An Inquisitive into the Indirect Measurement and Comparison of the Viscosity of Nanoconfined Polystyrene Nanoparticles

Abstract

The effects of nanoconfinement on the dynamic and the glass transition (Tg) of polymers remains the focus of a lot of research since over a decade. Particularly, the glass transition temperature (Tg) and the dynamic of polystyrene (PS) were found to be altered by nanoconfinement in thin films and on the bulk free-surface. However, the dynamic of polymer nanoconfined in nanoparticles has not been investigated, even though the close-packed nanoparticle geometry is commonly used in many applications such as waterborne coatings. We investigate the dynamic of polystyrene in nanoparticles by monitoring the closure of voids (interstices) between PS nanoparticles in the close-packed structure. Void-closure during the passage from the close-packed particles to bulk PS is monitored using small angle neutron scattering at the bulk Tg (100 °C). The relaxation time (τ) and the apparent viscosity (η) of nanoconfined polystyrene estimated from the void-closure decay is found to decrease only by ~2 times for particle diameters between 93 nm and 42 nm. These results infer that dynamic of nanoconfined PS in nanoparticles at the bulk Tg is not different from that of bulk polystyrene.