152 research outputs found
Demixing of colloid-polymer mixtures in poor solvents
The influence of poor solvent quality on fluid demixing of a model mixture of
colloids and nonadsorbing polymers is investigated using density functional
theory. The colloidal particles are modelled as hard spheres and the polymer
coils as effective interpenetrating spheres that have hard interactions with
the colloids. The solvent is modelled as a two-component mixture of a primary
solvent, regarded as a background theta-solvent for the polymer, and a
cosolvent of point particles that are excluded from both colloids and polymers.
Cosolvent exclusion favors overlap of polymers, mimicking the effect of a poor
solvent by inducing an effective attraction between polymers. For this model, a
geometry-based density functional theory is derived and applied to bulk fluid
phase behavior. With increasing cosolvent concentration (worsening solvent
quality), the predicted colloid-polymer binodal shifts to lower colloid
concentrations, promoting demixing. For sufficiently poor solvent, a reentrant
demixing transition is predicted at low colloid concentrations.Comment: 6 pages, 3 figure
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