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. Aimé11 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.
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