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Introduction: By using a proposed “two phase” model considering viscoelasticities from the bulky polymer phase and the “filler phase” composed of particles coated with bound polymer layer,we found that linear dynamic rheology of a series of nanoparticle filled polymer melts follows a polymer mediated filler jamming towards glass formation accounting for origin of the fluid‐to‐solid transition upon filling.To validate the propose model,nanosilica coated with crosslinked polystyrene(PS)shell(SCCSN)was used to prepare PS nanocomposites to investigate dispersion and viscoelasticity of SCCSN filled PS.The crosslinked PS shell does not only stabilize the nanosilica core but also avoids macromolecules in PS shell to entangle with bulk PS macromolecules,resulting an athermal model system for rheology study of the filled melts.Methods: SCCSN containing 79.1 wt%crosslinked PS shell was prepared by using miniemulsion polymerization and the shell was crosslinked by divinylbenzene under ultrasounding.The composites were prepared by mixing nanosilica or SCCSN,PS and antioxidant using a Haaker rheomix 600 mixer at 180℃ and 50 rpm for 10 min.Rheology was performed on a rheometric system(ARES‐G2)at 180℃.Results: The SCCSN filled nanocomposites are highly transparent and the melt exhibits high thermal stability(Figure 1).The excellently dispersed nanosilica core exhibits stronger reinforcement effect than the naked nanosilica.However,the melts containing either SCCSN or nanosilica show the same scaling exponent in a plot of low‐frequency storage modulus as a function of filler content.Discussion: A comparison of rheology of melts containing either SCCSN or nanosilica reveals a jamming rather than the traditional filler networking mechanism for the fluid‐to‐solid transition.The strain amplification factor of SCCSN is lower than naked nanosilica while it increases with increasing crosslinking degree of the shell.At filler contents above jamming concentration,the stress relaxation of SCCSN filled melts is much lower than PS and the nanosilica filled melts,suggesting a significant influence of filler dispersion on the rheology behaviour.Furthermore,both nanosilica and SCCSN reduce the onset strain rate for shear thinning while they do not introduce additional mechanism for origination of nonlinear rheology except for macromolecular disentanglement of the PS matrix.