Efficient transport of molecules and ions in polyelectrolytes is required for a number of applications, including drug delivery, fuel cells, actuators, and protective clothing. However, polyelectrolytes typically exhibit low mechanical strength in the hydrated state, where ionic transport is a highly water dependent process. Combining polyelectrolytes with high modulus polymers on the nanoscale requires exquisite control of the interface and resulting nanostructure for optimal transport-mechanical properties.

In this study, the transport properties of novel polymer-polymer nanocomposite membranes with polyelectrolyte nanodomains oriented normal to the plane of the membrane were investigated. To provide mechanical durability to the composite a track-etched polyester membrane with an oriented nanoporous structure was used as the matrix. Oxygen plasma-initiated surface graft polymerization was used to fill the pores with polyelectrolyte (poly(2-acrylamido-2-methyl-1-propanesulfonic acid)) gel (covalently bound and crosslinked), which regulates transport properties in the desired direction. Membranes with this oriented nanostructure exhibit high ionic conductivity, high water vapor transport, high selectivity (water over organic transport), and good mechanical properties. Additionally, electrosensitive permeability of these membranes was demonstrated. In other words, a permeable-impermeable response to off-on applied voltage was measured due to the electroactive stimuli responsive expansion and contraction of the polyelectrolyte gel network within the membrane. This electrosensitive permeability was investigated as a function of gel content (regulated through plasma treatment, polymerization conditions and a new masking technique), nanodomain size, and applied voltage.