Project A4: Synthesis, morphology and optoelectronic properties of hierarchically self-assembled donor-acceptor amphiphilic polymers

Principal Investigators: S. Ludwigs (Freiburg) / N. Giuseppone (Strasbourg)
PhD Student: Adrian Wolf

Current state of the research

One of the most important challenges today facing physics, chemistry, and materials science is to develop ways to program and assemble molecules into functional structures at the mesoscale using bottom-up approaches [1]. In particular, the self-organization of functional molecules or materials in well-defined nanopatterns is important for a number of devices, e.g. in optoelectonic applications.

Small monodisperse molecules can bear various chemical functionalities and well-defined supramolecular structures at the molecular scale. However, to manipulate these assemblies at larger scales is nontrivial, and processing for fabrication of functioning devices from small molecules is quite demanding. On the other hand, amphiphilic block copolymers formed from covalently linked homopolymers can self-assemble into nanopatterned arrays. However, the built-in functionality is limited and typically requires post-functionalization.

The synergistic association of block copolymers and small molecules can combine processability and self-assembly of block copolymers with the rich chemical functionality of small molecules. For example, Ikkala and ten Brinke developed a versatile methodology to construct supramolecules by attaching small molecules to the polymer side chain via hydrogen bonding, electrostatic interactions or metal coordination [2]. With this aim in view, we want to reach a high degree of organization of optoelectronically active materials by synthesizing single molecules that contain in their building blocks all molecular information to spontaneously self-assemble into functional supramolecular polymers via hierarchical organization.

Contributions of the participating groups

The present project is based on the discovery and implementation of a new kind of light responsive self-assembled triarylamines molecules – recently synthesized in the Giuseppone group – and that present unique cooperative properties of charge transport [3]. In general, the group has thorough experience in organic synthesis and supramolecular chemistry and has recently developed various functional self-assembled responsive systems to study their dynamic behaviors within networks of competing equilibria [4,5]. The Ludwigs group has its research focus on physicochemical characterization and expertise in studying optoelectronic properties of functional conjugated molecules and polymers including electrochemical, spectroscopical and charge-transport measurements [6]. Recent studies include the identification of conductivity mechanisms of polymeric bis(triarylamine) systems [7].

References
[1] Supramolecular Chemistry and Self-assembly Special Feature, Proc. Natl. Acad. Sci. USA. 2002, 99.
[2] Ikkala, O.; ten Brinke, G. Science 2002, 295, 2407.
[3] Moulin, E., Niess, F., Maaloum, M., Buhler, E., Nyrkova, I., Giuseppone, N. Visible light promotes the Hierarchical Self-assembly of Charge Nano-carriers by a Highly Cooperative Process, Angew. Chem. Int. Ed. 2010, in press, DOI: anie.201001833 (Frontispiece Angewandte).
[4] Tauk, L.; Schröder, A.-P.; Decher, G., Giuseppone, N., Nature Chem. 2009, 1, 649.
[5] Nguyen, R.; Allouche, L.; Buhler, E.; Giuseppone, N., Angew. Chem. Int. Ed. 2009, 48, 1093.
[6] Heinze, J.; Frontana-Uribe, B.; Ludwigs, S. The electrochemistry of conducting polymers. Persistent models, new concepts, Chemical Review 2010 asap.
[7] Yurchenko, O.; Heinze, J.; Ludwigs, S., Electrochemically induced formation of independent conductivity regimes in polymeric tetraphenylbenzidine systems Chem. Phys. Chem. 2010, 11, 1637.