Preparation of ultra-low dielectric constant silica/polyimide nanofiber membranes by electrospinning

Ultra-low dielectric constant silica/polyimide (SiO2/PI) composite nanofiber membranes are prepared by the combined sol–gel and electrospinning techniques. The emulsion composed of partially hydrolyzed tetraethoxysilane (TEOS) and polyamic acid (PAA) is spun to yield the precursor of the SiO2/PI fibers with a core–shell structure due to phase separation. The dielectric constant (k) of the composite membranes varies from 1.78 to 1.32 with increasing content of SiO2. The fibers accumulate and form the film with a large amount of pores leading the lower k. In addition, the interfacial reaction between SiO2 and the PI matrix reduces the value of k as the SiO2 concentration is increased. The thermal stability of PI increase after mixing with SiO2 and the SiO2/PI composite fibers have large commercial potential in the electronics industry.