Plenarvorträge - DPG-Tagungen

Chemische Physik und Polymerphysik Montag
CPP 8.2 Mo 16:00 H 37
Hypersonic relaxation in glass-formers: Thermodynamic theory
and experimental studies using Brillouin spectroscopy — •Jörg
Baller 1,2 , Jan Kristian Krüger 1,2 , Thomas Britz 1,2 , Wulff
Possart 1,3 , Wolfgang Manglkammer 1,2 , and Roland Sanctuary
1,4 — 1 Laboratoire Européen de Recherche Universitaire Saarland-
Lorraine (LERUSL) — 2 Universität des Saarlandes, Fakultät für Physik
und Elektrotechnik 7.2, Geb. 38, D-66041 Saarbrücken, Germany —
3 Universität des Saarlandes, Fakultät für Chemie, Pharmazie und Werkstoffwissenschaften
8.15, Geb. 22, D-66041 Saarbrücken, Germany —
4 Universitaire du Luxembourg, 162a av. de la Faïencerie, L-1511 Luxembourg,
Luxembourg
The presented work gives a theoretical framework for the relaxation
behaviour of the elastic moduli of glass-formers near the glass transition
temperature. Using linear irreversible thermodynamics, an expression for
the temporal evolution of the elastic moduli (measured at hypersonic frequencies)
after a step-like change of temperature is calculated. These theoretical
results are compared to measurements of the hypersonic elastic
modulus by Brillouin Light Scattering (BLS). Three different materials
- an oligomer, an epoxy resin and a classical polymer - have been examined
by measuring the relaxation behaviour of the hypersound velocity
after a temperature pertubation. A discussion of the importance and the
influence of thermodynamic equilibrium during accomplishment of an
relaxation experiment is given by comparison to the theoretical results.
CPP 8.3 Mo 16:15 H 37
Breakup of droplets in PS/PMMA blends after equibiaxial elongation
— •Ulrich A. Handge — Institute of Polymers, Department
of Materials, ETH Zürich, Switzerland
The breakup of liquid droplets in emulsions and molten blends of immiscible
polymers has attracted much attention since many decades. The
intensive research is motivated by the fundamentally oriented interest in
understanding the deformation of drops in definable fields of flow and
the technological relevance of dispersion processes. In this study, we investigated
the breakup of equibiaxially deformed PS droplets in molten
polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends using a
multiaxial elongational rheometer [1]. In equibiaxial deformation, the PS
drop is deformed into a flat circular disc. During subsequent relaxation,
the PS drop can retract to one single drop or breakup into many smaller
drops. The driving force for this phenomenon is the interfacial tension at
the interphase between the PS phase and the PMMA phase. During relaxation,
the interfacial tension attempts to minimize the surface area of
the PS drop. Using light microscopy, we observed the formation of fingers
and holes in the elongated PS drop which finally results in a breakup of
the extended drop into many smaller drops.
[1] P. Hachmann and J. Meissner, Rheometer for equibiaxial and planar
elongations of polymer melts, J. Rheol. 47, 989 (2003).
CPP 8.4 Mo 16:30 H 37
Microtribological Properties of Fluorine-Based Polymers Deposited
by Sol-Gel — •Phani Ayalasomayajula, Guiseppe Breliozzi,
Imad Ahmed, and Henry Haefke — CSEM Swiss Center
for Electronics and Microtechnology, Inc., Rue Jacquet-Droz 1, CH-2007
Neuchatel, Switzerland
The versatility of sol-gel processing makes this technology relevant to a
wide range of industries. Applications include high-performance, protective
coatings against scratch and corrosion, optical fibers and waveguides,
filters and membranes, etc. Compared to other deposition techniques, solgel
has many advantages, such as easy composition control, fabrication
of thin films on large surfaces area, film homogeneity, cost effectiveness
and simple operation cycles. In the present investigation, sol-gel deposition
has been applied to coat three fluorine-based polymer layers with a
maximum thickness of 50 nm onto silicon substrates. Prior to deposition,
the silicon substrates were etched using HF to remove the native oxide
layer. Adhesion, friction and wear were analyzed in the microNewton
load regime using a precision microtribometer and compared with the
properties of the native oxide covered silicon surface. Film composition,
wetting behavior and surface topography were characterized by Rutherford
backscattering spectroscopy, contact angle testing and atomic force
microscopy, respectively. The obtained structural data has been correlated
with the tribological results. It was also found that the degree of
hydrophobicity of the coating results in a decrease of the pull-off force.
Furthermore, an increase in the molecular weight of the polymer results
in a reduction of wear.
CPP 8.5 Mo 16:45 H 37
Strain-dependent localization, microscopic deformations, andmacroscopic
normal tensions in model polymer networks —
•Carsten Svaneborg 1 , Gary S. Grest 2 , and Ralf Everaers 1
— 1 Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzerstr.
38, 01187 Dresden, Germany — 2 Sandia National Laboratories, Albuquerque,
New Mexico 87185, USA
We use Molecular Dynamics simulations to characterize the microscopic
and macroscopic response of a polymer network to an imposed
macroscopic strain. Our motivation is to provide a framework for the
quantitative test and the controlled development of statistical mechanical
theories of rubber elasticity as well as for the validation of critical
steps in the data analysis of experiments addressing these issues. We
present a quantitative test of various tube models of rubber elasticity
and show that recent theory by Mergell and Everaers is quite successful
in rationalizing the observed behavior. By accounting for localization
effects due to chemical crosslinks and entanglements, the theory is able
to describe the length scale dependent microscopic deformations and to
predict the elastic response of the network. We also discuss the interpretation
of neutron scattering data for labelled paths through model polymer
networks.
CPP 8.6 Mo 17:00 H 37
Infrared ellipsometric study of miscibility in thin double layers
of two polymers — •K. Hinrichs 1 , A. Röseler 1 , E.H. Korte 1 ,
N. Nikonenko 2 , J. Pionteck 3 , and K.-J. Eichhorn 3 — 1 Institut
für Spektrochemie und Angewandte Spektroskopie - Institutsteil Berlin,
— 2 B.I. Stepanov Institute of Physics, National Academy of Sciences
of Belarus, F. Scaryna Ave. 68, 220072 Minsk, Belarus — 3 Institut für
Polymerforschung Dresden e.V., Hohe Str. 6, D-01069 Dresden
Mid infrared spectroscopic ellipsometry [1] has been applied for the
investigation of poly-(n-butyl methacrylate) / poly(vinyl chloride) double
layers (100 nm each) on gold substrates and to analyze the process
of mixing caused by interdiffusion during annealing [2]. Interpretation of
the ellipsometric spectra in optical layer models allows the determination
of the thickness, the high frequency refractive index and the parameters
of molecular vibrations of the different polymer compounds. For a more
detailed evaluation infrared ellipsometry is used in combination with a
regularized deconvolution method [3]. The deconvolution method allowed
to determine positions of overlapping vibrational bands and to investigate
the shape of their profile. Annealing induced spectral changes were
discussed with respect to the miscibility and conformational changes in
the polymer film. [1] Hinrichs, K., Tsankov, D., Korte, E.H., Röseler, A.,
Sahre, K., Eichhorn, K.-J. Appl. Spectrosc. 2002, 56, 737. [2] Dlubek G.,
Bondarenko, V., Pompe G., Taesler Ch., Petters K., Krause-Rehberg R.,
Macromolecules 2002, 35, 6313; Dlubek G., Pompe G., Pionteck J., Janke,
A., Kilburn, D. Macromol. Chem. Phys. 2003, 204, 1234. [3] Buslov, D.
K., Nikonenko, N. A. Appl. Spectrosc. 1997, 51, 666.
CPP 8.7 Mo 17:15 H 37
Generalized Cauchy-Relation and its Implications for Amorphous
and Nano-Structured Materials — •Jan Kristian
Krüger, Thomas Britz, Jörg Baller, Andrä le Coutre,
Wulff Possart, Patrick Alnot, and Roland Sanctuary —
Laboratoire Européen de Recherche Universitaire Saarland-Lorraine
(LERUSL). Universität des Saarlandes, Fakultät für Physik und
Elektrotechnik 7.2, Geb. 38, D-66041 Saarbrücken, Germany
The generalized Cauchy-Relation (GCR) shows an unexpected linear
transformation (LT) between the elastic stiffness constants c11 and c44
in materials with effective isotropic symmetry. The slope B of this LT is
identical to that of the classical Cauchy-relation (B=3) but the additive
constant A is far from beeing zero. The magnitude of A will be discussed
as a measure of nanostructuration. Astonishingly, the GCR holds true
during irreversible processes like the curing process of adhesives.
The thermal glass transition, on the other hand shows two different
behaviors of the GCR: on slow cooling, the glass transition is completely
hidden in the GCR whereas on fast cooling the parameter B deviates significantly
from its classical value. Thus, the GCR is able to distinguish
between two states of glasses. Aging drives the broken GCR towards the
undisturbed GCR