1. Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-36 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
2. Department of Materials Science and Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706
3. Department of Chemistry, National Research Lab. for Polymer Synthesis and Physics, Pohang Accelerator Laboratory, Center for Electro-Photo Behaviors in Advanced Molecular Systems, BK School of Molecular Science, and Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea