Evidence of shear-induced polymer release from a swollen gel particle

Abstract : The influence of simple shear flow on the behaviour of an isolated polyelectrolyte hydrogel particle swollen in an aqueous hydroxypropylcellulose solution was studied by rheo-optics. When submitted to a constant shear stress, an initially spherical particle deforms quickly to adopt a stable ellipsoidal form. Upon reaching a first stress threshold, some liquid is released from the particle. This liquid release is determined by a critical deformation value above which the gel cannot retain all of its solvent. At stresses above a second threshold value, small droplets of liquid are secreted from the particle and move away in the flow direction.