A novel pore-free strategy via interfacial effects in nanocomposites to produce polyethylene with ultra-low dielectric constants

Materials with an ultra-low dielectric constant (epsilon) have been the topic of much interest because they are widely used in integrated circuits and high frequency devices. Pores (epsilon = 1) have been generally introduced in materials to reduce their epsilon to below 2. In this work, an alternative but highly facile method is introduced to create ultra-low epsilon materials based on interfacial effects in nanocomposites. Typical nanocomposites, polyethylene/silica nanoparticle composites, were prepared by mechanical blending and hot-pressing. The composite's epsilon was dramatically decreased from 2.50 to 1.90 when incorporating 8 wt% silica. This epsilon value was much lower than the low extreme of predicted epsilon. The porosities of the composites are below 1%, indicating that the ultra-low epsilon is not a result of a porous structure. Instead, this ultra-low epsilon was found to be correlated with dielectric confinement effect of silica nanoparticles or crystalline rearrangement caused by interfacial effect. The interfacial effect was evidenced by the change of epsilon with loading ratios of silica and pressures, and a nanoparticle-induced crystallization. (C) 2018 Elsevier B.V. All rights reserved.