Coacervation of Spherical Polyelectrolyte Brushes with Additional Polyelectrolytes Bearing Positive or Negative Charges

By combining small-angle X-ray scattering, wide-angle X-ray scattering, and rheology, the effect of additional polyelectrolyte chains on interactions among spherical polyelectrolyte brushes (SPB) was systematically investigated both on microscopic and macroscopic levels. The negatively charged poly(acrylic acid) (PAA) chains and positively charged poly(dimethyl diallyl ammonium chloride) (PDDA) chains were used as additional polyelectrolyte chains to investigate the local ordered structure and the "polyelectrolyte peak" among SPB. Interestingly, coacervation appeared in the SPB emulsion while introducing additional free polyelectrolyte chains. The addition of excess positively charged PDDA chains would lead to the transformation of the SPB emulsion from the coacervation to the aggregation, while it has not been observed in the case of PAA chains. Moreover, it was further confirmed that the specific local ordered structure was caused by the electrostatic interaction among polyelectrolyte chains of adjacent SPB. This work could enrich our understanding of polyelectrolyte assembly in concentrated SPB, thereby greatly broadening the application fields of SPB.