Hybrid Carbon Nanoparticles in Polymer Matrix for Efficient Connected Networks: Self-Assembly and Continuous Pathways

Functional polymer composites based on hybrid carbon nanoparticles (CNPs) offer synergistic properties and have recently received a lot of attention for various applications including photovoltaic cells. In this context, the size dispersity inherent in CNPs such as carbon nanotubes (CNTs) is still a controversial topic in light of new experimental findings when it comes to the formation of percolating networks. Here, we show how nanotube models with different aspect ratios (ARs) dispersed in polyamide 12 (PA12) matrix differ in their equilibrium nanostructures. To this end, large-scale dissipative particle dynamics simulations are carried out, and CNPs with different ARs representing fullerene-like isomers up to realistic CNTs are studied separately or in hybrids. The continuous pathways in the CNP nanostructures are further assessed in Monte Carlo calculations by random electrons transporting through the network quantifying its continuity for electrical conductivity. The results confirm that the morphology of the composite depends on the AR and, by increasing it, changes from a random dispersion to a self assembled morphology and eventually to a bridging self-assembled network. The generic behavior predicted in the simulations is compared with the rheological and electrical conductivity measurements performed on PA12/CNT nanocomposites. Based on the results, the dispersion quality, the AR of CNPs, and the continuous pathways in the network are found to be interconnected in contrast to previous interpretations of hybrid nanocomposites.