1. School of Chemical Engineering and Hyperstructured Organic Materials Research Center, Seoul National University, Shimlim, Kwanak, Seoul 151-742, Korea, Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, and IBM Almaden Research Center, 650 Harry Road, San Jose, California 02148