Europhys. Lett.
Volume 61, Number 2, January 2003
Page(s) 268 - 274
Section Interdisciplinary physics and related areas of science and technology
Published online 01 January 2003
DOI: 10.1209/epl/i2003-00228-6
Europhys. Lett., 61 (2) , pp. 268-274 (2003)

Thermally activated lubrication with alkanes: The effect of chain length

L.-M. Qian1, 2, G. Luengo1 and E. Perez1

1  Laboratoire de Physique Statistique de l'Ecole Normale Supérieure associée au CNRS et aux universités Paris VI et Paris VII 24, rue Lhomond, 75231 Paris Cedex 05, France
2  Tribology Research Institute, Southwest Jiaotong University Chengdu 610031, Sichuan Province, PRC

(Received 24 July 2002; accepted in final form 29 October 2002)

Friction forces measurements between smooth surfaces across two layers of linear alkanes over five decades of speeds are presented. A maximum friction dissipation is observed at a characteristic speed. This behaviour is described by a new approach: the formation and destruction of molecular bridges between confined alkane layers. These bridges which interdigitate between the layers exhibit a thermally activated resistance to shear. An analytical model involving activation barriers accounts for the overall behaviour of the speed dependence of the forces over four decades. This first simple semi-quantitative description sheds new light on the subtle mechanisms of friction at the nanoscale level and shows how the molecular length influences the tribological properties of the liquid.

81.40.Pq - Friction, lubrication and wear.
68.35.Af - Atomic scale friction.
46.55.+d - Tribology and mechanical contacts.

© EDP Sciences 2003