Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Colloids and Complex Liquids II - Dynamics and Mechanical Properties
CPP 39.9: Topical Talk
Donnerstag, 17. März 2011, 12:30–13:00, ZEU 222
Combining structure and mechanical properties of colloidal systems — Marcel Roth1, Chris Grigoriadis2, Jinyu Zhao1, Burkhard Mayer1, Doris Vollmer1, George Floudas2, and •Günter. K. Auernhammer1 — 1MPI Polymerforschung, 55128 Mainz, Germany — 2University of Ioannina, 45110 Ioannina, Greece
While observing the sample with confocal microscopy we either determine the mechanical properties with a home-build piezo-rheometer or we submit the sample to electric or magnetic fields. Two examples will be discussed.
In case of PMMA colloids dispersed in the isotropic phase of the liquid crystalline compound 4 cyano-4’-biphenyl (5CB), aggregation is induced by simple cooling through the isotropic-nematic transition. This leads to a complete phase separation of a colloid-free nematic phase and a colloid-rich isotropic phase within a temperature range of (1-2)K, creating a sponge-like network. 5CB is a solvent of PMMA in its isotropic phase and plastificizes PMMA at lower temperatures, as confirmed by rheology [1] and dielectric spectroscopy.
In relatively weak colloidal systems, like colloidal crystals, magnetic probe particles can be used to test the mechanical properties of the system. With the confocal microscope we follow both the motion of the magnetic particles and of the surrounding matrix particles. This allows us correlating the structural changes in the matrix with the mobility of the probe particle.
[1] M. Roth, D’Acunzi, D. Vollmer, and G. K. Auernhammer, J. Chem. Phys. 132, 124702, (2010).