How Does the Polymer Chain Expand by Intramolecular Electrostatic Repulsion (FUNDAMENTAL MATERIAL PROPERTIES-Polymer Materials Science)

Abstract

The electrostatic correlation lengths x in salt-free polyelectrolyte solutions have been measured as functions of charge density and polymer concentration using a small-angle X-ray scattering (SAXS) technique. Water soluble poly(vinyl alcohol) ( PVA ) was employed as a parent polymer to avoid increasing hydrophobic interactions with decreasing the charge density; partially sulfuric-acid esterificated PVA's were used as samples. The charge density was changed from 0.008 to 0.499 in degree of esterification a. It was found that the maximum position qm of a characteristic SAXS peak, which is attributable to the electrostatic interchain correlation, is proportional to the square root of polymer concentration C at any charge density. This supports that the isotropic model of de Gennes et al. is valid. The a dependence of qm agrees with the theoretical prediction from the blob chain model for weakly charged polyelectrolytes proposed by Pfeuty and Khokhlov. This is the first and important experimental data which tells how the polymer chain expands by intramolecular electrostatic repulsion.