Scaling Behavior of Entanglement Dynamics in Polyelectrolyte Solutions: Insights from High-Frequency Rheometry

Yahya Rharbi ¹

⁰Univ. Grenoble Alpes, CNRS, Grenoble INP, LRP, 38000 Grenoble, France.

Acs Macro Letters +

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February 13, 2025

View abstract on PubMed

Summary

This study explores entanglement dynamics in polyelectrolyte solutions, revealing how single entanglement relaxation and reptation times transition to neutral scaling behavior. Electrostatic interactions uniquely influence these dynamics across different concentration regimes.

Area Of Science

Polymer physics
Rheology
Solution dynamics

Background

Understanding entanglement dynamics in polyelectrolyte solutions is crucial for predicting their viscoelastic properties.
Existing models often struggle to capture the full dynamic spectrum and align with scaling predictions in different concentration regimes.

Purpose Of The Study

To investigate the scaling behaviors of viscoelastic properties in cationic polyacrylamide solutions.
To determine how single entanglement relaxation time (τe) and reptation time (τrep) are affected by concentration and electrostatic interactions.
To compare experimental findings with theoretical scaling predictions in semidilute entangled (SE) and fully entangled (FE) regimes.

Main Methods

Utilized piezo compressional and classic rotational rheometry to study solutions of high molecular weight cationic polyacrylamide.
Analyzed viscoelastic properties over several decades of time scales across varying concentrations.
Determined crossover concentrations (Ce and CD) between different entanglement regimes.

Main Results

Specific viscosity (ηsp) and reptation time (τrep) scaled as predicted in Fuoss, SE, and FE regimes.
Single entanglement relaxation time (τe), plateau width (τrep/τe), and high-frequency modulus (Ge) initially followed SE predictions.
These properties then transitioned to neutral scaling at an intermediate concentration (CDe), indicating a shift in behavior.

Conclusions

Electrostatic interactions uniquely impact single entanglements and reptation dynamics in polyelectrolyte solutions.
A transition to neutral behavior occurs at CDe for single entanglements and at CD for reptation.
The findings provide critical insights into the complex entanglement dynamics of charged polymer solutions.