Dresden 2003 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 1: Polymerschmelzen
CPP 1.1: Hauptvortrag
Montag, 24. März 2003, 09:30–10:00, ZEU/160
Structural forces in free-standing liquid films — •Regine von Klitzing and Branko Kolaric — Stranski-Laboratorium für Physikalische und Theoretische Chemie, TU Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Germany
Free-standing liquid films of a thickness on a mesoscopic length scale present a cavity for solutions containing macromolecules or particles. With increasing outer pressure the films thin stepwise due to oscillatory forces between the interfaces. The period is related to the particle diameter or to the correlation length of the macromolecular system. This presentation focuses on the comparison between the structuring of polyelectrolyte chains of different molecular architecture. Disjoining pressure isotherms of films containing polyelectrolytes have been measured in a thin film pressure balance. The steps in film thickness scale as c−1/2 with the polymer concentration c for linear polyelectrolytes. Small angle neutron scattering spectra of the corresponding polyelectrolyte solutions show a correlation peak. Under the assumption that the peak position is related to a correlation length ξ via the simple Bragg equation (qmax = 2π/ξ), ξ is equal to the step size in the disjoining pressure isotherm. For branched polyelectrolytes the step size scales as c−1/3. The study shows that the same characteristic length is found in different geometries measured independently by different methods.