287613 Re-Entrant Behavior in Colloidal Disks with Adsorbing Polymer

Thursday, November 1, 2012: 12:55 PM
414 (Convention Center )
Anand Atmuri, Chemical Engineering, University of Massachusetts Amherst, Amherst, MA and Surita Bhatia, Chemical Engineering, University of Massachusetts, Amherst, Amherst, MA

We report a re-entrant colloidal glass transition in dispersions of model disk shaped colloid, laponite®, with the addition of an adsorbing low molecular weight polymer, poly(ethylene oxide) (PEO). In basic solutions laponite® forms a repulsive colloidal glass. With the addition of low molecular weight PEO, we observe a retardation in formation of the glass, and the system behaves as a viscous fluid. Upon aging, a glassy phase re-forms, with the time scale depending on the concentration of polymer.  For samples with polymer concentration high enough to saturate the laponite surface, we believe this arrested state to be an attractive glass where excess PEO chains in the suspension lead to a weak interparticle attraction. For the polymer molecular weight we considered, all the samples eventually age to form a disordered state.  We combine our results with previous work on laponite®-PEO dispersions to propose a qualitative state diagram with attractive glass, repulsive glass, liquid, and gel regimes as a function of polymer molecular weight, polymer concentration, and aging time. To our knowledge, the progression of repulsive glass-liquid-attractive glass states has not been previously observed in colloids with adsorbing polymers.

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See more of this Session: Colloidal Dispersions II
See more of this Group/Topical: Engineering Sciences and Fundamentals