Perfluorocyclobutyl aryl ether-based poly(silylene arylacetylene)s with a low dielectric constant for advanced wave-transparent composites

• Published in: European polymer journal 2022-12, Vol.181, p.111655, Article 111655
• Main Authors: Gong, Changjun, Huang, Xiaohan, Li, Jixian, Lv, Shuaikang, Zhou, Yan, Tang, Junkun, Huang, Farong
• Format: Article
• Language: English
• Subjects: Aerospace industry; Aromatic compounds; Composite materials; Crosslinking; Crosslinking polymerization; Decomposition reactions; Dielectric loss; Dielectric properties; Dielectrics; Flexural strength; Fluoropolymer; Frequency ranges; Functional polymer composite; Glass transition temperature; Low temperature; Mechanical properties; Permittivity; Poly(silylene arylacetylene); Positron annihilation; Temperature; Thermal decomposition; Thermal stability; Wave-transparent material
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2022.111655

[Display omitted] •The introduction of perfluorocyclobutyl (PFCB) unit reduces the dielectric constant of cured PSFCBs.•Large pendant phenyl units extend the free volume of the cured PSFCB-P.•Flexible ether linkages greatly improve the mechanical properties of the cured PSFCB-P. A high-performance matrix with good mechanical properties, low dielectric constant as well as high thermal stability for advanced composites is in demand for the aerospace industry. In this study, novel perfluorocyclobutyl aryl ether-based poly(silylene arylacetylene)s (PSFCBs) were synthesized, which can be converted to amorphous crosslinked networks via thermal crosslinking reactions at a low temperature. The thermal decomposition temperature at 5 wt% loss (Td5) of cured PSFCBs is around 440 °C and there is no glass transition temperature (Tg) below 380 °C. Among them, the cured PSFCB-P with the phenylmethylsilylene structure displays the optimal comprehensive performance. Dielectric constant (ε) and dielectric loss (tanδ) are respectively 2.45 and 1.5 × 10-3 at 30 MHz, and the theoretical transmittance |T|2 arrives at 95.1 %. The flexural strength of the cured PSFCB-P reaches 52.5 MPa. Quartz fiber cloth/PSFCB-P composites show good dielectric properties (ε of 3.22) in the high-frequency range (7 GHz to 17 GHz) and high mechanical properties (flexural strength of 324.5 MPa, ILSS of 30.5 MPa). Positron annihilation lifetime spectroscopy (PALS) indicates that the cured PSFCB-P has a high free volume beneficial to the decrease of the ε.