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Soft Matter and Biological Physics
Eur. Phys. J. E 10, 123-128 (2003)
DOI: 10.1140/epje/e2003-00011-4

Segment-sphere size ratio influence on the stability of a polymer-colloid mixture

R. Tuinier

Forschungszentrum Jülich, Institut für Festkörperforschung, 52425 Jülich, Germany


(Received 17 October 2002 and Received in final form 21 January 2003 Published online: 16 April 2003)

The influence of the sphere to segment size ratio on the effective depletion layer thickness around a sphere and the resulting phase behaviour of a colloid-polymer mixture is considered. An analytical expression for the excluded volume between an ideal freely jointed chain and a sphere [L. Lue, J. Colloid Interface Sci. 202, 558 (1998)] allows the effect of polymer characteristics (chain length, segment/sphere size ratio) on the depletion interaction in polymer-colloid mixtures to be calculated. For both small and intermediate polymer-to-colloid size ratios the respectively gas-solid and gas-liquid coexistence curves shift to larger polymer coil volume fractions as the relative segment size increases. It is further demonstrated that the conditions for optimal (protein) crystallization are affected when the segment to sphere size is altered.

61.25.Hq - Macromolecular and polymer solutions, polymer melts, swelling.
82.35.Pq - Biopolymers, biopolymerization.
82.70.Dd - Colloids.
83.80.Rs - Polymer solutions.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003