Interaction among Spherical Polyelectrolyte Brushes in Concentrated Aqueous Solution.

Interaction among concentrated spherical polyelectrolyte brushes (SPB) dispersions in water was systematically investigated by means of small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and rheological methods. SPB consist of a core of polystyrene (PS) and a poly(acrylic acid) (PAA) brush shell. The "polyelectrolyte peak" appeared in SAXS spectra and was observed in WAXS curves for the first time. The size of the polyelectrolyte peak and the rheological properties of SPB were found to be strongly effected by SPB concentration, pH, and ionic strength. Combined with SAXS, WAXS, and rheological results, it is confirmed that the polyelectrolyte peak is originated from local ordered structures of polyelectrolyte chains bridged by counterions in the overlapping area among SPB driven by electrostatic interactions.