(393j) Microstructure of Magnetic Nanoparticles in Spherical Polyelectrolyte Brushes Observed by Small Angle X-Ray Scattering

Small angle X-ray scattering (SAXS) was demonstrated as a powerful tool to “observe” the distribution of magnetic nanoparticles (MNP) in spherical polyelectrolyte brushes (SPBs). The MNP were prepared in situ by using SPB as a nano-reactor. SPBs consisting of a solid polystyrene (PS) core and linear poly(acrylic acid) (PAA) chains attached densely onto PS core by one end were prepared by photoemulsion polymerization and dispersed in water. MNP can be trapped inside SPB due to the chemical coordination between carboxyl groups in PAA and MNPs. A model is built to illustrate the variation of the absorbed amount and distribution of MNP and the radius of gyration of SPB at different pH and salt concentration. The scattering intensity curves of investigated samples could be fitted well by regulating fit parameters of this model. The SAXS curves legibly reveal that the PAA chains are virtually uncharged at low pH. With the increase of pH their length increase gradually until getting full extended at high pH (>8). The influence of salt concentration is mainly reflected in the interaction among SPB. High salt concentration can shield the interaction between PAA chains completely.