Dr. Roland Faller
University of California Davis

Abstract:
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) as well as on reactive modeling. After introducing the techniques, I will show three examples of current problems we can address with our techniques which include Organic Electronics, Morphology Prediction for Silica, and Drug Delivery. In all examples connections between connections between experiment and simulation will be pointed out.

We apply our multiscale modeling technique 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. Prediction of the active-layer microstructure based on the constituent materials remains challenging. Atomistic computer simulations are only feasible to study very small systems. 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. Recently we were able to turn to the very small length scale and explain neutron scattering data.

An industrially important question is to characterize silica gels and organo-silicon surface coatings. These are formed by reactive condensation of organo-silicon precursors. The morphologies of silica gels obtained from alkoxysilanes can be determined using newly developed models and simulation techniques. It is found that the gels obtained from trialkoxysilanes are more loosely bonded, and that the chemistry of the headgroup is important to the gel morphology. We furthermore can describe the chemisorption of alkoxysilanes with organic headgroups to hydroxylated silica surfaces.

Supported Lipid Bilayers are an abundant research platform for understanding the behavior of real cell membranes. 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 explain the problems of integrating proteins into supported membranes. These results are allowing us to more rationally design biosensors and drug delivery vehicles and even propose a novel class of drug delivery vehicles.

Biography:
Roland Faller studied physics at the University of Bayreuth, Germany and got his PhD in theoretical physics from the Max Planck Institute of Polymer Research and the University of Mainz for simulation work on polymer melts. Then he moved to the University of Wisconsin for his postdoc with Juan de Pablo in Chemical Engineering. In 2002 he accepted an assistant professor position in Chemical Engineering and Materials Science at UC Davis. His research interests are multiscale modeling of soft materials as well as model and algorithm development. In 2014 he became Co-Chair of the department and after the department split in Spring 2016 he is Chair of Chemical Engineering.

This seminar is sponsored by the Department of Chemical and Biomolecular Engineering.