(759b) Water Transport Through Carbon Nanotubes with Modified Water Models

Remarkably fast water flow through carbon nanotube (CNT) based membranes opens exciting possibilities for realizing both high-flux and high-selectivity molecular transport, manipulation, and separation at various scales. Broadening of the scope of nanotube research beyond CNT-water systems is daunted by the complex parameter space comprised of a wide range of possible NT materials (e.g., carbon, alumina, silica, aluminosilicate, etc.), vast potential nanotube modifications, and innumerable fluid compositions. Yet, it is critical for elucidating and tapping the unrealized potential of nanotube membranes for more generalized chemical transport. We will discuss the transport behavior of geometrically modified water models inside various diameters of CNTs using molecular dynamics simulations of the extended simple point charge (SPC/E) model of water. Here, we use the bond angle of water as a representative surrogate of non-aqueous molecular fluids. The geometric modification consists of altering the H-O-H angle of SPC/E water. We find that water transport inside CNTs varies in a nonmonotonic way as a function of bond angle, reaching a maximum for an bond angle of 90 degree. This trend could not be predicted based on water density inside and outside CNTs as a function of bond angle. We will present detailed analysis and theoretical justification for the observed behavior.