Effects of Ionic Groups On the Assembly of Polymer-Grafted Nanoparticles

Equilibrium anisotropic nanostructures from polymer-grafted iron oxide nanoparticles offer extensive potentials in forming ionically conductive ordered nanocomposites. By protecting particles with additional silane layer, grafted chains are effectively sulfonated and their original nanostructures are preserved up to 3 mol% sulfonation level. We show that randomly associated ionic units do not facilitate the aggregation of our functionalized particles which is confirmed with small-angle x-ray scattering and transmission electron microscopy results. We conjecture that ionic clustering driven by ionic interactions between sulfonic groups is inhibited with the poly(styrene) matrix chains. With the increase in the length of the brush, thus less interaction with the free chains, the sulfonated units interact strongly resulting in percolated clusters of nanoparticles. This facile strategy to design multifunctional polymer nanocomposites can be used as means of controlling the ion transport within ionically functionalized ordered polymer-grafted particles.