Analysis of Shear-Thickening in Physical Gel. A Stochastic Theory for Polymer Networks

TL;DR

This paper develops a stochastic model to analyze shear-thickening in physical gels, accounting for chain detachment and active chain formation, successfully explaining observed viscosity behaviors in polymer networks.

Contribution

It introduces a novel stochastic theory incorporating looped chain effects and chain detachment dynamics to explain shear-thickening in physical gels.

Findings

The model reproduces shear-thickening behavior in HEUR solutions.

Chain detachment and active chain formation influence viscosity increase.

Nonlinear forces on active chains cause sharp viscosity enhancement.

Abstract

A formula of steady shear viscosity is derived by introducing a model to describe the dynamics of physically cross-linked network (physical gel), and successfully analyzes the shear-thickening behavior observed in HEUR aqueous solutions by Jenkins, Sileibi and El-Aasser. We take into account the effects of looped chains at junctions which detach their one end from the junction as the shear rate increases due to the collisions with other chains. This process produces the weak and wide enhancement of the number of chains whose both ends stick to the separate junctions (active chains) leading to the weak increase in the shear viscosity. It is also shown that the nonlinear force sustained by active chains induces the strong and sharp enhancement of the steady shear viscosity.