Controlling the dispersion of carbon nanotubes (CNTs) in solvent is a particular problem in development of advanced CNT-based materials. Using simulation we would like to be able to predict if it is possible to process CNTs in a specific environment, or whether significant enhancement of physical properties is possible with the addition of very small quantities of CNTs. In this presentation we examine the specific case of how we might optimize electrical conductivity of thin film CNT-polymer composites and guide experimental efforts in this area. This is approached by way of the bottom up multiscale modelling scheme described below. We have initially approached the problem of dispersion of CNTs from the perspective of Flory-Huggins theory, by evaluating cohesive energy densities of CNT and polymer materials. This provides realistic input parameters for Dissipative Particle Dynamics (DPD) simulations, which were used to investigate, how the underlying polymer morphology affects the distribution of CNTs within the polymer [1,2]. Adopting such mesoscale approaches is required in order to access the time and length scales over which CNT composites evolve. Finally, the density fields were projected onto a finite-element grid in order to apply the MesoProp [3] software for evaluating the enhancement of electric conductance. We find that the electric conductance depends on the percolation of nanotubes across the polymer layer, through a dynamic process in which connections form and break, leading to a threshold for conductance of about 1/2 vol(percent) CNT. When CNTs are immersed into diblock copolymer systems there is a non-trivial dependence of percolation on the underlying block copolymer morphology. The polymer morphology in this case provides templates for altering the preferred arrangements of CNTs and we show that in most cases this is a frustration to percolation by comparing and contrasting with CNT dispersion in small-molecule fluids and mixtures. Application of shear to manipulate and align the polymer phases results in significant enhancement (c.a. 10 fold increase) of the composite conductivity in the direction of shear.
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