1. Department of Polymer Sci. & Eng.; Sunchon National Univ.; 315 Maegok-dong Sunchon Chonnam 540-742 Korea
2. Current address: Department of Fisheries System Eng.; National Fisheries R & D Institute; Busan 619-705 Korea
3. Institute for Technical and Macromolecular Chemistry; University of Hamburg; Bundesstrasse 45 D-20146 Hamburg Germany