Ultrafast Water Transport in Two‐Dimensional Channels Enabled by Spherical Polyelectrolyte Brushes with Controllable Flexibility

Fast water transport channels are crucial for water‐related membrane separation processes. However, overcoming the trade‐off between flux and selectivity is still a major challenge. To address this, we constructed spherical polyelectrolyte brush (SPB) structures with a highly hydrophilic polyelectrolyte brush layer, and introduced them into GO laminates, which increased both the flux and the separation factor. At 70 °C, the flux reached 5.23 kg m−2 h−1, and the separation factor of butanol/water increased to ≈8000, which places it among the most selective separation membranes reported to date. Interestingly, further studies demonstrated that the enhancement of water transport was not only dependent on the hydrophilicity of the polyelectrolyte chains, but also influenced by their flexibility in the solvent. Quartz crystal microbalance with dissipation and molecular dynamics simulations revealed the structure‐performance correlations between water molecule migration and the flexibility of the ordered polymer chains in the 2D confined space. Fast and high‐efficiency water transport behaviour in 2D GO confined spacing assisted by spherical polyelectrolyte brushes can be easily realized. Further studies revealed that the water transport capacity was not only dependent on the hydrophilicity of the polyelectrolyte chains but also influenced by their flexibility in the solvent.