Radiation grafting of pH-sensitive acrylic acid and 4-vinyl pyridine onto nylon-6 using one- and two-step methods

•A new binary graft of 4VP and AAc onto Ny6 films was synthesized by γ-radiation.•The binary grafted material has potential application for heavy ion retention.•The two-step method shows better conditions in swelling and reversibility properties.•Surface distribution of monomers was evaluate by XPS characterization.

Acrylic acid (AAc) and 4-vinyl pyridine (4VP) were γ-ray grafted onto nylon-6 (Ny6) films via pre-irradiation oxidative method. These monomers were grafted using a one-step method to render Ny6-g–(AAc/4VP). A two-step or sequential method was used to render (Ny6-g–AAc)-g–4VP. Random copolymer branches were obtained when the grafting was carried out via one-step method using the two monomers together. The two-step method was applied to graft chains of 4VP on both Ny6 substrate and previously grafted AAc chains (Ny6-g–AAc). The two types of binary copolymers synthesized were characterized to determine the amount of grafted polymers, the thermal behavior (DSC and TGA), the surface composition (XPS), and the pH responsiveness. In the two-step process, it is possible to achieve a higher graft yield, better control of the amount of each monomer, good reversibility in the swelling/deswelling process and shorter time to achieve equilibrium swelling.