1. Department of Chemistry, Korea Advanced Institute of Science and Technology, 373-1 Kusung-dong, Yusung-gu, Taejon, 305-701, Korea, Polymer Material Laboratory, Korea Institute of Science and Technology, P.O. Box 131, Cheangyangri, Seoul, Korea, Department of Polymer Science, Gyeongsang National University, Jinju 660-300, Korea, and Department of Macromolecular Science, Han Nam University, 133 Ojung-Dong, Taejon 300-791, Korea