Formation and Equilibration of Block Copolymer Micelle in Ionic Liquids via Co-solvent Method

Block copolymer micelles are versatile materials with potential in many applications such as drug delivery. However, the dynamics of how block copolymer chains actually self-assemble into nanostructures has not been well documented. In this work, 1,2-polybutadiene-b-poly(ethylene oxide) (PB-PEO) was first dissolved in a mixture of the PEO-selective ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and a neutral solvent dichloromethane. Dynamic light scattering and small angle X-ray scattering were then employed to monitor the development and size changes in micelles as a function of solvent selectivity as dichloromethane slowly evaporated. The effect of different dichloromethane evaporation rates was studied. The sigmoidal character of the obtained data suggested multiple equilibration processes are involved, including chain exchange and possibly micelle fusion.