DRUMMOND, Carlos; RODRIGUEZ-HERNANDEZ, Juan; LECOMMANDOUX, Sebastien; RICHETTI, Philippe

doi:10.1063/1.2730817

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DRUMMOND, Carlos

Centre de recherches Paul Pascal [CRPP]

RODRIGUEZ-HERNANDEZ, Juan
Laboratoire de Chimie des polymères organiques [LCPO]
Team 1 LCPO : Polymerization Catalyses & Engineering

LECOMMANDOUX, Sebastien
Laboratoire de Chimie des polymères organiques [LCPO]
Team 3 LCPO : Polymer Self-Assembly & Life Sciences

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Journal of Chemical Physics. 2007, vol. 126, n° 18, p. 184906

American Institute of Physics

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The normal interaction and the behavior under shear of mica surfaces covered by two different triblock copolymers of polylysine-polydimethysiloxane-polylysine were studied by combining the capabilities of the surface forces apparatus and the atomic force microscopy. At low pH values these copolymers spontaneously adsorb on the negatively charged mica surfaces from aqueous solutions as a consequence of the positive charge of the polylysine moieties. The morphology of the adsorbed layer is determined by the molecular structure of the particular copolymer investigated. This morphology plays a fundamental role on the behavior of the adsorbed layers under shear and compression. While nonadhesive smooth layers oppose an extremely small resistance to sliding, the presence of asperities even at the nanometric scale originates a frictional resistance to the motion. The behavior of uniform nonadhesive nanorough surfaces under shear can be quantitatively understood in terms of a simple multistable thermally activated junction model. The electric charge of the adsorbed copolymer molecules and hence the adhesion energy between the coated surfaces can be modified by varying the pH of the surrounding media. In the presence of an adhesive interaction between the surfaces the behavior under shear is strongly modified. Time-dependent mechanisms of energy dissipation have to be evoked in order to explain the changes observed< Réduire

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BLOCK

STATE

CONTACT

COPOLYMERS

RHEOLOGY

STICK-SLIP FRICTION

THIN-FILM

SURFACES

FORCES

LAYERS

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Boundary lubricant films under shear: effect of roughness and adhesion

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