Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States.
Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States.
ACS Macro Lett. 2022 Jul 19;11(7):854-860. doi: 10.1021/acsmacrolett.2c00213. Epub 2022 Jun 27.
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.
我们使用小角中子散射（SANS）和中子自旋回波（NSE）光谱研究了未缠结的半浓溶液中聚苯乙烯磺酸钠（NaPSS）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 谱呈现出特征结构峰，这是聚电解质溶液的标志，可以用排除体积相互作用的半柔性链和聚合物参考相互作用位点模型（PRISM）结构因子的组合来拟合。我们证实，静电相互作用随离子强度在几何形状相似的溶液中变化。NSE 的分段弛豫偏离了 Zimm 的理论预测，并表现出两种标度行为，两个区域之间的交叉发生在特征结构峰处。链动力学在相关斑点的长度尺度上受到抑制，并且与结构因子成反比。这些观察结果表明，聚电解质的高度相关性质呈现出额外的能量势垒，导致德根内尔变窄行为。
