Biointerphases

Journal for Biophysical Chemistry

Biointerphases Cover Image
Open Access

Confinement and compression of an oligomer brush

  • Stephen Foster1,
  • Christopher Wainwright1,
  • Douglas B. Staple1 and
  • Hans Jürgen Kreuzer1
Biointerphases5:50200069

https://doi.org/10.1116/1.3455152

Received: 20 April 2010

Accepted: 26 May 2010

Abstract

Self-assembled monolayers and oligomer brushes confined between two parallel plates show compressional forces that are nonmonotonic as a function of plate separation. In a realistic model of short alkanethiols, based on the rotationally isomeric state model with parameters from ab initio calculations, the authors show that nonmonotonic forces arise from the elimination of longer conformers as the distance between the plates is reduced. This nonmonotonicity is a size effect that disappears when the length of the polymer molecule is sufficiently increased. An analytical model is developed that allows experimentalists to extract energy-averaged brush height distributions from compressional force curves.