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
https://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)
Eggenstein-Leopoldshafen
Mail: wolfgang wenzel ∂does-not-exist.kit edu

Targetgroup
Interested / Everyone