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Séminaire Antonio Stocco

Amphiphilic block copolymers at the liquid-fluid interface

Antonio Stocco

Laboratoire de Physique des Solides
Université Paris-Sud

1) The structure and dynamics of a colloidal sample and two diblock copolymer systems at the air-water and dodecane-water interface were investigated by ellipsometry and evanescent wave light scattering, implemented in a new lab-made apparatus. High-resolution ellipsometric studies at several bare fluid interfaces are presented and different interfacial profile are found. Dynamics at the surface was studied by means of evanescent wave dynamic light scattering. Propagating capillary waves were observed at the air-water interface up to a relatively high value of scattering vector (q= 106 m-1). Diffusion of diblock polyisoprene-co-polyethyleneoxide with different block symmetries was investigated over a wide range of concentrations. Several diffusion mechanisms were observed at the interface and compared to the diffusion of micelles in the bulk. Combining the dynamic results with the ellipsometric data, it was possible to elucidate the organization of these systems at the interface. Formation of polymer brushes and phase transitions at the interface were discussed together with the micellization process of block copolymers.

2) Recently, foam and emulsion made by fumed silica nanoparticles are studied because of the excellent aging stability. Current studies are focussed on the effect of hydrophobicity, induced by the SiOH group, on the foaming behaviour and on the monolayer viscoelasticity. At the present the mechanisms underlying the surprising properties of these systems are still not fully understood. An overview and some preliminary results on interfacial adsorption are presented.