The effects of hydrophobic SiO2 nanoparticles on the realtime morphology evolution of the immiscible blend of polydimethylsiloxane(PDMS)/polyisobutylene(PIB)(90 wt%:10 wt%) were investigated under simple shear flow with an online optical-shear system.The theoretical predication indicated that SiO2 particles were mainly trapped in the interface between two phases.It was found that the droplet size of PIB dispersed phases was determined by the content of SiO2 nanoparticles and shear rate.The coverage of SiO2 particles on the PIB dispersion droplets suppressed the coalescence of the dispersed phases and decreased their size at low shear rate.A bimodal distribution of the droplet size which originated from the uncompleted coverage of SiO2 on PIB dispersed phase was observed.With the increase in the content of particles

the peak on the droplet size curve which corresponded to those large dispersed phases

shifted gradually towards another peak corresponding to those small dispersed phases

and finally merged into a single one.It was also found that the incorporation of SiO2 nanoparticles in PDMS/PIB blends decreased the dependence of droplet size on the shear rate.The synergetic effects of particle coverage

droplet breakup and coalescence resulted in similar droplet size in PDMS/PIB blends under two different shear rates when the contents of SiO2 particles exceeded 2.5 wt%.