Significantly Enhanced Porosity of Silicone Rubber Nanocomposite Foams via Cross-Linking Structure Regulation and Heterogeneous Nucleation by CNTs for Promising Ultralow-k Dielectrics

Ultralow-k materials with excellent thermal stability and good electrical insulation are urgently required taking into consideration the rapid development of 5G communication systems. Increasing the porosity of materials is the most effective way to reduce their dielectric constant. On this basis, with the help of cross-linking structure regulation and heterogeneous nucleation of CNTs, a polymethyl-vinyl siloxane (PMVS)/CNT foam with porosity up to 93.9% (density, 0.069 g/cm3) was fabricated via supercritical CO2 foaming. Therefore, promising dielectric properties were observed for the PMVS/CNT foam (0.5 wt % CNTs) with an ultralow dielectric constant (k = 1.52) and a low loss (tan δ = 0.0017) at 1 kHz. Additionally, the PMVS/CNT foams exhibited improved insulativity (RV > 1014 Ω·cm), prominent thermal stability (T5 > 444 °C), and good mechanical properties. These excellent PMVS/CNT foams afford a promising ultralow-k dielectric for modern integrated circuit development.