Paper Number
SC4 

Session
Suspensions, Colloids and Granular Media

Title
Soft colloid - polymer mixtures at extreme size ratios: Gelation and confinement effects

Presentation Date and Time
February 13, 2017 (Monday) 11:15

Track / Room
Track 1 / Audubon B

Authors (Click on name to view author profile)

1. Vlassopoulos, Dimitris (Foundation for Research and Technology - FORTH, Institute of the Electronic Structure and Laser)
2. Truzzolillo, Domenico (Universirty of Montpellier)
3. Merola, Maria C. (Stanford University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Dimitris Vlassopoulos¹, Domenico Truzzolillo², and Maria C. Merola^3
1Institute of the Electronic Structure and Laser, Foundation for Research and Technology - FORTH, Heraklion, Crete 70013, Greece; ²Universirty of Montpellier, Montpellier, France; ³Chemical Engineering, Stanford University, Stanford, CA 94305

Speaker / Presenter 
Vlassopoulos, Dimitris

Text of Abstract
We examine the rheology of mixtures of soft colloids with linear polymers. To this end, we use star polymers as model soft colloids and mix them with linear homopolymers, all polybutadienes, in good solvent squalene. For very small polymer/colloid size ratio (0.05) we find a soft star glass will melt and eventually form a re-entrant gel upon addition of linear polymers. The osmotic force of the additives leading to star shrinkage and depletion is responsible for this behavior that marks a departure from that of respective mixtures with hard spheres. On the other hand, for large size ratios (close to 1) we monitor the relaxation time and modulus of the linear chains in the mixture upon increasing their concentration. Their dependencies on concentration are much weaker compared to the respective ones in the absence of stars, suggesting an effective confinement effect due to the stars. This effect depends sensitively on the concentrations of both stars and linear polymers. We show how to obtain a universal description of the phenomenon with appropriate scaling analysis, and hence to control the chain dynamics. The key concept for rationalizing the observed behavior is, again, the osmotic shrinkage of the (close packed) stars and effective star-linear impenetrability. Work in collaboration with M. Gauthier (Waterloo) and C. N. Likos (Vienna).