2004/11/30 by Moreno Fasolo, Peter Sollich
Engineering · Materials Science · Physics and Astronomy · #Block Copolymer Self-Assembly #Phase Equilibria and Thermodynamics #Pickering emulsions and particle stabilization #cond-mat.mtrl-sci #cond-mat.soft
paper · pdf · doi:10.1088/0953-8984/17/6/002
published as J. Phys.: Condens. Matter, 17: 797-812, 2005 · Changes in v2: sketch in Figure 1 corrected, other figures improved; added references to experimental work and discussion of mapping from polymer chain length to effective radius
openalex publication_date 2005/01/29 · arxiv created 2005/02/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We study the equilibrium behaviour of a mixture of monodisperse hard sphere colloids and polydisperse non-adsorbing polymers at their θ-point, using the Asakura–Oosawa model treated within the free-volume approximation. Our focus is the experimentally relevant scenario where the distribution of polymer chain lengths across the system is fixed. Phase diagrams are calculated using the moment free energy method, and we show that the mean polymer size ξ c at which gas–liquid phase separation first occurs decreases with increasing polymer polydispersity δ. Correspondingly, at fixed mean polymer size, polydispersity favours gas–liquid coexistence but delays the onset of fluid–solid separation. On the other hand, we find that systems with different δ values but the same mass-averaged polymer chain length have nearly polydispersity-independent phase diagrams. We conclude with a comparison to previous calculations for a semi-grand-canonical scenario, where the polymer chemical potentials are imposed; there it was found that fluid–solid coexistence was favoured over gas–liquid in some areas of the phase diagram. Our results show that this somewhat counter-intuitive result arose because the actual polymer size distribution in the system is shifted to smaller sizes relative to the polymer reservoir distribution.