1. Department of Chemistry, MIT, Cambridge, Massachusetts 02139, USA
2. Institute for Soldier Nanotechnologies, MIT, Cambridge, Massachusetts 02139, USA
3. Department of Polymer Science & Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
4. U.S. Army Combat Capabilities Development Command, Army Research Laboratory, FCDD-RLW-MG, Aberdeen Proving Ground, Maryland 21005-5069, USA