Photophysics of supramolecular polymers
| PhD ceremony: | I. (Ioannis) Touloupas, MSc |
| When: | September 09, 2025 |
| Start: | 12:45 |
| Supervisors: | R.M. (Richard) Hildner, Prof, T.L.C. (Thomas la Cour) Jansen, Prof |
| Where: | Academy building RUG |
| Faculty: | Science and Engineering |
Supramolecular polymers are long chains of repeating units held together by secondary chemical bonds. These reversible interactions enable self-healing properties and tunable material behavior under typical environmental conditions (room temperature, atmospheric pressure). Their dynamic nature facilitates ease of fabrication and functional versatility without requiring complex chemical expertise. Molecules found in natural structures can be arranged in supramolecular polymers for organic semiconductors (e.g. photovoltaics, electronics) due to their tunable optical and electronic properties.
Aggregation due to supramolecular polymerisation of such molecules leads to unique quantum states. The simplest are J- and H-aggregates which exhibit distinct optical behaviors based on the specific arrangement of the molecules. These properties are further influenced by molecular vibrations, electron interactions, and disorder.
In his thesis, Ioannis Touloupas investigates supramolecular polymers based on two classes of functional molecules:
1. Porphyrins : Resembling chlorophylls with different side groups and metal centers (Zn, Pt), they form two aggregates types with different slipped stacking, which is interesting for organic electronics and biomimetic energy-harvesting systems. 2. Heterotriangulenes : Flat, disc-like molecules that form J-aggregates with complex emissive behaviour.
The key findings in Touloupas's thesis are: - Solution vs. solid state: Supramolecular polymers on substrates endure local structural rearrangements of molecules when solvent is removed. Disorder is increased which induces new emissions, complicating direct property extrapolation from solution to solid state. - Pt-centred porphyrins: Exhibit phosphorescence due to spin-orbit coupling, with mixed singlet-triplet exciton transport over 4 µm.- Hyperspectral imaging: Powerful, high-throughput method to reveal structure-property relationships in complex functional materials.