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With the rapid advances in detection technologies for modern warfare, it is of great significance to develop advanced infrared stealth technology. Owing to the complex operational environment of weapons and equipment during the practical application, a high thermal resistance is significant for infrared stealth materials. Therefore, in this study, a high-temperature coating with low infrared emissivity was developed via spraying of poly(phthalazinone ether nitrile ketone) (PPENK) resin as binder and flake aluminum powder as filler. The variation in infrared emissivity of the composite coating with respect to filler content was studied. Apart from the thermal resistance of the composite coating, the effects of temperature on the surface morphology, chemical composition, mechanical properties, and infrared emissivity of the composite coatings were systematically examined. The lowest infrared emissivity (0.136) was achieved with 40% filler. Even after being heated at 450[degrees] C for 1 h, the composite coating exhibited excellent adhesion and impact resistance with negligible increase in emissivity, exemplifying its robust performance. The PPENK/Al composite coating can be engineered on a large scale, thanks to the simple preparation route and, has great potential as a new material for high- temperature infrared stealth application. KEYWORDS high temperature resistance, infrared stealth, low infrared emissivity coating, poly (phthalazinone ether nitrile ketone), 1 | INTRODUCTION With rapidly evolving modern detection technologies, it is crucial to improve infrared stealth technology as an anti-detection method to increase the survivability and combat effectiveness of the [...]

With the rapid advancements of communication technology, developing multifunctional thermally conductive materials is crucial to addressing future heat management challenges. In this study, highly thermally conductive PPENK/PVP modified BN (PPENK/MBN) multilayer nanocomposite films inspired by wafer biscuits were constructed through a simple and efficient strategy. Verified by X-ray microscopy (XRM), the designed wafer biscuit-like structure provided abundant internal heat conduction pathways. As a result, the PPENK/MBN nanocomposite films with 39.2 wt% MBN content exhibited in-plane and out-of-plane thermal conductivities of 9.66 W m−1 K−1 and 1.13 W m−1 K−1, respectively, as well as excellent dielectric properties with a dielectric constant of 3.51 and a dielectric loss value as low as 0.010@15 GHz. Furthermore, the composites demonstrated a high thermal decomposition temperature of 511.3 °C. This study lays a foundation for the preparation of high thermal conductivity nanocomposites and provides possible applications in thermal management. [ABSTRACT FROM AUTHOR]

For large‐area electronic and high shape complexity structure applications, various solution‐processable materials are chosen as dielectric layer due to their simple molding process via spin‐coating, casting, or 3D printing at room temperature. Herein, the acrylic‐ended fluorinated hyperbranched polyaryletherketone (hb‐P6FAEK‐Ace) was used as the prepolymer and then, the composition of photosensitive resin formula was regulated by adjusting the addition ratio of hb‐P6FAEK‐Ace and diluents (acrylimorpholine [ACMO] 1,6‐Hexanediol diacrylate [HDDA]). These photosensitive resin solutions showed the relative low viscosities ranged ranging from 18 to 253 mPa S at 100°C which was in favor of the future 3D printing method and printing accuracy. Then, the obtained UV‐cured films show the maximum tensile strength up to 71.9 MPa and superior thermal properties with the Tg of 157°C–177°C and T5% of 314°C–351°C. Moreover, they also exhibited the good dielectric performance with dielectric constants of 2.43–2.20 and dielectric loss of 0.013–0.014 at 1 MHz–1 GHz. These abovementioned satisfactory performance could be ascribed to the aromatic skeleton of hb‐P6FAEK‐Ace, introduced polarizability‐CF3 groups and the inner cavities for the hyperbranched structures, also the precise control of formula composition. Additionally, the curing degree, shrinkage of solid, and moisture properties were also researched thoroughly. This work provides a simple formula design though to construct the high performance and low dielectric photosensitive resin for the requirements of microelectronic applications. [ABSTRACT FROM AUTHOR]

Advanced flexible display materials have drastically sparked considerable interest for heat‐resistant, low dielectric, and transparent polyimide (PI) materials. In light of this, our study aims to develop high‐performance semi‐aromatic PI films, followed by investigate the correlations between bridged‐alkyl/heteroaromatic ring structures and their thermal, dielectric, optical, and mechanical properties. Such PI films, namely AP‐PIs, were synthesized with a one‐step high‐temperature method between 4‐[4‐(4‐aminophenoxy) phenyl]‐2‐(4‐aminophenyl)‐1(2H)‐phthalazinone (DHPZDA) and various commercial alicyclic dianhydrides. The incorporation of rigid phthalazinone structures significantly enhanced thermal resistance and mechanical flexibility, while simultaneously reducing their dielectric constant (Dk), attributed to the large polymer internal free volume. Impressively, the prepared films exhibit exceptional glass transition temperature (Tg) as high as 419°C (DMTA tanδ peak), low Dk as low as 2.71, and elongation at break (ε %) up to 50.4%. Furthermore, AP‐PI films demonstrate reasonable solubility and optical transparency within the UV–visible region. The maximum optical transmittance at 550 nm (T550 nm) could reach 83.01%. These desirable properties position these materials as promising candidates for flexible substrate applications. [ABSTRACT FROM AUTHOR]

Limiting molecules' polarized motion effectively reduces the dielectric loss of materials. This article synthesized side chains with different lengths using p‐ethoxyphenol, p‐hydroxybenzoic acid, and long‐chain halohydrins through a two‐step process. These chains' movement was almost unaffected by the main chain of polymers, so they can fill up the free volume of polymers under certain conditions. 1,2‐dihydro‐4‐(4‐hydroxyphenyl)phthalazine‐1‐(2H)‐one(DHPZ), 4,4'‐Difluorophenyl sulfone(DFS), and 4,4‐Bis(4‐hydroxyphenyl) valeric acid(HPV) obtained three polymers with different carboxyl groups (10%, 30%, and 50%) through nucleophilic substitution. They were then grafted and treated with hot‐pressing. The introduction of side chains could reduce the free volume of polymers under hot‐pressing conditions, so further reducing the dielectric loss of materials. Polymer with the shortest and least (10%) side chains showed the most obvious dielectric loss tangent, the reduction rate of the film's dielectric loss tangent was 13.11% (at Tg + 15°C, while the non‐grafted one was only 3.69%) and 20.70% (at Tg + 80°C, while the non‐grafted one was only 8.35%), respectively. In addition, WXRD and DMA tests showed that films' intermolecular chain spacing ("d") and Tg changed after the hot‐pressing process, respectively. The change law of both was consistent with that of dielectric loss tangent. Confirm that grafting high‐motility side chains can significantly reduce polymer's dielectric loss by enhancing the free volume reduction effect after hot‐pressing. [ABSTRACT FROM AUTHOR]

Nearly infinite chemical space and the absence of well-established structure–property relationships have considerably challenged the purposeful design of copolymers for specific applications. To address these issues, a data-driven method called a polymer genome approach was proposed for rational design of linear random copolymers and implemented for developing poly(aryl ether)s (PAEs) with high glass transition temperature (Tg). By means of the polymer genome approach, machine learning (ML) models with high predictive accuracies and generalization abilities were established, favourable and unfavourable genes of PAEs (i.e., molecular fragments and physicochemical descriptors) for high Tg were unearthed, and consequently molecular design strategies and mechanistic insights for developing high-Tg PAEs were presented. Experimental synthesis work further verified that the Tg of new PAEs which were designed following the proposed design strategies could reach 328 °C, standing in the top 1% of the current database containing 2794 PAEs, and the constructed ML models could precisely forecast the Tg of new PAEs prior to synthesis, simply based on chemical structures of monomers and feed ratios. The proposed polymer genome approach opens a high-efficiency and low-cost avenue for accelerating the development of advanced PAEs and is supposed to be scalable to optimize versatile properties of other genres of linear random copolymers. [ABSTRACT FROM AUTHOR]