Membranes et fonctions cellulaires


Année de publication : 1997

Patricia Bassereau, Frédéric Pincet (1997 Dec 24)

Quantitative Analysis of Holes in Supported Bilayers Providing the Adsorption Energy of Surfactants on Solid Substrate.

Langmuir : 13 : 7003-7007 : DOI : 10.1021/la970515c En savoir plus

We investigated the topography of mixed bilayers consisting of a first monolayer of DMPE (dimyristoylphosphatidylethanolamine) and of a second monolayer of DOPC (dioleoylphosphatidylcholine) that were Langmuir−Blodgett deposited on mica. Using transfer ratio measurements and tapping mode atomic force microscopy experiments, we show that the subnanometric holes in the bilayers result from the desorption of lipids of the first monolayer during the transfer of the second monolayer. We present a new simple technique based on the quantitative analysis of these holes that allows determination of the adsorption energy of amphiphilic molecules on solid surfaces. This technique is valid for relatively low adsorption energies in the range 1 to 10 kBT.


Année de publication : 1995

P. Bassereau, T. P. Russell (1995 Feb 19)

Thermal expansion of thin diblock copolymer films.

Isreal Journal of Chemistry : 35 : 13-19 : DOI : 10.1002/ijch.199500004 En savoir plus

The thermal expansion of thin films of symmetric diblock copolymers of polystyrene (PS) and poly(methyl methácrylate) (PMMA) was investigated by X‐ray reflectivity. The confinement of the copolymer to the substrate, coupled with the multilayering of the copolymer where PS and PMMA layers are oriented parallel to the substrate, gives rise to unusual thermal expansion characteristics. The total thickness of the film increases as 3αL, where αL is the linear thermal expansion coefficient of the copolymer. Unlike homopolymer films, the thermal expansion of an ordered block copolymer film results in an excessive stretching of the copolymer chains at the interface between the PS and PMMA layers. This excess stretching is a result of the confinement of the junction points of the copolymer chains to the interfaces and the suppression of the lateral expansion of the copolymer. When the stretching of the chains becomes too high, relaxation occurs by transporting copolymer chains to the surface. This is evidenced by a reduction in the period of the multilayer. After the copolymer chains have relaxed, the change in the multilayer period with temperature closely follows αL.