Leipzig 1999 – scientific programme
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PO: Polymerphysik
PO 13: Spektroskopische Methoden
PO 13.1: Talk
Tuesday, March 2, 1999, 16:00–16:20, HS 19
X-Ray Photon Correlation Spectroscopy [XPCS] on Dense Polymeric Systems — •D. Lumma1, L. B. Lurio1, A. R. Sandy1, P. Falus1, M. A. Borthwick1, S. G. J. Mochrie1, M. Sutton2, J.-F. Pelletier2, A. Malik3, G. B. Stephenson3, and L. J. Regan4 — 1MIT — 2McGill Univ — 3Argonne Natl Lab — 4Yale Univ
XPCS has the potential to become an important technique for studying slow relaxation processes on molecular length scales. As a model system with characteristic relaxation times and length scales similar to those of (co-)polymer blends, an optically opaque, colloidal suspension of polystyrene [PS] spheres [R=67 nm] in glycerol has been studied by XPCS. The measured intensity autocorrelation functions show signal-to-noise levels comparable to those obtained with laser light scattering, span four orders of magnitude in the time domain [0.03 s < Δ t < 400 s], and extend over one order of magnitude in reciprocal space [0.0012 Å−1 ≤ Q ≤ 0.0140 Å−1]. The observed diffusion coefficients, extracted from the autocorrelation functions for varying PS volume fractions, demonstrate how suspended particles adopt different microscopic dynamics in response to the confinement imposed by their neighbors.
XPCS is capable of characterizing the mode structure of opaque systems, and moreover of supplying the static structure factor over a wide range in reciprocal space, even for concentrated samples. Our goal is to develop XPCS as a tool for investigating the microscopic dynamics of dense polymeric systems. Preliminary data on copolymer micelles and entangled homopolymer blends will be presented.