1. School of Aerospace Engineering and Applied Mechanics Tongji University 100 Zhangwu Road Shanghai 200092 China
2. Max Planck Institute for Polymer Research Ackermannweg 10 Mainz 55128 Germany
3. Department of Materials Science and Engineering Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213 USA
4. Chemistry Department Carnegie Mellon University 4400 Fifth Ave. Pittsburgh PA 15213 USA