1. Department of Polymer Materials and Engineering, College of Material Science and Engineering, Harbin University of Science and Technology, 4 Linyuan Road, Harbin 150040, P. R. China
2. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, Athens 11635, Greece
3. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022, P. R. China