Directed percolation identified as equilibrium pre-transition towards non-equilibrium arrested gel states.
The macroscopic properties of gels arise from their slow dynamics and load-bearing network structure, which are exploited by nature and in numerous industrial products. However, a link between these structural and dynamical properties has remained elusive. Here we present confocal microscopy experiments and simulations of gel-forming colloid-polymer mixtures. They reveal that gel formation is preceded by continuous and directed percolation. Both transitions lead to system-spanning networks, but only directed percolation results in extremely slow dynamics, ageing and a shrinking of the gel that resembles synaeresis. Therefore, dynamical arrest in gels is found to be linked to a structural transition, namely directed percolation, which is quantitatively associated with the mean number of bonded neighbours. Directed percolation denotes a universality class of transitions. Our study hence connects gel formation to a well-developed theoretical framework, which now can be exploited to achieve a detailed understanding of arrested gels.
Institute for Theoretical Physics II: Soft Matter, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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Kohl
Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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Capellmann
Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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0000-0003-1334-5940
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Laurati
Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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Egelhaaf
Institute for Theoretical Physics II: Soft Matter, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.|Institute of Theoretical Physics 1, Friedrich-Alexander University Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany.
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Schmiedeberg