Jozef Hodyl PhD Thesis - Theses - Flinders University

increase in surface coverage from the other forms of silica-based materials used. Thisis indicative of the significant increase in the isolated silanol population as observedin the DRIFT spectra, for this material, shown in Figure 4.7.Table 4.1Comparison of the loading of the linker species, GPTS, 32, on various forms of silicawith the non-cross-linking species GPDMES, 83. Also showing residual carbon presentin the dried silica materials, SiO 2 and MCM-41.Microanalysis % aLoadingSi-MaterialCHMicro bmmol g -1Thermal b wt Thermal b% b mmol g -1SiO 270-230SiO 2230-4000.25 0.92 -- -- --0.20 1.30 -- -- --MCM-41 0.01 1.33 -- -- --Si 70-230 -GPS, 33 7.64 1.43 1.10 11.98 1.04Si-GPDMS, 83 3.39 2.26 0.35 5.25 0.42Si 230-400 -GPS, 80 6.34 1.36 0.88 c cMCM-41-GPS, 81 12.23 2.17 1.70 c ca Error = ± 0.3%; b Error = ± 10%; c Not attempted.4.2.6 Loading level: Macrocyclic receptor ligand materialsLoading levels for the immobilised macrocycles are limited by the level of coverageof the linker molecules. Some linker molecules could be situated within the pores ofthe silica, whereas, others could reside beneath an oligomeric layer and consequentlybe inaccessible to the macrocycle. The significance in the linker's mode of coveragebecomes apparent in the degree of grafting of the macrocycle to the silica attachedlinker achieved, since covalent attachment can only occur to linker molecules thatare available for reaction.84