1. Department of Polymer Science and Technology, Chonbuk National University, 664-14 Dukjin, Chonju, 561-756, Korea
2. Department of Advanced Organic Materials Engineering, Chonbuk National University, 664-14 Dukjin, Chonju, 561-756, Korea
3. Biomaterials Laboratory, Korea Research Institute of Chemical Technology, PO Box 107, Yusung, Taejon, 305-606, Korea