Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L15: Fantastic Polyelectrolytes and How They Behave in Coacervates
8:00 AM–11:00 AM,
Wednesday, March 17, 2021
Sponsoring
Unit:
DPOLY
Chair: Michael Rubinstein, Duke University Scott Danielsen, Duke University
Abstract: L15.00003 : Entanglements between Polyelectrolytes in Solutions
9:12 AM–9:48 AM
Live
Presenter:
Carlos Lopez
(RWTH Aachen University)
Author:
Carlos Lopez
(RWTH Aachen University)
In dilute salt-free and excess salt solutions NaPSS and NaCMC are found adopt rod-like ([η] ∼ N2) and expanded coil ([η] ∼ N0.77) conformations respectively, in agreement with theoretical expectations. Combining viscosity and single-chain diffusion data for semidilute non-entangled data, we show that the Rouse-Zimm model quantitatively describes polyelectrolyte dynamics in this regime. Further, we find that the local friction coefficient of NaPSS is a strong function of polymer concentration. This means that crossovers in the viscosity-concentration power laws, often used in literature to identify the entanglement crossover (ce), do not always yield reliable estimates ce.
While addition of salt leads to a large decrease in the size of polymer chains, it does not, surprisingly, affect the entanglement properties of polyelectrolytes. This finding is at odds with the expectation of packing and scaling models of polymer entanglement and suggests that the density of binary contacts in solution may not affected by the solvent quality. We find that the entanglement crossover and entanglement plateau are unaffected by the concentration of added salt for NaPSS and NaCMC. Based on these observations, we work out the reptation dynamics of polyelectrolytes in salt-free solution, which differ appreciably from earlier models.
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