Comicellization of Binary PEO-PPO-PEO Triblock Copolymer Mixtures in Ethylammonium Nitrate

The micellization of dilute solutions of Pluronic block copolymers P123 (EO20-PO70-EO20) and F127 (EO106-PO70-EO106) and comicellization of binary mixtures in partially deuterated ethylammonium nitrate (d(3)EAN, a protic ionic liquid) are studied by small-angle neutron scattering. The average Pluronics composition in micelles shows a linear dependence on the bulk Pluronic composition. The mole ratio between P123 molecules in the micelles to those existing as unimers in solvent increases with temperature and P123 concentration. At a fixed F127/P123 ratio, the micelle core radius, the micelle corona thickness, and the aggregation number decrease with increasing temperature, while the total micelle volume fraction increases. At a fixed temperature, increasing P123 content in the binary mixtures leads to a weak minimum in micelle core size and aggregation number and a weak maximum in micelle corona thickness and total volume fraction of micelles. The comicellization behavior in d(3)EAN resembles that in aqueous solutions reported experimentally and theoretically. To our knowledge, this is the first experimental report on comicellization behavior of Pluronic triblock copolymers in a protic ionic liquid.