Adsorption of an alkane mixture on carbon nanotubes: Selectivity and kinetics

Adsorption and its dynamical process of polymer mixtures consisting of long and short alkane molecules around a carbon nanotube (CNT) are studied with molecular-dynamics (MD) simulations and master equation. Preferred adsorption is found for long chained molecules compared to short ones, due to favorable interfacial interaction energies of the former with the tube. A dominating ratio ~32 is calculated for the adsorption sites of hectane molecules vs decane molecules in their equal weight melt mixture when around a CNT (5, 5) at 420 K. The adsorption-desorption kinetics of the molecules is described through a master equation in combination with MD simulations. A fully adsorbed alkane molecule is found to be much more stable than a partially adsorbed one, regarding its monomer desorption rate from the nanotube. This results in a sharp peak in the population of the morphology of the adsorbed molecules at their maximum bound fraction fb=1. The crystallization in the mixture composite and the selectivity and molecule morphology during a cooling process were also discussed.