Investigation of macromolecular metallocomplexes of rare earth and transition metal ions with side chains of polymethacrylic acid regularly grafted to polyimide backbone in aqueous and aqueous-salt solutions by luminescence methods

Abstract

Using luminescent methods, interactions of rare earth metal ions (Tb3+, Eu3+, Sm3+, Gd3+) with side chains of ionized polymethacrylic acid (PMAA) regularly grafted to a polyimide (PI) backbone are studied in aqueous and aqueous-salt solutions. It is shown that the interaction of ions with carboxylate anionic groups leads to a sharp decrease in the intramolecular mobility of grafted PMAA side chains at the ratio [metal]/[СОО−] > 0.12. It is established that the luminescence duration of Tb3+ ions decreases from 790 to 660 μs when the degree of polymerization of side PMAA chains decreases from 200 to 36. By means of the methodology based on the ability of transition metal ions to quench luminescence, equilibrium stability constants of macromolecular complexes of transition metal ions (Ag+, Cu2+, Ni2+) with luminescent-labeled PI-grafted and free PMAA chains in aqueous and aqueous-salt solutions are determined. It is shown that the complex stability is essentially affected by the nature and valence of a metal and the ionic strength of solution. Grafting of PMAA chains to a PI backbone causes no significant effect on their ability to bind Ag+ and Cu2+ ions, but reduces considerably the ability of binding with Ni2+ ions. An explanation of this effect is suggested.