Eur. Phys. J. Special Topics 213, 343-353 (2012)
https://doi.org/10.1140/epjst/e2012-01681-4

Regular Article

Protein adsorption properties of OEG monolayers and dense PNIPAM brushes probed by neutron reflectivity

¹ Département de Physique, Faculté des Sciences, Université Libre de Bruxelles, Boulevard du Triomphe, CP. 223, 1050 Bruxelles, Belgique
² Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
³ Institut Max Von Laue-Paul Langevin, 38042 Grenoble, France
⁴ Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
⁵ University of Grenoble 1/CNRS, LIPhy UMR 5588, BP. 87, 38041 Grenoble, France

^a e-mail: msferraz@ulb.ac.be

Received: 20 July 2012
Revised: 27 September 2012
Published online: 3 December 2012

Abstract

The structure of dense poly(N-isopropylacrylamide) (PNIPAM) brushes and oligo(ethylene glycol) (OEG) monolayers has been probed using neutron reflectometry and ellipsometry. The PNIPAM brush is swollen below the Lower Critical Solution Temperature (LCST) of 32 ^∘C and is collapsed at 37 ^∘C. Neutron reflectivity shows that below the LCST, the brush is described by a two-layer model: an inner dense layer and a hydrated outer layer. Above the LCST the collapsed brush forms a homogenous layer. With a fully deuterated myoglobin protein to increase the neutron scattering length density contrast, the reflectivity data show no detectable primary adsorption on the grafted OEG surface. A bound on the ternary adsorption onto PNIPAM chains forming dense brushes below and above the LCST is obtained.