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Analytical phase diagrams for colloids and non-adsorbing polymer
Gerard J Fleer1, Remco Tuinier
1Laboratory of Physical Chemistry and Colloid Science, Wageningen University, 6703 HB Wageningen, The Netherlands.
Advances in Colloid and Interface Science
|September 12, 2008
Summary
This study extends the free-volume theory to better predict colloid-polymer mixture phase behavior, including solvent effects and curvature. The generalized model accurately describes both colloid and protein limits, offering simple analytical expressions for critical points and phase diagrams.
Area of Science:
- Colloid and Polymer Science
- Thermodynamics
- Phase Behavior
Background:
- The free-volume theory (FVT) describes phase behavior in colloid-polymer mixtures.
- Existing models often simplify solvent interactions and curvature effects.
- Understanding these interactions is crucial for predicting mixture properties.
Purpose of the Study:
- To extend the free-volume theory (FVT) for colloid-polymer mixtures.
- To incorporate solvent effects and curvature into the FVT.
- To develop analytical models for predicting critical points and phase diagrams across different size ratios.
Main Methods:
- Incorporated solvent as a separate component, defining polymer properties by insertion work.
- Included curvature effects using established methods, deriving simplified power laws.
- Derived analytical forms for grand potential derivatives to calculate thermodynamic properties and critical points.
Main Results:
- Developed a generalized free-volume theory (GFVT) applicable to both colloid and protein limits.
- Obtained simple analytical equations for critical and triple points as a function of polymer-to-colloid size ratio.
- Demonstrated universal scaling of phase diagrams in the protein limit and found the liquid window to be narrow (max factor 2.2).
Conclusions:
- The GFVT provides accurate predictions for colloid-polymer phase behavior across various size ratios.
- The model successfully captures experimental and simulation data, including crossover regimes.
- Analytical expressions simplify the analysis of critical phenomena and phase boundaries in these complex mixtures.
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