Molecular dynamics simulation based design of biomimetic membrane with artificial water channels

Inspired by nature’s design of pore proteins embedded in cell membranes, synthetic pore molecules embedded in self-assembled amphiphilic block copolymer membranes are the subject of intensive current research, as a possible route to more efficient reverse osmosis (RO) membranes. RO membranes are the key element in producing drinkable water from brackish or sea water; improved materials would help make this expensive process more widely applicable, increasing fresh water supplies worldwide. In this work, we simulated polybutadiene–polyethylene oxide (PB–PEO) bilayers containing peptide-appended pillar[5]arene (PAP5) channels. PB–PEO bilayers with PAP5 channels are a biomimetic alternative to aquaporin embedded lipid membranes, with high water permeability combined with excellent selectivity. In our simulations, we systematically varied the PB–PEO block copolymer structure to maximize water mobility. We measured water diffusivity in our best design by two complementary methods, and compared our values to that inferred from experimental channel permeability. In this design, we obtained a water diffusivity of 30.38 ± 0.19 × 10−8cm2s−1, comparable to the best experimentally reported result. We find that the highest permeability is achieved when the bilayer hydrophobic thickness matches the PAP[5] dimension, and the hydrophilic block is long enough that clogging the pore is entropically unlikely. [Display omitted] •Membrane hydrophobic thickness crucial for pore stability.•Entropic penalty disfavors long hydrophilic tails to clog the pore.•Einstein relation based short-time water diffusivity agrees with experiments.•Long-time diffusivity from kinetic model closely matches the short-time diffusivity.