266695 Confinement-Induced Solidification of Colloid-Polymer Mixtures

Thursday, November 1, 2012: 1:55 PM
414 (Convention Center )
Melissa Spannuth1 and Jacinta C. Conrad1,2, (1)Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, (2)Petroleum Engineering Program, University of Houston, Houston, TX

Using a model colloid-polymer suspension, we show that confinement induces solidification in attractive colloidal suspensions via a fundamentally different route from that active in hard sphere colloidal suspensions. For a range of polymer concentrations, the suspensions undergo a phase transition from a colloidal fluid of clusters to a colloidal gel as confinement increases while polymer and particle concentration are held constant. In both fluid- and solid-like attractive suspensions, effects of confinement on the structure and dynamics appear at much larger thicknesses than for hard-sphere suspensions. The solidification does not originate from structuring of the colloids by the walls. Instead, by analyzing cluster size distributions in the fluid phase and particle dynamics in the gel phase as a function of confinement, we find that the strength of the effective interparticle attraction increases as the samples are confined. We show that the increase in the effective attraction can be understood as a consequence of the increasing importance of excluded volume due to the walls to the free energy of the polymer as confinement is increased.

Extended Abstract: File Not Uploaded
See more of this Session: Colloidal Dispersions II
See more of this Group/Topical: Engineering Sciences and Fundamentals