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Soft Matter and Biological Physics

Eur. Phys. J. E 6, 15-24 (2001)

Orientation-dependent depletion interaction in rodlike colloid-polymer mixtures

A. Matsuyama and T. Kato

Department of Chemistry for Materials, Faculty of Engineering, Mie University, Tsu Mie 514-8507, Japan


(Received 23 May 2001 and Received in final form 18 July 2001)

Depletion interaction in a suspension of rodlike colloids with added non-adsorbing polymer coils is theoretically studied. We calculate an overlap volume of depletion zone between two rodlike colloids, based on the second virial approximation. We examine nematic-isotropic phase transition (NIT) and two-phase coexistence between an isotropic and a nematic phase at low polymer concentrations. We find that the depletion interaction is dependent on the orientational order parameter of rodlike colloids and leads to a decrease in the NIT concentration on the addition of polymer. The coexistence curves have a leaning-chimney shape and are shifted to lower rod concentrations on increasing the polymer concentration.

61.30.-v - Liquid crystals.
61.30.St - Lyotropic phases.
82.70.Dd - Colloids.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001