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Inspired by the molecular architecture of liquid-crystalline polyester resins that exhibit inherently low dielectric loss at high frequency, we incorporated ester moieties and fluorinated substituents for reducing dielectric constant, into polyimide backbones to develop polyimides with good processability, high mechanical performance, and low-dielectric characteristics. Firstly, effect of the number of ester linkages per repeat unit, their connection topology, and their chemical identity (phenyl vs. naphthyl esters) on the dielectric properties, mechanical properties, thermal properties, and water absorption of polyimides were systematically explored. On this basis, -CF3 pendent groups were subsequently introduced into ester-containing diamines to evaluate their influence on the dielectric, mechanical, and thermal properties of the resulting polyester-imides. The results demonstrate that the rigid and linear topology of ester-bearing monomers enhances the chain packing and crystallinity of polyimides, leading to a substantial reduction in dielectric loss of polyimides together with low water absorption, high tensile strength and excellent thermal properties. Concurrently, the incorporation of trifluoromethyl substituents does not disrupt the dense chain packing and crystallinity of polyester-imide chains, thereby preserving the low dielectric loss, low water absorption and high thermal properties of polyester-imides while further reducing the dielectric constant and improving mechanical robustness. These findings can provide theoretical guidance for the molecular design of high-performance polyimides with low dielectric constant and low dielectric loss for high-frequency applications.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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