1. Department of Chemistry, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202-3274, Lehrstuhl f. Makromolekulare Stoffe, Technische Universitaet Muenchen, Lichtenbergstr. 4, 85747 Garching, Germany, Department of Chemistry, Chemical Engineering and Materials Science, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201, and Manuel Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545