Relationship between the heterogeneity in particle dynamics and network topology in transient networks via a microrheological study

Soft materials encompass various hierarchical structures that determine their mechanical properties. However, the relationships between these hierarchical structures and mechanical properties remain unclear owing to a lack of studies on local information and the difficulty in controlling hierarchical structures. Herein, we demonstrate a multiple particle tracking method, which is a representative microrheological measurement method, within transient networks with a precisely controlled network topology. This is the most basic parameter of hierarchical structures. Our results reveal that the heterogeneity in particle dynamics is enhanced and reaches a maximum at the percolation threshold, which is a universal phenomenon in sol–gel transitions. Notably, this study is the first to report that the heterogeneity in particle dynamics within transient networks established via reversible bonds exhibits characteristics similar to those of percolation phenomena in hydrogels. These insights provide a basis for examining the relationships between the mechanical properties and hierarchical structures of soft materials. A multiple particle tracking method was used to track probe particles in Tetra-PEG slimes with various network connectivities, revealing that the deviation from the Gaussian distribution of the particle dynamics is greater than the percolation threshold (network connectivity = 0.34). This study is the first to report that the heterogeneity of particle dynamics in transient networks, formed through reversible bonds, exhibits characteristics similar to those observed during sol–gel transitions.