Poly(silylene arylacetylene)s containing hexafluoroisopropylidene with attractive mechanical properties and dielectric performance for wave-transparent composites†

High mechanical properties and excellent dielectric properties are important research subjects for the application of heat-resistant poly(silylene arylacetylene)s(PSAs) in advanced wave-transparent composites. Herein, three novel poly(silylene arylacetylene)s containing the hexafluoroisopropylidene structure were synthesized by Grignard reactions. The effects of aryl ether units and –CF₃ groups on the mechanical properties, dielectric properties, and thermal stability of the cured PSA resins have been investigated. The PSA resins exhibit good solubility, processability, and high thermal stability with the temperature at 5% weight loss (T_d5) above 478 °C. Due to the introduction of flexible aryl ether units, the flexural strength of the resins arrives at over 75.1 MPa. Due to the large free volume and electronic effect of –CF₃ groups, the dielectric properties of the cured PSA resins are largely improved. The dielectric constant (ε) and dielectric loss (tan δ) reach as low as 2.53 and 2.13 × 10⁻³ at 30 MHz, respectively. Finally, quartz fiber-reinforced wave-transparent composites are prepared. The composites exhibit good mechanical properties, with the highest flexural strength and interlaminar shear strength (ILSS) reaching 395 MPa and 32.0 MPa, respectively. Meanwhile, the ε and tan δ values of the composites are below 3.26 and 3.84 × 10⁻³ in the range of 7–17 GHz, respectively, and the wave transmittances (|T|²) are higher than 91%.