Viscoelastic behaviors of shell-crosslinked core-shell nanoparticles suspended in polystyrene solutions

Shell-crosslinked coreshell nanoparticles (SCCSNs) were prepared via miniemulsion polymerization of styrene in the presence of silane-modified inorganic silica. The polystyrene (PS) shell of 58.6% in weight fraction was crosslinked using divinylbenzene. SCCSNs were spherical with a diameter distribution from 32 to 98 nm determined by dynamic light scattering. Dynamic rheology of SCCSNs suspended in PS/toluene solution was compared with that of suspensions of naked silica. The critical strain for onset of rheological nonlinearity was independent of SCCSN concentration above a concentration threshold, which differs from the silica suspensions. Linear dynamic rheological investigation revealed that SCCSN suspensions with a PS volume fraction of 20% were fluid-like at low particle concentrations while suspensions containing 4.2 vol% SCCSNs formed a gel-like structure. On the contrary, the silica suspensions with 20.0 vol% PS underwent a fluid-to-solid-like transition with increasing silica concentration. Reasons for the different rheological behaviors of the naked silica and SCCSN suspensions are discussed. Copyright (c) 2012 Society of Chemical Industry