Emergence and evolution of a particulate network during gelation and coarsening of attractive colloids

Abstract

The process of gelation in attractive colloids involves formation of an interconnected and percolated network, followed by its coarsening and maturation. In this study, we analyze the formation and evolution of this particulate network and introduce deterministic quantitative measures to evaluate the key transition points. The rate of change in the number of colloidal clusters before and after percolation can be directly used to identify gelation as a continuous second order phase transition. Simultaneously the diameter of the particle network exhibits a distinguishable maxima, marking the precise moment of percolation transition. This is while the local measures of the structure such as coordination number do not reflect on the percolation. Alternatively, accumulative number of unique particle contacts can be used to indicate the long time coarsening of the particulate structure. Global structural measures such as Voronoi volume distribution and its changes over time can be also used to distinctly mark these two regimes. Finding a consistent behavior across varying attraction strength levels and volume fractions of colloids, we propose that percolation and coarsening of the particulate gels can be viewed as two distinct transitions with clearly distinguishable structural demarcations.