Oral: Role of Interaction Range on the Microstructure and Dynamics of Attractive Colloidal Systems

Colloidal gels, a class of complex materials, occupy a pivotal position at the interface of soft matter physics, materials science, and nanotechnology. They play a crucial role in various natural and industrial settings, from biological tissues to advanced materials. These gels form as colloidal particles form reversible bonds in a liquid medium, eventually creating a network structure that exhibits a remarkable interplay of solid and fluid-like properties. The colloid gelation phase diagram has been traditionally characterized using three key factors: particle volume fraction, strength of attraction, and range of attraction. While there's a rich body of literature on the role of attraction strength and particle volume fraction, majority of studies have been limited to short range interactions. Using molecular simulations, we explored the effect that the range of attractions has on the microstructure and dynamics of both weakly and strongly attractive colloidal systems. Although gelation occurs significantly faster at high attraction strength, by an order of magnitude compared to low strength, we did not observe any clear trend in gelation-rate with respect to a change in the range of interaction. However, as the attraction range increases in both systems, the final structure undergoes a transition from a fractal configuration to a fluid of dense clusters. In a very dilute system with very-long range attraction, we observed only a fluid of clusters, irrespective of the attraction strength.