Synthesis of complexing copolymers by the radiation-induced grafting method

Abstract

The radiation-induced grafting of acrylic acid with acrylamide onto polyethylene, PE, and poly(isobutylene oxide), PIBO, was carried out to synthesize graft copolymers of complexing ability with such metal ions as lanthanides and transition metals. The adsorption efficiency of Tb 3+ obtained at [metal]/[ligand] = 1/10 with PIBO grafted with acrylic acid (AAc), PIBO- g-AAc, markedly increased with the increase in number of graft chains while it slightly decreased with the increase in molecular weight of graft chains. The adsorption of Sm 3+ was suppressed by Cu 2+ when these metal ions coexisted in solution at pH>5. Introducing poly(acrylamide) PAAm in graft chains improved not only the hydrophilic property of the graft copolymer but also its adsorption ability of metal ions. Sm 3+ was preferentially adsorbed in the surface region while Cu 2+ was adsorbed well inside the graft copolymers. The application of the modified Bjerrum method to the complexation made it clear that the complex forms were Sm(carboxyl) 2 for PE- g-AAc/Sm 3+ system, Sm(carboxyl) 3 for PE- g-(AAc-co-AAm)/Sm 3+ system, and Cu(carboxyl) 2 for both PE- g-AAc and PE- g-(AAc-co-AAm)/Sm 3+ systems, respectively. The logarithm of overall formation constant, log β n, increased with the increase in the acid dissociation constant p K a of graft chains.