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Colloquium
Multiscale modeling of soft matter with applications for energy and biotechnology
Jul. 02, 2014, 16:30 - 18:00
Institute of
Nanotechnology
 
Talk given by Prof. Roland Faller

The systematic multiscale of heterogeneous soft matter systems is an
area of current research. Soft matter materials (including polymers and
biomembranes) involve complex multiscale problems. Several
techniques to systematically and directly link different length scales are
presented where the focus will be on the Iterative Boltzmann
Inversion (IBI). Then I will address two important current problems:
Organic Photovoltaics and Supported Lipid Bilayers.

We apply the IBI to a system for polymer-based solar cells which show
promise as a cheap alternative to current silicon-based photovoltaics.
Typical systems use a mixture of a light-absorbing conducting polymer
as the electron donor and a fullerene derivative as the electron
acceptor in the solar cell's photo-active layer which are generally mixed
together to produce a bicontinuous percolating network called a bulk
heterojunction (BHJ), thereby allowing optimization of both light
absorption and charge-carrier generation and transport from a donor-
acceptor interface. But prediction of the active-layer microstructure
based on the constituent electron-donor and electron-acceptor phases
and the processing conditions remains challenging. Atomistic computer
simulations are only feasible to studying systems not much larger than
an exciton diffusion length. We overcome this hurdle by developing a
coarse-grained (CG) simulation model of mixtures of the widely used
conducting polymer poly(3-hexylthiophene) (P3HT) and various
fullerenes. We then use the CG model to characterize the structure
and dynamic evolution of the BHJ microstructure as a function of
polymer:fullerene mole fraction and polymer chain length for systems
approaching the scale of photovoltaic devices.

Supported Lipid Bilayers are an abundant research platform for
understanding the behavior of real cell membranes as they allow for
additional mechanical stability. We studied systematically the changes
that a support induces on a phospholipid bilayer using coarse-grained
molecular modeling on different levels. We characterize the density
and pressure profiles as well as the density imbalance inflicted on the
membrane by the support. Changes in the pressure profile can
partially explain the problems of integrating proteins into supported
membranes. We determine the free energy of transfer of phospholipids
between the proximal and distal leaflet of a supported membrane
using a coarse-grained model. These results are in favorable
agreement with recent data obtained by very large scale modeling
using a water free model where flip-flop can be observed directly. We
compare results of the free energy of transfer obtained by pulling the
lipid across the membrane in different ways. All these results are
allowing us to more rationally design biosensors and drug delivery
vehicles.
 
This event is part of the eventgroup INT Talks
Homepage
http://www.int.kit.edu/events.php
Speaker
Prof. Roland Faller

UC Davis, USA
Department of Chemical Engineering and Materials Science
Organizer
Prof. (apl.) Dr. Wolfgang Wenzel
Institute of Nanotechnology (INT)
Karlsruhe Institute of Technology (KIT)
Mail:wolfgang wenzelChf6∂kit edu
Targetgroup
Interested / Everyone
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