1. Division of Chemical Engineering, College of Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea; Department of Polymer Science and Engineering, Sung Kyun Kwan University, 300 Chunchun-dong, Jangan-gu, Suwon, Kyunggi-do 440-746, Korea; and Electronic Materials and Devices Research Center and Biomaterials Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea