Applications of isothioureas in surface chemistry : modification of self-assembled monolayers and immobilisation on polymer supports

Abstract

The research outlined in this thesis describes the development of organocatalytic methodology for the modification of self-assembled monolayers on silicon dioxide surfaces and its extension towards an asymmetric protocol and immobilisation of isothiourea organocatalysts to polystyrene supports. Chapter 1 aims to describe the fundamental aspects of self-assembled monolayers and their place within the wider area of surface chemistry. A recent overview of catalytic surface functionalisation is discussed as well as the historical context of this project, with respect to research within the Smith group, is also presented. A statement of the initial aims and objectives of the research is presented. Chapter 2 describes the proof-of-concept study undertaken to develop methodology towards the functionalisation of silicon oxide surfaces using an isothiourea-catalysed organocatalytic Michael addition-lactonisation process. Subsequent characterisation of the resulting surfaces and a reaction scope is also carried out in this system. Chapter 3 describes an extension of the methodology carried out in the previous chapter to allow for an asymmetric protocol. The sense of enantioenduction of the resulting surfaces was then examined using chemical force microscopy using a novel AFM probe with the results show that chiral discrimination can be achieved using this methodology. Control experiments were also undertaken by depositing enantiopure starting materials on a surface and measuring the adhesion forces confirming the presence of a chiral surface. Chapter 4 describes the immobilisation (R)-BTM and (2R,3S)-HyperBTM analogues onto polystyrene supports and their evaluation in several different reaction classes previously investigated within the Smith group. Results show that the polymer-supported catalyst (2R,3S)- HyperBTM can be recycled up to 8 times without any major loss in yield or selectivity. Chapter 5 offers a brief summary of the work undertaken in this PhD and some of the conclusions that can be drawn from it as well as an insight into the potential future developments of this research and areas where it could possibly expand and develop.