Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: POSTERS Colloids, Nanoparticles and Aggregates

CPP 21.21: Poster

Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A

NMR Investigation of the Aggregation of Dye Molecules — Richard Szopko, Klaus Huber, and •Claudia Schmidt — Department Chemie, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany

The azodyes “Rot 2G” (red) and “Gelb GA” (yellow) are anionic direct dyes. A mixture of these dyes is used to produce orange hued paper. However, in the presence of alkaline-earth ions, such as Mg²⁺, aggregates are formed, which interfere with the dyeing process. Time-resolved static light scattering, observed within 15–20 minutes after mixing the two dye solutions, has shown the formation of short aggregates with a contour length of 250–300 nm in the presence of Na₂SO₄, whereas substituting Na⁺ ions with Mg²⁺ ions leads to a nearly tenfold increase of the contour length [1]. NMR spectroscopy revealed that even in dilute aqueous solutions of the pure dye Gelb GA aggregation occurs. The aggregation as a function of temperature and concentration has been investigated using high resolution NMR measurements of proton chemical shifts and pulsed gradient stimulated echo diffusion experiments.

[1] S. E. Inglés, A. Katzenstein, W. Schlenker, K. Huber, Langmuir, 16, 3010 (2000).