Article pubs.acs.org/Macromolecules
In Situ X‑ray Reflectivity Study of Polystyrene Ultrathin Films Swollen in Carbon Dioxide M. Souheib Chebil,†,‡ G. Vignaud,‡ Y. Grohens,‡ O. Konovalov,§ M. K. Sanyal,⊥ T. Beuvier,† and A. Gibaud*,† †
LUNAM Université, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS, Le Mans Cedex 9, 72000, France Laboratoire d’Ingénierie des MATériaux de Bretagne, Centre de Recherche, Rue de Saint Maudé, BP 92116, 56321 Lorient Cedex France § European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, BP 220, 38043 Grenoble, France ⊥ Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India ‡
ABSTRACT: We report here original in situ X-ray reflectivity (XRR) studies of thin films isothermally exposed to CO2 as a function of CO2 pressure starting from ambient pressure up to its supercritical state. Swelling of polystyrene confined films is investigated by this technique. Cycling through the supercritical state of CO2, the PS films show an irreversible behavior that is analyzed in terms of CO2 uptake that depends on Pg(h) (the pressure at which the film crosses thickness dependent Tg(h)). We evidence that this pressure is indeed thickness dependent and that CO2 can be up taken in the film in a condensed state as soon as P > Pg(h). We also evidence that the content of CO2 stored inside the film after depressurization can be determined by a careful analysis of the electron density of the film.
■
thin films. Several investigations are reported on the effects of scCO2 on the properties of thin polymer film.14−28 The swelling of polymer thin films have revealed an anomalous behavior in contact with supercritical CO2. For ultrathin films (
