At present, high-performance liquid crystalline polyesters with a good processability, low dielectric constant, and low dielectric loss at a high frequency (GHz) are in high demand ascribed to the rapid development of high-speed communication technology. Here, an imide dicarboxylic acid (IA) with a bulky phenyl side group is designed and synthesized. It is then copolymerized with 4-hydroxybenzoic acid (HBA), isophthalic acid (IPA), 4,4′-dihydroxybipheny (BP), and 4,4′-dihydroxydiphenyl ether (ODP) via solution polycondensation to obtain liquid crystalline poly­(ester imide)­s (LCPEIs). By controlling the feeding ratio of IA, the solubility, thermal stability, mechanical properties, and dielectric properties of the LCPEIs are tunable. When the molar fraction of IA reaches or exceeds 5%, the obtained LCPEIs are soluble in ordinary organic solvents, such as chloroform, N,N-dimethylformamide, N-methyl-2-pyrrolidinone, and so forth, which allows a simple solution casting to prepare isotropic LC films. The nematic LCPEIs show high glass transition temperatures (T g > 200 °C) but relatively low melting temperatures and isotropization temperatures (T m and T i, <340 °C). The LCPEI prepared with 10 mol % IA shows excellent combined properties, whose ηinh, M n (GPC), T g, T m, T i, T d 5%, tensile strength, tensile modulus, water uptake, dielectric constant, and dielectric loss (at 10 GHz) are 0.92 dL g–1, 20,900 g mol–1, 218 °C, 268 °C, 330 °C, 458 °C, 80.5 MPa, 4.0 GPa, 0.39%, 3.07, and 0.006, respectively. These LCPEIs can be promising candidates for flexible copper-clad laminate substrates.

With the rapid advancement of 5G communication technology, much attention has been paid on high-performance polymers with a low dielectric constant (D k), a low dielectric loss (D f) and good processability. In order to further research and improve dielectric properties of the liquid crystalline poly(ester imide)s (LCPEIs), four imide dicarboxylic acids (IAs) with fluorinated groups are designed and synthesized. They are then copolymerized with 1,3-phthalic acid (IPA), p-hydroxybenzoic acid (HBA), and bisphenol monomers via solution polycondensation to obtain fluorinated PEIs, whose fluorine content, position of the fluorinated group, and LC behavior are tunable by using different IAs and bisphenol monomers. These PEIs with the highest T g of 238 °C are soluble in general organic solvents, such as m-cresol, N-methyl-2-pyrrolidone (NMP), chloroform, and so on. PEI-6F25AF exhibits the lowest D k of 2.60, while LCPEI-6FD shows the lowest D f of 0.0053 at 10 GHz. It is found that high fluorine content and large pendent group can reduce the D k, while the fluorinated group grafted close to the nitrogen atom and the LC rigid rod-like conformation lead to low D f. We devoutly expect that this research offers some reference for structure design of LCPEIs with both low D k and D f at high frequency.

Lithium metal batteries with polyethylene oxide (PEO) electrolytes are considered as one of the ideal candidates for next generation power sources. However, the low ambient operation capability and conventional solvent‐based fabrication process of PEO limit their large‐scale application. In this work, a comb‐like quasi‐solid polymer electrolyte (QPE) reinforced with polyethylene glycol terephthalate nonwoven is fabricated. Combining the density functional theory calculation analysis and polymer structure design, optimized and synergized ion conductive channels are established by copolymerization of tetrahydrofurfuryl acrylate and introduction of plasticizer tetramethyl urea. Additionally, a unique two‐stage solventless UV polymerization strategy is utilized for rheology tuning and electrolyte fabrication. Compared with the conventional one‐step UV process, this strategy is ideally suited for the roll‐to‐roll continuous coating fabrication process with environmental friendliness. The fabricated QPE exhibits high ionic conductivity of 0.40 mS cm−1 and Li+ transference number (t = 0.77) at room temperature. LiFePO4//Li batteries are assembled to evaluate battery performance, which deliver excellent discharge capacity (144.9 mAh g−1 at 0.5 C) and cycling stability (with the retention rate 94.5% at 0.5 C after 200 cycles) at room temperature. The results demonstrate that it has high potential for solid‐state lithium metal batteries.

Hitherto, it remains a great challenge to stabilize the electrolyte–electrode interfaces and impede lithium dendrite proliferation in lithium metal batteries with high‐capacity nickel‐rich LiNxCoyMn1‐x‐yO2 (NCM) layer cathodes. Herein, a special molecular‐level designed polymer electrolyte is prepared by the copolymerization of hexafluorobutyl acrylate and methylene bisacrylamide to construct dual‐reinforced stable interfaces. Verified by X‐ray photoelectron spectroscopy depth profiling, there are favorable solid electrolyte interphase (SEI) layers on Li metal anodes and robust cathode electrolyte interphase (CEI) on Ni‐rich cathodes. The SEI enriched in lithiophilic N‐(C)3 guides the homogenous distribution of Li+ and facilitates the transport of Li+ through LiF and Li3N, promoting uniform Li+ plating and stripping. Moreover, the CEI with antioxidative amide groups could suppress the parasitic reactions between cathode and electrolyte and the structural degradation of cathode. Meanwhile, a unique two‐stage rheology‐tuning UV polymerization strategy is utilized, which is quite suited for continuous electrolyte fabrication with environmental friendliness. The fabricated polymer electrolyte exhibits a high ionic conductivity of 1.01 mS cm−1 at room temperature. 4.5 V NCM622//Li batteries achieve prolonged operation with a retention rate of 85.0% after 500 cycles at 0.5 C. This work provides new insights into molecular design and processibility design for polymer‐based high‐voltage batteries.This article is protected by copyright. All rights reserved

Polyhedral oligomeric silsesquioxane (POSS) is commonly used to lower the dielectric constant of polyimide (PI), but the toughness generally deteriorates.In this paper, trifluoropropyl POSS (FPOSS) is surprisingly found to impart superior dielectric constant and toughness to PI, even though the phase separation and aggregation of FPOSS are observed due to the thermodynamical immiscibility between FPOSS and PI. The dielectric constant of FPOSS/PI with 2.0 wt% FPOSS is reduced to 2.47 from 3.17. Furthermore, the tensile energy to break of FPOSS/PI is unexpectedly increased to 10.2 MJ/m 3 from 3.3 MJ/m 3 , indicating the great improvement in toughness. The toughening mechanism is ascribed to the debonding of FPOSS aggregates from PI matrix with a void growth during tensile test. Meanwhile, lateral coalescence of the voids is avoided due to the adequate inter-aggregate distance when the width of the ligaments between the aggregates decreases with elongation of matrix.