Supported ionic liquid membranes (SILMs) have been used for a variety of separations. Yet, a major weakness of SILMs is that the ionic liquid is held in the membrane pores by capillary forces, such that, when the transmembrane pressure is high enough, the ionic liquid is pushed out of the membrane. We report a solution to this problem. Surface-initiated atom transfer radical polymerization (ATRP) was used to covalently graft poly(ionic liquids) (PILs) from the surfaces of regenerated cellulose (RC) membranes. Because the PIL is attached to the pore surfaces covalently, there is no concern for leakage from the support. In this presentation, we will discuss the methodology in which we first graft a poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) nanolayer from the support. The thickness of the nanolayer is controlled by changing the polymerization time, and ATR-FTIR spectroscopy is used to follow the modification steps. The kinetics of polymerization was studied in parallel experiments on a model substrate that allows us to measure nanolayer thickness versus time. The chemistry of these charged nanolayers was varied by exchange of the Cl- anion (with, e.g., BF4-, PF6-), as confirmed by XPS.