Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: POSTERS Dynamics and Diffusion

CPP 8.4: Poster

Monday, February 25, 2008, 16:45–19:00, Poster A

Diffusion of liquid medium-chain molecules investigated by QENS and PFG-NMR — •Christoph Smuda¹, Gerd Gemmecker², Sebastian Busch¹, and Tobias Unruh¹ — ¹Forschungsneutronenquelle Heinz Maier-Leibnitz and Physik Department E13, TU München, Garching, Germany — ²Bayerisches NMR-Zentrum, Chemie Department, TU München, Garching, Germany

For the understanding of the functionality of colloidal drug delivery systems the molecule diffusibility inside the colloidal particles is an important parameter. In this contribution it is demonstrated that QENS is well suited for corresponding investigations. However, from measurements of the self-diffusion coefficients of the oligoisoprene derivative coenzyme Q₁₀ in nanosized droplets and in the bulk, respectively, at the time-of-flight spectrometer TOFTOF discrepancies to diffusion constants determined by PFG-NMR of more than one order of magnitude have been found. In order to find the origin of these deviations a systematical QENS study with a series of different medium chain n-alkanes was initiated. In accordance to the investigations on Q₁₀ it was found that in liquids of medium-chain molecules the diffusion mechanism changes on a nm length scale from a fast short range diffusion to a slower long range diffusion.

[1] T. Unruh, C. Smuda, G. Gemmecker, H. Bunjes, in Quasi-Elastic Neutron Scattering Conference 2006 (QENS2006), P.E. Sokol et al. (Eds.), Mater. Res. Soc. (2007) p. 137