Invited External Seminar, Monday December 19, 13:00 - 14:00 (in person) Department of Physics, Seminar room (Φ2 - 3nd fl.)
Rectangular ladder-type pentaphenyl helices: Synthesis and chiroptical properties
Prof. Dr. Ulli Scherf (abstract - short CV)
Department of Chemistry, Macromolecular Chemistry group and Wuppertal Institute for Smart Materials & Systems, Bergische Universität Wuppertal, D-42119 Wuppertal, Germany
scherf@uni-wuppertal.de
Ladder-type pentaphenyl chromophores contain a rigid, planar π-electron system and show bright fluorescence. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report on the synthesis of helical polymers with a rigid square structure, based on ladder- type pentaphenyls that are connected via chiral spirobifluorene linkers. Variation of the circular dichroism of the polymers with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The observed interplay between localized and delocalized excited states provides a new paradigm for interpreting the circular dichroism spectra also of other helical polymers, such as proteins or polynucleic acids.
Invited External Seminar (webinar), Tuesday, May 31, 2022, 16:00 -17:00 (zoom platform) Zoom link
Design of a Quiet Supersonic Aircraft Enabled by Shape Memory Alloy Actuators
Dimitris C. Lagoudas (abstract - short CV)
Aerospace Engineering and Materials Science and Engineering Texas A&M University, College Station, TX 77843, USA
lagoudas@tamu.edu
The return of commercial supersonic flight requires innovative solutions to be developed that meet noise and efficiency requirements for overland flight. To study such a possibility NASA is supporting a multi-disciplinary team of academic and industrial experts to explore the potential of structurally morphing the outer mold line of a supersonic vehicle. The team is considering recent advances in supersonic computational fluid dynamics, sonic boom propagation prediction tools and new design approaches of embedding high actuation energy density Shape Memory Alloys (SMAs) for in situ morphing, leading to optimal low boom signatures in different atmospheric environments and flight conditions. The presentation will focus on the development of the appropriate high temperature NiTiHf SMAs based on the requirement of reliable repeated actuation up to 100K thermal actuation cycles, under high levels of stress. The thermomechanical constitutive modeling of such alloys, their modeling of low cycle actuation fatigue and failure will be discussed. A unified constitutive modeling approach will be described to capture critical phenomena associated with the unique response of SMAs and the development of predictive tools for the design and reliable operation of phase transforming materials for aerospace applications.Invited External Seminar (webinar), Tuesday, December 7, 16:00 Teams link
Large-area nanostructured electronics manufactured at a flash
Prof. Thomas Anthopoulos (abstract - short CV)
King Abdullah University of Science and Technology (KAUST), Saudi Arabia
In traditional electronics the ability to downscale critical dimensions of its building block, the transistor, has proven extremely successful in advancing the computational power of modern-day microelectronics. However, the adaptation of existing manufacturing techniques in emerging technologies, such as large-area printed electronics, has proven challenging both in terms of technology and economics. Despite the difficulties new forms of electronics have been gaining ground, transforming both the research and development landscape as well as the broader marketplace of electronics and the relevant manufacturing infrastructure. In this talk I will discuss our recent efforts towards downscaling emerging forms of large-area, nanostructured electronics through the combination of new fabrication paradigms and advanced materials. Particular emphasis will be placed on the development and evolution of adhesion lithography (a-Lith) and its use in an expanding library of applications ranging from ultra-fast, solid-state opto/electronic devices to new forms of nano-reactors for solar fuel generation and energy storage.Invited External Seminar (webinar), Tuesday, November 23, 15:00 -16:00 Teams link
Chemical design rules for non-fullerene acceptors in organic solar cells
Denis Andrienko (abstract - short CV)
Max Planck Institute for Polymer Research, Mainz, Germany
Efficiencies of organic solar cells have practically doubled since the development of non-fullerene acceptors (NFAs). However, generic chemical design rules for donor-NFA combinations are still needed. We propose such rules by analyzing inhomogeneous electrostatic fields at the donor-acceptor interface. We show that an acceptor-donor-acceptor molecular architecture, and molecular alignment parallel to the interface, result in energy level bending that destabilizes the charge transfer state, thus promoting its dissociation into free charges. By analyzing a series of PCE10:NFA solar cells, with NFAs including Y6, IEICO, and ITIC, as well as their halogenated derivatives, we suggest that the molecular quadrupole moment of ca 75 Debye Angstrom balances the losses in the open circuit voltage and gains in charge generation efficiency.Invited (Inaugural) External Seminar (webinar), Tuesday, May 18, 16:00 -17:00 (zoom platform)
Graphene Nanoribbons – Closing the Gap between Graphene and Conjugated Polymers
Klaus Müllen (abstract - short CV)
Max Planck Institute for Polymer Research, Mainz, Germany
Graphene nanoribbons (GNRs) emerge as unique carbon nanostructures and versatile electronic materials. Their band structures can be widely tuned yielding semiconductors and even topological insulators. The most important features are i) the opening of a band gap due to the geometric confinement and ii) the occurrence of edge localized electronic states with spin polarization. Both characteristics offer new technological opportunities.Science 2019, 366, 1107; Nature Nanotechnology 2020, 15, 22; Nature 2018, 557, 69; 560, 209; 561, 507; Progr. Polym. Science 2020, 100; Nature Rev. Chem. 2017, 2, 01000; J. Am. Chem. Soc. 2021, 143, 5564; Nature Chemistry, accepted.
.Invited External Seminar (webinar), Tuesday, June 15, 16:00 -17:00 (zoom platform)
Nanostructured Hybrid Materials by Atom Transfer Radical Polymerization
Krzysztof Matyjaszewski (abstract - short CV)
Carnegie Mellon University, Center for Macromolecular Engineering, Pittsburgh, PA, 15213, USA
matyjaszewski@cmu.edu
Many advanced nanostructured functional materials were recently designed and prepared by reversible deactivation radical polymerization. Copper-based ATRP (atom transfer radical polymerization) catalytic systems with polydentate nitrogen ligands are among most efficient reversible deactivation radical polymerization systems. Recently, by applying new initiating/catalytic systems, Cu level in ATRP was reduced to a few ppm. ATRP of acrylates, methacrylates, styrenes, acrylamides, acrylonitrile and other vinyl monomers was controlled by various external stimuli, including electrical current, light, mechanical forces and ultrasound, also in the presence of air. ATRP was employed for synthesis of polymers with precisely controlled molecular architecture with designed shape, composition and functionality. Block, graft, star, hyperbranched, gradient copolymers, molecular brushes, various hybrid materials and bioconjugates were prepared with high precision. Special emphasis will be on nanostructured multifunctional hybrid materials for application related to biology, environment, and energy.| Date / Time: 16:00-17:00 | Presenters |
|---|---|
| 6/10 | Maria Louloudi |
| Elefterios Lidorikis | |
| George Floudas | |
| 13/10 | Sotiris Hadjikakou |
| Periklis Papadopoulos | |
| 20/10 | Michael Karakassides |
| Evangelos Evangelou | |
| Achilleas Garoufis | |
| 27/10 | Emmanouil Manos |
| George Papageorgiou | |
| 3/11 | Alexandros Tselepis |
| Leonidas Gergidis | |
| Alkiviadis Paipetis | |
| 10/11 | Mamas Prodromidis |
| John Plakatouras | |
| Angelos Kalampounias | |
| 17/11 | Ioannis Panagiotopoulos |
| Alexios Douvalis | |
| Dimosthenis Giokas | |
| 24/11 | Dimitrios Tasis |
| Yiannis Deligiannakis | |
| Andreas Tzakos | |
| 1/12 | Dimitrios Gournis |
| Angeliki Lekatou | |
| Christina Lekka | |
| 8/12 | George Evangelakis |