Walsh, Zarah (2010) Exotic Monoliths. PhD thesis, Dublin City University.
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This thesis is entitled 'Exotic Monoliths', which has been defined, in the context of this thesis, as monoliths; (1) synthesised by methods not previously described in the literature, (2) synthesised from commonly used silica or organic polymer materials but whose surface has been modified with a novel material such as dyes, nano-particles and biologically active compounds, and (3) synthesised from materials which are not based on silica or organic polymers, such as zirconia or titania. The first two of these definitions have been the main focus for this thesis.
The thesis itself comprises five chapters. Chapter 1 presents an introduction to polymer monolith stationary phases and a detailed summary of the many different methods of synthesis. The surface modification of the monoliths and their applications in separation science, along with a short comparison with particle packed columns and introduction to some more novel inorganic monoliths is also presented.
Following on from this, Chapter 2 shows the preliminary work carried out on synthesising monoliths in capillary. Presented in this chapter is an investigation of thermally initiated polymerisation in standard 100 μm i.d. capillary and in larger diameter fused silica and PEEK capillary moulds. Photo-initiated polymerisation using both conventional UV lamps and light emitting diodes is also investigated, along with a novel application of LED synthesised monoliths, i.e. using short plugs of monoliths as retaining frits for column packing. Finally a short study of the ability to reproduce literature methods of surface modification by successfully grafting a layer of
methacrylic acid and 2-aminoethyl methacrylate on the surface of a monolithic scaffold is shown.
Chapter 3 presents the research carried out on the modification of organic polymer monoliths with photochromic dyes and the synthesis of monoliths directly from
modified photochromic dyes with a polymerisable double bond. A novel application of these photochromic monoliths is their use as photo-switchable electroosmotic pumps
allowing eluent flow to be controlled by light in micro-fluidic devices, which is also presented in this chapter. It is shown that by switching the wavelength of irradiation
from visible to ultraviolet an increase or decrease, respectively, in the flow rate can be observed.
The final two chapters, 4 and 5, present novel methods of monolith synthesis using light emitting diodes in the visible region. Chapter 4 looks at the polymerisation of
methacrylate monomers within polyimide coated moulds using red light while Chapter 5 looks at the polymerisation of styrenic monomers in poly(tetrafluoroethylene) coated
capillaries using blue light emitting diode arrays. In both cases the characterisation and application of the synthesised monoliths is presented showing that they are suited to use in separation science. The suitability of this method to polymerise monoliths in chips moulds was also shown, as was the ability of the initiation system activated by red light to be used for the photo-initiated grafting of chromophoric monomers.
A final section entitled 'General Conclusions and Outlook' provides a summary of the thesis and areas for further work.
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