Stability constants of water-soluble and latex types of chelating polymers containing iminodiacetic acid with some transition-metal ions

Two polymeric chelating agents, water-soluble and latex types of poly(styrene-co-GMA–IDA), are formed by reacting styrene with a chelating vinyl monomer, GMA–IDA. Acid dissociation constants (Ka) and stability constants (Ks) of these chelating agents with Cu(II), Ni(II), Zn(II) and Co(II) are determined by potentiometric titration and UV–Vis spectrophotometer, respectively. The values of Ka1 and Ka2 for the latex type of poly(styrene-co-GMA–IDA) are smaller than those for solution types. Stability constants are ordered, latex types>solution types>GMA–IDA. Latexes are surfactant-free, nearly nano-particles and the mean size declines as the amount of metal ions increases, when the particles are complexed therewith. The stability constants of the latex–metal complexes exceed those of the corresponding GMA–IDA–metal complexes by a factor of 102–103, depending on the metal ions. These results are explained by the neighboring effect and high concentrations of GMA–IDA on latex’s particulate surface (cooperative effect).