Supramolecular architectures represent an increasingly interesting playground both in the chemistry and physics field. In fact, they give us the possibility to tailor the physical and chemical properties of conjugated systems, opening the doors to new applications. In this dissertation I will present my findings regarding different types of supramolecular structures. The first part is dedicated to the study of the optical properties of conjugated polyrotaxanes: conjugated polymers such as poly(4,4’-diphenylene vinylene) threaded through cyclodextrin macrocycles rings, that sterically impose increased intermolecular distances, leading to preserved single-molecule excitonic photophysics even in high concentration regimes, due to reduced pi-pi stacking of the chromophores. In particular, I will show how it is possible to tune their photoluminescence properties for different applications like polarized emission and optically pumped lasers. The incorporation of polyrotaxanes and their unthreaded analogue in a stretch-oriented polyvinyl alcohol matrix gives rise to a strongly polarized photoluminescence parallel to the stretching direction which I studied using steady-state and time-resolved optical techniques. Furthermore, by exploiting the water-solubility of polyrotaxanes is possible to embed them in three-dimensional photonic crystal and tune their radiative rate to achieve low-threshold optically pumped lasers. In the second part, I will present the application of supramolecular structures in light-emitting diodes. In fact, self-assembled monolayers represent an interesting system to tune the work function of commonly used electrodes in the plastic electronics field, therefore changing the injection barriers for holes at the interface between the organic semiconductor and the metallic electrode. Furthermore, I will show how supramolecular architectures are used to obtain efficient near-infrared photoluminescence and electroluminescence introducing a three-dimensional pi conjugation. Moreover, by adding a pyridine derivative it is possible to suppress the efficient self-quenching in this class of porphyrin based molecular assembly increasing further their applicability in light-emitting diodes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:565673 |
| Date | January 2012 |
| Creators | Di Stasio, F. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1350099/ |
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