Microrheological Approach for Probing the Entanglement Properties of Polyelectrolyte Solutions

Abstract

The entanglement dynamics and viscoelasticity of polyelectrolyte solutions remain active research topics. Previous studies have reported conflicting experimental results when compared to Dobrynin's scaling predictions derived from the Doi−Edwards (DE) tube model for entangled polymers. Herein, by combining classical bulk shear rheometry with diffusing wave spectroscopy (DWS) microrheometry, we investigate how the key viscoelastic parameters (the specific viscosity η sp , the plateau modulus G e , and the ratio of the reptation time to the Rouse time of an entanglement strand τ rep /τ e ) depend on the polymer concentration for semidilute entangled (SE) solutions containing poly(sodium styrenesulfonate) with high molecular weight. Our experimental measurements yield G e ∝ c 1.51±0.04 , in good agreement with the scaling of G e ∝ c 1.5 predicted by Dobrynin's model for salt-free polyelectrolyte SE solutions, suggesting that the electrostatic interaction influences the viscoelastic properties of polyelectrolyte SE solutions. On the other hand, the deviation in the scaling exponent for η sp ∝ c 2.56±0.04 and τ rep /τ e ∝ c 1.82±0.28 is observed between our DWS experiments and Dobrynin's model prediction (∝ c 1.5 ), likely due to the fact that Dobrynin's scaling model does not account for mechanisms such as the contour length fluctuation, the constraint release, and the retardation of solvent dynamics, which are known to occur for SE solutions of neutral polymers. Our results demonstrate that DWS serves as a powerful rheological tool to study the entanglement dynamics of polyelectrolyte solutions. The scaling relationships obtained in this study provide new insights to the long-standing debate on the entanglement dynamics of polyelectrolyte solutions.

Additive Manufacturing of a Super Toughened Biodegradable Polymer Blend: Structure–Property-Processing Correlation and 3D Printed Prosthetic Part Development

“…The reptation time (τ rep ), which represents the timescale of polymer chain mobility, plays an important role in determining the strength of interlayer bonding . To explore the relationship between τ rep and printing temperature, τ rep was measured at different temperatures by taking the inverse of the crossover frequency . As the print temperature increases, τ rep decreases.…”

“…50 To explore the relationship between τ rep and printing temperature, τ rep was measured at different temperatures by taking the inverse of the crossover frequency. 54 As the print temperature increases, τ rep decreases. Specifically, for print temperatures of 170, 180, and 190 °C, the corresponding τ rep values were found to be 1.075, 0.8, and 0.5 s, respectively, as shown in Figure 3d.…”

Dilute polyelectrolyte solutions: recent progress and open questions

“…This differs from Norisuye et al's approach, who introduced an ionic strength dependence of R 0 (or R g,0 ) via eqn (19), for this reason, we use a 0 S for the R g expansion factor instead of a S . The Bjerrum length is included in eqn (26) in two ways: first, the explicit term l B 1/5 accounts for the fact that as the dielectric constant decreases, the strength of the electrostatic repulsion between two like charges increases. According to Manning's theory, if the distance between ionic groups is smaller than l B , then f C bl B À1 , so eqn (26) indicates R g to be a decreasing function of l B (as shown in Fig.…”

“…Moreover, it is not possible to define a single solvent quality, and the chemical structure of the polyelectrolyte backbone, side-chain ions and counterions have to be considered separately. In concentrated solutions, the polyelectrolyte systems exhibited fascinating dynamics [18][19][20][21][22][23][24][25][26][27][28][29] which we are only beginning to understand. Their ability to form complexes with oppositely charged matter made them relevant to many industrial formulations and biological systems and is one of the main aspects of polyelectrolyte research today.…”

Rheology of Polyelectrolyte Solutions: Current Understanding and Perspectives

“…Following Dobrynin and Jacobs' suggestion, Matsumoto et al 77) recently investigated the entanglement properties of aqueous polyelectrolyte solutions containing a high molecular weight NaPSS (M w = 3.16×10 6 Da, N = 1.53×10 4 ) by using diffusing wave spectroscopy (DWS). The DWS is a dynamic light scattering technique for tubid samples, and enables the measurement of the complex modulus of viscoelastic materials at frequencies as large as 10 7 rad s −1 .…”