Interaction of poly(methacrylic acid) brushes with metal ions:: Swelling properties

The swelling behavior of poly(methacrylic acid) (PMAA) brushes in contact with aqueous solutions of sodium, silver, alkaline-earth metal, copper, and aluminum nitrate was studied by multiple angle null ellipsometry. Fundamentally different swelling behavior were found for the interaction of the polyacid brush with metal cations of increasing valency or when going from a main group to a transition metal ion at constant valency. The different cations were classified with respect to the nature of their interaction with the surface-attached poly(carboxylic acid), and the findings were compared to theoretical predictions as well as to experimental investigations of related systems, such as free polyacids in solution or polyacid gels interacting with different metal cations.