Paper Number
VP73 

Session
Pre-recorded Flash Presentations (virtual)

Title
Colloid-polymer mixtures revisited: Assessing the role of macromolecular depletant

Presentation Date and Time
All Week (Asynchronous) Any Time

Track / Room
Pre-recorded Presentation / Virtual

Authors (Click on name to view author profile)

  1. Moghimi, Esmaeel (IESL, FORTH and University of Crete)
  2. Parvin, Kiany (FORTH and University of Crete)
  3. Parisi, Daniele (FORTH, IESL)
  4. Vlassopoulos, Dimitris (IESL-FORTH and University of Crete)

Author and Affiliation Lines (in printed abstract book)
Esmaeel Moghimi1, Kiany Parvin2, Daniele Parisi3 and Dimitris Vlassopoulos1
1IESL-FORTH and University of Crete, Heraklion 71110, Greece; 2FORTH and University of Crete, Heraklion, Greece; 3IESL, FORTH, Heraklion, Crete, Greece

Speaker / Presenter 
Vlassopoulos, Dimitris

Keywords
experimental methods; colloids; gels; polymer solutions; suspensions

Text of Abstract
Recent Monte-Carlo simulations and mean-field density functional theory suggest that the organization of ring polymers close to walls differs from that of their linear counterparts [I. Chubak et al., Mol. Phys. 116, 2911-2926 (2018)]. Their density profile features pronounced oscillations which lead to a much stronger depletion force for rings compared to (typically used) linear polymers at the same size ratio. Here, we test this theoretical result and explore further the role of macromolecular architecture of the depletant. We use the established PMMA hard spheres at an intermediate volume fraction (0.44). By adding linear or ring polymer of the same molecular weight or size as depletant and systematically increasing its concentration, we investigate the formation of gel and examine its viscoelastic properties by means of linear and nonlinear shear rheological measurements. We focus in particular on probing the onset of gelation and the strength of the resultant gel. Our results indicate that, in the presence of rings gelation takes place at smaller concentrations and the resulting gels are much stronger compared to the respective gels based on linear chains. Our unambiguous results point to the importance of polymer molecular structure in influencing interactions and consequently gelation in colloid-polymer mixtures and open the route for further investigations using branched polymers and soft colloids, which we currently pursue.