Factors determining pore shape in polycarbonate track membranes

The formation of pores in polycarbonate films irradiated by accelerated ions upon their treatment with alkali solution containing a surfactant was studied. It was found that the pore shape is determined by both the structure of the initial film and the peculiarities of interaction of a surfactant with a polymer surface and its transfer to a track. Because of the inhomogeneity of the initial material, the "track" pore cross section varies along the pore length. The presence of a surfactant leads to an additional effect. Being adsorbed onto the film surface and at the entrances of etched tracks of heavy ions, surfactant molecules tend to decrease the etching, rate, thus leading to the formation of "spindle-shaped" pores. Thus, the use of a surfactant as a component of the chemical etching solution makes it possible to vary the pore shape of track membranes in a directional manner, optimizing their efficiency and selectivity.