1. W. A. Petka and D. A. Tirrell, Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA. J. L. Harden and D. Wirtz, Department of Chemical Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA. K. P. McGrath, Science and Technology Directorate, U.S. Army Natick Research Development and Engineering Center, Natick, MA 01760, USA.