Colloidal Interactions in Silica/Poly(Ethylene Oxide) Suspensions Investigated
by Small Angle X-ray Scattering
Chih-Chung Chen (陳致中), Yu-Ho Wen (溫玉合),
Chi-Chung Hua (華繼中), and Tai-Chou Lee (李岱洲)
Department of Chemical Engineering, National Chung Cheng University, Chiayi, Taiwan
Colloidal suspensions can be sterically stabilized by an adsorbed polymer layer. We
investigated the role of grafted polymer chains, far below its maximum adsorption, in controlling
the interparticle interactions, and analyzed the structure factors retracted from small angle x-ray
scattering for a series of silica/poly(ethylene oxide)(PEO) suspensions. While the thickness of the
adsorbed PEO layer was estimated using the experimental form factor and the core-shell model, the
interparticle interaction was analyzed using the experimental structural factor and the
Hayter-Penfold-Yukawa (HPY) model which accounts for the pair electrostatic repulsion. The
results revealed that, as the thickness of the grafted chains remains substantially smaller than that of
the electrical double layer, an increasing PEO adsorption leads to an unexpected decrease in the
interparticle repulsion. This phenomenon is ascribed to the screening effect of the adsorbed PEO
chains, as contrasted with the more usual case in which the grafted material sterically stabilizes the
colloidal suspension.