Phase behaviour of a dispersion of charge-stabilised colloidal spheres with added non-adsorbing interacting polymer chains.
We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains in good and theta -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that, we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a theta -solvent. For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for charged colloids plus polymers in a theta -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion. Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction.
Gögelein
C
C
Institut für Festkörperforschung, Teilinstitut Weiche Materie, Forschungszentrum Jülich, D-52425 Jülich, Germany. c.goegelein@fz-juelich.de
Tuinier
R
R
Phys Rev Lett. 2002 Sep 16;89(12):128302
12225127
J Chem Phys. 2005 Jun 22;122(24):244911
16035820
Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Aug;64(2 Pt 1):021514
11497596
Phys Rev Lett. 2003 Feb 14;90(6):068304
12633336
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Jun;59(6):6853-78
11969674
J Cell Biol. 2006 Dec 4;175(5):681-6
17145959
Adv Colloid Interface Sci. 2003 Mar 19;103(1):1-31
12689758
Phys Rev Lett. 2008 Feb 8;100(5):055703
18352391
Biochem J. 1913 Jan;7(1):92-6
16742228
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Oct;76(4 Pt 1):041802
17995014
J Chem Phys. 2004 Aug 15;121(7):3253-8
15291637
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 May;59(5 Pt B):5744-71
11969558
Biopolymers. 1998 Feb;45(2):97-104
9461844
Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Apr;63(4 Pt 1):041405
11308841
J Chem Phys. 2005 Jun 1;122(21):214502
15974749
Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Aug;68(2 Pt 1):021407
14524973
Phys Rev Lett. 2000 Sep 18;85(12):2522-5
10978097
Biophys J. 2001 Mar;80(3):1186-94
11222283
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Apr;73(4 Pt 1):041404
16711797
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1996 Aug;54(2):1134-1152
9965182