Temperature-sensitive colloidal phase behavior induced by critical Casimir forces

We report Monte Carlo simulations of phase behavior of colloidal suspensions with near-critical binary solvents using effective pair potentials from experiments. At off-critical solvent composition, the calculated phase diagram agrees well with measurements of the experimental system, indicating that many-body effects are limited. Close to the critical composition, however, agreement between experiment and simulation becomes poorer, signaling the increased importance of many-body effects. Both at and off the critical solvent concentration, the colloidal phase diagram is qualitatively similar to those of molecular systems and obeys the principle of corresponding states with one striking difference: it occurs in a narrow temperature interval of <1C below the solvent phase separation temperature.This work was supported by the Foundation for Fundamental Research on Matter (FOM). P. S. acknowledges support from the Innovational Research Incentives Scheme (VIDI grant) of the Netherlands Organization for Scientific Research (NWO). A. V. V. acknowledges financial support by the Department of Theory and Bio-Systems at the Max Planck Institute of Colloids and Interfaces. We thank A. Maciolek and D. T. F. Mohry for helpful discussions

Interacting Living Polymers Confined between Two Surfaces

We present predictions on the equilibrium behavior of solutions of living polymers confined in a gap between surfaces, including the ensuing potential of mean force between those surfaces (the disjoining potential). We highlight the occurrence of a transition upon narrowing the gap, which arises from a cooperative simultaneous increase of the local density and degree of polymerization. At this transition, many properties of the confined solution, including the disjoining potential, change by orders of magnitude over a minute change of the surface separation. These results were obtained owing to two extensions to a previously introduced self-consistent field–propagator formalism. (i) We derive this formalism from a free-energy functional of the distribution of chain lengths and configurations. This enables evaluation of thermodynamic properties, including the disjoining potential. (ii) We solved for a system confined between two surfaces.ChemE/Chemical EngineeringApplied Science