The primary goal of this study is to employ all-atom MD simulations for probing the coupled dynamics of the brushes, the brush-supported water molecules and counterions, and the resulting EOS transport in a nanochannel grafted with the PMETAC brushes. To achieve this, we developed an atomistic model of a representative volume element (RVE) of the nanochannel. Fig. provides an overall snapshot of the system. The nanochannel has a length of 268.3 Å in the x direction, a width of 89.4 Å in the y direction, and a height of 147.72 Å in the z direction. Periodic boundary conditions were applied in the x and y directions in order to reduce the effect of the finite length and the finite width, while a fixed boundary condition was applied in the z direction. The PE chains were grafted on each wall (of the nanochannel), in a 4 by 12 array (a total of 96 chains), which corresponds to a grafting density of 0.2 chains/nm 2 . Such grafting density was previously considered in experimental studies. Each PE chain consisted of 24 monomers and the methyl end cappings [see Fig. ]. The length of the PE chains was considered to be large enough to accurately represent the brush-nanochannel interface while remaining computationally feasible. Short brushes avoid phenomena like entanglement or pinned micelles 79 that arise for longer chains and therefore enables a more focused capture of the effect of the chemical nature of the monomer on the EOS flow. The RVE dimensions and PE chain lengths were similar to that studies that probed the flow through PE-grafted nanochannels. OPLS-AA forcefield was used to model the interaction of the PE chains. In our previous articles, we have validated the use of the OPLS-AA forcefield by showing that it was able to capture the experimental results 81 on the solvation properties of the functional groups of the PMETAC brushes as well as the brush responses to the changes in the counterions. For the present case, each PMETA monomer was neutralized by an equal number of Cl -counterions. Additionally, an extra 64 Na + and Cl -ions were placed in the bulk nanochannel, which corresponds to approximately 0.2 M of added NaCl salt. We used Joung-Chetham parameters to model the interactions of the ions. The PE chains were solvated in water and the SPC/E water model was used for our simulations. We used the SHAKE algorithm to fix the bonds and angles of the water molecules. The different interaction potentials and the relevant parameters corresponding to the different atoms in the system and employed to use these potentials have been provided in section S1 of the Supporting Information (SI).