Wednesday 16:00 pm - 17:15 pm FIT SR

livMatS Colloquium | Prof. Mehdi Vahdati (Charles Sadron Institute - University of Strasbourg) | Quasi-Complex Coacervates: Single-Phase Viscoelastic Analogues of Complex Coacervates

Water-based complex coacervates (CC) from associative phase separation of oppositely-charged polyelectrolytes are an emerging class of functional soft materials with tunable mechanical properties from stiff solids to viscous liquids. [1,2] Despite the potential of these materials as sustainable alternatives to chemically crosslinked systems, the occurrence of phase separation is a major limitation for their large-scale production and manipulation.
Exploring uncharted regions of the phase diagram of a moderately hydrophilic model system, I will introduce quasi-complex coacervates (quasi-CC), salty solutions of fully-doped oppositely-charged polyelectrolytes that specifically mimic the viscoelastic response of their phase-separated CC counterparts without phase separation. It is proposed that obtaining the quasi-CC of a reference CC is only possible by lowering the added salt concentration in highly concentrated polyelectrolytes solutions. The presence of non-interacting oppositely-charged PEs makes quasi-CC a precursor material for further manipulation, an aspect that distinguishes these materials from both single polyelectrolyte solutions and complex coacervates.
[1] Q. Wang, J. B. Schlenoff, Macromolecules, 2014, 47.
[2] M. Vahdati*, D. Hourdet, C. Creton, Prog Polym Sci, 2023, 139.

Brief Bio
With a background in polymer science and engineering from Tehran Polytechnic, Mehdi Vahdati received his PhD in polymer physical chemistry from ESPCI Paris and Sorbonne University in 2019, where he worked under the supervision of Costantino Creton and Dominique Hourdet on salt and temperature responsive soft underwater adhesives. After two postdoctoral experiences, Mehdi accepted a tenure track position at the University of Strasbourg and CNRS in France. He leads a group working on (i) complex coacervation of model and bio-sourced polyelectrolytes, (ii) physics of polymers in green solvents, and (iii) adhesion and fracture of soft polymer networks.