title: From Homogeneous to Segregated Structure of Poly(dimethylsiloxane)/Cellulose Derivative Mixed Langmuir Films Depending on Composition: An in Situ Neutron Reflectivity Study.
abstract: The mixing behavior of deuterated polydimethylsiloxane (PDMSd) and cellulose acetate butyrate (CAB) spread as Langmuir films at the air-water interface was studied by means of surface pressure-area isotherms, Brewster angle microscopy (BAM) observations, and in situ neutron reflectivity. The contrast variation method was used with different D2O/H2O mixtures as subphase, allowing contrast matching to either CAB, PDMSd, or PDMSd/CAB mixed film if homogeneous. At PDMSd volume fractions Φ lower than 0.6, the mixed film is a homogeneous monolayer throughout the film compression, in agreement with the monophasic film observed by BAM and the attractive interactions between PDMSd and CAB evidenced from the isotherm measurements. In contrast, at PDMSd volume fractions Φ higher than 0.6, a vertically segregated structure of the mixed film is highlighted. Indeed, whatever the surface pressure, a bilayer structure is observed with a PDMSd layer in contact with the air over a thin CAB layer in contact with the subphase. These results show that the structure of the film is mainly driven by the PDMSd volume fraction which allows obtaining either a homogeneous membrane which composition can be tuned or a vertically segregated system. In contrast, only the thickness of the layers varies with the surface pressure while the structure of the film is not affected.
authors.affiliation: †Laboratoire de Physicochimie des Polymères et des Interfaces (LPPI, EA 2528), Institut des Matériaux, Université de Cergy-Pontoise, 5 mail Gay-Lussac Neuville/Oise, Cergy-Pontoise Cedex 95000, France.
authors.forename: Alae
authors.initials: A
authors.lastname: El Haitami
authors.affiliation: ‡Institut des Nanosciences de Paris (INSP, UMR 7588), Université Pierre et Marie Curie, 4 place Jussieu, Paris 75252 Cedex 05, France.|§UFR Biomédicale des Saints-Pères, Université Paris Descartes, 45 rue des St pères, 75006 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Goldmann
authors.affiliation: ∥Laboratoire Léon Brillouin (LLB), CEA-CNRS, Saclay, Gif-sur-Yvette Cedex 91191, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Cousin
authors.affiliation: †Laboratoire de Physicochimie des Polymères et des Interfaces (LPPI, EA 2528), Institut des Matériaux, Université de Cergy-Pontoise, 5 mail Gay-Lussac Neuville/Oise, Cergy-Pontoise Cedex 95000, France.
authors.forename: Gilberte
authors.initials: G
authors.lastname: Dosseh
authors.affiliation: †Laboratoire de Physicochimie des Polymères et des Interfaces (LPPI, EA 2528), Institut des Matériaux, Université de Cergy-Pontoise, 5 mail Gay-Lussac Neuville/Oise, Cergy-Pontoise Cedex 95000, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Cantin
mesh_terms: D000388:Air / Q000032:analysis*; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D003903:Deuterium / Q000737:chemistry; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D015394:Molecular Structure; D009502:Neutrons; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D004129:Dimethylpolysiloxanes; D014867:Water; C005062:acetylcellulose; C013830:baysilon; D002482:Cellulose; D003903:Deuterium