Gelation and Re-entrance in Mixtures of Soft Colloids and Linear Polymers of Equal Size

Daniele Parisi, Domenico Truzzolillo, Ali H. Slim, Phillippe Dieudonné-George, Suresh Narayanan, Jacinta C. Conrad, Vishnu D. Deepak, Mario Gauthier, D. Vlassopoulos

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Liquid mixtures composed of colloidal particles and much smaller non-adsorbing linear homopolymers can undergo a gelation transition due to polymer-mediated depletion forces. We now show that the addition of linear polymers to suspensions of soft colloids having the same hydrodynamic size yields a liquid-to-gel-to-re-entrant liquid transition. In particular, the dynamic state diagram of 1,4-polybutadiene star-linear polymer mixtures was determined with the help of linear viscoelastic and small-angle X-ray scattering experiments. While keeping the star polymers below their nominal overlap concentration, a gel was formed upon increasing the linear polymer content. Further addition of linear chains yielded a re-entrant liquid. This unexpected behavior was rationalized by the interplay of three possible phenomena: (i) depletion interactions, driven by the size disparity between the stars and the polymer length scale which is the mesh size of its entanglement network; (ii) colloidal deswelling due to the increased osmotic pressure exerted onto the stars; and (iii) a concomitant progressive suppression of the depletion efficiency on increasing the polymer concentration due to reduced mesh size, hence a smaller range of attraction. Our results unveil an exciting new way to tailor the flow of soft colloids and highlight a largely unexplored path to engineer soft colloidal mixtures.
Original languageEnglish (US)
StatePublished - Feb 22 2023
Externally publishedYes

ASJC Scopus subject areas

  • Materials Chemistry
  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry


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