Considérations sur l'adsorption de n-lcanes et de perfluoroalcanes à la surface de polymères de même structure chimique

Centre de recherches sur la physico-chimie des surfaces solides, 24, avenue du Président Kennedy, 68200 Mulhouse, France

Résumé

Une relation entre l'énergie de surface de liquides apolaires (n-alcanes, n-perfluoroalcanes) et l'énergie de surface de polymères qui leur sont homostructuraux (polyéthylène, polytétrafluoroéthylène) et l'aire d'une molécule de ces liquides adsorbée sur le solide a été établie.

Une méthode permettant la détermination de l'énergie superficielle des polymères considérés, en fonction de la température, a été proposée. De surcroît, certains paramètres structuraux correspondant à l'arrangement des molécules adsorbées en surface de ces polymères ont été déterminés.

Abstract

Knowing the spreading pressure of a liquid on a solid surface and considering that the ideal gas equation of state is also valid in two dimensions, a relationship between the surface free energy of both liquid and solid and the surface area of one molecule adsorbed on the solid surface has been established. This relationship is particularly well adapted to study the adsorption of non-polar liquids, n-alkanes and n-perfluoroalkanes, on "homostructural" polymer surfaces, i.e. polyethylene and polytetrafluoroethylene respectively.

With the help of this relationship, an original method has been proposed for determining the surface free energy of non-polar polymers. The values obtained by this method, at different temperatures, are in good agreement with the experimental values determined by contact angle measurements or those calculated by other theoretical approaches.

Moreover, structural parameters corresponding to the packing of the molecules adsorbed on the solid surface have been also determined. In agreement with other studies, it has been shown that the average distances between adsorbed molecules are close to those exhibited by these molecules in a crystalline state.