1. State Key Laboratory of Polymer Physics and Chemistry; Changchun Institute of Applied Chemistry; Chinese Academy of Sciences; Changchun 130022 P. R. China
2. Polymer Materials Research Center; College of Materials Science and Chemical Engineering; Harbin Engineering University; Harbin 150001 P. R. China
3. Department of Mechanical Engineering; University of Akron; Akron OH 44325-3903 USA