Creation of Ion-Selective Membranes from Polyethylene Terephthalate Films Irradiated with Heavy Ions: Critical Parameters of the Process

A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis and photolysis products from tracks makes it possible to create ion-selective membranes from polyethylene terephthalate (PET) films irradiated with heavy ions. These membranes exhibit high selectivity for singly charged cations and high transport characteristics in the electrodialysis mode. The aim of this study is to analyze the mechanisms of the transformation of latent tracks into a system of through pores of the subnanometer range in more detail. Polyethylene terephthalate films are irradiated with accelerated Xe and Bi ions with energy losses in the polymer of 11 and 18 keV/nm, respectively. The evolution of the free volume and the accumulation of carboxyl groups in the irradiated films at different stages of the treatment are studied using gravimetry, IR and UV spectroscopy, conductometry, and electron microscopy methods. It is found that the properties of the resulting membranes depend on several critical parameters, which include, in addition to temperature during extraction, the energy loss of the bombarding ion, the pH of the solution used for extraction, and ion fluence. Dramatic changes in the membrane properties are observed at ion fluences at which individual tracks begin to overlap.