Time-resolved microstructural changes in large amplitude oscillatory shear of model single and double component soft gels

TL;DR

This study uses molecular dynamics simulations to investigate the microstructural evolution of soft gels under large amplitude oscillatory shear, linking microscopic changes to macroscopic rheological behavior.

Contribution

It introduces a time-resolved analysis method that connects microstructural dynamics with non-linear rheology in model soft gels during LAOS.

Findings

Microstructural changes correlate with dynamic moduli variations.

Bond breakage and formation drive non-linear rheological response.

Two-component networks show enhanced mechanical stability.

Abstract

Soft particulate gels can reversibly yield when sufficient deformation is applied, and the characteristics of this transition can be enhanced or limited by designing hybrid hydrogel composites. While the microscopic dynamics and macroscopic rheology of these systems have been studied separately in detail, the development of direct connections between the two has been difficult, particularly with regard to the non-linear rheology. To bridge this gap, we perform a series of large amplitude oscillatory shear (LAOS) numerical measurements on model soft particulate gels at different volume fractions using coarse-grained molecular dynamics simulations. We first study a particulate network with local bending stiffness and then we combine it with a second component that can provide additional crosslinking to obtain two-component networks. Through the sequence of physical processes (SPP) framework we define time-resolved dynamic moduli and, by tracking the changes in these moduli through the period, we can distinguish transitions in the material behavior as a function of time. This approach helps us establish the microsopic origin of the non-linear rheology by connecting the changes in dynamic moduli to the corresponding microstructural changes during the deformation including the non-affine displacement of particles, and the breakage, formation, and orientation of bonds.