Dynamics of polymer-grafted nanoparticles controlled by soft confinement

The efficacy of polymer-grafted nanoparticles (PGNPs) in applications depends on their transport within complex soft matrices featuring heterogeneities similarly sized to the PGNPs. Further, the deformability of the grafted polymers leads to soft interactions that may alter the dynamics, depending on the relative size of the grafted polymer and particle core. When the radius of gyration R_g of grafted polymer is much smaller than NP radius R_NP, dynamics of PGNPs are expected to be similar to a hard sphere. Conversely, when R_g is much larger than R_NP, PGNPs behave like a dendritic polymer or a star. In the intermediate regime where R_g and R_NP are comparable, the structure and dynamics become influenced by both the hard (NP-NP) and soft (polymer-polymer) interactions. This regime is not well understood. Using a “grafting-to” method, we attach linear polystyrene chains to comparably sized spherical particles and disperse them in polystyrene dissolved in 2-butanone. We probe the structure and dynamics of our system using a combination of neutron and X-ray scattering. Our results show that grafted corona compresses and dynamics deviate from predictions of hard spheres in polymer solutions, suggesting an introduction of a soft potential due to grafted-free polymer interactions.