Plenarvorträge - DPG-Tagungen

Chemische Physik und Polymerphysik Montag
W. Nadler, P. Grassberger, J. Chem. Phys. 118 (2002) 444.
[2] T. Prellberg, A.L. Owczarek, Phys. Rev. E 62 (2000) 3780.
CPP 5.5 Mo 11:00 H 39
Time-depedent density functional theory applied in molecules,
liquids and solids — •Ari P Seitsonen and Jürg Hutter — Universität
Zürich
Time-dependent density functional theory (TDDFT) is a versatile
method which can be applied also to the determination of excitation
CPP 6 Self-organising Systems
energies in materials similarly as the density functional theory (DFT)
in the ground state. We apply the new implementation [J. Hutter, JCP
(2003)] of the method in the CPMD code. This enables us to calculate
the excitation energies and properties such as forces on the ions in the excited
state, employing the plane wave basis set/pseudo potential method.
We report applications in molecules, liquids and solids, and we discuss
both the advantages and the shortcomings of the method. As examples
we mention small molecules, solvation of tetrazine and acetone in water
and defects in diamond.
Zeit: Montag 11:30–12:15 Raum: H 39
CPP 6.1 Mo 11:30 H 39
Combinatorial mapping of PS-b-P2VP-b-PtBMA triblock
copolymers in thin films — •S. Ludwigs 1 , K. Schmidt 1 , R.
Magerle 1 , G. Krausch 1 , C. Stafford 2 , M. Fasolka 2 , A. Karim 2 ,
E. Amis 2 , A. Zvelindovsky 3 , and A. Sevink 3 — 1 Physikalische
Chemie II, Universität Bayreuth, Bayreuth, Germany — 2 NIST
Combinatorial Methods Group, Gaithersburg, USA — 3 Leiden Institute
of Chemistry, Leiden, Netherlands
Using sequential living anionic polymerization we synthesized a series
of monodisperse PS-b-P2VP-b-PtBMA triblock copolymers (SVT)with
increasing molecular weight of the poly(tert butyl methacrylate) block 1 .
In the present contribution we show experimental results on the thin
film behavior of SVT with volume fractions φPS : φP2V P : φPtBMA =
1 : 1.2 : x (with x ranging from 3.05 to 4). Gradients in film thickness
were prepared via thin film flow coating of dilute solutions in chloroform.
On controlled annealing in a non-selective solvent the films form
terraces of well-defined thickness exhibiting a highly ordered perforated
lamellar structure. With an additional gradient in substrate surface energy
orthogonal to the gradually increasing film thickness we find that
the perforated lamellar phase is formed irrespective of the chemical nature
of the substrate which makes the structure useful for applications in
nanotechnology 2 . We support our experimental results with simulations
based on the dynamic density functional theory: with increasing size of
the simulation box we find a similar sequence of structures as in the experiments.
1 S. Ludwigs et al., Polymer 44, 6815 (2003). 2 S. Ludwigs et
al., Nature Materials 2, 744 (2003).
CPP 6.2 Mo 11:45 H 39
AFM CHARACTERIZATION OF SUPPORTED PHOSPHO-
LIPID LAYERS FORMED BY SOLUTION SPREADING —
•T. Spangenberg 1 , N.F. de Mello 2 , T.B. Creczynski-Pasa 3 ,
A.A. Pasa 4 , and H. Niehus 1 — 1 Humboldt-Universität zu Berlin, Institut
für Physik, Newtonstr. 15, 12489 Berlin — 2 Pós-graduação em
Química, Universidade Federal de Santa Catarina, Florianópolis, Brazil
— 3 Departamento de Ciências Farmacêuticas, Universidade Federal de
Santa Catarina, Florianópolis, Brazil — 4 Departamento de Física, Universidade
Federal de Santa Catarina, Florianópolis, Brazil
CPP 7 Physics of Polymers I
The morphology and the stability of supported phospholipid (DPPC,
DOPC) layers prepared by solution spreading on mica were investigated
by atomic force microscopy. The samples were analyzed after the solvent
evaporation, the hydration step and after immersion in a buffer solution.
The phospholipid layers prepared by solution spreading method were successfully
characterized by ex-situ and in-situ AFM measurements. This
sequence of measurements allows us to follow the surface rearrangement
of the lipidic material, from non-uniform deposits, through multilayer
structures, to a final pattern with large bilipidic terraces. The most significant
result was the imaging of the prepared phospholipid layers in-situ
after the immersion in the liquid cell. The systems investigated exhibited
a stable surface configuration during the measurements, which is suitable
for studying time dependent biological and physical phenomena.
CPP 6.3 Mo 12:00 H 39
Chemically driven running drops — •Uwe Thiele, Karin John,
and Markus Bär — Max-Planck Institut für Physik komplexer Systeme,
Nöthnitzer Str.38, 01138 Dresden
A continuous dynamic model for the movement of a drop on a solid
substrate is derived for (1) driving by an externally given gradient using
a wettability gradient as an example and (2) driving by a self-produced
wettability gradient. The latter case of self-propelled drops on reactive
substrates corresponds to such experimentally found free-running
droplets (Dos Santos, D. F. and Ondarcuhu, T., PRL 75, 2972 (1995)).
The moving-droplet solutions of the model are investigated in detail.
Zeit: Montag 14:00–15:30 Raum: H 37
CPP 7.1 Mo 14:00 H 37
Scaling properties of critical polymer blends and polymer solutions
near the glass transition — •Werner Köhler, Wolfgang
Enge, and Jürgen Rauch — Physikalisches Institut, Universität
Bayreuth, 95440 Bayreuth
Critical polymer blends show Ising-like critical scaling close to Tc and
mean-field behavior for larger ǫ = (T − Tc)/Tc. Because of the thermal
activation of the Onsager coefficient, however, the critical exponent γ cannot
be directly observed in the temperature dependence of the diffusion
coefficient D within the mean-field regime. Similarly, the diffusion coefficient
of semidilute and concentrated polymer solutions typically only approaches
the concentration scaling law but then rapidly decreases because
of the increasing glass temperature of the solution. Contrary to D, the
Soret coefficient ST is neither sensitive to thermal activation of the Onsager
coefficient nor to the increase of local friction at the glass transition
and shows clean scaling in both cases. Experiments have been performed
on semidilute and concentrated solutions of polystyrene in toluene and
on critical poly(dimethylsiloxane)/poly(ethyl-methylsiloxane) mixtures.
CPP 7.2 Mo 14:15 H 37
Surface glass transition of monodisperse polystyrenes and
their bimodal mixtures investigated by the embedding of
noble metal nanoclusters and the XPS-charging effect —
•Jörn Erichsen, Tesfaye Shiferaw, Jörn Kanzow, Ulrich
Schürmann, Vladimir Zaporojtchenko, and Franz Faupel —
Lehrstuhl für Materialverbunde, Faculty of Engineering,
The temperature dependent embedding process of noble metal nanoclusters
into polymers was used to probe the surface glass transition.
X-ray photoelectron spectroscopy (XPS) was applied to study the embedding
of Au nanoclusters into polystyrene [1]. Previously a small decrease
of glass transition temperature (Tg) at the surface compared to the bulk,
which decreases at low Mw, was detected with this method [1]. The Tg of
thin PS films was additionally determined by the charging and discharg-