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Séminaire MSC
"Matière et Systèmes Complexes"

                      

Jeudi 12 juin 2008 à 11h30
Bâtiment Condorcet, 6ème étage, salle 646 A.

Ilja Voets
(
Univ. of Wageningen, Pays-Bas)


Opposites attract?! On the electrostatically driven co-assembly of oppositely charged polymers in aqueous solution

Electrostatically driven co-assembly of two oppositely charged double hydrophilic block copolymers in aqueous solutions results in core-shell micelles with a mixed core, consisting of polyelectrolyte blocks, and a mixed corona, consisting of neutral solvent-swollen blocks. The miscibility of the shell-forming blocks, and thereby the extent of chain mixing / segregation in the micellar corona, can be tuned by, for example, segment chemistry and solvent quality. A mixed shell is observed for PGMA / PAAm, and PNIPAAm / PEO, while a de-mixed shell (Janus-type) is observed for PAAm / PEO.[1,2] These ‘complex coacervate core micelles’; i.e. C3Ms, form spontaneously and tend to be equilibrium structures.[3] Hence, C3Ms possess the unique ability to combine a compartmentalized internal structure with full responsiveness to external stimuli, such as pH, ionic strength, and mixing fraction.[4] Furthermore, temperature sensitivity can be achieved through incorporation of a LCST block in the micellar corona, such as PNIPAAm or PDEAAm. Micellar stability can be enhanced by selection of polyelectrolyte blocks with a rather hydrophobic backbone, such as a modified poly(butadiene) block.[5] A wide variety of active compounds, such as proteins, nanoparticles, and drugs, can easily be incorporated via electrostatic interaction.

[1] Voets, I. K.; de Keizer, A.; Cohen Stuart, M. A.; de Waard, P., Macromolecules, 2006, 39, 5952-5955.

[2] Voets, I. K.; de Keizer, A.; de Waard, P.; Frederik, P. M.; Bomans, P. H. H.; Schmalz, H.; Walther, A.; King, S. M.; Leermakers, F. A. M.; Cohen Stuart, M. A., Angew. Chemie-Int.Ed., 2006, 45, 6673-6676.

[3] Cohen Stuart, M. A.; Hofs, B.; Voets, I. K.; de Keizer, A., Curr. Op. Coll. Int. Sc., 2005, 10, 30-36.

[4] Hofs, B.; Voets, I. K.; de Keizer, A.; Cohen Stuart, M. A., Phys. Chem. Chem. Phys., 2006, 8, 4242-4251.

[5] Voets, I. K.; de Keizer, A.; Cohen Stuart, M. A.; Justynska, J.; Schlaad, H., Macromolecules, 2007, 40, 2158-2164.