1. Research Institute for Soft Matter and Biomimetics; College of Materials & Department of Physics; Xiamen University; Xiamen 361005 P.R. China
2. College of Material Science and Engineering & State Key Laboratory for Modification of Chemical Fibers and Polymer Materials; Donghua University; Shanghai 201620 P.R. China
3. Department of Physics; National University of Singapore; 2 Science Drive 3 117542 Singapore