises at least one in the following steps: centrifugation step: centrifuging the mixed solution after the ion exchange step, removing the suspension to obtain a precipitate; Cleaning step: washing the precipitate with an organic solvent to clean the precipitate; Dispersion step: stirring the precipitate that has undergone the cleaning step in chloroform to disperse; Forming step: suction filter the dispersed precipitate onto the filter membrane, and then peel off the filter membrane to obtain the layered photochromic film. 8. The method for preparing a layered photochromic film according to claim 7, wherein the temperature of the water during the ion exchange is 50-90°C, and the mixed solution obtained after the ion exchange needs to be cooled to room temperature. 9. The method for preparing a layered photochromic film according to claim 7, wherein the organic solvent in the cleaning step is a chloroform/methanol mixed solvent.