Extensional rheology of all-polystyrene nanocomposites

All-polystyrene nanocomposites have been proved as an ideal model system due to the identical chemistry of the nanoparticles and the polymer matrix. Previous neutron scattering measurements have confirmed that the nanoparticles are homogeneously dispersed in the polymer matrix when the radius of the nanoparticles is smaller than the radius of gyration of the polymer chains. In the recent work [Ouyang et al., “The second network of soft-nanoparticles in linear polymers of the same chemistry,” Polymer 283, 126216 (2023)], linear viscoelasticity and dynamics of all-polystyrene nanocomposites involving nanoparticles of different fraction and rigidness have been systematically studied. Here, we prepared similar samples and studied their nonlinear rheological behavior in extensional flow. We show that with harder and more fraction of the nanoparticles, strain hardening in fast extensional flow is weakened, probably due to flow-induced phase separation.