Functional nanoporous polymer membranes with expanded surface area can be applied in broad fields, including separation, filtration, catalysis and energy applications. There are a number of established methods for the preparation of nanoporous membranes using neutral or weakly charged polymers. However, fabrication of nanoporous polymer membranes from strong polyelectrolytes is far more difficult. Here we present our approach to nanoporous polyelectrolyte membranes by using poly(ionic liquid)s.1
Poly(ionic liquid)s (PILs) are the polymerization products of ionic liquids (ILs), which combine certain properties and functions of polymeric materials (e,g. durability and good processability) and ILs (e.g. ion conductivity and thermal stability). We have exploited these favorable properties in the fabrication of nanoporous membranes from imidazolium based PILs through electrostatic complexation of PILs with polyacids.2 The porous structure forms as a result of microphase separation of the hydrophobic PIL chains from the aqueous environment and is simultaneously stabilized by ionically crosslinked networks between the cationic PIL and the negatively charged neutralized polyacids. The as-obtained nanoporous membrane features a gradient profile in the cross-linking density along the membrane cross-section, triggered by the diffusive penetration of a base molecule from the top to the bottom into the PIL-polyacid blend film. The membrane pore sizes can be tuned from nano- to micrometer scale by varying the degree of electrostatic complexation.
Furthermore, the membrane features high actuation speed in response to acetone vapor phase (also some other organic vapors) on account of its gradient in cross-linking density and the intrinsic porous nature of the membrane that enhances the internal mass transport. Such membranes may serve as environmental sensors to detect solvent quality.3 Our latest advance pushes forward the application scope of nanoporous polymer membranes further to nanoporous carbon membranes that have tremendous potential in electrochemical energy conversion/storage field.4-6
 Q. Zhao, M. Yin, A. P. Zhang, S. Prescher, M. Antonietti, and J. Yuan, J. Am. Chem. Soc. 135 (2013) 5549.
 Q. Zhao, J. W. C. Dunlop, X. Qiu, F. Huang, Z. Zhang, J. Heyda, J. Dzubiella, M. Antonietti, and J. Yuan, Nat. Commun. 5 (2014) 4293.
 Z. Qiang, J. Heyda, J. Dzubiella, J. W. C. Dunlop, and J. Yuan, Adv. Mater. 27 (2015) 2913.
 H. Wang, Yuan, J., et al. Nat. Commun. 8 (2017) 13592.
 Wang, H.; Yuan, J., et al. Angew. Chem. Int. Ed. 56 (2017),7847.
 Wang, H.; Yuan, J., et al. ACS Nano, 11 (2017), 4358.
Jiayin Yuan studied chemistry at Shanghai Jiao Tong University(China) in 1998. He received his M.Sc. from University of Siegen (Germany) in 2004, and Ph.D (Summa cum laude) from University of Bayreuth (Germany) in 2009. He joined the Max Plank Institute of Colloids and Interfaces in Germany and stayed there as a research group leader till 2016. In 2017 he was appointed as associate professor at Clarkson University, USA, and in 2018 he moved back to EU as an associate professor at Stockholm University, Sweden. He received Emil-Warburg award in 2009, an European Research Council Starting Award in 2014, Dr. Hermann-Schnell Award in Germany in 2015, the Dozentenpreis from the Fund of German Chemical Industry in 2016 and the Wallenberg-Academy-Fellowship in Sweden in 2017. Currently, his research interest focuses on functional polymers and carbons. He published so far 134 papers, 6 book chapters and 2 patents with an H-index of 39.