S-1 Supporting Information Address the Challenge of Fabricating High Content of Regenerated Cellulose/Nanomaterial Composite: Magical Effect of Urea Kai Wu,* a b Dingyao Liu, a b Feng Gong c , Chuxin Lei b and Qiang Fu * b a Key Laboratory for Soft Chemistry and Functional Materials of Ministry of Education, Department of Polymer Science and Engineering, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China. b College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, PR China. c School of Energy and Environment, Southeast University, Nanjing 210094, PR China. Corresponding author E-mail: kaiwu@njust.edu.cn (K. Wu); E-mail: qiangfu@scu.edu.cn (Q. Fu), Tel./Fax: +86 28 8546 1795; Electronic Supplementary Material (ESI) for Green Chemistry. This journal is © The Royal Society of Chemistry 2020