Dresden 2020 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Charged Soft Matter, Polyelectrolytes and Ionic Liquids
CPP 39.7: Talk
Tuesday, March 17, 2020, 11:00–11:15, ZEU 114
The Kinetic Pathway for Polyelectrolyte Coacervate Formation revealed by Time-resolved Synchrotron SAXS — Matthias Amann1, Jakob Diget1, Jan-Skov Pedersen2, Theyencheri Narayanan3, and •Reidar Lund1 — 1Department of Chemistry, University of Oslo, Norway — 2Aarhus University, Denmark — 3ESRF, France
The kinetic pathways for coacervation and micelle formation are still not fully understood. Driven by electrostatic interactions and entropically driven counter-ion release, complexation of oppositely charged macromolecules lead to the formation of micellar nanostructures. Here we study the coacervation process, from initial formation and growth of stable micelles, on a nanometric length scale using time-resolved small-angle X-ray scattering (TR-SAXS). The micellar coercevates are formed through the complexation of anionic polyelectrolyte (PSSS) and cationic block copolymer (PEO-b-PVBTA). The results reveal that the formation polyelectrolyte coacervates follows a two-step process; i) first, metastable large-scale aggregates are formed upon a barrier-free complexation immediately after mixing; ii) Subsequently the clusters undergo charge equilibration upon chain rearrangement and exchange processes yielding micellar-like aggregates with net neutral charge that are pinched off to yield the final stable micelle-like coacervates. Interestingly, the overall kinetic process was essentially concentration independent, indicating that the rearrangement process is mainly accomplished via noncooperative chain rearrangement and chain exchange processes.