Conductivity of Insulating Diblock Copolymer System Filled with Conductive Particles Having Different Affinities for Dissimilar Copolymer Blocks.

A.I Chervanyov

doi:10.3390/polym12081659

Abstract

We investigate the electrical response of the insulating diblock copolymer system (DBC) filled with conductive spherical fillers depending on the affinities of these fillers for copolymer blocks and the interaction between fillers. We demonstrate that the contrast (difference) between the affinities of the fillers for dissimilar copolymer blocks is a decisive factor that determines the distribution of these fillers in the DBC system. The distribution of filler particles, in turn, is found to be directly related to the electrical response of the DBC-particle composite. In particular, increasing the affinity contrast above a certain threshold value results in the insulator-conductor transition. This transition is found to be caused by the preferential localization of the fillers in the microphases of the DBC system having larger affinity for these fillers. The effect of the interaction between fillers is found to be secondary to the described effect of the affinity contrast that dominates in determining the distribution of fillers in the composite. This effect of the inter-particle interactions is shown to be significant only when the affinity contrast and filler volume fraction are sufficiently large.

Highlights

Composites comprised of polymeric insulating materials filled with conductive fillers have broad spectrum of applications ranging from sensors and actuators [1,2,3,4,5,6,7] to micro-electromechanical systems [8,9] and electronic packaging [10,11,12]
In the present work we have investigated the conductivity of the insulating diblock copolymer (DBC) system filled with spherical conductive fillers depending on the affinities of these fillers for copolymer blocks
The distribution of fillers is found to be determined by the interaction between fillers and the contrast between the affinities of these fillers for dissimilar copolymer blocks quantified by the parameter σ. σ, in turn, is determined by the surface part of the immersion energy of a filler given by Equation (7)

Summary

Introduction

Composites comprised of polymeric insulating materials filled with conductive fillers have broad spectrum of applications ranging from sensors and actuators [1,2,3,4,5,6,7] to micro-electromechanical systems [8,9] and electronic packaging [10,11,12]. Few theoretical studies [13,16,17] address homogeneous insulating host polymer systems containing conducting fillers In these models, the role of the host polymer matrix is restricted to insulating the contacts between the conductive fillers. The role of the host polymer matrix is restricted to insulating the contacts between the conductive fillers This insulating effect is used to induce the conductor-insulator transition that occurs when the fraction of conductive fillers in a composite reaches a certain percolation threshold. This threshold can be shifted [2,3,13,14] by applying stress to a polymer-particle composite that causes restructuring the conductive filler network formed in this composite. This restructuring results, in turn, in switching among conductivity mechanisms (e.g., constriction and hoping) and changing overall conductivity of the composites

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