1. Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.
2. Department of Mechanical and Civil Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
3. Institute for Materials Chemistry and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan.