Molecular Dynamics Simulations of Hydrated Poly(amidoamine) Dendrimer/Graphene Oxide Nanocomposite Membranes

All-atom molecular dynamics simulations were employed to explore graphene oxide/poly­(amidoamine) (GO/PAMAM) dendrimer hydrated composite systems, as a function of temperature and dendrimer generation, at neutral pH conditions. Our main focus was to provide a detailed description regarding structural features at the microscopic level and assess key aspects of the interfacial interactions related to the associative behavior between the two main components of the composites. It was found that the average separation between the GO sheets depended in a nonmonotonical manner on the dendrimer generation. The structural coherence of the membranes increased as the size and compactness of the dendrimer molecules increased. The dendrimers were found to physically adsorb on the GO surface. The GO/PAMAM association was driven by electrostatic interactions due to the development of a polar character in both components, as well as hydrogen bonding involving charged groups. The latter was found to increase with temperature. Examination of the GO/PAMAM hydrogen-bonding dynamics revealed a temperature- and generation-independent mechanism, which was persistent over the several-hundred-nanosecond-wide trajectories examined in the simulations. The detail afforded by this study provides new insight into the optimization of the performance of such membranes based on a rational design at the microscopic level.