J. Phys. II France
Volume 7, Numéro 2, February 1997
Page(s) 271 - 283
DOI: 10.1051/jp2:1997124
J. Phys. II France 7 (1997) 271-283

Nanorheology of Adsorbed Diblock Copolymer Layers

Eric Pelletier1, Gérald F. Belder1, Georges Hadziioannou1 and Andrei Subbotin2

1  Department of Polymer Chemistry and Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
2  Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninski Prospect 29, Moscow 117 912, Russia

(Received 13 May 1996, received in final form 4 October 1996, accepted 7 November 1996)

We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate as a rheometer at the molecular level. Two systems are studied: "brush/wall" and "brush/brush". A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rather than interpenetrate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall system. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviour of a brush confined by a neutral surface.

© Les Editions de Physique 1997