A transparent photochromic hydrogel and its preparation method

Abstract

The present invention discloses a transparent photochromic hydrogel and a method for preparing the same. The present invention uses photoinitiator quantum dots and photochromic quantum dots, both of which are less than 5 nm in size and can be uniformly dispersed in water to form a transparent colloidal solution. The photoinitiator quantum dots are then used to accelerate the rapid solidification of the precursor, greatly shortening the gelation time to a few minutes. Therefore, the photochromic quantum dot clusters can be effectively reduced, ultimately forming a uniform and transparent photochromic hydrogel.

Description

Technical Field

[0001] The invention relates to a photochromic hydrogel and a preparation method thereof, and belongs to the field of hydrogel and photochromism. Background Art

[0002] Hydrogels are hydrophilic polymer materials with a three-dimensional network structure that swell in water but do not dissolve. They are widely used in the biomedical field, particularly as implants, drug carriers, biosensors, or contact lenses. Hydrogels are also recyclable and environmentally friendly. The gel itself is non-toxic and does not pollute the environment. Therefore, hydrogels are often used in everyday life, such as hydroponic plants and water babies. However, these hydrogels are mostly colorless and transparent, and have a single form.

[0003] On the other hand, photochromic materials undergo reversible photochemical reactions under light excitation, presenting two reversible states with different structures. They are widely used in automotive glass, laser printing, displays, ultra-high-density optical information storage, optoelectronic devices, stimulus-responsive materials, etc.

[0004] Therefore, combining hydrogels and photochromics to create color-changing hydrogels has important application value. However, simply adding photochromic materials (typically nanopowder materials) during the hydrogel synthesis process can cause the hydrogel to become opaque due to its inability to completely dissolve or disperse in water, thus losing its important properties. Even if organic photochromic materials or quantum dot photochromic materials are used, although they can dissolve or disperse in water, they can still cause clustering during the hydrogel synthesis process due to thermal initiators (which take hours or days to solidify), ultimately resulting in opaque hydrogels. Summary of the Invention

[0005] In order to combine hydrogel and photochromism to form a uniform and transparent photochromic hydrogel, the present invention provides a transparent photochromic hydrogel and a preparation method thereof.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a photochromic hydrogel, comprising the following steps:

[0008] (1) Dispersing TiO2 quantum dot initiator and K-Ca-Nb-O / MoS2 quantum dots in ultrapure water and mixing them thoroughly under ultrasound until a uniform solution is formed;

[0009] (2) adding a crosslinking agent to the above solution and stirring at a certain stirring rate to uniformly disperse the crosslinking agent in the solution, then adding a monomer and maintaining the same stirring rate to fully prepolymerize the monomer and the crosslinking agent;

[0010] (3) The above solution is subjected to polymerization reaction under light to finally obtain a photochromic hydrogel.

[0011] Preferably, in step (1), the photochromic material K-Ca-Nb-O / MoS2 is immersed in a butylamine solution and stirred for 7 days to expand the K-Ca-Nb-O / MoS2 layered structure by displacement to obtain K-Ca-Nb-O / MoS2 quantum dots.

[0012] Preferably, in step (1), the particle size of TiO2 quantum dots and K-Ca-Nb-O / MoS2 quantum dots is less than 5 nm.

[0013] Preferably, in step (1), the mass ratio of K-Ca-Nb-O / MoS2 quantum dots to TiO2 quantum dots is 1:1.

[0014] Preferably, in step (2), the cross-linking agent is N,N'-bis(acryl)cystamine, and the mass ratio of the cross-linking agent to the initiator is 1:5.

[0015] Preferably, in step (2), stirring is performed at a stirring rate of 200 rad / min.

[0016] Preferably, in step (2), the monomer is acrylamide, and the mass ratio of the monomer to the cross-linking agent is 1000:1.

[0017] Preferably, in step (3), ultraviolet light is used for illumination.

[0018] Preferably, in step (3), the polymerization reaction time is 1 to 10 minutes, preferably 5 minutes.

[0019] In a second aspect, the present invention provides a photochromic hydrogel prepared by the method described in the first aspect.

[0020] In a third aspect, the present invention proposes a use of a photochromic hydrogel produced by the method described in the first aspect. The photochromic hydrogel is placed under sunlight or irradiated with ultraviolet light indoors. The hydrogel undergoes photochromism under light irradiation and can restore its original color under no light conditions.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1) combining the hydrogel and the photochromic to form a uniform and transparent photochromic hydrogel;

[0023] 2) Using photoinitiator quantum dots to shorten the hydrogel gelation time to a few minutes, thereby suppressing the clustering of quantum dot photochromic materials (which causes the hydrogel to be opaque). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a photo of the photochromic hydrogel prepared using titanium dioxide quantum dots as photoinitiators in Example 1.

[0025] Figure 2 This is a photo of the photochromic hydrogel prepared with titanium dioxide quantum dots as photoinitiators in Example 1 after being irradiated with light.

[0026] Figure 3 This is a photo of the photochromic hydrogel prepared at a stirring speed of 1000 rad / min in Example 2.

[0027] Figure 4 This is a photo of the photochromic hydrogel prepared using large-particle titanium dioxide as a photoinitiator in Example 3.

[0028] Figure 5 This is a photo of the photochromic hydrogel prepared using g-C3N4 quantum dots as initiator in Example 4.

[0029] Figure 6 These are photos of the photochromic hydrogel made from non-quantum dot K-Ca-Nb-O / MoS2 in Example 5 before (a) and after (b) illumination.

[0030] Figure 7 These are photos of the colloidal solution of TiO2 quantum dots and K-Ca-Nb-O / MoS2 quantum dots in Example 1 (1) and the mixed solution of large-particle titanium dioxide and K-Ca-Nb-O / MoS2 quantum dots in Example 3 (2). DETAILED DESCRIPTION

[0031] It should be noted that the terms such as "upper", "lower", "left", "right", and "middle" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of this application without substantially changing the technical content.

[0032] 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 application belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0033] In the examples, if specific conditions are not specified, conventional conditions or those recommended by the manufacturer were followed. Reagents and instruments used without manufacturer identification are commercially available. The photochromic material, K-Ca-Nb-O / MoS2, was prepared according to the method described in Patent 202211310270.3.

[0034] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One skilled in the art can readily determine the degree of flexibility for a particular variable.

[0035] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" explicitly includes only A, only B, only C, and combinations of each thereof.

[0036] Concentration, amount and other numerical data can be presented in range format in this article.Should be understood that such range format is only used for convenience and brevity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all independent numerical values ​​or subranges encompassed within the scope, just as each numerical value and subrange are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including independent numerals (such as 2,3,4) and subranges (such as 1 to 3,2 to 4 etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all above-mentioned values ​​and scopes.In addition, no matter how the breadth of described scope or feature is, this explanation should be applicable.

[0037] In order to combine hydrogel and photochromism to form a uniform and transparent photochromic hydrogel, the present invention uses a highly transparent hydrogel as a substrate and disperses quantum dot photochromic materials therein, so that photochromism can occur under light irradiation and the original color can be restored under no light conditions. The present invention uses initiator quantum dot light and photochromic quantum dots, both of which are less than 5nm in size and can be evenly dispersed in water to form a transparent colloidal solution. The photoinitiator quantum dots are then used to accelerate the rapid solidification of the precursor. At this time, the gel time is greatly shortened to a few minutes, thereby effectively reducing the photochromic quantum dot clusters and ultimately forming a uniform and transparent photochromic hydrogel. Based on the two characteristics of high light transmittance and photochromism, the present invention can be used to make handicrafts such as photochromic contact lenses (similar to traditional sunglasses) and color-changing water babies.

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] Example 1 (Initiator: Titanium Dioxide Quantum Dots (<5 nm), Coagulation Time: 5 min)

[0040] The synthesis method of titanium dioxide quantum dots (<5 nm) is as follows: 30 mL of ethanol and a stirrer are added to a beaker, which is then placed on a magnetic stirrer and the stirrer speed is set to 500 rad / min; 0.5 mL of a 15% titanium trichloride solution and 0.5 mL of a prepared 6 mol / L hydrochloric acid solution are slowly added dropwise to the ethanol using a pipette; after stirring for two minutes, the beaker is sealed with a PE film and then placed in a digital constant temperature stirring water bath at 75°C for 6 h; the beaker is taken out and centrifuged and washed with deionized water to obtain titanium dioxide quantum dots.

[0041] The photochromic material quantum dots K-Ca-Nb-O / MoS2 were prepared as follows: 50 mg of K-Ca-Nb-O / MoS2 was soaked in butylamine solution (5 mL), stirred for 7 days, and the K-Ca-Nb-O / MoS2 layered structure was expanded by displacement to obtain a single-layer K-Ca-Nb-O / MoS2 quantum dot.

[0042] Preparation of photochromic hydrogel: Disperse the initiator TiO2 quantum dots (10 mg) and the photochromic material quantum dots K-Ca-Nb-O / MoS2 (10 mg) in ultrapure water (10 mL). Place the mixture under ultrasound and mix thoroughly until a uniform colloidal solution is formed (e.g. Figure 7 1). Add 2 mg of the crosslinker N,N'-bis(acryloyl)cystamine to the colloidal solution and stir at a stirring rate of 200 rad / min to evenly disperse the crosslinker in the colloidal solution. Then, add 2 g of the monomer acrylamide to the solution, maintaining the same stirring rate, and stir until the solution is clear, allowing the monomer and crosslinker to fully prepolymerize. The precursor solution is polymerized under a xenon lamp for 5 minutes to produce a photochromic hydrogel. During the polymerization process, the hydrogel undergoes photochromic changes under the action of ultraviolet light. For practical applications, the photochromic hydrogel can be dried and dehydrated for later use.

[0043] How to use photochromic hydrogel: Indoors, soak the dried and dehydrated photochromic hydrogel in pure water for several hours to restore it to a gel state, and obtain a colorless and transparent photochromic hydrogel, such as Figure 1 When the hydrogel is irradiated with a xenon lamp, the hydrogel instantly undergoes photochromic changes, as shown in FIG. Figure 2 As shown, it quickly returns to colorless and transparent under no light conditions (such as Figure 1 shown).

[0044] Example 2 (stirring speed 1000 rad / min)

[0045] The initiator TiO2 quantum dots (10 mg) and the photochromic material quantum dots K-Ca-Nb-O / MoS2 (10 mg) were dispersed in ultrapure water (10 mL). The mixture was placed in ultrasound and mixed thoroughly until a uniform colloidal solution was formed. The mixture was placed in ultrasound and mixed thoroughly until a uniform colloidal solution was formed. 2 mg of cross-linker N, N'-bis(acryl) cystamine was added to the above colloidal solution and stirred at a stirring rate of 1000 rad / min to uniformly disperse the cross-linker in the colloidal solution. 2 g of monomer acrylamide was then added to the above solution, maintaining the same stirring rate and stirring until the solution was clear, so that the monomer and the cross-linker were fully pre-polymerized. The above precursor solution was polymerized under a xenon lamp for 5 minutes to obtain a photochromic hydrogel. Due to the high stirring speed (friction), the colloidal solution flocculated and the photochromic hydrogel finally obtained was opaque. The results are as follows. Figure 3 shown.

[0046] Example 3 (Initiator: Large-particle titanium dioxide (>10 nm), Coagulation time: 45 min)

[0047] The initiator was replaced with large-particle titanium dioxide (>10 nm, commercial TiO2, Degussa Co., Ltd.), and the initiator large-particle titanium dioxide (10 mg) and the photochromic material quantum dots K-Ca-Nb-O / MoS2 (10 mg) were dispersed in ultrapure water (10 mL). The mixture was placed in an ultrasonic and thoroughly mixed to obtain a turbid and opaque mixed solution (such as Figure 7 2 mg of the crosslinker N,N'-bis(acryl)cystamine was added to the mixed solution and stirred at a stirring rate of 200 rad / min to uniformly disperse the crosslinker in the mixed solution. 2 g of the monomer acrylamide was then added to the solution and stirred at the same stirring rate until the solution was clear, allowing the monomer and crosslinker to fully prepolymerize. The precursor solution was polymerized under a xenon lamp for 45 minutes to obtain a photochromic hydrogel, as shown in FIG. Figure 4 shown.

[0048] Example 4 (Initiator is quantum dot g-C3N4, coagulation time is 2h, resulting in flocculation)

[0049] Initiator is replaced by g-C3N4 quantum dots (Wenjian Fang, Junying Liu, Lei Yu, Zhi Jiang, Wenfeng Shangguan, Novel (Na, O) co-doped g-C3N4 with simultaneously enhanced absorption and narrowed bandgap for highly efficient hydrogen evolution, Applied Catalysis B: Environmental, 209, 2017, 631-636.), initiator g-C3N4 quantum dots (10 mg) and photochromic material quantum dots K-Ca-Nb-O / MoS2 (10 mg) are dispersed in ultrapure water (10 mL). The mixed solution is placed in ultrasound and fully mixed until a uniform colloidal solution is formed. 2 mg of cross-linking agent N, N'-bis (acryl) cystamine is added to the above-mentioned colloidal solution, stirred at a stirring rate of 200 rad / min, so that the cross-linking agent is uniformly dispersed in the colloidal solution. Then add 2g of monomer acrylamide to the above solution, maintain the same stirring rate, and stir until the solution is clear to allow the monomer and cross-linking agent to fully prepolymerize. The above precursor solution is polymerized under a xenon lamp for 2h to obtain a photochromic hydrogel, such as Figure 5 As shown in Figure 3, long-term illumination can also cause the colloidal solution to flocculate, and the resulting hydrogel is opaque.

[0050] Example 5 (Hydrogel prepared using non-quantum dot K-Ca-Nb-O / MoS2)

[0051] The photochromic material was replaced with non-quantum dot K-Ca-Nb-O / MoS2, and the initiator TiO2 quantum dots (10 mg) and K-Ca-Nb-O / MoS2 (10 mg) were dispersed in ultrapure water (10 mL). The mixed solution was placed in ultrasound and thoroughly mixed. 2 mg of cross-linker N, N'-bis(acryl) cystamine was added to the above colloidal solution and stirred at a stirring rate of 200 rad / min to uniformly disperse the cross-linker in the colloidal solution. 2 g of monomer acrylamide was then added to the above solution, maintaining the same stirring rate and stirring until the solution was clear, so that the monomer and cross-linker were fully pre-polymerized. The above precursor solution was polymerized under a xenon lamp for 5 minutes to obtain a photochromic hydrogel, which was then dried and dehydrated for use.

[0052] In the room, the dried and dehydrated photochromic hydrogel is immersed in pure water for several hours to restore it to the gel state, and a colorless photochromic hydrogel is obtained, such as Figure 6As shown in a, since K-Ca-Nb-O / MoS2 cannot be evenly dispersed in water, it will eventually cluster inside the hydrogel. When the hydrogel is irradiated with a xenon lamp, the K-Ca-Nb-O / MoS2 clusters in the hydrogel undergo photochromic changes, as shown in Figure 6 As shown in b.

Claims

1. A method for preparing a transparent photochromic hydrogel, characterized in that: The following steps are involved: (1) Disperse TiO2 quantum dot initiator and K-Ca-Nb-O / MoS2 quantum dots in ultrapure water and mix thoroughly under ultrasound until a uniform solution is formed; Add a crosslinking agent to the above solution, stir at a certain stirring rate to uniformly disperse the crosslinking agent in the solution, then add the monomer, maintain the same stirring rate to fully prepolymerize the monomer and the crosslinking agent; The above solution is subjected to polymerization reaction under light to obtain a transparent photochromic hydrogel.

2. The method according to claim 1, wherein The photochromic material K-Ca-Nb-O / MoS2 was immersed in butylamine solution and stirred for 7 days. The K-Ca-Nb-O / MoS2 layered structure was expanded by displacement to obtain K-Ca-Nb-O / MoS2 quantum dots.

3. The method according to claim 1, wherein The particle sizes of TiO2 quantum dots and K-Ca-Nb-O / MoS2 quantum dots are both less than 5 nm.

4. The method according to claim 1, wherein The mass ratio of K-Ca-Nb-O / MoS2 quantum dots to TiO2 quantum dots is 1:

1.

5. The method according to claim 1, wherein The cross-linking agent is N,N'-bis(acryloyl)cystamine, and the mass ratio of the cross-linking agent to the initiator is 1:

5.

6. The method according to claim 1, wherein Stirring was performed at a stirring rate of 200 rad / min.

7. The method according to claim 1, wherein The monomer is acrylamide, and the mass ratio of the monomer to the cross-linking agent is 1000:

1.

8. The method according to claim 1, wherein The polymerization reaction time is 1 to 10 minutes.

9. The method according to claim 1, wherein The polymerization reaction time is 5 minutes.

10. A transparent photochromic hydrogel produced by the method according to any one of claims 1 to 9.

11. Use of a transparent photochromic hydrogel prepared by the method according to any one of claims 1 to 9, characterized in that: The hydrogel undergoes photochromic changes under light irradiation and returns to its original color under no light conditions.

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