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Accueil du site > Séminaires > Archives séminaires > Séminaires 2012 > Séminaire MSC lundi 2 juillet 2012 à 11h30. Paul Dubin (University of Massachusetts Amherst).

Séminaire MSC lundi 2 juillet 2012 à 11h30. Paul Dubin (University of Massachusetts Amherst)

Sauf mention contraire, les séminaires et les soutenances se déroulent à 11h30 en salle 454A du bâtiment Condorcet.


Structural Evolution in Polyelectrolyte-colloid Coacervates : Recapitulation or Reorganization

Paul Dubin

Department of Chemistry, University of Massachusetts Amherst, USA

dubin@chem.umass.edu

Complex coacervation, the spontaneous formation of equilibrium dilute and dense fluids phases from solutions of oppositely charge macroions, has applications in microencapsulation, food systems, bioseparations, and biomimetic adhesion. More fundamentally, coacervates are unique states of soft matter whose rheological and optical properties reveal complex mesophase structures underlying their apparent homogeneity. Soluble complexes are coacervate precursors, but details of the phase transition itself are often obscured by system polydispersity. Mixtures of narrow MWD polyelectrolytes and well-defined mix micelles enable us to sort out the key roles of : of polyelectrolyte MW and linear charge density, micelle surface charge density, ionic strength and macroion stoichiometry. All these variables can induce phase transitions, but exquisite temperature dependence best allows us to explore structural evolution before, during and after coacervation. Dynamic light scattering, small angle neutron scattering and Cryo-transmission electron microscopy help us to compare structures present at incipient coacervation to those within the subsequent dense phase. We conclude that driving forces of ion-pairing and counterion release, in one-phase and dense phase states, use similar strategies of disproportionation and local charge neutralization to form analogous transient structures.


Contact : Équipe séminaires / Seminar team - Published on / Publié le 20 mars 2012


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