Conformational dynamics of charged polymers interacting with charged nanoparticles

TL;DR

This study investigates how charged nanoparticles influence the conformational dynamics of charged polymers under shear flow, revealing charge-dependent shifts in critical shear rates and new scaling relationships.

Contribution

It introduces a model showing how charged nanoparticles modify polymer behavior under shear, with new scaling laws involving nanoparticle charge and size ratios.

Findings

Charged nanoparticles alter the critical shear rate for polymer conformational transitions.

The critical zeta potential of CNP scales linearly with shear rate.

The critical zeta potential scales cubically with the size ratio of CNP-polymer composite.

Abstract

The transition from globular to elongated states of biopolymers in shear flow occurs at a distinct critical shear rate, $\dot{\gamma }^{*}$. The magnitude of $\dot{\gamma }^{*}$ depends on the internal potential and the polymer length. For example, the critical shear is much larger for von Willebrand Factor (vWF) compared to DNA. Furthermore, it is shown through computational analysis of vWF (model-vWF) that $\dot{\gamma }^{*}\sim N^{1/3}$, where N is the number of dimeric units in the vWF. In this study, we show that in the presence of charged nanoparticles (CNP) and polymer, the critical shear rate scales differently depending on the polymer length and the charge-strength of the CNP. It is shown that CNP alter the conformational dynamics of polymers under shear flow when the polymer beads have an opposite charge. The introduction of CNP shifts the critical shear rate and alters the scaling. Furthermore, it is shown that the critical zeta potential of CNP, $\zeta^{*}$, scales linearly with shear rate, and scales cubically with ratio $\beta$ between final CNP-polymer composite size and original polymer size, that is $\zeta^{*}\sim \dot{\gamma }\beta ^{-3}$.