All-atom molecular dynamics (MD) simulations were performed to investigate the coupled dynamics of PMETAC polyelectrolyte (PE) brushes, brush-supported water molecules, counterions, and the resulting electroosmotic (EOS) flow (in the presence of an applied axial electric field) inside a nanochannel grafted with such PMETAC PE brushes. The nanochannel dimensions were 268.3 Å × 89.4 Å × 147.72 Å. We employed periodic boundary conditions in x and y directions, and fixed boundaries in z direction. The PE brushes were grafted on both the nanochannel walls in a 4 × 12 array; therefore, there were 96 PMETAC chains with a grafting density of 0.2 chains/nm 2 . Each PE chain contains 24 monomers and methyl end cappings. This setup captures the brush-nanochannel interface while avoiding complications from long-chain effects like entanglement.