Phase Behavior of an Amphiphilic Block Copolymer in Ionic Liquid: A Dissipative Particle Dynamics Study

We systematically investigated the self-assembly behavior of poly(1,2-butadiene)-b-poly(ethylene oxide) (PB-b-PEO) block copolymer in [Bmim][PF6] ionic liquid (IL) via dissipative particle dynamics simulations. An expanding scope of nanostructures, such as spherical micelles, rodlike micelles, entangled cylinders, sheets, branched lamellae, lamellae, platelets, tubes, and IL microphase structures, was observed under different polymer concentrations and polymer block ratios. When the polymer concentration was lower than 30 vol %, self-assembled morphologies transformed from spherical to rodlike or sheetlike micelles as the fraction of PEO block decreased. When the copolymer concentration was higher than 30 vol %, new morphologies such as wormlike micelles and branched lamellae emerged. Platelet and tube nanostructures were obtained when the concentration of PEO was lower than 10 vol %. In addition, lamellae structure was observed, represented as a triangular area in the phase diagram, and the IL microphase nanostructure appeared in the bottom right of the phase diagram. These various nanostructures observed in our study suggest a universal mechanism for the self-assembly of amphiphiles in given solvents.