Leipzig 1999 – wissenschaftliches Programm

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PO: Polymerphysik

PO 4: Poster: Kolloide und Polyelektrolyte

PO 4.1: Poster

Dienstag, 2. März 1999, 14:00–16:00, Foyer

Filmbildung von Latexpartikeln untersucht mit Hilfe der Röntgenkleinwinkelstreuung — •Nico Dingenouts and Matthias Ballauff — Polymer Institut, Universität Karlsruhe, Kaiserstr. 12, 76128 Karlsruhe

The packing of latex spheres achieved in the first step of film formation is considered. The latexes consisting of PMMA- or poly(styrene)-particles were dried at temperatures far below the glass temperature of both materials. The spatial order was investigated using small-angle X-ray scattering (SAXS) which yielded the structure factor S(q) of the system of dried spheres. No deformation of the particles occurred when going from the dilute suspension to a system of closely packed spheres. In all cases studied herein it could be demonstrated that no true long- range order was achieved in the process of drying. Model calculations showed that ordering of the spheres into small but perfect crystallites can be ruled out experimentally. It is demonstrated that the order achieved upon drying these latexes is intimately connected to the polydispersity of the system: If the polydispersity of the latex particles increases the maximum of the first peak of S(q) decreases whereas its breadth increases. This feature could be described quantitatively by the Percus- Yevick theory augmented by Vrij for systems of polydisperse hard spheres.