Capillary suspensions of colloidal rods
Date
2021
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Publisher
University of Delaware
Abstract
Colloidal suspensions, composed of micron-sized attractive particles in fluids, are a prevalent type of soft material abundantly found in cosmetics, paints, dairy products, cements, and pharmaceuticals. Capillary suspensions are solid-liquid-liquid suspensions in which a sample-spanning particle network forms due to the capillary bridging forces. When a small amount of the secondary immiscible liquid is added to the bulk phase, gel transition is observed and the rheological properties become drastically altered. ☐ In this work, we develop new capillary suspensions of colloidal rods and study the anisotropic effects on the microstructure. Suspensions of rods exhibit unique microstructural behavior depending on the rod aspect ratio due to large excluded volumes and orientation-dependent attractions. However, the link between the rod network microstructure and macroscopic behavior still remains a mystery. A series of experimental methods are introduced to systematically control the components of rod-based capillary suspensions. This is achieved through the synthesis of highly tunable rods of varying aspect ratio, fluorescence labeling of solid particles, design of the new capillary suspension, and three-dimensional confocal imaging. Upon increasing the rod aspect ratio, we observe enhanced sample-spanning particle networks in the capillary suspensions. A very small increase in secondary liquid content also leads to the formation of a percolated network. These findings can be further integrated to study the rheological properties of the rod-based capillary suspensions and bridge the gap between the microstructural changes and macroscopic rheological behavior.
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Keywords
Anisotropic particles, Aspect ratio, Capillary suspension, Colloidal suspension, Confocal microscopy, Colloidal rods