Absorption of Polyelectrolytes on Colloidal Surfaces as Studied by Electrophoretic and Dynamic Light-Scattering Techniques

✍ Scribed by Tsuneo Okubo; Mitsuhiro Suda

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 102 KB
• Volume: 213
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6171

✦ Synopsis

Potential and the effective diameter of the colloidal spheres absorbed with the macro-cations and macro-anions are studied by the electrophoretic light-scattering and dynamic light-scattering measurements. Colloidal spheres used are monodispersed polystyrene (220 nm in diameter) and colloidal silica spheres (110 nm). Macro-ions used are sodium polyacrylate, sodium polymethylacrylate, sodium poly(styrene sulfonate), and poly-4-vinyl pyridines quaternized with ethyl bromide, n-butyl bromide, benzyl chloride, and 5% hexadecyl bromide and 95% benzyl chloride. Reversal of colloidal surface charges from negative to positive occurs abruptly above the critical concentration of macroions by the excess absorption of the macro-cations onto the anionic colloidal spheres, i.e., avalanche-type absorption. The effective diameter of colloidal spheres including the absorbed layers increases substantially by four-to tenfold. In the presence of large amount of macro-cations aggregation of colloidal spheres mediated by the layers of absorbed macro-cations may occur. Absorption also occurs on the anionic colloidal spheres in the presence of an excess amount of macro-anions by the dipole-dipole-type attractive interactions.