Molecular dynamics of transient oil flows in nanopores. II. Density profiles and molecular structure for decane in carbon nanotubes

Abstract

We report molecular dynamics simulations of nanotubes imbibing decane at an oil/vapor interface at 300 K. We find that the smallest (7,7) nanotubes imbibe extremely rapidly (< or =800 ms), with the imbibition speed slowing as the tube's radius increases. The density profiles of the imbibing fluid in the pores are analyzed as a function of time. We find that the imbibing liquid is well described by the advection-diffusion equation and present expressions for the density profiles (in x and t) of the imbibing fluid as a function of the adsorption energy and surface friction of the pore. In addition we have analyzed the molecular structure of the imbibed fluid in nanotubes and describe how molecular conformations change with nanotube radius and position in the pore. We are therefore able to provide a complete description of the imbibition of a wetting fluid, decane, for a wide range of nanopores.