Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Polyelectrolytes
CPP 18.1: Vortrag
Dienstag, 24. März 2009, 09:30–09:45, ZEU 114
Small-angle x-ray scattering of lignosulfonate in aqueous methanol solutions — •Ulla Vainio1, Rolf Andreas Lauten2, Sylvio Haas3, Kirsi Leppänen4, Larissa Veiga1, Ritva Serimaa4, Armin Hoell3, and Rainer Gehrke1 — 1HASYLAB at DESY, Hamburg, Germany — 2Borregaard Lignotech, Sarpsborg, Norway — 3Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany — 4Department of Physics, University of Helsinki, Helsinki, Finland
Lignosulfonate is a binder, dispersant, and emulsion stabilizer. It may be used as a component in plastics and low-cost methanol fuel cell membranes. We studied the structure and aggregation of sodium and rubidium lignosulfonate particles in water-methanol mixtures by small-angle x-ray scattering (SAXS). Volume fraction of lignosulfonate in solution ranged from 0.01 to 0.17, covering the semi-dilute regime. Interestingly, rubidium lignosulfonate particles self-associated more than sodium lignosulfonate particles even though both ions have valence +1. The effect was most pronounced in 1:1 methanol-water mixtures. Measurements were made also for 1:3 methanol-water solution and aqueous solution. We conclude that the heavier rubidium ions associate to the sulfonate groups more readily than sodium ions. Methanol enhanced the self-association tendency for both rubidium and sodium lignosulfonate. A contrast variation method, anomalous small-angle x-ray scattering (ASAXS), was used to study how rubidium is distributed in the lignosulfonate solutions. The measurements were made at the 7T MPW SAXS beamline at BESSY in Berlin.