Electrostatic Repulsion Slows Relaxations of Polyelectrolytes in Semidilute Solutions

Published

July 19, 2022

Author(s)

Ali Slim, Winnie Shi, Farshad S. Samghabadi, Antonio Faraone, Amanda Marciel, Ryan Poling-Skutvik, Jacinta Conrad

Abstract

We investigate the structure and dynamics of unentangled semidilute solutions of sodium polystyrene sulfonate (NaPSS) using small-angle neutron scattering (SANS) and neutron spin-echo (NSE) spectroscopy. The effects of electrostatic interactions and chain structure are examined as a function of ionic strength and polymer concentration, respectively. The SANS profiles exhibit a characteristic structural peak, signature of polyelectrolyte solutions, that can be fit with a combination of a semiflexible chain with excluded volume interactions form factor and a polymer reference interaction site model (PRISM) structure factor. We confirm that electrostatic interactions vary with ionic strength across solutions with similar geometries. The segmental relaxations from NSE deviate from theoretical predictions from Zimm and exhibit two scaling behaviors around the characteristic structural peak. The chain dynamics are suppressed across the length scale of the correlation blob, and inversely related to the structure factor. These observations suggest that the highly correlated nature of polyelectrolytes presents an additional energy barrier that leads to de Gennes narrowing behavior.

Citation

ACS Macro Letters

Volume

11

Issue

7

Pub Type

Journals

Keywords

Polyelectrolytes, NSE

Citation

Slim, A. , Shi, W. , Samghabadi, F. , Faraone, A. , Marciel, A. , Poling-Skutvik, R. and Conrad, J. (2022), Electrostatic Repulsion Slows Relaxations of Polyelectrolytes in Semidilute Solutions, ACS Macro Letters (Accessed April 26, 2024)