Phase diagram for a mixture of colloids and polymers with equal size

¹  Forschungszentrum Jülich, Institut für Festkörperforschung - D-52425 Jülich, Germany
²  SUPA and School of Physics, The University of Edinburgh, Edinburgh - EH9 3JZ, UK
³  Condensed Matter Physics Laboratory, Heinrich-Heine-University - Universitätsstrasse 1, D-40225 Düsseldorf, Germany
⁴  Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford South Parks Road, Oxford OX1 3QZ, UK
⁵  Van't Hoff Laboratory, Utrecht University - Padualaan 8, 3584 CH Utrecht, The Netherlands
⁶  Laboratory of Physical Chemistry and Colloid Science, Wageningen University - 6703 HB Wageningen, The Netherlands

Corresponding author: remco.tuinier@googlemail.com

Received: 29 February 2008
Accepted: 21 April 2008

Abstract

We present the phase diagram of a colloid-polymer mixture in which the radius a of the colloidal spheres is approximately the same as the radius R of a polymer coil (q = R/a≈ 1). A three-phase coexistence region is experimentally observed, previously only reported for colloid-polymer mixtures with smaller polymer chains (q ≲ 0.6). A recently developed generalized free-volume theory (GFVT) for mixtures of hard spheres and non-adsorbing excluded-volume polymer chains gives a quantitative description of the phase diagram. Monte Carlo simulations also agree well with experiment.