Effect of Polymer Charge and Geometrical Confinement on Ion Distribution and the Structuring in Semidilute Polyelectrolyte Solutions: Comparison between AFM and SAXS

详细信息    查看全文

• 作者：Dan Qu ; Jan S. Pedersen ; Sé ; bastien Garnier ; André ; Laschewsky ; Helmuth M&ouml ; hwald ; Regine v. Klitzing
• 刊名：Macromolecules
• 出版年：2006
• 出版时间：October 17, 2006
• 年：2006
• 卷：39
• 期：21
• 页码：7364 - 7371
• 全文大小：298K
• 年卷期：v.39,no.21(October 17, 2006)
• ISSN：1520-5835

文摘

This paper focuses on the effect of geometrical confinement on the structruring of a semidilutepolyelectrolyte solution in a thin film geometry. Studying poly-N-[tris(hydroxymethyl)methyl]acrylamide-co-2-acrylamido-2-methylpropanesulfonate (PTRIS-co-AMPS) with different degrees of charge allows a deeper insightinto the ion distribution around the polymer chains. Results from atomic force microscopy (AFM) force-distancemeasurements in films are compared with results from small-angle X-ray scattering (SAXS) in bulk. It is foundthat the characteristic lengths obtained from force oscillation measured by AFM, such as the intermediate chaindistance (mesh size) and the correlation length, correlate well with those obtained from the structure peak measuredby SAXS. In the direction perpendicular to the film surface, both length scales of the meshlike structure, i.e., theaverage chain distance and the correlation length, are not influenced by the geometrical confinement. Thedependencies of force period and decay length on the polymer charge are analyzed in detail and related to thecounterion distribution in the solutions. A new model for counterion condensation is proposed, in which thecondensed ions are not fixed on the polyion chains and can exchange freely with the free ions. However, thereis still a length scale beyond which the ion condensation theory of Manning and Oosawa is valid. Results fromconductivity measurements support the proposed model.