Molecular interface anchoring in PI-b-PDMS/SiO₂@BN block copolymer foams for flexible, ultra-low dielectric, and enhanced terahertz communication performance

In the context of the future sixth-generation (6G) communication system, the development of multi-functional materials with ultra-low dielectric permittivity (D_k) and ultra-low dielectric loss (D_f) is of paramount importance for the design of terahertz (THz) frequency electromagnetic wave transmission devices. In this work, polyimide-block-polydimethylsiloxane (PI-b-PDMS copolymer, PIC) material with low D_k, high flexibility and high supercritical fluid foaming ability was fabricated via copolymerization. Additionally, core–shell SiO₂@BN nanofillers were synthesized by condensing tetraethyl orthosilicate (TEOS) on hexagonal boron nitride (BN) nanofiller surface. Subsequently, flexible polyimide/SiO₂@BN foam was fabricated via supercritical N₂ foaming. The resulting PIC/SiO₂@BN nanocomposites exhibit exceptional flexibility and impressive thermal resistance (thermal decomposition temperature 472.2 °C). Notably, the incorporation of core–shell SiO₂@BN nanofillers leads to the formation of a molecular interface anchoring structure through hydrogen bonding effect. This structure effectively reduced the mobility of the flexible PIC polymer chains on the SiO₂@BN nanofiller surfaces. Consequently, the porous PIC/SiO₂@BN materials show a low shrinkage ratio, low dielectric property (D_k = 1.21, D_f = 0.012 at 1 THz), excellent THz transmission rate (91.4 %) and long distance 6G THz signal coverage (125.99 m). Furthermore, porous PIC/SiO₂@BN materials show superior flame-retardant and thermal infrared stealth properties.