Experimental Phase Diagrams of Polymer and Colloid Mixtures

Abstract

Phase diagrams of a set of three monodisperse polystyrene lattices in the presence of non-adsorbing polymer molecules (hydroxyethyl cellulose) have been determined. Polymer molecules induce reversible phase transitions involving gas, liquid and solid-like states. We find that the phase diagrams can have two distinct topologies: fluid-solid only or fluid-solid plus fluid-fluid equilibria. The preference for one topology is governed by the ratio 6 / ~, where 6 and U are the polymer and colloidal particle sizes. Moreover, a three-phase coexistence is noticed instead of a triple point. The attractive effect of polymer molecules is investigated through light scattering experiments and we propose direct vizualisation of the critical fluctuations in these colloidal systems.

Strong, weak and metastable liquids

“…Note that for q > 0.3 the triple line in the Zp--Pc representation transforms in a three-phase triangle bordered by three two-phase regions in the pp-Pc representation. This phase scenario has indeed been observed experimentally [12][13][14].…”

Density functional theory for a model colloid polymer mixture: bulk fluid phases

“…Other studies have investigated the equilibrium pair correlation functions in the AO model [5,[7][8][9] and the formal status of the mapping to a one-component fluid [8]. Although the AO model is highly idealized the variation of bulk phase behaviour with q predicted by studies of the model is in keeping with the experimental results [10,11]. More recently attention has shifted towards inhomogeneous mixtures.…”

Measurement of the Interfacial Tension of a Phase-Separated Colloid−Polymer Suspension

“…Phase transitions in colloid-polymer suspensions have attracted considerable attention, both theoretically and experimentally; see, for example, refs [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. It has become clear that for small polymer to colloid size ratios (<0.3) the transition is of the fluid-solid type, while for large size ratios (>0.3) three different phases can occur: two different fluid phases, i.e., a gaslike and a liquidlike phase, and one solid phase, a colloidal crystal.…”