Oscillatory shear rheology of dilute solutions of flexible polymers interacting with oppositely charged particles

Abstract

in Wiley Online Library (wileyonlinelibrary.com) Fluids with both attractions and repulsions among its constituents can exist in multiple states depending on nature of the interactions. An external flow can induce such systems to transition between the different states, such as the globule-stretch transition for polymers in poor solvents. Brownian dynamics simulations of a dilute solution of polymers and colloids interacting via short-ranged potentials are presented. For some values of the strength and range of interactions, compact structures of polymers and colloids are formed. An external flow is capable of pulling these globules apart, causing the polymers to stretch at a critical shear rate. In oscillatory shear, the shear rate can cycle between being above and below this critical shear rate leading to interesting dynamics. These dynamics are quantified using the rheological response in large amplitude oscillatory shear.

An adaptive parallel tempering method for the dynamic data‐driven parameter estimation of nonlinear models

“…This model also involves comparison to the equilibrium value of the structure parameter, based on current stress or shear rate, to calculate the new value. It uses the difference between current conditions and equilibrium conditions as the driving force to calculate the next value of structure parameter, modulus, viscosity, etc …”

“…Finally, the algorithm is applied to the parameter estimation in fitting complex nonlinear rheology models to measurement data. Such experiments include several dynamic sets of experiments, such as large amplitude oscillatory shear data (LAOS) . LAOS flow is a regime used in rheological systems to physically probe a nonlinear mechanical response, both temporally and spatially, either by programming a sinusoidal strain oscillation and measuring the stress response or vice versa, using a rheometer.…”

“…Such experiments include several dynamic sets of experiments, such as large amplitude oscillatory shear data (LAOS). [55][56][57][58][59] LAOS flow is a regime used in rheological systems to physically probe a nonlinear mechanical response, both temporally and spatially, either by programming a sinusoidal strain oscillation and measuring the stress response or vice versa, using a rheometer. LAOS presents a unique way to measure and quantify material properties using nonlinear flow conditions.…”

“…LAOS presents a unique way to measure and quantify material properties using nonlinear flow conditions. [55][56][57][58][59] In the following it is shown that our approach ensures, for reasonably complex realistic problems, the reproducible approximation of the global minimum independent of the initial guess in a systematic way and with very few adjustable algorithmic parameters that also do not sensitively affect the performance of the method. Consequently, we anticipate application to be of value for a broad range of parameter fitting challenges concerning dynamic data.…”

Influence of shear on globule formation in dilute solutions of flexible polymers

“…Recently, we have used the model developed in this article and found interesting stress versus strain response due to hopping between the different states of the system in large amplitude oscillatory shear. 36 This article examines the formation and dynamics of such states in steady shear flow.…”