Coupling relationship between molecule structure at silica/silicone gel interfaces and ionic conductivity in polymer composites

Abstract

Herein, the coupling relationship between molecule structure and ion conductivity in silica filled silicone gel are established. Based on the broadband dielectric spectrum, the concentration of ion charges and ions diffusion coefficients, two key roles for ion conductivity, are calculated. The concentration of ion charges is increased by about four orders of magnitude after the addition of silica. Because of the more short-length chains conformations and more amorphous regions at interfaces, the chains at interfaces are easier to rearrange with higher relaxation frequency, which enhances the ions diffusion process and contributes to negative decoupling exponents between the interface molecule relaxations and ion diffusion coefficients in silicone gel composites. With the increase of fumed silica loading, the ionic conductivity increases first and decreases owing to percolation phenomenon about silica dispersion. Meanwhile, decoupling exponents of the interface molecules are closer to 0. Our findings deepen the understanding how the interface structures act on ions conductivity in insulating polymer composites, which is critical to rationally design interface structures for manipulating the insulation performances.