1. School of Materials Science, Japan Advanced Institute of Science and Technology, Asahidai, Nomi, Ishikawa 923-1292, Japan, Department of Polymer Science and Engineering, Graduate School of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, 992-8510, Japan, and Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan