Low-emissivity polybenzodifuran-dione composite infrared stealth material and preparation method thereof

Abstract

This invention belongs to the field of infrared stealth materials technology, and relates to a low-emissivity polyphenylene difuran diketone (PPD) composite infrared stealth material and its preparation method. The material comprises adjacent PPD coatings and a substrate layer; the PPD has a molecular weight ≥10 kDa and a self-doping rate ≥81%. Preparation method: After coating the upper surface of the substrate layer with a PPD solution, the solvent is removed by drying. Then, the lower surface of the substrate layer and the upper surface of the heat insulation layer are connected to obtain the low-emissivity PPD composite infrared stealth material. The low-emissivity PPD composite infrared stealth material provided by this invention achieves a lower average infrared emissivity through a self-doping mechanism, and the doping state is stable, maintaining a low emissivity for a long time. This overcomes the problems of limited emissivity reduction effect, easy oxidation, and easy dopant loss of existing coatings.

Description

Technical Field

[0001] This invention belongs to the field of infrared stealth materials technology, and relates to a low emissivity polyphenylene difuran diketone composite infrared stealth material and its preparation method. Background Technology

[0002] In today's era of rapid development in military technology, infrared detection and stealth technology occupy a pivotal position in the defense field. Whether it is the need for concealment during individual combat or the consideration of avoiding detection by enemy infrared detection systems for combat weapons, materials with excellent infrared stealth capabilities (referred to as infrared stealth materials) have become crucial.

[0003] Coating is a core technology for controlling infrared characteristics through surface modification, and it is also the mainstream technology for preparing infrared stealth materials.

[0004] Coating materials are mainly divided into two types: metals and conductive polymers. Conductive polymers have the following advantages over metals:

[0005] (1) The density of conductive polymers is much lower than that of metal materials (such as aluminum foil and copper mesh), which is of great significance for the lightweighting of equipment;

[0006] (2) Conductive polymers themselves or their composites usually have good flexibility, can fit various complex curved surfaces, are not easy to crack or fall off, and meet the stealth requirements of curved surface equipment.

[0007] (3) Conductive polymers can be processed into thin films or coatings in a variety of ways, which is beneficial for large-area, low-cost manufacturing, especially suitable for irregular surfaces.

[0008] However, existing infrared stealth materials containing conductive polymer coatings generally have high average infrared emissivity (8~14μm band), as shown in the following examples:

[0009] Reference 1 (Construction of Multifunctional Flexible Materials Based on LowInfrared Emissivity Camphor Sulfonic Acid Doped Polyaniline Film[J]. AdvancedMaterials Technologies, 2017, e00267.) uses camphor sulfonic acid-doped polyaniline as the coating material, and the average infrared emissivity of the resulting infrared stealth material is 0.347.

[0010] Reference 2 (Further Understanding of the Mechanisms of Electrochromic Devices with Variable Infrared Emissivity Based on Polyaniline Conducting Polymers[J]. Journal of Materials Chemistry C, 2019, 7(32): 9878 - 9891.) uses perchloric acid-doped polyaniline as a coating material, and the average infrared emissivity of the resulting infrared stealth material is 0.316.

[0011] Reference 3 (Hierarchically Porous Polypyrrole Foams Contained Ordered Polypyrrole Nanowire Arrays for Multifunctional Electromagnetic Interference Shielding and Dynamic Infrared Stealth[J]. Nano - Micro Letters, 2025, 17(1):1 - 20.) describes the formation of a coating material by combining polypyrrole with melamine foam, and the resulting infrared stealth material has an average infrared emissivity of 0.55.

[0012] Reference 4 (Scalable and Tunable PEDOT:PSS Emitter for Thermal Camouflage[J]. Advanced Optical Materials, 2024, 12(1): 2301303.) used poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a coating material, and the average infrared emissivity of the resulting infrared stealth material was 0.25.

[0013] Reference 5 (Polymer‐regulating MXene@Dopamine electroactive gel‐inks for textile‐based multi‐protective wearables[J]. Advanced Functional Materials,2024, 34(36): 2401097.) prepared electroactive gel inks by combining PEDOT:PSS as a dopant with MXene and forming a coating. The average infrared emissivity of the resulting infrared stealth material was 0.34.

[0014] Therefore, it is necessary to study an infrared stealth material with a conductive polymer coating and a lower average infrared emissivity, as well as its preparation method. Summary of the Invention

[0015] The purpose of this invention is to solve the problems existing in the prior art and provide an infrared stealth material with a conductive polymer coating and a lower average infrared emissivity, and a method for preparing the same, specifically a low-emissivity polyphenylene difuran diketone composite infrared stealth material and a method for preparing the same.

[0016] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0017] A low-emissivity polyphenylene difurandione composite infrared stealth material, comprising an adjacent polyphenylene difurandione (PBFDO) coating and a substrate layer;

[0018] Polyphenylene difuran diketone has a molecular weight ≥10kDa and a self-doping rate ≥81%.

[0019] The self-doping rate refers to the percentage of carbonyl oxygen atoms in the total number of carbonyl oxygen atoms that interact with carbonyl oxygen as a balance charge during the molecular-level self-doping process of polyphenylene difuran diketone, resulting in a change in its chemical state.

[0020] According to Kirchhoff's laws, for an opaque object, its infrared emissivity (ε) = 1 - infrared reflectivity (ρ). This means that for a material to achieve extremely low infrared emissivity, it must have extremely high infrared reflectivity in the corresponding infrared band (such as 8-14μm).

[0021] This invention has found that the key parameters determining the infrared reflectivity of infrared stealth materials are: the self-doping rate of polyphenylene difuran diketone and the molecular weight of polyphenylene difuran diketone.

[0022] Metals can efficiently reflect electromagnetic waves in the infrared and even visible light bands because they contain a large number of free electrons. These electrons collectively form a "free electron gas." When lower-frequency electromagnetic waves (such as infrared light) are incident, the free electron gas interacts strongly with them and reflects them efficiently. When the self-doping rate of polyphenylene difuran diketone is ≥81%, it can produce an extremely high carrier concentration, reaching a level comparable to that of real metals. This makes polyphenylene difuran diketone behave like an "organometal" at the electronic level, naturally giving it extremely high infrared reflectivity.

[0023] Conductive polymers commonly used in infrared stealth applications, such as PANI (polyaniline), PEDOT (poly(3,4-ethylenedioxythiophene), and PPy (polypyrrole), rely on external doping methods. Due to physical diffusion limitations and steric hindrance, no matter how the process is optimized, it is impossible to stably increase the doping efficiency to ≥81%, thus preventing them from reaching this metal-like state. Among these limitations, physical diffusion is the biggest bottleneck. External dopants (whether small molecule acids or other substances) must physically diffuse from the solution or gas phase through the densely packed structure of polymer particles or films to reach the internal doping sites. This process is very slow and inefficient, especially for the core layer of the material, where many sites cannot be effectively doped, resulting in a very low overall doping efficiency.

[0024] This invention utilizes the doping characteristics of polyphenylene difuran diketone (PPD) to simultaneously complete doping during the polymerization process, avoiding the complex processes of traditional conductive polymers that require additional acid doping or composite modification. This simplifies the preparation process and further enhances material stability through a molecular-level self-doping mechanism. Extensive experiments have shown that, at the same self-doping rate, the infrared reflectivity of PPD increases significantly when the molecular weight is ≥10 kDa.

[0025] This effect is achieved because 10 kDa is a critical performance threshold for polyphenylene difuran diketone. Above this threshold, the macroscopic properties of the material begin to be primarily determined by its ideal conjugated long-chain structure, rather than by defects such as chain ends. The specific reasons are as follows:

[0026] (1) Overcoming the chain end effect and ensuring effective carrier transport: For conjugated polymers, the chain end is a structural discontinuity point, which will form an energy level trap and play a role in scattering and capturing the transport of carriers. When the molecular weight is low (e.g., below 10 kDa), the number of chain ends accounts for a high proportion in the whole system, and the "end effect" has a very significant negative impact on conductivity, which will severely limit the delocalization degree and mobility of carriers. However, when the molecular weight is ≥10 kDa, the polymer chain is long enough, the relative proportion of chain ends is greatly reduced, and the transport of carriers mainly takes place on the long chain. At this time, the material begins to exhibit its intrinsic and excellent conductivity.

[0027] (2) Promote ordered stacking and build a three-dimensional conductive network: Long-chain and regular polymers (≥10kDa) are more likely to form an ordered layered stacking structure through π-π interactions in the solid state, thereby building an efficient three-dimensional charge transport network. However, due to the chain length limitation and higher steric hindrance of the terminal groups, short-chain oligomers are difficult to form a large-scale, high-quality ordered stacking, which makes it difficult for inter-chain charge transitions.

[0028] The molecular weight ≥10kDa and the self-doping rate ≥81% designed in this application have a synergistic effect. When the molecular weight of polyphenylene difuran diketone is lower than 10kDa, even if the doping efficiency is ≥81%, this doping is "ineffective" or "inefficient" because when the polymer chain is very short (<10kDa), even if each short chain is highly doped (e.g., 81%), these charge carriers will be severely confined within their respective short chains. These charge carriers confined to the short chains contribute very little to the macroscopic conductivity. Therefore, its infrared reflectivity will be very low.

[0029] In summary, this invention achieves high infrared reflectivity and thus low infrared emissivity through the combined effect of "molecular weight ≥10kDa and self-doping rate ≥81%".

[0030] Furthermore, the doping mechanism of polyphenylene difuran diketone does not rely on volatile and reactive external small molecule dopants. Instead, it uses stable protons as a balance charge, which further enhances the stability of the doped state. These protons mainly interact strongly with the carbonyl group in the form of Lewis acids, making them difficult to ionize and detach. At the same time, the chemical structure of polyphenylene difuran diketone makes its highly doped "metal-like state" inherently very stable, so the high carrier concentration can be maintained for a long time. This ensures that its infrared reflectivity will not easily decay (i.e., the infrared emissivity will not easily increase), thus achieving long-lasting and sustainable infrared stealth performance.

[0031] As a preferred technical solution:

[0032] As described above, a low-emissivity polyphenylene difuran diketone composite infrared stealth material is provided, wherein the polyphenylene difuran diketone coating and the substrate are physically connected by van der Waals forces, hydrogen bonds, and anchoring effects.

[0033] The thickness of the polyphenylene difuran diketone coating is 5~30μm;

[0034] The base layer is a PET film, PI film, or PP film, with a thickness of 0.025~1mm; or, the base layer is nylon 66 fabric with a thickness of 0.2~1mm.

[0035] The low-emissivity polyphenylene difurandiketone composite infrared stealth material described above has an electrical conductivity of 1500~1800 S / cm; an average infrared emissivity of 0.18~0.21 in the 8~14μm band, and an increase of 16%~20% in the average infrared emissivity in the 8~14μm band after 3 months of exposure to air (indoor environment); and an adjustable radiation temperature range of 24.8~121℃ in a low voltage range of 0~4V. Adjusting the radiation temperature can simulate thermal radiation under different temperature environments, so that the area covered by the material appears the same image color as the target environment under the detection of the thermal imager, thus avoiding detection. It can also simulate the radiation temperature of other heat sources to create false heat source targets to interfere with the detection of infrared thermal imaging.

[0036] The low-emissivity polyphenylene difurandiketone composite infrared stealth material of this invention can simulate various temperatures with only a small driving voltage, while existing technologies require a larger voltage (5~30V). The fundamental reason is that polyphenylene difurandiketone achieves "metal-like" conductivity through a "molecular-level proton balance self-doping" mechanism. Its doping is "endogenous" during the polymerization process, and protons are "locked" on the polymer backbone as balance charges, achieving a doping efficiency that reaches the theoretical limit and a carrier concentration as high as 10²²cm⁻³. Moreover, the protons are anchored through strong interactions, resulting in a stable doping state and extremely low and stable resistance. In contrast, existing technologies rely on external doping, which has low doping efficiency, low carrier concentration, weak binding force between the dopant and the polymer, and easy loss of the dopant, resulting in high and variable resistance. Therefore, a larger voltage is required than that of this invention. According to the Joule heating formula P=V² / R (P is power, V is voltage, and R is resistance), the low resistance of polyphenylene difuran diketone allows it to generate significant heating power with a small voltage, enabling the low emissivity polyphenylene difuran diketone composite infrared stealth material to achieve radiation temperature regulation of 24.8~121℃ within a low voltage range of 0~4V.

[0037] The low emissivity polyphenylene difuran diketone composite infrared stealth material described above also includes a heat insulation layer; the polyphenylene difuran diketone coating, the substrate layer, and the heat insulation layer are sequentially adjacent; the material's low emissivity and the ability of the material to reduce the target surface temperature through heat insulation together contribute to the material's excellent infrared stealth effect.

[0038] The low-emissivity polyphenylene difuran diketone composite infrared stealth material described above has a substrate layer and a heat insulation layer physically connected by polydimethylsiloxane (PDMS). The heat insulation layer is an aramid nanofiber aerogel layer with a thickness of 1-2 mm. The preparation method of the aramid nanofiber aerogel layer is referenced in (Aramid Nanofiber Aerogels: Preparation, Modification, Composite Fabrication, and Applications[J]. Advanced Materials, 2025). 2502508.) can be prepared using the following general steps: First, aramid fibers (such as PPTA yarn) are shredded and dissolved by deprotonation in KOH / DMSO solution. Then, deionized water is added for reprotonation to regenerate aramid nanofibers. The aramid nanofibers are centrifuged and washed until neutral, then dispersed in deionized water and ultrasonically treated to obtain a uniform and stable aqueous dispersion of aramid nanofibers. A certain volume and concentration of the aqueous dispersion of aramid nanofibers is taken and vacuum filtered in a sintered glass funnel to form a wet gel with a specific thickness. Finally, the wet gel is pre-frozen at -80℃ for 2 hours and then dried in a freeze dryer (-50℃, <10Pa) for 48 hours to obtain an aramid nanofiber aerogel layer.

[0039] Aerogel materials, due to their unique porous structure, possess excellent thermal insulation properties, thereby reducing the thermal radiation of target objects. This has led to their increasing research and application in the field of infrared stealth materials. Aramid fibers, as a flame-retardant material, can also be processed into aerogel materials with excellent thermal insulation properties through simple processes, further reducing infrared thermal radiation. Therefore, combining polyphenylene difuran diketone (PPD) materials with aramid nanofiber aerogel materials, addressing both low emissivity and thermal insulation, allows for the preparation of infrared stealth composite materials. This enables the achievement of excellent infrared stealth capabilities while maintaining good flexibility and strength, and endowing the material with multifunctional properties such as thermal insulation, waterproofing, and flame retardancy, leading to the development of infrared stealth materials with more diverse application scenarios.

[0040] This invention also provides a method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material as described in any of the preceding claims. The method involves coating a polyphenylene difuran diketone solution onto the upper surface of a substrate layer, drying to remove the solvent, and then connecting the lower surface of the substrate layer to the upper surface of the heat insulation layer to obtain the low-emissivity polyphenylene difuran diketone composite infrared stealth material. The polyphenylene difuran diketone has a molecular weight ≥10 kDa and a self-doping rate ≥81%.

[0041] As a preferred technical solution:

[0042] The method described above, using an automated coating machine (AFA-IV), ensures uniform coating and prevents damage to the substrate.

[0043] The preparation steps of the polyphenylene difuran diketone solution are as follows:

[0044] (1) First, H-BFDO (3,7-dihydrobenzo(1,2-b:4,5-b)difuran-2,6-dione) crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, under the protection of nitrogen or inert gas, the mixture was reacted at 80~120℃ for 40~150min (stirred during the reaction at a stirring rate of 1000r / min). Finally, the mixture was cooled to 30~35℃ to obtain product A (product A is a gel-like substance). The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 0.3~1g:0.5~1.5g; the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide in step (1) was 0.3~1g:25~100mL. The self-doping mechanism of polyphenylene difuran dione is stoichiometric. As long as the feed ratio of reactants (monomers and oxidants) is within this range, the self-doping rate can be ≥80%.

[0045] (2) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (2) to dimethyl sulfoxide in step (1) is 1:1 to 2:1.

[0046] (3) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide (specifically, dialysis can be: add solution A to the dialysis bag, then place the dialysis bag in dimethyl sulfoxide for 1 to 14 days, and replace the dimethyl sulfoxide every three days) to obtain solution B; wherein, the molecular weight cutoff must be ≥10 kDa in order to remove low molecular weight polybenzodifuran diketone to ensure its infrared stealth performance;

[0047] (4) Filter the undissolved precipitate in solution B (the precipitate includes polymer aggregates, reaction residue particles and external dust, which can be filtered with a 0.45μm polytetrafluoroethylene filter), and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 8~20mg / mL.

[0048] In the above steps, product A in step (1) is polyphenylene difuran diketone, which has a high viscosity and is gel-like. Step (2) is to dilute the product in step (1) for subsequent purification. Step (3) is to perform dialysis purification to obtain high-quality polyphenylene difuran diketone after removing impurities. Step (4) is to filter out some undissolved precipitates and control the concentration of polyphenylene difuran diketone by rotary evaporation.

[0049] As described above, the doctor blade speed during coating is 0.5~3 cm / s, and the coating amount of polyphenylene difuran diketone solution is 0.125~0.25 mL / cm. 2 The drying process after coating is vacuum drying, with a temperature of 60℃ and a drying time of 12-24 hours. The solvent dimethyl sulfoxide (DMSO) in polyphenylene difuran diketone has a high boiling point (approximately 189℃). During ordinary pressure drying, the solvent evaporates slowly and easily leaves residues, affecting the purity and performance of the material. A vacuum environment lowers the solvent boiling point and accelerates its complete evaporation. Furthermore, uneven solvent evaporation during ordinary drying can easily lead to defects such as bubbles and cracks in the coating. Vacuum drying allows for more uniform solvent evaporation, ensuring the smoothness and density of the coating. Therefore, using a vacuum drying process can guarantee its performance.

[0050] The specific process of connecting the lower surface of the substrate and the upper surface of the insulation layer using the method described above is as follows: First, a polydimethylsiloxane prepolymer with a mass ratio of 10~10.5:1 is mixed evenly with a platinum catalyst and then applied to the lower surface of the substrate and the upper surface of the insulation layer. Then, the lower surface of the substrate and the upper surface of the insulation layer are bonded together and prepolymerized at 70~90℃ for 0.5h~1h. Finally, the mixture is heat-cured at 115~120℃ for 2~3h.

[0051] Polydimethylsiloxane (PDMS) primarily relies on strong mechanical interlocking and extensive interfacial physical adsorption to achieve a firm bond between the low-emissivity coating substrate and the insulation layer. For example, when the insulation layer is an aramid nanofiber aerogel layer, the liquid PMS prepolymer can deeply penetrate into the porous nanonetwork of the aramid aerogel and solidify therein, forming a three-dimensional mechanically interlocking structure that interpenetrates and entangles with the fiber skeleton, providing the most important bonding force. At the same time, PMS can effectively wet the surface of the low-emissivity coating substrate, achieving tight interfacial physical adhesion through van der Waals forces and the mechanical anchoring effect of the microstructure of the filled surface, thereby bonding the substrate layer and the insulation layer together.

[0052] Beneficial effects:

[0053] (1) The low emissivity polyphenylene difuran diketone composite infrared stealth material in this invention has an average infrared emissivity of 0.18~0.21 in the 8~14μm band. Compared with similar coating materials in the prior art, it has a better effect on reducing the average infrared emissivity of the material surface (e.g. 0.347 in reference 1, 0.316 in reference 2, 0.55 in reference 3, 0.25 in reference 4, and 0.34 in reference 5), and can better achieve infrared stealth.

[0054] (2) This invention utilizes polyphenylene difuran diketone to achieve self-doping through the "molecular-level proton balance self-doping" mechanism. It does not rely on easily volatile and reactive external small molecule dopants. The self-doping rate is ≥81%, and the protons interact strongly with the carbonyl group in the form of Lewis acid, making it difficult to ionize and fall off. Its chemical structure also makes the highly doped "metal-like state" inherently stable, which can maintain a high carrier concentration for a long time and ensure that the infrared reflectivity is not easily decayed. It solves the problem of dopant loss and difficulty in maintaining a stable low emissivity state for a long time caused by external doping in the prior art. It achieves long-term and sustainable infrared stealth performance. After being exposed to air for 3 months, the average infrared emissivity in the 8~14μm band only increases by 16%~20%.

[0055] (3) The conductivity of the infrared stealth material of the present invention is 1500~1800 S / cm. Due to the low resistance of polyphenylene difuran diketone, the radiation temperature can be adjusted from 24.8 to 121°C in a low voltage range of 0~4V. Compared with the existing technology which requires a high voltage of 5~30V, it is easier to simulate thermal radiation under different temperature environments or create false heat source targets in practical applications, thereby improving the flexibility of infrared stealth. Attached Figure Description

[0056] Figure 1 The curves showing the radiation temperature of the low-emissivity polyphenylene difuran diketone composite infrared stealth material in Example 1 as a function of voltage (0~4V) are shown. Detailed Implementation

[0057] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0058] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturer information of the substances is specified in this invention; in addition, products from other manufacturers that conform to the limitations of this invention are also applicable.

[0059] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0060] Self-doping rate: The elemental composition and content of polyphenylene difuran diketone (PPD) were characterized using an Escalab 250Xi X-ray photoelectron spectroscopy (XPS) instrument. The tested elements were C and O. By analyzing the changes in chemical shifts of the O1s orbitals of characteristic elements (such as carbonyl groups) in PPD, which are related to doping, the characteristic peaks corresponding to "proton-treated carbonyl oxygen" and "non-proton-treated carbonyl oxygen" were distinguished. The self-doping rate was then calculated as (proton-treated carbonyl oxygen peak area / total carbonyl oxygen peak area) × 100%.

[0061] Conductivity: The conductivity was tested using an RTS-9 four-probe conductivity meter. The test was performed in parallel five times and the average value was taken.

[0062] Average infrared emissivity in the 8~14μm band: Based on Kirchhoff's law, for opaque materials, their infrared emissivity (ε) and infrared reflectivity (ρ) satisfy ε=1-ρ; the test uses a Nicolet IS50 infrared spectrometer equipped with an integrating sphere. First, the infrared reflectivity (ρ) of the sample in the 8~14μm band is measured, and then the emissivity ε(λ) of the corresponding wavelength (λ) in this band is calculated according to ε(λ)=1-ρ(λ) (λ is any wavelength in the 8~14μm range).

[0063] Average emissivity in the 8~14μm band ( ) is calculated using the following formula:

[0064] ;

[0065] ;

[0066] In the formula, λ is the wavelength in the range of 8~14μm; ε(λ) is the emissivity at wavelength λ; B(λ,T) is the spectral irradiance of a blackbody at wavelength λ and temperature T, where T is defined as 300K; c0 is the speed of light in vacuum (3×10⁻⁶). 8 m / s); h is Planck's constant (6.626 × 10⁻³). 4 J·s);k B It is the Boltzmann constant (1.381×10⁻²³ J / K).

[0067] Within a low voltage range of 0~4V, the radiation temperature can be adjusted by using a DC regulated adjustable power supply (MS-152D) to apply voltage to the sample while simultaneously recording the changes in the sample's radiation temperature using an infrared thermal imager (FLIR T540).

[0068] Example 1

[0069] A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material, the specific steps of which are as follows:

[0070] (1) Preparation of materials;

[0071] H-BFDO crystals;

[0072] Tetramethyl-1,4-benzoquinone;

[0073] Dimethyl sulfoxide;

[0074] Substrate: PI film, 0.025 mm thick;

[0075] Polydimethylsiloxane prepolymer, platinum catalyst; manufacturer: Dow Corning, brand name DC184;

[0076] Thermal insulation layer: Aramid nanofiber aerogel layer, 1 mm thick;

[0077] (2) Prepare a polyphenylene difuran diketone solution;

[0078] (a) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, the mixture was reacted at 105 °C for 60 min under the protection of nitrogen or an inert gas, and finally cooled to 35 °C to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 0.3 g:0.5 g, and the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide was 0.3 g:25 mL.

[0079] (b) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (b) to dimethyl sulfoxide added in step (a) is 1:1.

[0080] (c) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B;

[0081] (d) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 12 mg / mL;

[0082] (3) A polyphenylene difuran diketone coating is formed on the substrate layer;

[0083] The polyphenylene difuran diketone solution was coated onto the upper surface of the substrate using an automatic coating machine, and then vacuum dried at 60°C for 12 hours. During coating, the doctor blade speed was 0.5 cm / s, and the coating amount of polyphenylene difuran diketone solution was 0.175 mL / cm. 2 ;

[0084] (4) Connect the base layer to the insulation layer;

[0085] First, a polydimethylsiloxane prepolymer with a mass ratio of 10:1 is mixed evenly with a platinum catalyst and then applied to the lower surface of the substrate and the upper surface of the heat insulation layer. Then, the lower surface of the substrate and the upper surface of the heat insulation layer are bonded together and prepolymerized at 80℃ for 0.8h. Finally, it is heat-cured at 120℃ for 3h to obtain a low-emissivity polyphenylene difuran diketone composite infrared stealth material.

[0086] The final low-emissivity polyphenylene difuran diketone composite infrared stealth material consists of a polyphenylene difuran diketone coating, a substrate layer, and a heat insulation layer arranged from top to bottom. The thickness of the polyphenylene difuran diketone coating is 15 μm, and the self-doping rate of the polyphenylene difuran diketone is 86%.

[0087] The low-emissivity polyphenylene difurandiketone (PPD) composite infrared stealth material has an electrical conductivity of 1780 S / cm; its average infrared emissivity in the 8–14 μm band is 0.18; after being exposed to air for 3 months, the average infrared emissivity of the PPD composite infrared stealth material in the 8–14 μm band increased by 16%; and its radiation temperature can be adjusted from 24.8 to 121 °C within a low voltage range of 0–4 V. Figure 1 (As shown).

[0088] Comparative Example 1

[0089] The method for preparing an infrared stealth material differs from that in Example 1 in that:

[0090] Step (c) is as follows: First, place solution A in a dialysis bag with a molecular weight cutoff of 10 kDa, dialyze with dimethyl sulfoxide, collect and retain the dimethyl sulfoxide solution that can penetrate the dialysis membrane and enter the outside of the dialysis bag to obtain solution C, which contains polyphenylene difuran diketone with a molecular weight of less than 10 kDa; then place solution C in a dialysis bag with a molecular weight cutoff of 5 kDa, dialyze with dimethyl sulfoxide, collect and retain the solution inside the dialysis bag to obtain solution D; the molecular weight of polyphenylene difuran diketone in solution D is greater than 5 kDa and less than 10 kDa (the reason for being greater than 5 kDa is mainly to remove unreacted monomers and tetramethyl-1,4-benzoquinone).

[0091] Step (d) is as follows: filter the undissolved precipitate in solution D and rotary evaporate the filtered solution D to obtain a polyphenylene difuran diketone solution with a concentration of 12 mg / mL.

[0092] The final infrared stealth material has an electrical conductivity of 526 S / cm and an average infrared emissivity of 0.54 in the 8-14 μm band.

[0093] Compared with Example 1, the conductivity of the infrared stealth material decreased significantly, while the average infrared emissivity of the infrared stealth material in the 8-14 μm band increased significantly. This is because the molecular weight of polyphenylene difuran diketone in Comparative Example 1 is less than 10 kDa, which does not reach the critical performance threshold of ≥10 kDa. At this time, the number of chain ends accounts for a high proportion in the system, and the "end effect" is significant, which limits the delocalization degree and mobility of charge carriers. Moreover, it is difficult for short chains to form an ordered stack to build a three-dimensional conductive network. Charge carriers are easily bound inside their respective short chains, contributing little to the macroscopic conductivity, resulting in a decrease in infrared reflectivity. According to Kirchhoff's law (ε=1-ρ), the average infrared emissivity increases accordingly, so the infrared stealth performance of the material deteriorates.

[0094] Comparative Example 2

[0095] The method for preparing an infrared stealth material differs from Example 1 only in that: in step (a), the feeding ratio of H-BFDO crystal and tetramethyl-1,4-benzoquinone is changed (0.3g:0.4g), which results in a self-doping rate of 70% for polyphenylene difuran diketone in the final product.

[0096] The final infrared stealth material has an electrical conductivity of 833.3 S / cm and an average infrared emissivity of 0.29 in the 8-14 μm band.

[0097] Compared with Example 1, the conductivity of the infrared stealth material in Comparative Example 2 was significantly reduced, while the average infrared emissivity of the infrared stealth material in the 8-14 μm band was significantly increased. This is because the self-doping rate of polyphenylene difuran diketone in Comparative Example 2 was too low, which could not generate an ultra-high carrier concentration comparable to that of metals, making it difficult to form an "organic metal" state, resulting in a low infrared reflectivity. According to Kirchhoff's law, the average infrared emissivity increased accordingly. At the same time, the insufficient carrier concentration also reduced the conductivity of the material, thus affecting the infrared stealth performance.

[0098] Comparative Example 3

[0099] The method for preparing an infrared stealth material differs from Example 1 only in that: after step (4), step (5) is performed: the low emissivity polyphenylene difurandione composite infrared stealth material is soaked in a 10 mM ferric chloride acetonitrile solution for 12 h (to restore the low emissivity polyphenylene difurandione composite infrared stealth material to an electrically neutral state) to obtain the dedoped material, then washed with deionized water and dried, and then placed in a tetramethyl-1,4-benzoquinone dimethyl sulfoxide solution (the mass-volume ratio of tetramethyl-1,4-benzoquinone to dimethyl sulfoxide is 0.5 g: 25 mL) for 90 min to obtain the infrared stealth material.

[0100] The final infrared stealth material has an electrical conductivity of 3.704 S / cm; the average infrared emissivity of the infrared stealth material in the 8-14 μm band is 0.71; after being exposed to air for 3 months, the average infrared emissivity of the infrared stealth material in the 8-14 μm band increased by 26%.

[0101] Compared to Example 1, Comparative Example 3 showed a significant decrease in electrical conductivity and a significant increase in average infrared emissivity in the 8-14 μm band. The increase in emissivity was even greater after three months of exposure to air. This is because Comparative Example 3 employed an external doping method, requiring the dopant tetramethyl-1,4-benzoquinone to physically diffuse from the solution into the solid film. This process was severely limited by physical diffusion and steric hindrance, resulting in extremely low efficiency. Most of the dopant remained only on the film surface and could not reach the internal doping sites, leading to an overall carrier concentration far lower than that of the self-doped system in Example 1, failing to reach a level comparable to metals. Insufficient carrier concentration prevented the material from forming the "organometallic" state required for high infrared reflectivity, resulting in extremely low electrical conductivity. According to Kirchhoff's laws, infrared reflectivity decreased significantly, and emissivity increased significantly. Simultaneously, the external doping state lacked stability (dopant was easily lost), thus the increase in emissivity was even greater after three months of exposure to air, leading to a deterioration in overall infrared stealth performance.

[0102] Example 2

[0103] A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material, the specific steps of which are as follows:

[0104] (1) Preparation of materials;

[0105] H-BFDO crystals;

[0106] Tetramethyl-1,4-benzoquinone;

[0107] Dimethyl sulfoxide;

[0108] Base layer: PP film, 0.05mm thick;

[0109] Polydimethylsiloxane prepolymer, platinum catalyst; manufacturer: Dow Corning, brand name DC184;

[0110] Thermal insulation layer: Aramid nanofiber aerogel layer, 1.5mm thick;

[0111] (2) Prepare a polyphenylene difuran diketone solution;

[0112] (a) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, the mixture was reacted at 110 °C for 50 min under the protection of nitrogen or an inert gas. Finally, the mixture was cooled to 30 °C to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 1 g:1.35 g, and the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide was 1 g:100 mL.

[0113] (b) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (b) to dimethyl sulfoxide added in step (a) is 1.5:1.

[0114] (c) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B;

[0115] (d) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 8 mg / mL;

[0116] (3) A polyphenylene difuran diketone coating is formed on the substrate layer;

[0117] The polyphenylene difuran diketone solution was coated onto the upper surface of the substrate using an automated coating machine, and then vacuum dried at 60°C for 24 hours. During coating, the doctor blade speed was 1 cm / s, and the coating amount of polyphenylene difuran diketone solution was 0.125 mL / cm. 2 ;

[0118] (4) Connect the base layer to the insulation layer;

[0119] First, a polydimethylsiloxane prepolymer with a mass ratio of 10.5:1 is mixed evenly with a platinum catalyst and then coated onto the lower surface of the substrate and the upper surface of the heat insulation layer. Then, the lower surface of the substrate and the upper surface of the heat insulation layer are bonded together and prepolymerized at 70°C for 1 hour. Finally, the material is heat-cured at 115°C for 2.5 hours to obtain a low-emissivity polyphenylene difuran diketone composite infrared stealth material.

[0120] The final low-emissivity polyphenylene difuran diketone composite infrared stealth material consists of a polyphenylene difuran diketone coating, a substrate layer, and a heat insulation layer arranged from top to bottom. The thickness of the polyphenylene difuran diketone coating is 5 μm, and the self-doping rate of the polyphenylene difuran diketone is 83%.

[0121] The electrical conductivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 1650 S / cm; the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band is 0.2; after being exposed to air for 3 months, the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band increased by 17%; the radiation temperature adjustment range of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 25.1~115℃ in a low voltage range of 0~4V.

[0122] Example 3

[0123] A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material, the specific steps of which are as follows:

[0124] (1) Preparation of materials;

[0125] H-BFDO crystals;

[0126] Tetramethyl-1,4-benzoquinone;

[0127] Dimethyl sulfoxide;

[0128] Base layer: PET film, 1mm thick;

[0129] Polydimethylsiloxane prepolymer, platinum catalyst; manufacturer: Dow Corning, brand name DC184;

[0130] Thermal insulation layer: Aramid nanofiber aerogel layer, 2mm thick;

[0131] (2) Prepare a polyphenylene difuran diketone solution;

[0132] (a) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, the mixture was reacted at 80 °C for 150 min under the protection of nitrogen or an inert gas. Finally, the mixture was cooled to 32 °C to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 0.75 g:1 g, and the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide was 0.75 g:75 mL.

[0133] (b) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (b) to dimethyl sulfoxide added in step (a) is 2:1.

[0134] (c) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B;

[0135] (d) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 20 mg / mL;

[0136] (3) A polyphenylene difuran diketone coating is formed on the substrate layer;

[0137] The polyphenylene difuran diketone solution was coated onto the upper surface of the substrate using an automated coating machine, and then vacuum dried at 60°C for 18 hours. During coating, the doctor blade speed was 1.5 cm / s, and the coating amount of polyphenylene difuran diketone solution was 0.25 mL / cm. 2 ;

[0138] (4) Connect the base layer to the insulation layer;

[0139] First, a polydimethylsiloxane prepolymer with a mass ratio of 10.2:1 was mixed evenly with a platinum catalyst and then coated onto the lower surface of the substrate and the upper surface of the heat insulation layer. Then, the lower surface of the substrate and the upper surface of the heat insulation layer were bonded together and prepolymerized at 90℃ for 0.5h. Finally, the material was heat-cured at 118℃ for 2h to obtain a low-emissivity polyphenylene difuran diketone composite infrared stealth material.

[0140] The final low-emissivity polyphenylene difuran diketone composite infrared stealth material consists of a polyphenylene difuran diketone coating, a substrate layer, and a heat insulation layer arranged from top to bottom. The thickness of the polyphenylene difuran diketone coating is 30 μm, and the self-doping rate of the polyphenylene difuran diketone is 84%.

[0141] The electrical conductivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 1667 S / cm; the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band is 0.19; after being exposed to air for 3 months, the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band increased by 19%; the radiation temperature adjustment range of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 26.5~121℃ in a low voltage range of 0~4V.

[0142] Example 4

[0143] A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material, the specific steps of which are as follows:

[0144] (1) Preparation of materials;

[0145] H-BFDO crystals;

[0146] Tetramethyl-1,4-benzoquinone;

[0147] Dimethyl sulfoxide;

[0148] Base layer: Nylon 66 fabric, 0.2mm thick;

[0149] Polydimethylsiloxane prepolymer, platinum catalyst: manufacturer Dow Corning, brand name DC184;

[0150] Thermal insulation layer: Aramid nanofiber aerogel layer, 1.5mm thick;

[0151] (2) Prepare a polyphenylene difuran diketone solution;

[0152] (a) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, the mixture was reacted at 100°C for 90 min under the protection of nitrogen or an inert gas. Finally, the mixture was cooled to 33°C to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 1 g:1.5 g, and the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide was 1 g:75 mL.

[0153] (b) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (b) to dimethyl sulfoxide added in step (a) is 1.8:1.

[0154] (c) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B;

[0155] (d) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 10 mg / mL;

[0156] (3) A polyphenylene difuran diketone coating is formed on the substrate layer;

[0157] The polyphenylene difuran diketone solution was coated onto the upper surface of the substrate using an automated coating machine, and then vacuum dried at 60°C for 16 hours. During coating, the doctor blade speed was 2 cm / s, and the coating amount of polyphenylene difuran diketone solution was 0.2 mL / cm. 2 ;

[0158] (4) Connect the base layer to the insulation layer;

[0159] First, a polydimethylsiloxane prepolymer with a mass ratio of 10.3:1 was mixed evenly with a platinum catalyst and then coated onto the lower surface of the substrate and the upper surface of the insulation layer. Then, the lower surface of the substrate and the upper surface of the insulation layer were bonded together and prepolymerized at 80℃ for 0.75h. Finally, the mixture was heat-cured at 116℃ for 3h to obtain a low-emissivity polyphenylene difuran diketone composite infrared stealth material.

[0160] The final low-emissivity polyphenylene difuran diketone composite infrared stealth material consists of a polyphenylene difuran diketone coating, a substrate layer, and a heat insulation layer arranged sequentially from top to bottom. The thickness of the polyphenylene difuran diketone coating is 12.5 μm, and the self-doping rate of the polyphenylene difuran diketone is 86%.

[0161] The electrical conductivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 1782 S / cm; the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band is 0.18; after being exposed to air for 3 months, the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8~14μm band increased by 16%; the radiation temperature adjustment range of the low-emissivity polyphenylene difurandiketone composite infrared stealth material is 25.1~124℃ in a low voltage range of 0~4V.

[0162] Example 5

[0163] A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material, the specific steps of which are as follows:

[0164] (1) Preparation of materials;

[0165] H-BFDO crystals;

[0166] Tetramethyl-1,4-benzoquinone;

[0167] Dimethyl sulfoxide;

[0168] Base layer: Nylon 66 fabric, 1mm thick;

[0169] Polydimethylsiloxane prepolymer, platinum catalyst: manufacturer Dow Corning, brand name DC184;

[0170] Thermal insulation layer: Aramid nanofiber aerogel layer, 1 mm thick;

[0171] (2) Prepare a polyphenylene difuran diketone solution;

[0172] (a) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone were dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, the mixture was reacted at 120°C for 40 min under the protection of nitrogen or an inert gas, and finally cooled to 34°C to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone was 0.6 g:0.8 g, and the mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide was 0.6 g:100 mL.

[0173] (b) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (b) to dimethyl sulfoxide added in step (a) is 1.6:1.

[0174] (c) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B;

[0175] (d) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 15 mg / mL;

[0176] (3) A polyphenylene difuran diketone coating is formed on the substrate layer;

[0177] The polyphenylene difuran diketone solution was coated onto the upper surface of the substrate using an automated coating machine, and then vacuum dried at 60°C for 14 hours. During coating, the doctor blade speed was 3 cm / s, and the coating amount of polyphenylene difuran diketone solution was 0.22 mL / cm. 2 ;

[0178] (4) Connect the base layer to the insulation layer;

[0179] First, a polydimethylsiloxane prepolymer with a mass ratio of 10:1 is mixed evenly with a platinum catalyst and then coated onto the lower surface of the substrate and the upper surface of the heat insulation layer. Then, the lower surface of the substrate and the upper surface of the heat insulation layer are bonded together and prepolymerized at 75°C for 1 hour. Finally, the material is heat-cured at 120°C for 2.5 hours to obtain a low-emissivity polyphenylene difuran diketone composite infrared stealth material.

[0180] The final low-emissivity polyphenylene difuran diketone composite infrared stealth material consists of a polyphenylene difuran diketone coating, a substrate layer, and a heat insulation layer arranged from top to bottom. The thickness of the polyphenylene difuran diketone coating is 20 μm, and the self-doping rate of the polyphenylene difuran diketone is 81%.

[0181] The low-emissivity polyphenylene difurandiketone composite infrared stealth material has an electrical conductivity of 1580 S / cm; its average infrared emissivity in the 8-14 μm band is 0.21; after being exposed to air for 3 months, the average infrared emissivity of the low-emissivity polyphenylene difurandiketone composite infrared stealth material in the 8-14 μm band increased by 20%; and its radiation temperature can be adjusted from 28.7 to 109 °C in a low voltage range of 0-4 V.

Claims

1. A low-emissivity polyphenylene difuran diketone composite infrared stealth material, characterized in that, This includes the adjacent polyphenylene difuran diketone coating and the substrate layer; Polyphenylene difuran diketone has a molecular weight ≥10kDa and a self-doping rate ≥81%. The self-doping rate refers to the percentage of carbonyl oxygen atoms in the total number of carbonyl oxygen atoms that interact with carbonyl oxygen as a balance charge during the molecular-level self-doping process of polyphenylene difuran diketone, resulting in a change in its chemical state.

2. The low emissivity polyphenylene difuran diketone composite infrared stealth material according to claim 1, characterized in that, The thickness of the polyphenylene difuran diketone coating is 5~30μm; The base layer is a PET film, PI film, or PP film, with a thickness of 0.025~1mm; or, the base layer is nylon 66 fabric with a thickness of 0.2~1mm.

3. The low emissivity polyphenylene difuran diketone composite infrared stealth material according to claim 2, characterized in that, The low-emissivity polyphenylene difuran diketone composite infrared stealth material has an electrical conductivity of 1500~1800 S / cm; its average infrared emissivity in the 8~14μm band is 0.18~0.21, and after being exposed to air for 3 months, the average infrared emissivity in the 8~14μm band increases by 16%~20%; and its radiation temperature can be adjusted from 24.8~121℃ in a low voltage range of 0~4V.

4. The low emissivity polyphenylene difuran diketone composite infrared stealth material according to claim 3, characterized in that, It also includes a heat insulation layer; the polyphenylene difuran diketone coating, the base layer and the heat insulation layer are arranged in sequence.

5. The low emissivity polyphenylene difuran diketone composite infrared stealth material according to claim 4, characterized in that, The base layer and the insulation layer are physically connected by polydimethylsiloxane; the insulation layer is an aramid nanofiber aerogel layer with a thickness of 1~2mm.

6. A method for preparing a low-emissivity polyphenylene difuran diketone composite infrared stealth material as described in any one of claims 1 to 5, characterized in that, After coating the upper surface of the substrate with a polyphenylene difuran diketone solution, the solvent is removed by drying. Then, the lower surface of the substrate and the upper surface of the heat insulation layer are connected to obtain a low emissivity polyphenylene difuran diketone composite infrared stealth material. The polyphenylene difuran diketone has a molecular weight ≥10kDa and a self-doping rate ≥81%.

7. The method according to claim 6, characterized in that, The specific steps for preparing the polyphenylene difuran diketone solution are as follows: (1) First, H-BFDO crystals and tetramethyl-1,4-benzoquinone are dissolved in dimethyl sulfoxide to obtain a reaction mixture. Then, under the protection of nitrogen or an inert gas, the mixture is reacted at 80~120℃ for 40~150 min. Finally, the mixture is cooled to 30~35℃ to obtain product A. The mass ratio of H-BFDO crystals to tetramethyl-1,4-benzoquinone is 0.3~1g:0.5~1.5g. The mass-volume ratio of H-BFDO crystals to dimethyl sulfoxide in step (1) is 0.3~1g:25~100mL. (2) Add dimethyl sulfoxide to product A and ultrasonically pulverize it to obtain diluted solution A; wherein the volume ratio of dimethyl sulfoxide added in step (2) to dimethyl sulfoxide in step (1) is 1:1 to 2:

1. (3) Add solution A to a dialysis bag with a molecular weight cutoff of 10 kDa and dialyze it with dimethyl sulfoxide to obtain solution B; (4) Filter the undissolved precipitate in solution B and rotary evaporate the filtered solution B to obtain a polyphenylene difuran diketone solution with a concentration of 8~20 mg / mL.

8. The method according to claim 7, characterized in that, The doctor blade speed during coating is 0.5~3 cm / s, and the coating amount of polyphenylene difuran diketone solution is 0.125~0.25 mL / cm. 2 .

9. The method according to claim 6, characterized in that, The specific process of connecting the lower surface of the base layer and the upper surface of the insulation layer is as follows: First, a polydimethylsiloxane prepolymer with a mass ratio of 10~10.5:1 is mixed evenly with a platinum catalyst and then applied to the lower surface of the base layer and the upper surface of the insulation layer. Then, the lower surface of the base layer and the upper surface of the insulation layer are bonded together and prepolymerized at 70~90℃ for 0.5h~1h. Finally, the mixture is heat-cured at 115~120℃ for 2~3h.

Images