1. Department of Chemistry, Soongsil University 1-1, Sangdo-5 dong, Dongjak-gu, Seoul, Korea 156-743, Polymer Materials Laboratory, Korea Institute of Science and Technology, CheongRyang P.O. Box 131, Seoul, Korea 130-650, and Cleantech Center, Korea Institute of Science and Technology, CheongRyang P.O. Box 131, Seoul, Korea 130-650