Microstructure of Rod-Based Capillary Suspensions with Different Rod Aspect Ratios under Quiescent and Shear Flow

A particle-assembled microstructure in ternary capillary suspensions consisting of polyisobutylene (PIB) as the matrix phase, poly(ethylene oxide) (PEO) as the minor fluid phase, and silica (SiO2) particles with different aspect ratios (ARs) is probed by an in situ optical-shear technique, scanning electronic microscopy, and confocal laser scanning microscopy as well as rheometry. It is found that the capillary bridging force brought by the presence of the PEO wetting layer between particles can be influenced by the AR of particles and shear rate, which all play decisive roles in determining the microstructure and rheological properties of suspensions. Moreover, two novel aggregation modes of rods and an interesting spatiotemporal organization phenomenon of particle aggregates (vorticity-aligned particle bands) are found under shear flow.