Name: Dr. Diddo Diddens
Diploma / M.Sc degree: Westfälische Wilhelms-Universität Münster, Germany
(May 2008)

PhD Project: Computer Simulations of Polymer Electrolytes


Homepage: http://www.uni-muenster.de/Chemie.pc/heuer/diddens.html

Abstract of Research Project

Polymer electrolytes are important candidates for many technological devices such as batteries or fuel cells. The rst studied polymer electrolytes contained poly-(ethylene oxide) (PEO) doped with various lithium salts. Since their discovery a wide variety of these materials has been studied. Design of the chemical structure of the polymer matrix gives many possibilities to change the properties of the network such as crosslinking or the use of comb-branched polymers. Another common approach to modify these materials is the addition of nanoparticles or organic solvents.
Despite this variety of empirically studied types of polymer electrolytes the detailed charge transport mechanism remains unknown. A closer understanding of this complex mechanism could thus play an important role in further improvement of these materials. Here, molecular dynamics (MD) simulations provide a useful tool for the investigation of the microscopic ion transport mechanisms.
The focus of my PhD research therefore lies on the understanding of the ion and polymer dynamics in polymer electrolytes. Basically, my PhD project consists of two dierent research topics:

1. The determination of local mobilities in polymer electrolytes. In polymer electrolytes one observes a local slowing down of the polymer motion due to ions attached to the polymer chains. However, it is often diffcult to quantify this eect within general polymer theories. A new statistical method recently developed in our workgroup promises to be a fruitful approach to extract local mobilities from MD simulation data. This method can generally be applied to many polmyeric systems and is also utilized for the determination of dynamical heterogeneieties in PEO/PMMA blends within our cooperation with the Richter group from the Forschungszentrum Jülich.

2. MD simulations of polymer electrolytes and investigation of the ion transport properties. After PEO-based polymer electrolytes have been intensely studied in our workgroup, my work focuses on the simulation of electrolytes containing polysiloxanes with oligoether sidechains. The conductivity of these electrolytes is dependent on the side chain length with a maximum at about six ether units, indicating a complex relationship between the structure and the dynamics of the system.


Publications

D. Diddens, M. Brodeck, A. Heuer
Microscopic understanding of the complex polymer dynamics in a blend —A molecular-dynamics simulation study
EPL 95 (2011), 56003.

D. Diddens, M. Brodeck, A. Heuer
Characterization of local dynamics and mobilities in polymer melts — A simulation study
EPL 91 (2010), 66005.

D. Diddens, A. Heuer, O. Borodin
Understanding the Lithium Transport within a Rouse-Based Model for a PEO/LiTFSI Polymer Electrolyte
Macromolecules 43 (2010), 2028–2036.


Diddo Diddens
eMail: Diddo Diddens