0406656_Lodge

1. The Micelle Shuttle: Automatic, Reversible Extraction Timothy P. Lodge, University of Minnesota –Twin Cities, DMR 0406656 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. We have shown that the phenomenon is general, and that the transfer temperature can be tuned in simple ways (e.g., added salt or sugar). This discovery offers a means to use aqueous streams to do the final separation and purification steps, with little or no adverse environmental consequence. [1]. “The Micellar Shuttle: Reversible, Intact Transfer of Block Copolymer Micelles Between an Ionic Liquid and Water ”, Y. He and T. P. Lodge, J. Am. Chem. Soc.,128, 12666-12667 (2006). [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, in revision (2008). Photographs of the micelle shuttle, and accompanying cartoons. The upper liquid is water and the lower liquid is ethylmethyl imidazolium bis(trifluoromethyl sulfonimide) [emi][tfsi]. The micelles are formed from poly(butadiene-block-ethylene oxide) (PB-PEO) copolymers. The cloudiness indicates that the micelles are in the aqueous phase at room temperature, but above 65 ºC they prefer the ionic liquid. In this system it is the fact that water becomes a poor solvent for PEO at high temperature that drives the process.

2. Broader Impacts: Introducing K-12 Students to Polymers Tim Lodge, University of Minnesota, DMR 0406656 July 15, 2008: 26 high schoolers learn to make polymers with T. Lodge and grad students during “Polymer Day”, part of a week-long Exploring Careers in Engineering and Physical Sciences summer camp. March 17, 2008: A tour of the research labs, especially the glove box, for a group of students from Minneapolis North High. July 16, 17, 22, 24, 2008: Meetings, lunch, and lab tours with participants in the 3M Summer Bridge Program, for incoming freshmen in the Institute of Technology who are members of under-represented groups.