Preparation and characterization of porous polyelectrolyte complex membranes for nanofiltration

Polyelectrolyte complex membranes were prepared from poly(acrylic acid-co-acrylonitrile)s and imidazolium-based polycations via a combination of blend film casting and ammonia solution immersion procedures. The membranes were free-standing and tough, showing excellent mechanical properties (with tensile strength of 6.71–23.7 MPa and elongation at break of 15–59%). Hierarchically structured nanopores were formed in the membranes during the ammonia soaking step, due to NH3-triggered –COOH deprotonation and in situ ionic crosslinking with polycations. Zeta potential measurements indicated that the membranes were negatively charged under neutral conditions. The membranes exhibited moderate rejection to salts in the order of Na2SO4 > NaCl > MgCl2, but high rejection to methyl orange (>99.9%).