Optimizing the structure and performance of biomimetic water channels

Abstract

Peptide appended pillar[5] arene (PAP[5]) is an artificial water channel that has been extensively studied for its potential for water desalination. Owing to their rigid pore dimension and surface chemistry, PAP[5] embedded polymer membranes have high water permeability and excellent selectivity, because the pore diameter is less than the size of a hydrated ion. To pass through the channel, ions must give up part of their hydration shells, which incurs a large free energy penalty. As a result, tubular molecules like PAP[5] offer a possibility to elude the selectivity-permeability trade-off, up to a critical pore diameter. In this study, we use atomistic molecular dynamics simulations to explore the effect of PAP pore diameter on water mobility and ion rejection, and identify the limiting PAP geometry that has the highest water permeability while still rejecting ions.