Shear localization in associating polymer gels

Abstract

Despite the ubiquity of phys. crosslinked polymer gels in natural and synthetic systems, a fundamental understanding connecting the dynamics and microstructure to the bulk rheol. behavior under large deformations remains a challenging and open problem. To explore this connection, we perform startup shear computer simulations on phys. assocg. polymer gels and track the temporal and spatial dynamical and structural response. For deformation rates exceeding the characteristic relaxation time of the gel, we observe stress overshoot corresponding to network yielding. Upon yielding, cage breaking results in a significant decrease in the chain relaxation time, which is reflected in the enhanced chain diffusivity relative to the quiescent state. Below a crit. shear rate and upon yielding, we observe the formation of steady-state shear bands in the gradient direction that have a marked difference in the polymer concn. and are dynamically and structurally distinct.

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