Emergent Jamming Dynamics of Interfacial Nanoparticles in Polymer Blends Undergoing Phase Separation

The interfacial assembly and jamming of nanoparticles (NPs) in phase separating blends is a potentially useful strategy for creating nanoporous gels and Pickering emulsions. However, the lack of experimental methods to obtain microscopic insights into the kinetics of this interfacial NP jamming presents challenges. We use grazing incidence standing wave X-ray photon correlation spectroscopy on a novel bilayer blend geometry embedded with polymer grafted nanoparticles (GNPs) to in situ study the temporal evolution of GNP interfacial jamming during binary polymer blend phase separation. Using two parameters - graft density and volume fraction - of GNPs, their controlled interfacial assembly and jamming are enabled to induce a systematic arrest of phase separation of lower critical solution temperature (LCST) binary blends of poly(styrene) (PS) and poly(vinylmethyl ether) (PVME). Using the combination of the novel geometry and depth sensitive, nondestructive technique we probe for the first time the dynamics of GNPs at the interface with aging time and elucidate the conditions for the emergence of nanoparticle jamming during the temporal evolution of phase separation. We also identify a time scale for the onset of interfacial nanoparticle jamming, tjam, which correlates with the time scale, tarrest, of arrested blend phase separation. To the best of our knowledge, this is the first direct experimental report that measures interfacial nanoparticle jamming dynamics and also correlates it with arrested phase separation kinetics.