Control of Particle Shape by Adjusting Solidification Rates in Aggregation of Dispersed Gels

Abstract

This paper reports a chemical method, phase-separation/aggregation (PSA), to prepare CPT particles with surface morphology tuned by adjusting the process parameters during aggregation and coalescence of the particles. It is shown a highly hydrophilic organic solvent favors the formation of spherical particles due to the facile gel formation and expeditious solidification. Deviations of spherical particle shape can be achieved by inclusion of a less aqueous-soluble organic solvent in which the viscosity of gel colloids is increased gradually, allowing shear force of the non-solvent phase to apply its effect on the particle shape. The particles can be made potato-shaped or elliptically shaped by adjustments of the aqueous solubility of the organic solvent. The effect of shear force can also be magnified by increasing the speed of stirring during particle coalescence, with a finding showing a distorted, elliptical shape as a result of increasing agitation speed. The viscosity or the solid content values of the aqueous non-solvent phase solution are also found to have effects on the particle shape. It is found a dilute aqueous phase solution is prone to forming spherical particles, whereas a concentrated aqueous phase allows the particles to become non-spherical. These parameters are studied to elucidate the interplay of viscosity and surface tension, and to understand their effects on the particle shape. The results of this paper show that the particle shape obtained from the PSA method can be fine tuned by modulating the process parameters.