Effective interaction between nanoparticles mediated by a symmetric polymer blend

Temperature dependence of the conductivity of filled diblock copolymers

We demonstrate that an insulating diblock copolymer system (DBC) filled with conductive fillers can be used as an electrically responsive soft composite that changes its conductivity in response to temperature-induced changes in its morphology. By combining the phase field model describing the morphology of the DBC system with the Monte Carlo simulations and the resistor network model describing electrical properties of the filler network, we calculate the conductivity of this composite. The calculated conductivity is found to essentially depend, in particular, on the temperature of the composite. Changing the temperature is shown to result in morphological changes in the DBC system causing the structural changes in the filler network. In particular, the order-disorder transition in the host DBC system is found to be accompanied by the conductor-insulator transition in the filler network. The effect of the difference between the affinities of the fillers for dissimilar copolymer blocks on the composite conductivity, as well as the effect of the repulsive and attractive interaction between fillers, is considered in detail.

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

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.