Dynamic Behavior of Polystyrene Soft Nanoparticles by Neutron Spin Echo

The inclusion of soft polystyrene nanoparticles improves the dynamic properties of bulk polystyrene, a behavior that is not yet fully understood. To provide insight into this phenomenon, the dynamics of the nanoparticles are evaluated using neutron spin echo (NSE) spectroscopy. These particles consist of a crosslinked polystyrene core with loosely connected loops and tails, which we term a fuzzy interface. NSE spectroscopy of dilute solutions of the nanoparticles (NPs) show the nanoparticle with the lowest crosslinking density and molecular weight exhibits the most Zimm-like dynamics. Varying the synthetic procedure to create nanoparticles with lower molecular weights and fuzzier surfaces results in more heterogeneous relaxation processes, indicating that the dynamics of the core differs significantly from that of the outer shell. Combined with our previous studies showing the relationship between the fuzziness of the nanoparticle and diffusion of bulk polystyrene, these results exemplify the importance of the NP molecular weight and the interaction of the fuzzy interface with linear chains in determining the dynamics of all polymer nanocomposite system.