Jozef Hodyl PhD Thesis - Theses - Flinders University

(glycidoxypropyl)dimethylethoxysilane (GPDMES), 82, which has just a singlehydrolysable group bonded to the silicon atom and, therefore, GPDMES, 82, isunable to cross-link with itself to form a polymeric layer across the silica surface inthe way shown in Figure 4.3.Figure 4.3Representation of the ability of GPTS, 32, to form oligomers and extendmultidirectionally in a layer across the silica surface.Si-GPDMS, 83, was synthesised as it was thought that due to its inability tocross-link, silanisation of the silica surface would involve a single molecule ofGPDMES, 82, reacting with one silanol producing, in effect, a series of monolithiclinker moieties randomly scattered over the silica surface, as opposed to a tegumentalpolymeric spread by GPTS, 32. The difference between these two modes of bindingto the silica surface is illustrated in Figure 4.4. It can be seen that GPTS, 32, is ableto form bonds in all directions and may even hang from GPS units already attachedto the silica surface whereas GPDMES, 82, is only able to bond to the silica surface.A comparison of the DRIFT spectra and the loading capacities for 33 and 83 wouldgive an indication of the level and mode of coverage on the silica surface.73