Single chains of strong polyelectrolytes in aqueous solutions at extreme dilution: Conformation and counterion distribution

Guofeng Xu; Shuangjiang Luo; Qingbo Yang; Jingfa Yang; Jiang Zhao

doi:10.1063/1.4964649

Single chains of strong polyelectrolytes in aqueous solutions at extreme dilution: Conformation and counterion distribution

J Chem Phys. 2016 Oct 14;145(14):144903. doi: 10.1063/1.4964649.

Authors

Guofeng Xu¹, Shuangjiang Luo¹, Qingbo Yang¹, Jingfa Yang¹, Jiang Zhao¹

Affiliation

¹ Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

PMID: 27782532
DOI: 10.1063/1.4964649

Abstract

The molecular conformation of two typical polyelectrolytes, sodium polystyrene sulfonate (NaPSS) and quarternized poly-4-vinylpyridine (QP4VP), was studied in aqueous solutions without salt addition at the single molecular level. By fluorescence correlation spectroscopy, the hydrodynamic radius (R_h) of NaPSS and QP4VP with the molecular weight ranging more than one order of magnitude was measured. The scaling analysis of R_h exhibits scaling exponent of 0.70 and 0.86 for NaPSS and QP4VP in solutions without added salts, respectively, showing the conformation is much more expanded than random coil. Numerical fittings using the model of diffusion of a rod molecule agree with the data well, indicating that the polyelectrolyte chains take the rod-like conformation under the condition without salt addition. Further investigations by determining the electric potential of single PSS^- chains using the photon counting histogram technique demonstrate the enhanced counterion adsorption to the charged chain at higher molecular weight.