NMR paramagnetic probing of polymer solutions using manganese(II) ions

Abstract

Nuclear magnetic relaxation studies show that manganese(II) ions can serve as paramagnetic probes for investigation of aqueous solutions of polyelectrolytes (polystyrene sulfonate and polyethylenimine) and their mixtures. The analysis of the measured rates of spin–lattice (R 1) and spin–spin (R 2) relaxations reveals the differences in the binding character of manganese(II) ions with polystyrene sulfonate and polyethylenimine. In a mixture of the polymers in acidic and neutral media, manganese(II) forms two types of ternary complexes. Using the suggested method for definition of the hydration degree of a coordination sphere of the bound probe ions, the number of water molecules in the first sphere of the polymer-bound manganese(II) ions is found on the basis of the value of the R 2/R 1 ratio.