(41f) A Computational Investigation of the Surfactant-Mediated Carbon Nanotube Stabilization in a Liquid Epoxy Resin

We have investigated the carbon nanotube (CNT) stabilization in a liquid epoxy resin using a set of cationic and anionic surfactants with varying concentrations at room and elevated temperatures. Our main objective has been to gain a fundamental molecular understanding of the effects of surfactant type, concentration, and temperature on the mitigation of CNT â??bundleâ? formation (aggregation) in the epoxy resin, which arises due to strong van der Waals interactions between the nanotubes. Epoxy, being one of the widely used resins in aerospace-grade carbon fiber-based composites, has been enhanced by CNTs to provide, for example, lighting strike protection. However, the uniform dispersion of the CNTs in the resin has to date remained challenging. In this work, we have performed a series of molecular dynamics (MD) simulations of single-CNT and dual-CNT systems containing three different concentrations of 1) cationic surfactants, i.e., cetyltrimethylammonium bromide (CTAB) and sodium cholate (SC), 2) anionic surfactants, i.e., sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (NaDDBS), and 3) a 1:1 mixture of CTAB+SDS. We have performed the simulations at room (298 K) and elevated temperature (398 K). All simulations have been performed in the LAMMPS simulation package. We have quantified the CNT-surfactant interfacial interactions, and the surfactant geometries on the CNT surfaces to elucidate their CNT stabilizing mechanism. We have also investigated the effect of temperature increase on the CNT-surfactant interactions in the single-CNT systems. As for the dual-CNT systems, we have calculated the potential of mean force (PMF) and compared the stabilizing effects of the different surfactants at different concentrations.