Triazine derivative copolymerized polyaniline-based reflective electrochromic device and preparation method thereof

Abstract

The invention discloses a triazine derivative-based copolymerized polyaniline-based reflective electrochromic device and a preparation method thereof, and belongs to the field of anti-infrared detection. The reflective electrochromic device comprises a visible light-thermal infrared transparent packaging film, a visible light / thermal infrared electrochromic working electrode, an electrolyte layer, a counter electrode and a visible light-thermal infrared transparent packaging film which are arranged in sequence; the visible light / thermal infrared electrochromic working electrode is composed of a porous metal conductive layer and an electrochromic layer formed on the porous metal conductive layer, and the electrochromic layer is a trident star-shaped molecular network formed by grafting polyaniline on a triazine derivative. Compared with pure polyaniline, the triazine derivative copolymerized polyaniline adopted by the invention has a more regular structure, and a stable trident star-shaped molecular network is formed on a polyaniline long chain graft and a triazine ring, so that the triazine derivative copolymerized polyaniline has high infrared regulation and control capability, and the service life of the triazine derivative copolymerized polyaniline is longer than that of a common polyaniline-based electrochromic device.

Description

Technical Field

[0001] This invention belongs to the field of countering infrared detection, specifically relating to a triazine derivative copolymer polyaniline-based reflective electrochromic device and its preparation method, which is used to improve the infrared modulation range of the device. Background Technology

[0002] Infrared camouflage technology is an indispensable strategic and tactical element in modern warfare. In recent years, detection technologies for high-value targets have developed rapidly, making countering infrared detection a key research focus for various countries. The main method of countering infrared detection is to reduce or alter the infrared radiation characteristics of an object, making its emitted infrared radiation as close as possible to the radiation of its surrounding environment, thus preventing infrared sensors from detecting the object's presence or distinguishing it from the target. Any object with a surface temperature above zero degrees Celsius will emit infrared radiation.

[0003] PANI (polyacrylonitrile nanoparticles) are widely used in electrochromic and energy storage fields due to their advantages such as low raw material and preparation costs, good environmental stability, and excellent photoelectric and electrochemical properties. With the development of characterization methods, its infrared electrochromic properties have been discovered, and its visible light and infrared color-changing effects give it excellent potential for applications in smart windows, thermal control, and counter-reconnaissance. According to the Stefan-Boltzmann equation, the decisive factors affecting the total radiant energy of a target object are surface emissivity and surface temperature. Therefore, there are two main ways to counter infrared detection: first, to change the emissivity of the target object's surface; and second, to change the temperature conducted to the object's surface. Reflective broadband electrochromic devices counter infrared detection by changing the surface emissivity of the target object.

[0004] Although PANI can be integrated into RECDS (reflective electrochromic devices) and modified to improve its multi-band modulation performance, there are still problems to be solved before it can be applied in practical scenarios. Currently, the emissivity modulation range of most PANI-based devices in the 8-14μm band is less than 0.5, and the device surface temperature modulation range is mostly less than 10℃, which is difficult to meet the apparent temperature requirements in actual situations. At the same time, ordinary polyaniline-based electrochromic reflective devices will show significant degradation after 1000 cycles, which will undoubtedly greatly affect the unavoidable cost and lifespan issues in the practical application of RECDS.

[0005] Therefore, developing a RECDS with wide infrared modulation effect and long lifespan will help in the field of camouflage, making the device more suitable for different thermal infrared radiation environments and evading infrared detection. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by proposing a triazine derivative copolymer polyaniline-based reflective electrochromic device and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A triazine derivative copolymer polyaniline-based reflective electrochromic device includes, from top to bottom, a visible light-thermal infrared transparent encapsulation film, a visible light / thermal infrared electrochromic working electrode, an electrolyte layer, a counter electrode, and a visible light-thermal infrared transparent encapsulation film;

[0009] The visible light / thermal infrared electrochromic working electrode consists of a porous metal conductive layer and an electrochromic layer formed on the porous metal conductive layer. The electrochromic layer is a tri-point star-shaped molecular network formed by grafting polyaniline onto a triazine derivative.

[0010] Furthermore, the porous metal conductive layer is formed on a porous substrate by electron beam evaporation or magnetron sputtering to form a conductive thin film; the porous substrate is a porous polyamide-66 film, polyester film or cellulose film, etc., and the conductive thin film is one or more of gold, silver, platinum and aluminum, with a thickness of 0.1 to 50 μm.

[0011] Furthermore, the triazine derivatives are cyanuric chloride, melamine, etc.

[0012] Furthermore, the visible light-thermal infrared transparent encapsulation film is a film with visible light / infrared transparent properties.

[0013] Furthermore, the electrolyte layer is composed of a solvent, a backbone polymer, and an electrolyte, and has a thickness of 0.05–0.5 mm.

[0014] A method for preparing a triazine derivative copolymerized polyaniline reflective electrochromic device includes the following steps:

[0015] Step 1. Preparation of porous metal conductive layer:

[0016] A porous metal conductive layer is obtained by forming a conductive thin film on a porous substrate using electron beam evaporation or magnetron sputtering.

[0017] Step 2. Preparation of triazine-based polyaniline deposition solution;

[0018] 2.1 Add acid and aniline to deionized water and stir until homogeneous to obtain mixture A; wherein, in mixture A, H + The concentration of amine is 2–2.5 mol / L, and the concentration of aniline is 0.08–0.12 mol / L;

[0019] 2.2 Add triazine derivative powder in small amounts to a mixed solvent of deionized water and ethanol, and stir at 20-30°C for 1.5-2 hours to obtain mixture B; wherein the volume ratio of deionized water to ethanol is 2:1, and the concentration of triazine derivative in mixture B is 0.016-0.024 mol / L;

[0020] 2.3 Slowly add mixture B to mixture A and stir at 20-30℃ for 1-2 hours to obtain a sediment; wherein the volume ratio of mixture A to mixture B is 2.5:1.

[0021] Step 3. Form the electrochromic working electrode and counter electrode using chemical oxidative polymerization, electrochemical polymerization, emulsion polymerization, interfacial polymerization, or enzyme-catalyzed polymerization;

[0022] Step 4. Preparation of gel electrolyte;

[0023] The solvent, the backbone polymer, and the electrolyte are mixed and stirred until homogeneous to obtain a gel electrolyte; wherein the mass ratio of the solvent, the backbone polymer, and the electrolyte is 10:2:1.

[0024] Step 5. Component assembly;

[0025] The gel electrolyte obtained in step 4 is coated onto the surface of the working electrode, and then the side of the working electrode with the electrolyte is attached to the counter electrode. The electrode is then encapsulated with a visible light-thermal infrared transparent encapsulation film to obtain the electrochromic device.

[0026] Furthermore, in step 1, the porous substrate is a porous polyamide-66 film, a polyester film, or a cellulose film, etc.; the conductive film is one or more of gold, silver, platinum, and aluminum, with a thickness of 0.1 to 50 μm.

[0027] Furthermore, in step 2.1, the acid is one or more of H2SO4, oxalic acid, hydrochloric acid, etc.

[0028] Furthermore, in step 2, the triazine derivative is cyanuric chloride, melamine, etc.

[0029] Furthermore, in step 3, when forming the working electrode and counter electrode using electrochemical polymerization, the deposition solution is first transferred to a deposition tank, and then prepared in an electrochemical workstation using a constant potential step method or a cyclic voltammetry method. Preferably, when using the constant potential step method, the voltage is set to 0.75–0.9V and 0.6–0.7V, respectively; after one step, the surface is rinsed with ethanol and distilled water to remove oligomers and impurities; this operation is repeated 5–7 times to complete the preparation of the working electrode and counter electrode.

[0030] Furthermore, in step 4, the solvent is one or more of propylene carbonate, fluoroethylene carbonate, ethyl acetate, and acetonitrile; the backbone polymer is one or more of polymethyl methacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-co-hexafluoroethylene); and the electrolyte is one or more of ionic liquid, lithium salt, sodium salt, and protic acid.

[0031] Furthermore, the electrochromic device obtained in step 5 is connected to an electrochemical workstation and activated using a dual-electrode system, i.e., voltages of 0.2–0.4V and -0.5–-0.7V are applied to activate the device.

[0032] This invention provides a triazine derivative copolymerized polyaniline-based reflective electrochromic device, using triazine derivative copolymerized polyaniline as the electrochromic working electrode. Polyaniline is grafted onto the triazine derivative to form a tri-pointed star-shaped molecular network. The π orbital energy of the triazine ring is lower than that of the benzene ring in polyaniline. After coupling with the polyaniline conjugated network, new intermediate energy levels (such as the π* orbitals of the triazine ring or the hybrid orbitals of crosslinking bonds) are introduced between the original HOMO and LUMO. The energies of these intermediate energy levels are more closely matched with the infrared photon energies (0.05–1.5 eV), allowing electrons to transition between the intermediate energy levels and the HOMO / LUMO, directly enhancing the absorption / reflection response of 2.5–15 μm infrared light. The "filling / cavitation" of these intermediate energy levels changes sensitively with redox states. The core of electrochromism is the formation and migration of polarons (single-electron defects): in the oxidized state, polyaniline loses electrons to form polarons, and the delocalization of their π electrons triggers absorption in a specific wavelength band; in the reduced state, the polarons are filled with electrons, and the absorption disappears. Pure polyaniline molecular chains are prone to conjugation interruption due to interchain entanglement and twisting, and polarons are easily captured by local defects (such as chain ends and twisted sites), making stable delocalization difficult and resulting in a weak "switching effect" in infrared absorption. However, the crosslinking of cyanuric chloride creates a rigid network in the molecular structure (the planar structure of the triazine ring restricts chain twisting): the rigid structure ensures a higher spatial overlap of conjugated orbitals (enhanced coplanarity of π orbitals in the benzene ring, quinone ring, and triazine ring), and the electrons of the polarons can be delocalized across chains in the crosslinked network (migrating from one polyaniline chain to another through the triazine ring), reducing the probability of being captured by defects and significantly improving stability. The stable delocalization of polarons makes its infrared absorption stronger in the oxidized state (the larger the delocalization range, the wider the infrared band covered by absorption), while in the reduced state, the polarons are completely filled, and the absorption disappears more completely. Therefore, the difference in infrared absorption (modulation rate) between the oxidized and reduced states is significantly increased. At the same time, the copolymerized polyaniline has a regular chain structure, which has better cycle life and modulation effect than pure polyaniline chains.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. This invention provides a triazine derivative copolymerized polyaniline-based reflective electrochromic device. It utilizes a triazine ring (strong electron-withdrawing group, A) in the triazine derivative to connect with a polyaniline chain (containing electron-donating amino groups, D) via CN bonds, forming a "D-π-A" conjugated structure (D = polyaniline chain, π = conjugated bridge, A = triazine ring). In this structure, the intramolecular charge transfer (ICT) from D to A is the core of the low-energy transition (corresponding to the infrared band), thereby achieving a high infrared modulation width and solving the problem of insufficient infrared modulation effect. Furthermore, by applying different voltages, the emissivity of the device can be controlled, providing an effective approach for the development of reflective electrochromic devices in the field of infrared camouflage and anti-infrared detection.

[0035] 2. In the triazine derivative copolymer polyaniline-based reflective electrochromic device provided by the present invention, the triazine derivative copolymer polyaniline has a more regular structure than pure polyaniline. The long-linked polyaniline branches form a stable tri-pointed star-shaped molecular network on the triazine ring, which gives it high infrared modulation capability and a service life that is superior to that of ordinary polyaniline-based electrochromic devices. Attached Figure Description

[0036] Figure 1 SEM image of the porous metal conductive layer in the embodiment;

[0037] Figure 2 The molecular structure of the trichlorocyanuric acid copolymer polyaniline in the example;

[0038] Figure 3 This is a schematic diagram of the oxidized state (left) and reduced state (right) of the electrochromic device prepared in the example.

[0039] Figure 4 The temperature regulation of the electrochromic device prepared for the example at -1.5V (left) and 0.6V (right) under a 50°C background infrared camera;

[0040] Figure 5 The infrared emissivity modulation results of the electrochromic device prepared as an example. Detailed Implementation

[0041] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example

[0043] A method for preparing a triazine derivative copolymerized polyaniline reflective electrochromic device includes the following steps:

[0044] Step 1. Preparation of porous metal conductive layer:

[0045] A porous metallic conductive layer was fabricated by evaporating a gold film onto a porous polyamide-66 thin film using electron beam evaporation, with a background vacuum of less than 3.5 × 10⁻⁶. -5 Pa, electron beam current of 110 mA, evaporation time of 70 s; the surface morphology of the resulting porous metallic conductive layer is as follows: Figure 1 As shown, the porous structure of the nylon / gold film is beneficial for electron migration;

[0046] Step 2. Preparation of triazine-based polyaniline deposition solution;

[0047] 2.1 Pour 11 ml of H2SO4 and 2 ml of aniline into a polytetrafluoroethylene beaker containing 140 ml of distilled water, stir and mix well to obtain mixture A;

[0048] 2.2 Add 0.0808g of cyanuric chloride powder in small amounts several times to a polytetrafluoroethylene beaker containing a mixed solvent of 40ml distilled water and 20ml ethanol, and stir at 25℃ for 2h to obtain mixture B;

[0049] 2.3 Slowly add mixture B to mixture A and stir at 25°C for 1 hour to obtain the sediment, which is then stored in a brown medicine bottle;

[0050] Step 3. Preparation of the working electrode and the counter electrode:

[0051] The deposition solution was transferred to a deposition tank. Using the porous conductive metal layer obtained in step 1 as the conductive metal layer, the working electrode and counter electrode were formed by electrochemical polymerization in an electrochemical workstation. A three-electrode system was used, employing a constant potential step method with voltages set to 0.81V and 0.65V, respectively. After one step, the surface was rinsed with ethanol and distilled water to remove surface oligomers and impurities. The molecular structure of the resulting copolyaniline is as follows: Figure 2 As shown;

[0052] Step 4. Preparation of gel electrolyte;

[0053] 0.5g of lithium perchlorate and 1g of polymethyl methacrylate were added to a reaction vessel, followed by the addition of propylene carbonate. The mixture was stirred at 60°C for 6 hours to obtain a gel electrolyte.

[0054] Step 5. Encapsulate the electrode and counter electrode obtained by electrodeposition;

[0055] Cut conductive metal sheets such as iron, titanium, or silver sheets to approximately 1cm x 3cm as tabs. Use adhesive materials such as acrylate polymers to attach the tabs to the upper left corner of the device, assembling the tabs for the working electrode. Preheat the hot press to 100–130℃. After preheating, place the electrochromic working electrode / counter electrode on tin foil and attach an encapsulation film to encapsulate the electrode. Perform hot pressing. The encapsulation film can be a polymer film such as polypropylene, high-density polyethylene, low-density polyethylene, polyester, or polytetrafluoroethylene, or an electrodeless film such as germanium or high-alumina-silicon glass, with a thickness of 0.005–1mm. Cut the hot-pressed working and counter electrodes accordingly.

[0056] Step 6. Component Assembly:

[0057] The gel electrolyte obtained in step 4 is coated onto the working electrode after encapsulation in step 5. Then, the side of the working electrode with electrolyte is attached to the counter electrode, and the device is encapsulated with a visible light-thermal infrared transparent encapsulation film to obtain the electrochromic device.

[0058] The assembled device was connected to an electrochemical workstation and activated using a dual-electrode system by applying voltages of 0.4V and -0.6V respectively.

[0059] The activated device was subjected to visible light performance testing, such as... Figure 3 As shown, the cyanuric chloride copolymer polyaniline film appears dark green, almost black, at 0.6V, and yellow at -1.5V.

[0060] Infrared performance tests were performed on the activated device, such as... Figure 4 and 5 As shown, under the control temperature of a 50℃ background infrared camera, the device control temperature reaches 15.5℃; the average modulation range of 8-14μm reaches 0.69, which is much greater than the modulation effect of pure polyaniline device (0.47).

[0061] In the triazine derivative copolymer polyaniline-based reflective electrochromic device of the present invention, the triazine derivative copolymer polyaniline has an ordered structure, which enhances the orderliness of the polyaniline chain and the electron transport efficiency, making the polyaniline chain relatively strong and not easy to break during cycling, thereby improving the cycling stability of the device; the porous nylon gold film provides sites for polyaniline growth, and the gold film has total reflectivity. When polyaniline is in the reduced state, the total reflectivity of the gold film can make the device have low emissivity; the oxidized polyaniline film has high emissivity characteristics, and the emissivity of the device can be controlled by controlling the voltage to achieve adjustable and variable emissivity.

[0062] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A triazine derivative copolymer polyaniline-based reflective electrochromic device, characterized in that, It includes a visible light-thermal infrared transparent encapsulation film, a visible light / thermal infrared electrochromic working electrode, an electrolyte layer, a counter electrode, and a visible light-thermal infrared transparent encapsulation film arranged sequentially. The visible light / thermal infrared electrochromic working electrode consists of a porous metal conductive layer and an electrochromic layer formed on the porous metal conductive layer. The electrochromic layer is a tri-point star-shaped molecular network formed by grafting polyaniline onto a triazine derivative.

2. The triazine derivative copolymer polyaniline-based reflective electrochromic device according to claim 1, characterized in that, The porous metal conductive layer is formed on a porous substrate by electron beam evaporation or magnetron sputtering to form a conductive thin film; the porous substrate is a porous polyamide-66 film, a polyester film or a cellulose film, and the conductive thin film is one or more of gold, silver, platinum and aluminum.

3. The triazine derivative copolymer polyaniline-based reflective electrochromic device according to claim 1, characterized in that, The triazine derivatives are cyanuric chloride or melamine.

4. The triazine derivative copolymer polyaniline-based reflective electrochromic device according to claim 1, characterized in that, The visible light-thermal infrared transparent encapsulation film is a film with visible light / infrared transparency properties.

5. The triazine derivative copolymer polyaniline-based reflective electrochromic device according to claim 1, characterized in that, The electrolyte layer is composed of a solvent, a backbone polymer, and an electrolyte, and has a thickness of 0.05–0.5 mm.

6. A method for preparing a triazine derivative copolymerized polyaniline-based reflective electrochromic device, characterized in that, Includes the following steps: Step 1. Preparation of porous metal conductive layer: A porous metal conductive layer is obtained by forming a conductive thin film on a porous substrate using electron beam evaporation or magnetron sputtering. Step 2. Preparation of triazine-based polyaniline deposition solution; 2.1 Add acid and aniline to deionized water and stir until homogeneous to obtain mixture A; wherein, in mixture A, H + The concentration of amine is 2–2.5 mol / L, and the concentration of aniline is 0.08–0.12 mol / L; 2.2 Add the triazine derivative powder to a mixed solvent of deionized water and ethanol, and stir for 1.5 to 2 hours to obtain mixture B; wherein the concentration of the triazine derivative in mixture B is 0.016 to 0.024 mol / L; 2.3 Add mixture B to mixture A and stir until homogeneous to obtain a sediment; wherein the volume ratio of mixture A to mixture B is 2.5:1; Step 3. Form the electrochromic working electrode and counter electrode using chemical oxidative polymerization, electrochemical polymerization, emulsion polymerization, interfacial polymerization, or enzyme-catalyzed polymerization; Step 4. Preparation of gel electrolyte; The solvent, backbone polymer, and electrolyte are mixed and stirred until homogeneous to obtain a gel electrolyte. Step 5. Component assembly; The gel electrolyte obtained in step 4 is coated onto the surface of the working electrode, and then the side of the working electrode with the electrolyte is attached to the counter electrode. The electrode is then encapsulated with a visible light-thermal infrared transparent encapsulation film to obtain the electrochromic device.

7. The method for preparing the triazine derivative copolymerized polyaniline reflective electrochromic device according to claim 6, characterized in that, In step 2.1, the acid is one or more of H2SO4, oxalic acid, and hydrochloric acid.

8. The method for preparing the triazine derivative copolymerized polyaniline reflective electrochromic device according to claim 6, characterized in that, In step 3, when electrochemical polymerization is used to form the working electrode and the counter electrode, the deposition solution is first transferred to the deposition tank and prepared in an electrochemical workstation by constant potential step method or cyclic voltammetry.

9. The method for preparing the triazine derivative copolymerized polyaniline reflective electrochromic device according to claim 6, characterized in that, In step 4, the solvent is one or more of propylene carbonate, fluoroethylene carbonate, ethyl acetate, and acetonitrile; the backbone polymer is one or more of polymethyl methacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-co-hexafluoroethylene); and the electrolyte is one or more of ionic liquid, lithium salt, sodium salt, and protic acid.

10. The method for preparing the triazine derivative copolymer polyaniline reflective electrochromic device according to claim 6, characterized in that, The electrochromic device obtained in step 5 is connected to an electrochemical workstation and activated using a dual-electrode system.

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