Abstract
We investigate the structure and dynamics of unentangled semidilute solutions of sodium polystyrenesulfonate (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, with the crossover between the two regimes taking place 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.
| Original language | English |
|---|---|
| Pages (from-to) | 854-860 |
| Number of pages | 7 |
| Journal | ACS Macro Letters |
| Volume | 11 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 19 2022 |
Funding
We thank Megan Robertson for access to the rheometer. This research was partially supported by the National Science Foundation (CBET-2004652, CBET-2113767, and CBET-2113769), the Welch Foundation (E-1869 and C-2003-20190330), and the Rhode Island Foundation (Medical Research Award 3.2021). Access to NSE was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. This work utilized SasView software, which was developed by the DANSE project from NSF Award DMR-0520547. Certain trade names and company products are identified in order to specify adequately the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best for the purpose.