Eur. Phys. J. E 6, 387-397 (2001)

Experimental determination of the viscosity at the nanometer scale on a block copolymer with an oscillating nanotip

F. Dubourg¹, S. Kopp-Marsaudon¹, Ph. Leclère², R. Lazzaroni² and J.P. Aimé<sup>1

1</sup>  CPMOH Université Bordeaux I, 351 Cours de la Libération, F-33405 Talence Cedex, France
²  Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Sciences des Matériaux Polymères, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium

jpaime@cribx1.u-bordeaux.fr

( Received 16 May 2001 and Received in final form 2 August 2001)

Abstract
This work is an attempt to investigate viscosities at the nanometer scale. To do so, the tapping mode atomic force microscopy is used on a triblock copolymer exhibiting a well-defined periodic structure at the nanometer scale. Variations of the oscillator amplitude and phase delay as a function of the tip-sample distance are recorded on the glassy and rubbery domains of the copolymer. The experimental data are compared to analytical expressions derived from Stokes law. In the present study, among the different possible expressions of the viscous forces depending on the tip shape and on the experimental length scale, only a force proportional to the indentation depth is able to describe the experimental data. In this particular case, quantitative measurements are possible. Finally, the oscillator is shown to be sensitive to local variations of the viscosity within few nanometers.

PACS
07.79.Lh - Atomic force microscopes.
47.80.+v - Instrumentation for fluid dynamics.
83.85.Jn - Viscosity measurements.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001