Understanding the role of sample preparation parameters on gelation of a colloidal dispersion

Colloidal gels have been of interest for several years due to their central role in the design of products and technologies across pharmaceuticals to cosmetics, coatings, and advanced materials. Particularly, hydrophilic clay gels are widely studied owing to their tunable rheological properties and rich phase behavior. In this work, we perform a study on Laponite® (a synthetic clay) dispersion to investigate the underappreciated yet critical role of preparation protocols on gelation behavior of colloidal gels. We perform rheological experiments to monitor the effect of preparation parameters, such as drying, stirring time, stirring speed, stirring technique, salt purity, sample volume, and rheometer geometry on the gelation behavior of Laponite dispersion. The aqueous dispersion of Laponite unanimously exhibits all rheological signatures of sol–gel transition across multiple sample preparation protocols adopted in this study. The attractive gel microstructure is also confirmed by Small-Angle X-ray Scattering (SAXS). Our findings indicate that variations in these preparation parameters lead to differences in the gelation behavior and are related to the surface and edge charge acquired by the particle upon dispersion in aqueous media. We also perform Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FE-SEM), and Powder X-Ray Diffractometer (PXRD) measurements to have insights into the thermal stability and particle-level architecture. The findings highlight the importance of preparation parameters in determining gelation behavior and provide a framework for improving the reproducibility of Laponite-based colloidal gels.