Use of Molecular Modelling for the Understanding of Self-Assembly Processes in Supramolecular Polymers

Abstract

There is an increasing need to further improve and obtain new materials for biomedical and technological applications. The tools and intricacies of material discovery and design have been exponentially multiplying, especially in recent years, opening the way for new discoveries for next generation materials. This thesis investigates in silico conjugated organic supramolecular assemblies with the use of selected tools at the molecular level. The computational examination entails the geometrical and architectural design of the assemblies, and the study of their energetic details. A directed focus on OPE oligo(p-phenyleneethynylene)s, a photoisomerizing wire aggregate, and a series of porphyrinic assemblies is made in the evolution of this examination. These are versatile structures for supramolecular assembly, able to bind via a combination of non-covalent interactions, with interesting applications. The OPEs form 1D (one dimensional) wires with notable electronic properties. Furthermore, photoisomerizing aggregates have sparked abundant interest due to the control of assembly via light induction. Lastly, porphyrins are highly conjugated and readily functionalised molecules with the ability to form supramolecular assemblies from one to three dimensions. Porphyrin aggregates are also offered in crucial applications such as in photodynamic therapy, as well as an immensely wide and versatile spectrum of applications in further scientific sectors. The first part of this thesis assesses the recent relevant computational methods through a benchmark study for their accuracy and computational cost for their predictivity of conjugated organic self-assemblies. Subsequently, the chosen assessed method is further evaluated by comparison with a set of published experimental data of OPE assemblies. The newly published method, GFN2-xTB, is then evaluated as the most efficient for this type of entitiy. The aggregation motifs and polymer properties two of two OPEs and a photoisomerizing 1D wire assembly are initially studied. Subsequently, a set of porphyrinic supramolecular aggregations first in the 1D, and then in 3D are studied by utilising reference experimental data for further validation of the predictive capacity of GFN2-xTB. Lastly, for the first-time, chemical tuning recommendations are presented for promoting specific aggregations motifs. The combined results produce structure-property trends that purvey model assembly suggestions for supramolecular architectural synthesis and design.