Controlled Functionality and Self-Assembly of PDI-Based Supramolecular Polymers by Targeted Modification

Supramolecular polymers (SMPs) are an interesting and promising field in material science, owing to their attractive properties, including reversible degree of polymerisation and self healability. A current challenge in the field of supramolecular polymerization is the lack of control over structure (and thus function) of these dynamic systems. The aim of this project is to explore various strategies to improve the control of perylene diimide (PDI)-based supramolecular polymers The choice of PDIs as the building blocks for this study is based on their high stability (thermal as well as chemical), high fluorescence quantum yield, which makes them favourable candidates for fluorescence imaging strong interactions between cores and their properties as N type semiconductors. These factors therefore ensure that these are promising compounds to investigate. Proposed routes to obtain the desired control are:
The use of different degrees of thionation on the core to explore the influence on assembly (due to changes of the sterics of the thionated species) and optoelectronic properties (e.g., resulting in a decrease of the LUMO and increase of the HOMO energy levels, resulting in Fluorescence quenching by a faster triplet formation, resulting in a redshift of the absorption maxima).
The introduction of different groups in the imide position to enhance different non covalent interactions between the monomers, e.g. multiple hydrogen bonding, aromatic stacking and ion-ion interactions, resulting in faster and stronger assembly, or by introducing sterically hindering groups, aggravating the stacking. However, the influence on the electronic properties by imide substitution is small, due to nodes in the molecular orbitals at the imide nitrogen atoms
) Furthermore, substitution in bay position leads to a distortion of the planarity of the PDI core, resulting in a different stacking behaviour. This difference may be used to tune the self-assembly and, additionally, the effect on the optical properties of the PDI is much larger than substitution on the nitrogen imide.
The expected outcome is to gain more control over the self-assembly behaviour regarding length, polydispersity and location of functional groups of the polymers, resulting in tuneable and customisable function and properties.
This project falls within the EPSRC "Physical sciences" research area, more precisely in the subgroups "Polymer Materials", "Synthetic Organic", "Photonic Materials" and "Materials For Energy Application".