Synthesis of multilayered, polyelectrolyte membranes begins with immersion of a porous, charged substrate into a solution containing a polyelectrolyte, as shown above.  A second immersion in a solution containing an oppositely charged polyelectrolyte results in an additional layer on the surface, and repetition of the process produces multilayer films.  Streaming potentials confirm that terminating films with polycations leads to positively charged membranes whereas termination with polyanions gives a negatively charged membrane.  The minimal thickness of the films leads to high fluxes, and films terminated with polyanions show Cl^-/SO₄^2- selectivities as high as 30, whereas polycation-terminated films exhibit Na⁺/Mg²⁺ selectivities around 23.  Recent work with nanofiltration membranes as substrates for forming polyelectrolyte films suggests that selectivities can be even higher.  

    Polyelectrolyte membrane might also help to alleviate membrane fouling.  In this case removal of the polyelectrolyte film and deposited foulants from the substrate followed be redeposition of the polyelectrolyte can create a regenerated, unfouled membrane (see below).  In collaboration with Professor Volodymyr Tarabara (J. Membr. Sci. 349, 268-278(2010)), we recently demonstrated the removal and regeneration of polyelectrolyte membranes.