Organic Self-Assembled Monolayers: Chemical and Structural Responses to Temperature, Light, and Reactive Gas Species

Characterising the structural dynamics of materials is crucial to their implementation in real-world applications. Knowing how a system will respond to a particular stimulus, and understanding that response from a fundamental chemistry standpoint, is key to success in nanoscience. Accordingly, this thesis describes the use of kinetics and dynamics experiments to relate the structural behaviour of organic self-assembled monolayers to their environmentalconditions. The work herein examines three different self-assembled monolayers perturbed by three different external stresses. First, we present the classic self-assembly system of alkanethiols on Au(111) and show how their ability to effectively passivate metal surfaces when bombarded with reactive gas species is strongly dependent on both film thickness and substrate temperature. The use of localised imaging techniques such as scanning tunnelling microscopy (STM) allows us to relate these observations to the monolayer restructuring and surface rearrangement that occurs throughout the reaction. Second, we study how the topographical and crystalline nature of novel wafer-scale two-dimensional (2D) porphyrin polymers (specifically, metal-organic frameworks (MOFs)) are impacted by sample annealing and post-anneal cooling rates. Understanding these temperature-dependent structural phases is important for knowing the application limitations of such films – and for recognising previously unknown application potential. Finally, we explore the cooperative dynamics of azobenzene-functionalised liquid crystal (LC) thin films in response to irradiation with ultraviolet (UV) light. Although much work has already been done on the production of azo-functionalised thin films, it remains challenging to induce simultaneous and coherent isomerisation of an entire film. Understanding the dynamic interaction between molecules within the film is therefore crucial to making uniformly switchable films a molecular engineering reality