1. Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, Korea, Polymer Chemistry Laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan, and Graduate School of Engineering, Osaka University, 2-1 Yamadagaoka, Suita, Osaka 565-0871, Japan