1. Department of Materials Science and Engineering College of Engineering Key Laboratory of Polymer Chemistry and Physics of Ministry of Education Peking University Beijing 100871 China
2. Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China
3. Fujian Key Laboratory of Polymer Materials College of Materials Science and Engineering Fujian Normal University Fuzhou 350007 China
4. State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Xi'an 710049 China
5. Department of Chemistry University of North Carolina at Chapel Hill Chapel Hill NC 27599‐3290 USA
6. National Center for Nanoscience and Technology Beijing 100190 China