Extreme enhancement and reduction of the dielectric response of polymer nanoparticulate composites via interphasial charges

Abstract

An analytical solution is constructed for the homogenized (i.e., macroscopic) dielectric response of particulate composites comprising a random distribution of particles bonded to a matrix material through interphases of finite size that contain space charges. By accounting for interphasial charges, the solution is able to describe and explain both the extreme enhancement and the reduction of the dielectric response typically exhibited by emerging polymer nanoparticulate composites. More generally, the solution reveals that judicious manipulation of interphasial charges provides a promising path forward for the design of materials with exceptional dielectric properties.

Homogenization of Elastic Dielectric Composites with Rapidly Oscillating Passive and Active Source Terms

“…The effective permittivity tensor ε. The effective permittivity tensor (26) 1 that emerges in the homogenized equation 25is independent of the choice of the domain Ω occupied by the composite, the boundary conditions on ∂Ω, and the presence of Downloaded 11/16/17 to 130.126.162.126. Redistribution subject to SIAM license or copyright; see http://www.siam.org/journals/ojsa.php space charges.…”

“…The effective space-charge density q(x). The effective space-charge density (26) 2 that emerges in the homogenized equation 25depends fundamentally on the presence of space charges through both of the constitutive functions f(x) and g(y) defining their density (10). It follows from the regularity (11) 1 of the function f(x) and the definiteness of the integrals in (27) that q ∈ H 1 (Ω).…”

“…Instead, they appear within the composite as a result of externally applied stimuli, for instance, by a charge injection process [21,30]. Dielectric elastomers filled with (semi)conducting or high-dielectric nanoparticles are thought to be an example of such a class of materials [25,21,26,20]. In this work, we shall consider active charges that appear in proportionality to the electric field induced within the composite by externally applied electrical stimuli.…”

The overall elastic dielectric properties of a suspension of spherical particles in rubber: An exact explicit solution in the small-deformation limit

“…Whatever their origin, the presence of interphasial charges has been recently shown to have the potential to lead to extreme enhancements of the overall dielectric properties of particulate composites and, by the same token, extreme enhancements of their electrostrictive properties. 14…”

“…[3][4][5][6][7][8][9][10] The precise nature behind the enhancement in electrostrictive properties generated by the addition of particles remains unresolved, but a number of microscopic mechanisms have been identified, including the nonlinear electromechanical nature of elastomers (which heightens the role of the fluctuations of the electric field) 11,12 and the presence of high-dielectric interphases and/or interphasial free charges. 13,14 In this paper, we seek to gain precise quantitative insight into the enhancement that the nonlinear electromechanical nature of elastomers bestows on dielectric elastomer composites. To this end, we construct a rigorous solution for the homogenization problem of the elastic dielectric 15 response of rubber filled with a random isotropic distribution of firmly bonded polydisperse spherical particles.…”