Plenarvorträge - DPG-Tagungen

Chemische Physik und Polymerphysik Dienstag
Wir berechnen z.B. die mittlere radiale Dichteverteilung in einer Mikrodomäne.
Ferner haben wir mit Minkowskifunktionalen die Dynamik
von Strukturwandlungen zwischen geordneten und ungeordneten Phasen
untersucht, die wir mit dynamischer Dichtefunktionaltheorie simulieren.
Wir vergleichen unsere Ergebnisse mit Fourieranalysen und Analysen von
Skeletten der Mikrodomänenstrukturen.
CPP 15.35 Di 17:00 B
Adsorption of a heteropolymer on a structured surface —
•Thorsten Bogner, Friederike Schmid, and Andreas Degenhard
— Condensed Matter Theory, Fakutät für Physik, Universität
Bielefeld, Postfach 100131, 33501 Bielefeld
The specific adsorption of a molecule, especially of a protein, on a
surface is of interest in biological processes as well as for technical applications.
The specificity within such molecular recognition processes
results from unspecific non-covalent interactions. For proteins in a solvent,
the spatial arrangements of the single monomers is determined by
the same non-covalent interactions that lead to molecular recognition. As
a result, the structure and therefore the physical shape of the protein is
affected by the adsorption.
We have calculated the energy spectra of a single heteropolymer for
both, the non adsorbed as well as the adsorbed case, considering all possible
compact folds. The heterogeneity of the polymer, as well as the
structure of the surface was characterised by a sequence or respectively
a pattern of hydrophobic and hydrophilic (polar) sites.
Our calculations allowed to identify a preference of a surface pattern
and to make a first attempt to define selectivity. We found general features
among sequences that are selective for a particular surface pattern.
These allow to identify relevant positions on the polymer chain, that decide
if a particular surface is recognised. Furthermore, we were able to
find sets of sequences that can recognise all surfaces by a process similar
to mutations.
CPP 15.36 Di 17:00 B
Brillouin-microscopy, a versatile technique to study the
mechanical properties of polymers — •Ravindrakumar BAC-
TAVATCHALOU 1,2 , Roland SANCTUARY 1,3 , Jan Kristian
KRÜGER 1,2 , Uli MÜLLER 1,2 , and Wolfgang MANGLKA-
MMER 1,2 — 1 Laboratoire Européen de Recherche Universitaire
Saarland-Lorraine (LERUSL) — 2 Universität des Saarlandes, Experimentalphysik,
Postfach 151150, D-66041 Saarbrücken, Germany
— 3 Université du Luxembourg, Avenue de la Faïencerie, L-1511,
Luxembourg
Brillouin spectroscopy (BS) is a versatile method to study the elastic
properties of bulk and film-like samples. In contrast to the well established
micro-Raman technique such a spatial resolving technique was not
yet available for BS. We propose here a new kind of Brillouin microscopy
(BM) without using a standard optical microscope, instead we use a home
made optical magnifier in combination with a spatial filtering and scanning
set-up. We will show that this new Brillouin technique is especially
valuable for the investigation of polymers. Recently, a spatial resolution
about 1µm was demonstrated (J. Phys. D: Appl. Phys. 36 (2003) 2738-
2742). In order to prove the capability of BM we present and discuss the
mechanical properties of interphases in ’substrate-1/adhesive/substrate-
2’ sandwiches.
CPP 15.37 Di 17:00 B
Slippage and Nanorheology of Thin Polymer Films — •Renate
Konrad and Karin Jacobs — Experimental Physics, Saarland University,
POB 151 150, 66041 Saarbrücken
The properties of a liquid in contact with a solid interface are very
important for applications involving e.g. flow through porous media or
in lab-on-a-chip devices. Solving the hydrodynamic equations for a liquid
flowing over a solid surface, one usually assumes the relative velocity
between liquid and solid to be zero, which is the so-called ”no-slip boundary
condition”. Experiments with complex fluids and, very recently, also
with simple (Newtonian) fluids have shown that there can be a non-zero
velocity (”slippage”) at the boundary. The sizes involved are expected to
be on the nm-scale. On the same scale we therefore determine the velocity
and the shape of a moving liquid front. Both are known to serve as
extremely sensitive ”nano-rheometers”. It is expected from theory that
slippage is enforced for smooth and low surface-energy substrates. In our
experiments, we vary the substrate properties as well as the ones of the
liquid like viscosity and viscoelasticity. A significant correlation between
these system properties and the sliding friction can be found.
CPP 15.38 Di 17:00 B
Microdomain Ordering and Slippage of a Structured Liquid —
•Daniel Podzimek and Karin Jacobs — Saarland University, FR
7.2 Experimental Physics, D-66123 Saarbrücken
In this contribution we present flow properties and flow induced microdomain
ordering of a confined structured liquid that is dewetting a
solid substrate. The microdomains emerge, since the two blocks of the
copolymer poly(styrene-ethylene/propylene) are incompatible and phase
separate. The equilibrium film structure shows lamellae which are aligned
parallel to the substrate. We find that dewetting induced shear causes a
structural rearrangement of the microdomains into cylinders. AFM observations
furthermore show that the dewetting process can be separated
into two distinct stages. The first stage is characterized by round hole formation
and structural rearrangements of the domains. The second stage
of dewetting is defined by an irregular hole shape and the alignment of
the microdomain structure along the three phase contact line. Additional
to the experiments on the polymer surface we present AFM scans of the
film-substrate interface. Effects due to slippage of the melt are apparent.
CPP 15.39 Di 17:00 B
Characterisation of plasma treated fluorinated copolymers —
•Thorsten Meyer, Manfred ap. Prof. Neumann, Markus
Bach, and Andreas Selinger — Universität Osnabrück, FB Physik,
Barbarastrasse 7, 49069 Osnabrück
The functionalisation of polymer surfaces with plasma is established
for many fields and has several advantages compared to other chemical
modification methods.
For many industrial applications a rapid switching from hydrophobic to
hydrophilic surfaces is required. With plasma treatments chemical modifications
can be obtained, not reachable by simple wet chemical treatment.
In order to study and optimize the inner parameters of the plasma
treatment, the processing was studied under ultra clean conditions. The
plasma treated surfaces were investigated by x-ray photoelectron spectroscopy
(XPS), and atomic force microscopy (AFM) in combination with
contact angle measurments. The relation between the fractal dimension
and the wettability of the surface was studied.
CPP 15.40 Di 17:00 B
Zum Glaszustand dünner adsorbierter Polymerschichten —
•Richard Hofmann und Dietmar Göritz — Fakultät für Physik,
Universität Regensburg, 93040 Regensburg
Die Frage der Beweglichkeit von Polymerketten dünner adsorbierter
Schichten konnte bisher experimentell und theoretisch nicht widerspruchsfrei
geklärt werden. Insbesondere besteht Uneinigkeit über den
Einfluss des Trägermaterials auf die Glastemperatur und die kinetischen
Vorgänge in dessen Umgebung. Ziel unserer Untersuchungen ist es, den
Zustand der adsorbierten Polymerschicht durch die Messung der mechanischen
Eigenschaften des Adsorbats auf einem Füllstoff zu erfassen.
Die Experimente wurden an dem Modellsystem Hochorientierter Graphit
(HOPG) und Polymer mit Hilfe der AFM durchgeführt.
CPP 15.41 Di 17:00 B
Influence of preparation conditions on the piezoelectric activity
of ferroelectric polyamide 11 — •Alexander Kremmer1 , Peter
Fruebing1 , Michael Wegener1 , Werner Wirges1 , Reimund
Gerhard-Multhaupt1 , and Harald Goering2 — 1Department of
Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam —
2Federal Institute for Materials Research and Testing, Unter den Eichen
87, 12205 Berlin
The piezoelectric d33 coefficient of electrically poled commercial
polyamide-11 films as well as of ferroelectric films, prepared by melting
the powder in a hot press at 210◦C, quenching in ice-water, uniaxially
stretching with a ratio of 3:1 and subsequent electrical poling above the
coercive field (75 MV/m) is studied by use of dynamic piezoelectrical
measurements where a force acts on the film periodically and the piezoelectric
voltage across the film is measured. The influence of processing
conditions (particularly stretching and annealing temperatures) on the
piezoelectric activity and the temperature dependence of the piezoelectric
coefficient is investigated in detail. The aim is the enhancement of
the piezoelectric coefficient of the film material without losing its excellent
thermal stability up to temperatures just below the melting region.