(592a) Fundamental Characteristics of Water Flow Through Functionalized Nanotubes

Studies of fluid flow through nanoscopic pores of carbon nanotubes (CNTs) have highlighted several interesting characteristics of their behavior such as breakdown of continuum hydrodynamics by several orders of magnitude, temperature dependent hydrophobic to hydrophilic transition, etc. Owing to rapid water flow through CNTs, nanotube-based membranes are expected to perform better than existing technologies for water desalination if appropriate levels of salt rejection can simultaneously be achieved by pore-mouth functionalization. To understand how the flow characteristics are affected by this chemical functionalization and then leverage this for designing membranes with high flux and high selectivity towards salt rejection, we have performed extensive molecular dynamics simulations of model pores. We find that the water flux is sensitive to the degree of functionalization and nanotube diameter. Interestingly, flux is found to be largely independent of the specific location or spatial patterning of functionalized atoms along the tube length deeming it an irrelevant design parameter. We also present a simple thermodynamic model that can explain our results in terms of effective water-pore interactions.