Regensburg 2007 – scientific programme

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SYPE: Symposium Polyelectrolytes

SYPE 1: Polyelectrolytes Poster

SYPE 1.10: Poster

Wednesday, March 28, 2007, 16:00–18:30, Poster B

Molecular weight dependence of PEO permeation through the walls of hollow polyelectrolyte capsules — •Rudra Prosad Choudhury¹, Petrik Galvosas², and Monika Schönhoff¹ — ¹Institute of Physical Chemistry and Graduate School of Chemistry, WWU Münster, Germany — ²Faculty of Physics and Earth Sciences, University of Leipzig, Germany

The exchange dynamics of polyethylene oxide (PEO) in colloidal dispersions of hollow polymeric capsules is stidued by pulsed field gradient (PFG)-NMR and diffusion-relaxation correlation spectroscopy. The capsules are prepared by self-assembly of polyanions and polycations onto silica particles, followed by dissolution of the silica core in HF. In PFG-NMR two echo decay components with diffusion coefficients corresponding to free PEO and capsules, respectively, are found. In addition, relaxation- diffusion correlation spectra reveal two peaks with different diffusion coefficients, but almost identical relaxation times. This implies the presence of mobile PEO chains in the capsule interior. From variations of the diffusion time, the exchange behaviour is analysed by a two- site exchange model of free and encapsulated PEO. Exchange times and permeation rates through the capsule wall are extracted for different molecular weight. Permeation rates are decreasing with increasing molecular weight of PEO. While for short chains (Mw < 10000 Da) the dependence on Mw is strongly pronounced, another, less pronounced dependence is found for larger Mw. This suggests a transition between two different mechanisms of permeation as the molecular weight is increased.