1. Department
of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, United States
2. Department of Materials Science & Engineering, University of Delaware, Newark, Delaware 19716, United States
3. Key
Laboratory of Polymer Chemistry and Physics of the Ministry of Education,
College of Chemistry and Molecular Engineering, Center for Soft Matter
Science and Engineering, Peking University, Beijing 100871, P. R. China