Structural, Solvent Quality Changes and Flow Regulation through PEO- Grafted Gold Nanopore

G Chen, MACROMOLECULES, 57, 4855-4866 (2024).

DOI: 10.1021/acs.macromol.4c00163

Polymer-grafted nanopores are widely used for controlled material transportation and flow regulation. Using atomistic nonequilibrium molecular dynamics simulations, we systematically investigate the effect of external flow on the morphological and hydration properties of poly(ethylene oxide) (PEO) grafted gold nanopore and especially how this effect is further regulated by the PEO chain length, grafting density, and pore sizes. We found that PEO undergoes a coil-to-stretch transition and becomes more aligned with the flow direction with an increased pressure gradient imposed in the nanopore. The PEO segment is found to be nonuniformly stretched, in general, along the chain in flow, and the largest stretch is located near grafting points. The PEO layer thickness is decreased as the flow strength increases in most cases except that for compressed PEO layer (polymer size is larger than the pore radius) where the thickness increases slightly (similar to 5%), and that for systems with very high grafting density under low-pressure gradients, little change in the layer thickness is observed. The hydration of PEO or the solvent quality is found to be increasingly poor as the flow strength increases due to the PEO conformational change and water depletion near the pore surface. Water radial velocity profile is found to be exclusively Poiseuille-like without slip when PEO is not fully stretched and water can penetrate into the PEO layer, while it transits into plug-like with slip when PEO chains are stretched to their rod- limit and water is fully depleted in the PEO layer, leading to a nonmonotonic flow rate dependence on PEO chain length or grafting density.

Return to Publications page