Fluorine-Containing Polyether Ketones Based on Fluorene Side Groups with Low Dielectric Constants and Excellent Thermal Performance

The rapid advancement of high-frequency communication networks has imposed more rigorous demands on the overall characteristics of dielectric materials. Poly(aryl ether ketone)s (PAEKs) are good candidate materials for applications in microelectronic devices due to their excellent thermal stability, mechanical properties, and chemical stability. In this work, we endeavored to incorporate large-volume fluorene structures into fluoro-PAEKs, employing strategies to enhance the polymer free volume and reduce polarizations in order to decrease the values of Dk and Df at high frequency. Therefore, a series of poly(ether ketone) (PEK-pOCFBPF-X) copolymers were designed and synthesized through nucleophilic polymerization using 4,4-difluorobenzophenone (DFK), phenolphthalein anilide-containing trifluoromethoxy groups (PPPBP-pOCF3), and a structurally ordered bisphenol fluorene (BPF) as the monomers. The results demonstrate that the introduction of BPF into fluoro-PAEKs resin leads to a low dielectric constant (2.713–2.782@10 GHz) and dielectric loss (0.00597–0.00825@10 GHz), as well as exceptional thermal properties (Tg = 232–240 °C, Td5% = 518–536 °C). Moreover, the copolymer exhibits high mechanical strength (tensile strength ≥ 81 MPa), minimal water absorption (≤0.0063), and excellent solubility. The incorporation of trifluoromethoxy and fluorenyl groups into copolymers significantly enhances the free volume fraction (5.5%–5.8%), resulting in a lower density and reduction in the dielectric constant. Simultaneously, by introducing C–F bonds with lower polarizability, the overall polarizability of the polymer is effectively diminished. These fluoro-PAEKs films, which exhibit superior thermal stability and a low dielectric constant, have great potential for applications in the high-performance flexible electronic packaging field and communication usage.