1. Department of Organic Materials and Fiber Engineering; Soongsil University; Seoul 156-743 Korea
2. Department of Chemical Engineering; Soongsil University; Seoul 156-743 Korea
3. Department of Physics; Soongsil University; Seoul 156-743 Korea
4. Department of Chemical Engineering; Pohang University of Science and Technology; Pohang 790-784 Korea
5. Department of Chemical Engineering; Stanford University; Stanford CA 94305-5025 USA
6. Department of Chemistry; Purdue University; West Lafayette IN 47907 USA