Molecular Investigations of the Electroosmotic Transport in Nanochannels Grafted with Cationic Polymer Chains

Liquid transport in nanochannels can be significantly influenced by grafting the nanochannel walls with environmental-stimuli-sensitive polymer chains. In this study, we employ all-atom molecular dynamics (MD) simulations to study the electroosmotic (EOS) water transport in nanochannels grafted cationic polyelectrolyte (PE) chains, namely PMETA [Poly[(2-(Methacryloyloxy)Ethyl) Trimethylammonium] chains, screened with chloride counterions. Our previous study has demonstrated the most remarkable coion-driven EOS transport and reversal of the direction of the EOS flow field via alteration of the electric field strengths in nanochannels grafted with sodium-counterion-screened anionic PE chians (polyacrylic acid or PAA chains). In this present study, we shall probe the possibility of such coion-driven EOS flow and the effect of cationic PE chain charges and the nature of the screening counterions on the resulting EOS flow. These findings will be specially interesting given our recent discovery of significantly large cholride counterion mobility inside the PMETA PE layer owing to the locally hydrophobic nature of the PMETA chains. This enhanced mobility of the chloride counterions inside the PMETA PE layer is several times more than the sodium counterion mobility inside the grafted anionic PAA layer, and hence is expected to significantly influence the overall nanochannel EOS flows.