Self-crosslinking reversible color-changing coating as well as preparation method and application thereof
By introducing self-crosslinking active sites onto viologen molecules, a self-crosslinking reversible color-changing coating was synthesized and coated, solving the problems of uniformity and sensitivity of viologen molecular coatings and achieving efficient color change and strong substrate bonding.
Patent Information
- Application Number
- CN202511244381.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-12-12
AI Technical Summary
Existing viologen molecular coatings suffer from uneven distribution of functional molecules, low sensitivity to color changes, and weak adhesion to the substrate, resulting in easy peeling off of the coating from the substrate surface.
By introducing self-crosslinking active sites on viologen molecules, viologen molecules with silane groups are synthesized by reacting organosilanes with 4,4'-bipyridine, and then hydrolyzed under acidic conditions to form a self-crosslinking coating. This coating is then applied to the surface of a substrate to form a self-crosslinking reversible color-changing coating.
This achieves improved coating uniformity and sensitivity. Viologen molecules are covalently connected to the substrate, resulting in a coating with high mechanical strength that is not easily detached, making it suitable for a variety of substrates.
Smart Images
Figure CN121108874A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of functional coating materials and color-changing materials, and particularly relates to a self-crosslinking reversible color-changing coating, a preparation method and application thereof. BACKGROUND
[0002] Reversible color-changing coating is a functional coating that can undergo reversible color change under external influence. It can realize dynamic adjustment of color under different environmental conditions, thereby endowing the material with the ability of "perception-response", and has important applications in temperature detection, light regulation and intelligent sensing, etc. According to the difference of functional molecules and the conditions of influencing color change, this kind of coating can be divided into thermally induced reversible color-changing coating, photo-induced reversible color-changing coating, oxidation-reduction reversible color-changing coating, etc.
[0003] Violets are N,N'-disubstituted-4,4'-bipyridine salt compounds. The molecule can undergo reversible changes in structure between dicationic state (V 2+ ), cationic radical (V +· ) and neutral state (V 0 ), thereby switching colors between colorless, blue-purple and yellow. Therefore, the molecule can be used for oxidation-reduction indication and preparation of electrochromic coating. However, the color development of violets is mainly in the form of powder and solution, and there are few coatings.
[0004] In the prior art, there are two methods for preparing coating of organic molecules. The first method is to use the functional molecules as fillers and simply physically blend with polymers, and then coat on the surface of the substrate to form a coating by solvent evaporation. The second method is to use chemical reaction to graft functional molecules with functional groups to the main chain of the polymer, and use the polymer forming method to form a coating. However, the current method of introducing high molecules has significant limitations: first, there may be a problem of poor compatibility between the functional molecules and the polymer matrix, resulting in uneven distribution of functional molecules in the coating, which in turn affects the color-changing performance of the coating. In addition, in order to obtain a complete and uniform coating, a large amount of polymer is often used in the preparation process, which leads to a low content of functional molecules in the coating, low sensitivity of color change of the coating, and is not conducive to use. Therefore, it is a challenge to prepare a coating with high sensitivity and complete uniformity from violets.
[0005] Adjusting the type of organic molecules in the synthesis of viologen molecules can make the viologen molecules have self-crosslinking active sites at both ends. By using these self-crosslinking active sites, not only can the use of high molecules be avoided, but also the viologen molecules can be self-crosslinked on the target substrate to form a coating, thereby improving the sensitivity and uniformity of the viologen molecule coating, and the viologen molecule coating can be firmly combined with the surface of the target substrate to effectively avoid the peeling of the coating on the substrate surface. Therefore, it is of great significance to study the self-crosslinking viologen molecules. The reversible color-changing coating obtained by using the self-crosslinking viologen molecules has wide application prospects in the technical fields of redox indication, dynamic anti-counterfeiting, life decoration, information encryption and the like. SUMMARY
[0006] The present application provides a self-crosslinking reversible color-changing coating, a preparation method and application thereof.
[0007] The technical scheme adopted by the present application is as follows:
[0008] The preparation method of the self-crosslinking reversible color-changing coating comprises the following steps:
[0009] 1) Synthesizing a viologen molecule with a silane group by reacting 4,4'-bipyridine with an organic silane under heating;
[0010] 2) Hydrolyzing the viologen molecule synthesized in step 1) under acidic conditions to obtain a self-crosslinkable molecule with a silicon hydroxyl group;
[0011] 3) Coating the self-crosslinkable molecule synthesized in step 2) on the surface of a substrate, and drying to obtain a self-crosslinking reversible color-changing coating.
[0012] Further, in the preparation method of the self-crosslinking reversible color-changing coating, in step 1), the organic silane is one or a combination of two or more of chloro or bromo organic silanes.
[0013] Preferably, the organic silane is γ-chloropropyl triethoxysilane.
[0014] Further, in the preparation method of the self-crosslinking reversible color-changing coating, in step 1), the molar ratio of 4,4'-bipyridine to organic silane is 1:2.
[0015] Further, in the preparation method of the self-crosslinking reversible color-changing coating, in step 3), the substrate is ordinary glass, conductive glass, metal, resin, non-woven fabric or cotton cloth.
[0016] Further, the preparation method of the self-crosslinking reversible color-changing coating specifically comprises the following steps:
[0017] 1) Take 0.25-1.00 g 4,4'-dipyridine, ultrasonic dispersion in 20-30 mL acetonitrile in water bath, then add 0.78-3.10 g organic silane in the system, reflux at 50-80 ℃ for 18-48 h, after the reaction is completed, remove the solvent at 35-50 ℃ by rotary evaporation, obtain the primary product, named as product A;
[0018] 2) After adding the mixed solution composed of 3-7 mL anhydrous ethanol and 20-30 mL 0.1 M hydrochloric acid aqueous solution in the product A prepared in step 1), reflux at 50-80 ℃ for 18-36 h, after the reaction is completed, obtain the final product, named as product B;
[0019] 3) Coating the product B prepared in step 2) on the surface of the substrate, drying at 60-90 ℃ to obtain the material with self-crosslinking reversible color-changing coating.
[0020] The self-crosslinking reversible color-changing coating according to any one of the above is applied in the functional coating material.
[0021] The self-crosslinking reversible color-changing coating according to any one of the above is applied in the color-changing material.
[0022] Further, the application of the above, the self-crosslinking reversible color-changing coating is applied in the redox reversible color-changing material.
[0023] Further, the application of the above, the self-crosslinking reversible color-changing coating is applied in the electrochromic material.
[0024] Compared with the prior art, the beneficial effects of the present application are:
[0025] 1) The self-crosslinking reversible color-changing coating provided by the present application has simple preparation method, simple raw materials and easy-to-realize reaction conditions, and the prepared self-crosslinking reversible color-changing coating is uniform and continuous, has high functional molecule content and high color-changing sensitivity.
[0026] 2) In the self-crosslinking reversible color-changing coating prepared by the present application, the viologen molecules are connected through covalent bonds, and the coating and the substrate are connected through covalent bonds, so that the coating has high mechanical strength, the coating and the substrate are firmly combined, and there is no falling phenomenon.
[0027] 3) The self-crosslinking reversible color-changing coating prepared by the present application has good universality for substrates, and can construct coating on the surface of ordinary glass, conductive glass, fabric and the like. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1 It is the synthesis route map of product B in Example 1.
[0029] Figure 2The image shows the FT-IR spectrum of product B from Example 1.
[0030] Figure 3 The images show the solutions of product B in Example 1: (a), product B with added appropriate amount of Na2S2O4 (b), and product B with added excess Na2S2O4 (c).
[0031] Figure 4 The image shows the UV-Vis absorption spectrum of product B solution after adding an appropriate amount of Na2S2O4 solution in Example 1.
[0032] Figure 5 This is a cyclic voltammetry curve of product B molecule in Example 1.
[0033] Figure 6 These are photographs of the self-crosslinking reversible color-changing coating on the surface of ordinary glass in Example 3 before (a) and after (b) the oxidation-reduction color change.
[0034] Figure 7 These are photographs of the conductive glass surface coating in Example 3 before (a) and after (b) color change in a two-electrode system.
[0035] Figure 8 These are photographs of the conductive glass surface coating in Example 3 before (a) and after (b) color change in a three-electrode system.
[0036] Figure 9 The images show (a) a nonwoven fabric with a self-crosslinking reversible color-changing coating on its surface, as well as (b) a fabric that has been reduced to blue and (c) a fabric that has been oxidized and faded, in Example 3.
[0037] Figure 10 These are photographs of the anti-counterfeiting fabric before (a) and after (b) color change in Example 3. Detailed Implementation
[0038] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.
[0039] Example 1: Synthesis of self-crosslinked viologen molecules
[0040] (I) Preparation method
[0041] 1) Place 0.50 g of 4,4'-bipyridine in a single-necked round-bottom flask, add 25 mL of acetonitrile, and sonicate to dissolve. Then add 1.55 g of γ-chloropropyltriethoxysilane and sonicate in a water bath for 5 min. After sonication, place the flask in a heating mantle or oil bath and reflux at 80 °C for 24 h (with an anhydrous calcium chloride drying tube connected above the condenser). After the reaction is complete, remove the solvent by rotary evaporation at 40 °C to obtain the primary product, named product A.
[0042] 2) Add a mixed solution consisting of 5 mL of anhydrous ethanol and 25 mL of 0.1 M hydrochloric acid aqueous solution to product A, and reflux at 60 °C for 24 h. After the reaction is completed, the hydrolysis product is obtained and named product B.
[0043] The synthesis processes in steps 1) and 2) are as follows: Figure 1 As shown.
[0044] (ii) Characterization
[0045] The FT-IR spectrum of product B is as follows: Figure 2 As shown. At 3440 cm -1 The strong, broad peak centered at 1606 cm⁻¹ corresponds to the stretching vibration of the OH bond, proving the presence of Si-OH in the product molecule. -1 The strong absorption peak is attributed to the stretching vibration of C=N, proving the presence of a pyridine ring in the molecule. 2960 cm⁻¹ -1 and 2832 cm -1 Corresponding to the CH stretching vibration on the alkyl chain, 1122 cm -1 This is due to the asymmetric stretching vibration of CO-Si. These typical absorption peaks demonstrate the successful synthesis of the product.
[0046] Add Na2S2O4 solution dropwise to product B solution, which is caused by Figure 3 (a) shows the colorless color change to Figure 3 (b) shows a blue-purple color. Upon further addition of excess Na₂S₂O₄, the solution color changes to [the following value]. Figure 3 (c) shows the yellow color. Then, H₂O₂ solution was added dropwise to this yellow solution, causing it to change from yellow to blue-violet, which then faded, demonstrating that the viologen molecule solution exhibits redox reversibility.
[0047] Figure 4 The image shows the UV-Vis absorption spectrum after adding an appropriate amount of Na2S2O4 solution to product B solution. It can be seen that the maximum absorption peak of the solution after color development appears at 595 nm, and the wavelength of the maximum absorption peak corresponds to the characteristic blue-violet color of the molecular solution.
[0048] The cyclic voltammetry curve of product B molecule is as follows: Figure 5 As shown in the figure, two distinct pairs of redox peaks appear, indicating that the molecule exhibits redox reversibility. The redox peaks are stable and well-symmetrical, suggesting that the molecule possesses persistent cyclic reversibility.
[0049] Example 2: Preparation of self-crosslinking reversible color-changing coating
[0050] Coatings were prepared on different substrates using product B solution, including but not limited to the following substrates:
[0051] 1) Ordinary glass surface: Use a pipette to transfer 5 mL of product B solution into a clean glass dish (d = 5 cm), and gently swirl the dish to spread the solution evenly. Then place the dish in an oven at 80 ℃ and heat. After the solvent has completely evaporated, a self-crosslinking reversible color-changing coating will be obtained on the surface of the glass dish.
[0052] 2) Conductive glass surface: The product B solution is uniformly dropped onto the conductive surface of the conductive glass, leaving a 1 / 6 blank space on one side for electrode clamping. Then it is heated in an oven at 80 ℃ to obtain a self-crosslinking reversible color-changing coating.
[0053] 3) Fabric surface: Immerse the nonwoven fabric in product B solution to wet the surface of the nonwoven fabric. Then place it in an oven at 80 ℃ to dry, and a self-crosslinking reversible color-changing coating is obtained on the fabric surface.
[0054] Example 3: Application of self-crosslinking reversible color-changing coating
[0055] (a) Oxidation-reduction discoloration of self-crosslinking reversible color-changing coatings on ordinary glass surfaces
[0056] Under the influence of air and a reducing agent, the color change of the coating before and after is as follows: Figure 6 (a) and Figure 6 As shown in (b). Towards Figure 6 (a) After Na2S2O4 solution was dropped onto the coating surface, the coating color changed rapidly. The color of the coating after the change is as follows: Figure 6 As shown in (b), it is confirmed that viologen molecules in the coating form can still be reduced to free radical cations (V). 2+ →V +· After being left to stand in air for 10 minutes, the coating spontaneously recovered. Figure 6 (a) state. This process indicates the state of V. +· Violet molecules in their active state are unstable in air and can be spontaneously oxidized to V. 2+ When Na2S2O4 solution is added again to the coating surface, which has returned to white, the coating color changes again, demonstrating that the coating's color-changing behavior has cyclic stability.
[0057] (ii) Conductive glass surface
[0058] 1) Color change in the two-electrode system
[0059] The conductive glass surface coating changes color before and after in a two-electrode system, as shown below. Figure 7 (a) and Figure 7As shown in (b), by using PVA gel as the electrolyte, the coating is bonded to another conductive glass to obtain an electrochromic glass controlled by two electrodes. When a DC voltage of 2.0 V is applied to the self-crosslinking reversible color-changing coating, the coating quickly turns purple after being energized; when the power supply is reversed, the color of the coating gradually fades and eventually returns to the initial colorless oxidation state.
[0060] 2) Color change in the three-electrode system
[0061] The conductive glass surface coating changes color before and after in a three-electrode system, as shown below. Figure 8 (a) and Figure 8 As shown in (b). During the test, an electrochemical workstation was used to apply a voltage of -1.1 to -0.4 V (vs. Ag / AgCl) to the coating using a three-electrode system. During the forward scan, the coating turned purple instantly upon energization, and the color gradually lightened as the voltage increased. During the negative scan, the coating color exhibited the opposite trend. Through CV cycling, the reversible electrochromic capability of the coating was fully demonstrated.
[0062] (iii) Fabric surface
[0063] 1) Oxidation-reduction color change of reversible color-changing fabrics
[0064] Figure 9 In the image, (a) is a photograph of a nonwoven fabric with a self-crosslinking reversible color-changing coating; (b) is a photograph of the nonwoven fabric shown in (a) after being immersed in a Na2S2O4 solution, showing that the nonwoven fabric turns blue; (c) is a photograph of the nonwoven fabric shown in (b) after being immersed in an H2O2 solution, showing that the color of the nonwoven fabric disappears after immersion in the H2O2 solution. This demonstrates that the constructed fabric also exhibits reversible redox color-changing properties.
[0065] 2) Anti-counterfeiting fabric
[0066] The color change of the anti-counterfeiting fabric before and after is as follows: Figure 10 (a) and Figure 10 As shown in (b), a pattern is drawn on the surface of the nonwoven fabric using product B solution. After drying, no visible pattern is visible on the nonwoven fabric surface, forming an invisible anti-counterfeiting layer. When Na2S2O4 solution is evenly sprayed using a spray bottle, a bright blue pattern gradually appears on the surface, completing the visualization of the anti-counterfeiting information. After standing for approximately 2 minutes, the blue pattern fades naturally through oxidation in the air, returning to its initial invisible state. This color-changing process can be reversibly cycled multiple times.
Claims
1. A self-crosslinking reversible color-changing coating, characterized in that, Its preparation method includes the following steps: 1) Under heating conditions, 4,4'-bipyridine was reacted with organosilanes to synthesize viologen molecules with silane groups; 2) The viologen molecule synthesized in step 1) is hydrolyzed under acidic conditions to obtain a self-crosslinking molecule with silanol groups; 3) Coat the self-crosslinking molecules synthesized in step 2) onto the surface of the substrate, and after drying, a self-crosslinking reversible color-changing coating can be obtained.
2. The self-crosslinking reversible color-changing coating according to claim 1, characterized in that, In step 1), the organosilane is one or a combination of two or more chlorinated or brominated organosilanes.
3. The self-crosslinking reversible color-changing coating according to claim 2, characterized in that, In step 1), the organosilane is γ-chloropropyltriethoxysilane.
4. The self-crosslinking reversible color-changing coating according to claim 1, characterized in that, In step 1), the molar ratio of 4,4'-bipyridine to organosilane is 1:
2.
5. The self-crosslinking reversible color-changing coating according to claim 1, characterized in that, In step 3), the substrate is ordinary glass, conductive glass, metal, resin, non-woven fabric or cotton cloth.
6. The self-crosslinking reversible color-changing coating according to claim 1, characterized in that, Its preparation method specifically includes the following steps: 1) Take 0.25-1.00 g of 4,4'-bipyridine and disperse it in 20-30 mL of acetonitrile by ultrasonication in a water bath. Then add 0.78-3.10 g of organosilane to the system and reflux at 50-80 °C for 18-48 h. After the reaction is completed, remove the solvent by rotary evaporation at 35-50 °C to obtain the primary product, which is named product A. 2) Add a mixed solution consisting of 3-7 mL of anhydrous ethanol and 20-30 mL of 0.1 M hydrochloric acid aqueous solution to product A prepared in step 1), and reflux at 50-80 °C for 18-36 h. After the reaction is completed, the final product is obtained and named product B. 3) Coat the product B prepared in step 2) onto the surface of the substrate and dry it at 60-90 °C to obtain a material with a self-crosslinking reversible color-changing coating.
7. The application of the self-crosslinking reversible color-changing coating according to any one of claims 1-6 in functional coating materials.
8. The application of a self-crosslinking reversible color-changing coating as described in any one of claims 1-6 in color-changing materials.
9. The application according to claim 8, characterized in that, The application of the self-crosslinking reversible color-changing coating in redox reversible color-changing materials.
10. The application according to claim 8, characterized in that, The application of the self-crosslinking reversible color-changing coating in electrochromic materials.