Graphene oxide nanosheet as a two-dimensional polyelectrolyte: pH-responsive behavior of a multilayered nanomembrane

Graphene oxide (GO) is a promising two-dimensional (2D) nanomaterial that could improve the performance of membranes due to its unique mechanical stability and chemical tunability. Moreover, GO nanosheets may act as 2D polyelectrolytes in solution because the abundant surface functional groups confer them high dispersity. Unlike conventional polyelectrolyte systems, the assembly behavior of this 2D polyelectrolyte and its resulting characteristics in multilayered membranes have not been thoroughly investigated. Herein, we employed a layer-by-layer (LbL) assembly technique to assemble GO multilayered membranes with highly controlled thickness, roughness, and charge density depending on the assembly pH conditions. Compared to conventional GO membranes prepared by vacuum filtration, the LbL assembled GO multilayered membranes presented different internal structure, wettability, and ion-permeability. The unique properties of the 2D polyelectrolytes obtained in this study may broaden their potential in the field of materials science and membrane applications.