Formation of Diode-Like Composite Membranes by Plasma Polymerization

A method for the preparation of polymer “diode-like” composite membranes with a conduction asymmetry in electrolyte solutions (rectification effect) exhibited under different orientations of the membranes in an electric field is examined. To produce such membranes with diode-like properties, thin polymer films formed by plasma polymerization of organic precursors were deposited onto one side of a track membranes made of poly(ethylene terephthalate) and polypropylene used as a porous substrate. It is established that the achievement of asymmetric conduction is mainly caused by change in the geometry of pores owing to a substantial decrease in their diameter in the deposited polymer layer, as well by an interface between the initial membrane and deposited polymer layer in the pores. It is shown that, in the case of a hydrophobic polymer layer, for the description of the electrochemical properties of the membranes, along with the consideration of electrostatic interaction between the electrolyte ions and the charge of pore walls, one should take into account the phenomenon of electrolyte slipping along the hydrophobic surface. The revealed effects indicate a possible way to create composite membranes with conduction asymmetry for their use in developing various feedback systems, as well as chemical and biochemical sensors.