Nonequilibrium continuous phase transition in colloidal gelation with short-range attraction

• Published in: Nature communications Vol. 11; no. 1; p. 3558
• Main Authors: Rouwhorst, Joep, Ness, Christopher, Stoyanov, Simeon, Zaccone, Alessio, Schall, Peter
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.07.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/923/916; 639/766/94; Attraction; Biophysics; Clusters; Colloiding; Computer simulation; Exponents; Gelation; Humanities and Social Sciences; Jamming; Kinetic equations; Materials science; Mathematical models; multidisciplinary; Nanotechnology; Particle density (concentration); Percolation; Percolation theory; Phase transitions; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-17353-8

The dynamical arrest of attractive colloidal particles into out-of-equilibrium structures, known as gelation, is central to biophysics, materials science, nanotechnology, and food and cosmetic applications, but a complete understanding is lacking. In particular, for intermediate particle density and attraction, the structure formation process remains unclear. Here, we show that the gelation of short-range attractive particles is governed by a nonequilibrium percolation process. We combine experiments on critical Casimir colloidal suspensions, numerical simulations, and analytical modeling with a master kinetic equation to show that cluster sizes and correlation lengths diverge with exponents  ~1.6 and 0.8, respectively, consistent with percolation theory, while detailed balance in the particle attachment and detachment processes is broken. Cluster masses exhibit power-law distributions with exponents  −3/2 and  −5/2 before and after percolation, as predicted by solutions to the master kinetic equation. These results revealing a nonequilibrium continuous phase transition unify the structural arrest and yielding into related frameworks. Jamming and gelation constitute a longstanding challenge in materials science due to their out-of-equilibrium nature. Rouwhorst et al. show the hallmarks of a nonequilibrium phase transition in a tunable critical Casimir colloidal system, with critical exponents of cluster growth in agreement with percolation theory.