1. School of Materials Science and Engineering; National Institute for Advanced Materials; Nankai University; Tianjin 300350 China
2. School of Science; Xi'an University of Technology; Xi'an Shaanxi 710048 China
3. Applied Mechanics Laboratory; Department of Engineering Mechanics and Center for Nano and Micro Mechanics; Tsinghua University; Beijing 100084 China
4. Department of Materials Science and Engineering; Henry Samueli School of Engineering and Applied Science; University of California Los Angeles; Los Angeles CA 90095 USA
5. Key Laboratory of Functional Polymer Materials of Ministry of Education; College of Chemistry; Nankai University; Tianjin 300350 China