Porous Transition of Polyelectrolyte Film through Reaction-Induced Phase Separation Caused by Interaction with Specific Metal Ions

We describe a novel method for the simple and eco-friendly fabrication of porous polyelectrolyte films. A polyelectrolyte with many amine groups undergoes structural transformation from a dense to a porous structure upon immersion in a specific metal ion solution. The porous transition was the result of a reaction-induced phase separation, which was caused by the formation of new bonds between the polyelectrolyte and metal ions. This method enables control of the pore size of the porous structure in the nanoscale (54 nm) to microscale (1.63 μm) range through variation of the concentration or type of metal ions in the solution. To the best of our knowledge, this is the first report illustrating wide-range control of the pore size of a porous polyelectrolyte structure achieved by metal ions. These porous polyelectrolyte films with adjustable pore size and metastable metal ions can be employed in applications such as adsorption and catalysis.