Small angle X-ray scattering study of coated porous materials

Abstract

The paper presents the small angle X-ray scattering (SAXS) studies of series of porous materials coated with aliphatic alcohol layer. Silica gel and porous glass covered with varying amounts of dodecanol or octadecanol were investigated. Both positive and negative deviations from the Porod law were observed. The former were caused by thermal density fluctuations within the alcohol phase, the latter were related to the existence of the transition layer (a layer of alcohol) on the surface of porous material. The papers presents the basics of Ruland's and Vonk's method for estimating the thickness of the transition layer. So far, this method has been used in investigating polymers; this paper discusses the applicability of the method in estimating the thickness of coatings in coated porous materials. A significant influence of the presence of loadings (their amount and the thickness value) upon the SAX scattering was observed. The Ruland and Vonk method was used to determine the thickness of the transition layer from the direct analysis of slit smeared intensity data. The obtained thickness values of the transition layer correspond with the theoretically anticipated thickness of alcohol layers on the surface. Generally, it can be stated that the investigation has proved that the SAX scattering curve analysis of coated porous materials can be successfully conducted using the Ruland and Vonk relation.