Evidence of repulsive Yukawa tail for copolymer micelles in room temperature ionic liquid

A PS-PEO diblock copolymer dissolved in a room temperature ionic liquid displays aggregation and interaction properties similar to those observed in aqueous solution. The selective binding between the ether oxygen of EO units and the salt cations turns the non ionic micelles into ionic ones and seems to be responsible for the repulsive interaction between micelles. This repulsion is not totally screened by the charge fluctuations of the solvent and it is well described by a pair potential constituted by a hard sphere term plus a repulsive Yukawa tail. The screening length is in the range 1–2 nm, in agreement with theoretical and simulation results on the spatial scale of the charge fluctuations of molten salts