1. Department of Chemistry and Macromolecular Science and Engineering Program University of Michigan 930 North University Avenue Ann Arbor MI 48109 USA
2. Mechanical Engineering Department University of Michigan Ann Arbor MI 48109 USA
3. Materials Science and Engineering Applied Physics Program, and University of Michigan Energy Institute University of Michigan Ann Arbor MI 48109 USA
4. Current address: Walker Department of Mechanical Engineering Texas Materials Institute and Oden Institute for Computational Engineering and Sciences University of Texas at Austin 204 E. Dean Keeton Street, ETC II 5.160 Austin TX 78712-1591 USA