Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 34: POSTERS Polymerphysics
CPP 34.48: Poster
Donnerstag, 28. Februar 2008, 17:00–19:30, Poster A
Logarithmic chain-exchange kinetics of diblock copolymer micelles — Reidar Lund1,2, Lutz Willner1, •Jörg Stellbrink1, and Dieter Richter1 — 1IFF, Forschungszentrum Jülich, D-52425 Jülich — 2Donostia International Physics Center, 20018 San Sebastián, Spain
We present a study of equilibrium chain-exchange kinetics of a well-defined model system for starlike PEP-PEO micelles in water/DMF mixtures [1, 2]. In this study we used time resolved small angle neutron scattering (TR-SANS) technique employing a particular H/D labeling scheme. This technique is perfectly suited for determination of exchange kinetics in equilibrium as, unlike other techniques,virtually no chemical or physical perturbations are imposed on the system.
The exchange kinetics crucially depends on the interfacial tension γ. By variation of γ the rate could be tuned over a wide time scale spanning from milliseconds to infinity. The results show that the kinetics follows a logarithmic time dependence [3] in sharp contrast to theory where single exponential behavior is predicted [4]. The logarithmic time dependence hints towards strongly coupled chain dynamics within the micellar cores induced by geometrical constraints. The same feature has been found for two other micellar systems confirming a general feature of exchange kinetics of block copolymer micelles.
[1] R. Lund et al., Macromolecules, 37, 9984-9993, 2004.
[2] M. Laurati et al., Phys. Rev. Letters, 94, 195504, 2005.
[3] R. Lund, et al., Phys. Rev. Letters, 96, 068302, 2006.
[4] A. Halperin and S. Alexander, Macromolecules, 22, 2403, 1989.