Chelation properties of polymer complexes of poly(acrylic acid) with poly(acrylamide), and poly(acrylic acid) with poly(N,N-dimethylacrylamide)

The metal-complexing properties of intermolecular complexes of poly(acrylic acid) with poly(acrylamide), and poly(acrylic acid) with poly(N,N-dimethylacrylamide) were studied by means of the liquid-phase polymer based retention (LPR) technique. The metal ion retention ability at pH 5 for 400 mu g of Cu(II), Cd(II), Co(II), Cr(III), Hg(II), NI(II), Pb(II), and Zn(II) was investigated due to their environmental and analytical interest in the presence of 1.1 M of carboxylic acid units and variable amounts of amide groups. The retention profiles of the intermolecular complexes were compared with those of the correspondent homopolymers and copolymers. The retention capacity of poly(acrylic acid) is 100% for all metal ions except for Co(II), Ni(II), and Zn(LI) whose values were about 90%, while poly(acrylamide) does not retain any of the metal ion studied. The presence of poly(acrylamide) decreases the retention capacity down to 60% for Co(II) and Ni(II) and to 70% for Zn(II). The decrease on the retention values is dependent on the polymer ratio. A smaller effect is observed by the addition of poly(N,N-dimethylacrylamide) which also decreases the retention capacity down to 80% for Co(IT) and Ni(II) for a ratio poly(acrylic acid)poly(N,N-dimethylacrylamide) = 1/2. The metal ion binding behavior of the interpolymer complexes is very close to that of the copolymers.