Electrostatic Repulsion Slows Relaxations of Polyelectrolytes in Semidilute Solutions
Electrostatic Repulsion Slows Relaxations of Polyelectrolytes in Semidilute Solutions
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DOI：
10.1021/acsmacrolett.2c00213
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发表时间：
2022-06-27
影响因子：
7.015
通讯作者：
Conrad，Jacinta C.
中科院分区：
文献类型：
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作者：
Slim，Ali H.;Shi，Winnie H.;Conrad，Jacinta C.
用小角中子散射(SANS)和中子自旋回波谱(NSE)研究了聚苯乙烯磺酸钠(NaPSS)无纠缠半稀溶液的结构和动力学。分别考察了静电相互作用和链结构对离子强度和聚合物浓度的影响。SANS图谱显示了一个特征的结构峰，这是聚电解质溶液的特征，它可以与具有排除体积相互作用形状因子的半柔性链和聚合物参考相互作用位置模型(PRISM)结构因子的组合相匹配。我们证实，在具有相似几何结构的溶液中，静电相互作用随离子强度而变化。NSE的分段驰豫偏离了Zimm的理论预测，并表现出两种标度行为，两种区域之间的交叉发生在特征结构峰附近。链动力学在相关斑点的长度范围内被抑制，并且与结构因子成反比。这些观察表明，聚电解质的高度相关性提供了一个额外的能量障碍，导致了De Gennes的狭窄行为。
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.