Low reflective index, highly transparent, and ultra-low dielectric constant materials prepared via effective copolymerization of 4-methyl-1-pentene and a Si-containing α,ω-diolefin†

Manufacturing composites with low-dielectric constants is essential for the development of communication-related technologies. Here, we present a simple method for preparing a series of novel ultra-low dielectric constant materials with tunable properties. These polycarbosilane-based polymers with excellent properties were prepared via the copolymerization of 4-methyl-1-pentene with 3,3-dimethyl-3-silane-1,5-hexadiene using a dimethyl(pyridylamido) hafnium/[Ph₃C][B(C₆F₅)₄]/AlⁱBu₃ catalytic system. The resulting thin film samples, without porosity, showed excellent dielectric properties, maintaining stable and ultra-low dielectric constants below 2.0 (at 25 °C, 1 MHz). As the incorporation of DSH into the copolymers increased, the dielectric constant gradually decreased to 1.98. In addition, the introduction of C–Si-containing cyclic units allowed for easy tuning of the copolymers’ glass transition temperature, and tensile properties. The introduction of C–Si bonds provides a simple and generally feasible strategy for developing new materials with low dielectric constants at high frequencies.