The Micelle Shuttle Timothy P. Lodge, University of Minnesota – Twin Cities, DMR 0804197

1. The Micelle Shuttle Timothy P. Lodge, University of Minnesota – Twin Cities, DMR 0804197 Ionic liquids have received much attention as potential “green” solvents for industrial scale chemical transformations. The appealing environmental aspect of ionic liquids is that they have no vapor pressure, thereby enabling compete containment and recycling. However, as many possible ingredients of chemical reactions, or their products, are not readily soluble in a chosen ionic liquid, it is desirable to develop surfactant systems that can reliably and rapidly transport such insoluble molecules into or out of an ionic liquid medium. We have developed a remarkable, thermoreversible shuttle system, in which block copolymer surfactant micelles can be made to pass intact from water into an ionic liquid, and vice versa. The key feature is to design the copolymer and the ionic liquid such that at low temperature the micelles reside exclusively in the aqueous phase, but at high temperature they prefer the ionic liquid. This discovery offers a means to use aqueous streams to do the final separation and purification steps, with little or no adverse environmental consequence. We have recently quantified the mechanism and thermodynamic parameters f this process [1]. “Thermodynamics and Mechanism of the Block Copolymer Micelle Shuttle between Water and an Ionic Liquid”, Z. Bai and T. P. Lodge, J. Phys. Chem. B, submitted. [2]. “Block Copolymer Micelle Shuttles with Tunable Transfer Temperatures Between Ionic Liquids and Aqueous Solutions”, Z. Bai, Y. He and T. P. Lodge, Langmuir, 24, 5284-5290 (2008). [3]. A Thermoreversible Micellization-Transfer-Demicellization Shuttle Between Water and an Ionic Liquid”, Z. Bai, Y. He, N. P. Young, and T. P. Lodge, Macromolecules, 41, 6615-6617 (2008). The micelle shuttle as it transfer from the (upper) aqueous phase to the (lower) ionic liquid. The micelles are formed from poly(butadiene-block-ethylene oxide) (PB-PEO) copolymers, and contain Rhodamine B labeled PB homopolymers as “cargo”. During the first two hours, ionic liquid slowly displaces water in the PEO corona, leading to an increase in density and sedimentation to the interface. Then the micelles complete the solvent exchange, and diffuse into the ionic liquid. In practical situations the system would be stirred vigorously, greatly accelerating the transfer.

2. Broader Impact: Undergraduates doing Polymer Research Timothy P. Lodge, University of Minnesota – Twin Cities, DMR 0804197 A faculty-student team from Winston-Salem State University, Professor Lei Zhang and Ms. Elizabeth Esquivel, spend the summer in Minneapolis working on block copolymer micelle equilibration Jessica Santiago, recipient of a Multicultural Student Research Opportunity Award (MSROP) at the University of Minnesota, presents a poster on her work. She is a co-author on a manuscript currently in preparation. Dr. Luciana Meli has gained valuable experience in mentoring undergraduates, including Jessica and Elizabeth, in their introduction to research.