Free and Grafted Polymer in Polymer Grafted Nanoparticle Solutions by Small Angle Neutron Scattering

Liquid-like polymer grafted nanoparticles have shown great promise in applications such as electrochemistry, gas separation, and redox flow batteries due to their enhanced conductivity, tunability, and negligible vapor pressure. However, to employ these nanoparticle assemblies in these applications, it is important to understand the conformation and structure of the polymer in these assemblies in the electrochemical milieu. Here, we report the use of small-angle neutron scattering to probe the structure and dispersion of polymer grafted to SiO₂ nanoparticle in an aqueous solution with and without supporting electrolyte. Our results indicate that in aqueous solution, there exists a large amount of free polymer that is not grafted to the functionalized nanoparticles, which may also strongly interact with the grafted polymer layer. The presence of supporting electrolyte dramatically alters the structure of these solutions, as it not only alters the structure of the free polymer but also hinders the interaction of the polymer with the functionalized nanoparticles. These results also correlate well to changes in the viscosity of the solutions, providing valuable insight into the importance of the polymer-nanoparticle interface in these promising functional constructs.