Plenarvorträge - DPG-Tagungen

Chemische Physik und Polymerphysik Dienstag
substrates (Silicon, glass) using the layer-by-layer method developed in
the early 1990s by Decher. In the present work the response of external
stimuli like relative humidity and outer salt concentration is investigated.
The multilayer structure is investigated by ellipsometry, AFM X-ray and
neutron reflectometry. We found that the amount of water absorbed by
the polymer film increases with increasing film thickness, but the net
percentage of water absorbed decreases after reaching a maximum for
a certain number of layers. The absorbed amount of water depends on
the type of polyelectrolyte in the outer layer which leads to an odd/even
effect in swelling. While small changes in salt concentration have a pronounced
effect on the multilayer structure during the dipping process,
high amounts of salt are required to change the structure after the adsorption
process has been finished.
CPP 15.7 Di 17:00 B
Polymer films with thickness gradients: A new class of heterogenous
films — •T. Titz 1 , N. Hermsdorf 2 , and P. Müller-
Buschbaum 1 — 1 TU München Physik Department LS E13, James-
Franck-Str.1, 85747 Garching (Germany) — 2 IPF Dresden, Hohe Str.
6, 01069 Dresden
applications such as functional coatings. Polymer gradient samples resemble
a powerful tool to investigate nanostructures and their creation
process by changing an external variable along one direction of the sample.
A film thickness gradient was prepared by solution casting on a tilted
substrate. The thickness gradient increase from 30 to more than 300 nm
over a distance of 50 mm. The prepared polymer film is homogenous perpendicular
to the thickness gradient to allow for an investigations based
on scattering techniques. We applied x-ray reflectivity and gracing incidence
small angle x-ray scattering (GISAXS) to determine the density
profile as well as the lateral structuring. In addition optical microscopy
and AFM were performed to give access to the real space surface structure.
From the continuous change of the film thickness changes in the
surface and bulk morphology of the polymer films resulted.
CPP 15.8 Di 17:00 B
Influence of substrate cleaning on the dewetting of thin
polystyrene films — •E. Bauer 1 , M. Stamm 2 , and P. Müller-
Buschbaum 1 — 1 TU München Physik Department LS E13,
James-Franck-Str.1, 85747 Garching — 2 IPF Dresden, Hohe Str. 6,
01069 Dresden
applications, such as coatings and dielectrics. As the first basic step
in any dewetting experiment resembles the cleaning of the substrate,
to guarantee equal starting conditions, we treated silicon substrates
by different cleaning procedures. Next, the dewetting behavior of thin
polystyrene films, spin-coated on top, was investigated by exposure to
heat load. Different stages of dewetting, beginning by hole creation and
ending-up with drops were observed. These structures were locally probed
by AFM and additionally investigated by grazing incidence small angle
x-ray scattering (GISAXS) to get a statistical relevant information about
the whole sample. We observed a strong influence of the chosen surface
clean on the time scales of the dewetting. This underlines the importance
of giving detailed information about this preparation step to allow for a
comparison of experiments.
CPP 15.9 Di 17:00 B
Phase separation of ternary polymer blend films: A kinetic investigation
— •P. Panagiotou 1 , E. Maurer 1 , R. Cubitt 2 , and P.
Müller-Buschbaum 1 — 1 TU München Physik Department LS E13,
James-Franck-Str.1, 85747 Garching (Germany) — 2 ILL, b.p. 156, 38042
Grenoble (France)
polymers with different molecular weights and glass transition temperatures
is investigated with neutron reflectometry and AFM. Thin films
were prepared by spin-coating on top of pre-cleaned silicon substrates.
Afterwards the samples were annelead yielding changes in the surface
morphologies due to phase separation. In a subsequent preparation step
the pre-annealed samples were stored under a solvent vapor atmosphere.
The resulting morphological changes were monitored in-situ with neutron
reflectometry. A high time resolution was achieved by applying a timeof-flight
(TOF) mode at the neutron reflectometer D17 at ILL. AFM
(atomic force microscopy) pictures the topography resulting in the most
prominent length scales parallel to the surface as calculated with 2d-
Fourier analysis.
CPP 15.10 Di 17:00 B
The effect of surface interactions on the molecular dynamics
under the confinement of thin layers — •Anatoli Serghei and
Friedrich Kremer — Institute for Experimental Physics I, University
of Leipzig, Linnestr. 5, 04103, Leipzig, Germany
A novel method for preparation of thin polymeric films was developed
and employed to investigate the molecular dynamics of cis-polyisoprene
under confinement using BDS (Broadband Dielectric Spectroscopy, 0.1
Hz-10 MHz, 200 K-400 K). The method consists in placing a thin polymer
film via spin-coating or solvent-casting between two hard, flat, conductive
electrodes (optical polished highly doped silicon wafers having a
macroscale roughness of 2 nm), as spacers being used silica nanocolloids
with a well-defined size distribution. The film thickness, reaching values
of tens of nanometers, can be additionally controlled by measuring the
sample capacity. By chemically treating the surface of one or of both electrodes,
our method allows us to investigate the effect of the interfacial
interactions on the dynamics of thin films.
CPP 15.11 Di 17:00 B
Active Networks Studied by Magnetic Tweezers Microrheometry
and Torsional Macrorheometry — •R. Tharmann, J. Zhang,
M. Bärmann, and A. R. Bausch — Technische Universität München,
James-Franck-Straße 1, Garching, 85747 Germany
Although the defining property of polymer networks is their viscoelastic
behavior, a microscopic understanding of the underlying mechanisms
is still lacking. In biological processes, e.g. the migration of cells, the
temporal and spatial regulation of the activation of cross-linkers is very
important, yet not understood. Even more importantly, biology uses a
huge number of distinct cross-linkers which have different effects on the
viscoelastic behavior of biological networks.
One class of cross-linkers are molecular motors such as myosins. Under
ATP-rich conditions the molecular motors are active, while in the ATP
depleted regime the motors act as passive cross-linkers (rigor mortis).
Here we use both the technique of Magnetic Tweezers Microrheometry
and Torsional Macrorheometry to study the local and the averaged viscoelastic
properties of actin networks which are linked by myosin II,
myosin V and HMM fragments at different ATP concentrations.
CPP 15.12 Di 17:00 B
Water-Soluble Terpolymer Mediated Calcium Carbonate Crystal
Modification — •Ranith Krishna Pai 1 , Sabine Hild 1 , Othmar
Marti 1 , and Andreas Ziegler 2 — 1 Experimental Physics, University
of Ulm, Albert-Einstein-Allee 11, 89081 Ulm — 2 Department
Electronmicroscopy, University of Ulm, Albert-Einstein-Allee 11, 89081
Ulm
The structure of the polymeric substrates plays an important role
in the nucleation of calcium carbonate crystals. In this study a
synthetic water-soluble poly (acrylamide-co-2-acrylamido-2-methyl-1propane
sodium sulfonate-co-n-vinyl pyrrolidone) will be introduced
which is a substrate favoring the nucleation of polymorphs of calcium
carbonate crystals under specific experimental conditions. Morphological
characterization of the polymorphs was done using Atomic Force Microscopy,
Scanning Electron Microscopy, Energy Dispersive Spectroscopy,
FTIR Analysis and X-ray Diffraction. If calcium carbonate was precipitated
in presence of the polymer a remarkable increase in nucleation
density was observed. Stacked crystals of rhombohedral morphology were
formed may be due to the presence of sodium sulfonate groups on the
terpolymer. However, in the presence of polymer and poly-L-aspartic
acid only hollow crystals of aragonite with needle like or plate like morphologies
had been found. This change in calcium carbonate morphology
could be explained by the variation of the polymer conformation if poly-
L-aspartic acid is present.
CPP 15.13 Di 17:00 B
Grazing-incidence small-angle X-ray scattering on thin lamellar
diblock copolymer films: Modelling the scattering cross section
— •Christine M. Papadakis 1 , Peter Busch 1 , Markus Rauscher
2 , Detlef-M. Smilgies 3 und Dorthe Posselt 4 — 1 Fakultät
für Physik und Geowissenschaften, Universität Leipzig — 2 MPI für Metallforschung,
Stuttgart — 3 CHESS, Cornell University — 4 Roskilde University,
Denmark
Grazing-incidence small-angle X-ray scattering (GISAXS) is a powerful
method to elucidate the mesoscopic structures formed by thin polymer
films. We have studied a series of thin films of lamellar polystyrenepolybutadiene
(PS-PB) diblock copolymers. In this system, the lamellar