Volume 90, Number 2, April 2010
|Number of page(s)||6|
|Section||Interdisciplinary Physics and Related Areas of Science and Technology|
|Published online||20 May 2010|
Charged diblock copolymers at interfaces: Micelle dissociation upon compression
Complex Fluids Laboratory, CNRS UMR 166 - 350 George Patterson Blvd, Bristol, PA 19007, USA
2 Laboratoire Adhésion et Inflammation, INSERM U600, CNRS UMR 6212 - Case 937, 163 Avenue de Luminy, Marseille F-13009, France, EU
3 Aix-Marseille Université, Faculté des Sciences/de Médecine ou de Pharmacie - Marseille, F-13000, France, EU
4 Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory Upton, NY 11973, USA
5 Université de Strasbourg, Institut Charles Sadron, CNRS UPR 22 - 23 rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2, France, EU
Corresponding author: firstname.lastname@example.org
Accepted: 14 April 2010
We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are “frozen”. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters.
PACS: 82.35.Jk – Copolymers, phase transitions, structure / 82.35.Rs – Polyelectrolytes / 82.70.Uv – Surfactants, micellar solutions,vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
© EPLA, 2010
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