Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Focus: Structure and Dynamics of Responsive Hydrogels I

CPP 3.6: Talk

Monday, March 22, 2010, 11:45–12:00, H37

Temperature sensitivity of colloidal gels measured by multispeckle DLS — •Martin Medebach, Michael Gradzielski, and Regine v. Klitzing — Stranski Laboratory, Technische Univeristät Berlin, Strasse des 17.Juni 124, 10623 Berlin

We investigated the dynamical behaviour of colloidal systems by the multispeckle DLS method. The multispeckle method is useful to measure the correlation function on a time regime of τ=0.1seconds up to several days. It also provides the possibility to measure time resolved dynamics. Using this method it was found in the past that vesicle gels behaves heterogeneous. In our measurements we could also verify that vesicle gels react sensitive on temperature changes. This could also be the reason of the temporal fluctuations that are visible in distinct τ-channels. This temperature sensitivity was checked in more detail by applying temperature pulses of different amplitudes. The T-sensitivity depends on particle concentration and on how strong the noise is correlated at the measured τ-channel. A system that reacts very sensitive on temperature changes are concentrated PNIPAM microgel particles. The phase transition is detected by the multispeckle method and shows a slowing down of the dynamics at the LCST and a minimum of the noise in the τ-channels. On higher scattering vectors it was possible to do the multispeckle correlation on length scales smaller than the particle size. Here, the fluctuations inside of a particle could be detected at different temperatures.