Microstructure of polydisperse colloidal gels

Abstract

We use confocal microscopy to image colloidal gels formed from highly polydisperse particles. We suspend our polydisperse particles in a density matched solvent, and let the particles spontaneously aggregate through the van der Waals force. The particle size distribution $P(R)$ is roughly log-normal, with the largest particles more than 15 times the size of the smallest particles. The pairing of nearest neighbor particles is consistent with a null hypothesis that pairings are made randomly, that is, any two particle sizes have a probability of being neighbors consistent with their proportionality in $P(R)$. That being said, as expected, larger particles have more nearest neighbors than small ones. This leads to an over-representation of large particles in tetrahedral structures where four particles are mutually nearest neighbors, showing that large particles help provide rigidity to the gel structure. The tetrahedral structures also suggest that particles are able to rearrange during the gelation process, until their motion is stabilized by the multiple contacts with their neighbors. We discuss the implications of how other size distributions $P(R)$ would affect the gel structure.

Fig. 1 has a pretty confocal microscope image

References in corpus (21)

• The Physics of the Colloidal Glass Transition
• Equilibrium cluster phases and low-density arrested disordered states: The role of short-range attraction and long-range repulsion
• Influence of Particle Size Distribution on Random Close Packing
• Glasses in hard spheres with short-range attraction
• On measuring colloidal volume fractions
• Structure and dynamics of colloidal depletion gels: coincidence of transitions and heterogeneity
• Dynamical heterogeneities close to a colloidal gel
• Gelation as condensation frustrated by hydrodynamics and mechanical isostaticity
• Crystalline phases of polydisperse spheres
• Sudden collapse of a colloidal gel
• Real Space Analysis of Colloidal Gels: Triumphs, Challenges and Future Directions
• Local structure and dynamics in colloidal fluids and gels
• The role of weak charging in metastable colloidal clusters
• Theory of elastic constants of athermal amorphous solids with internal stresses
• Coupling between criticality and gelation in "sticky" spheres: A structural analysis
• The role of quench rate in colloidal gels
• Polyhedral colloidal `rocks': low-dimensional networks
• Direct Imaging of Contacts and Forces in Colloidal Gels
• Effect of polydispersity in concentrated magnetorheological fluids
• Circle radius distributions determine random close packing density
• Aging of colloidal gels in microgravity