Europhys. Lett., 76 (3), pp. 519-525 (2006)
DOI: 10.1209/epl/i2006-10278-2

Entropic approach curves of a polymer of fixed topology

D. Marenduzzo¹ and E. Orlandini<sup>2

1</sup>  SUPA, School of Physics, University of Edinburgh - Edinburgh EH9 3JZ, UK
²  Dipartimento di Fisica and Sezione INFN, Università di Padova Via Marzolo 8, 35131 Padova, Italy

received 24 February 2006; accepted in final form 6 September 2006
published online 29 September 2006

Abstract
We determine how the force needed to place a polymer close to a solid wall varies with the positioning of the chain origin, which is kept pinned. This force is purely entropic in origin as it arises from the loss of available structures close to the wall. We show that with present-day micromanipulation experiments it should be possible to determine whether an initially linear chain forms a loop, e.g. when its ends are rendered sticky, by measuring this entropic force. We discuss the possibility to characterise knot topology via the same procedure.

PACS
82.35.Lr - Physical properties of polymers.
36.20.Ey - Conformation (statistics and dynamics).

© EDP Sciences 2006