Advanced Polymer Division, KRICT, P.O. Box 107, Yusung, Taejeon 305-600, Korea; Department of Polymer Science & Technology, Chonbuk National University, Chonju, Chonbuk 561-756, Korea; and Department of Chemistry, Yonsei University, Shinchon 134, Seoul 120-749, Korea(1999-03-11時点)