Can one detach a fully adsorbed flexible polymer chain by an ultra-small external force?

¹ Chemical-Pharmaceutical Academy - Prof. Popova 14, 197022 St.-Petersburg, Russia
² Department of Physics, American University of Beirut - P.O. Box 11-0236, Beirut 1107 2020, Lebanon
³ Institute of Macromolecular Compounds, Russian Academy of Sciences - 31 Bolshoy pr., 199004 St.-Petersburg, Russia
⁴ Institut für Physik, Johannes-Gutenberg Universität Mainz - Staudinger Weg 7, 55099 Mainz, Germany

Received: 24 July 2013
Accepted: 1 October 2013

Abstract

Full adsorption of flexible chains onto typical solid substrates occurs at a surface interaction energy of (5–10) k_BT. The corresponding detachment force is in the range 10–50 pN. In contrast to “bare” solid substrates common to non-living materials, surfaces coated with brush-like polymer layers are very common in biological soft matter. We employ a simple mean-field approach to describe the effects of weak attraction between a floating long macromolecule and the brush. We show that even for a moderately thick brush a very small effective attraction is enough to produce complete binding of the long chain. The detachment force scales as , where W is the brush thickness. Hence the force could be 1 to 2 orders of magnitude smaller than in the case of typical solid substrates.