Fourier transform infrared studies on the dissociation behavior of metal-chelating polyelectrolyte brushes

The dissociation behavior of surface-grafted polyelectrolytes is of interest for the development of stimuli-responsive materials. Metal-chelating polyelectrolyte brushes containing acrylic acid (PAA) or hydroxamic acid (PHA) chelating moieties were grafted from the surface of polypropylene (PP). Fourier transform infrared (FTIR) spectroscopy was used to determine the effective bulk pKa of the polyelectrolyte brushes (pKa(bulk)) and to characterize metal-chelating behavior. The pKa(bulk) values of PP-g-PAA and PP-g-PHA were 6.45 and 9.65, respectively. Both PP-g-PAA and PP-g-PHA exhibited bridging bidentate and chelating bidentate iron chelation complexes. This is the first reported determination of the pK(a,bulk) of surface-grafted poly(hydroxamic) acid.