Preparation Of Spherical Silica Using Inexpensive Silica Sources And Its Application As Restricted Access Materials

Due to their high mechanical strength, stable physical and chemical properties,easy access to surface modification and many other advantages, silica based materialshave been widely used in chemical synthesis, bio-medicine, environmental monitoringand other areas. Spherical silica materials with porous structure have importantapplications in chromatography, catalysis and biological probes because of theirregular shape, controllable size range and high specific surface area and pore volume.Several methods including sol-gel, polymerization-induced aggregation andspray drying have been developed for preparation of spherical silica materials. Thesemethods, however, all have some limitations. In sol-gel method, expensive rawmaterials are employed and long aging time is required. Polymerization-inducedaggregation suffers from dimer formation and insufficient utilization of raw materials.Spray drying method produces particles of poor mechanical strength and irregularshape, and this method needs expensive equipment. All these disadvantages havelimited the large-scale production of spherical silica.The goal of this thesis is to develop simple yet effective methods for preparationof porous spherical silica with good spherical shape and high mechanical strength.Using inexpensive materials as silica sources, inverse suspension polymerization andW/O/W interfacial reaction were adapted to reduce the cost for large-scale production.The specific surface area and pore structure properties were controlled by tuningconditions during the synthetic procedure.Porous spherical silica with regular shape, good dispersion and high mechanicalstrength was prepared by inverse suspension polymerization using silica sol as silicasource. Porous spherical silica with high specific surface area and large average poresize and pore volume was prepared by W/O/W interfacial reaction using water glassas silica source. In an effort to combine the advantages of the above methods, silicicacid prepared from water glass by cation-exchange reaction was used as silica sourceand porous spherical silica of regular shape, good dispersion, high mechanicalstrength and high specific surface area were prepared by inverse suspensionpolymerization. This method can be adapted for large-scale production, and thespherical silica had narrow particle size distribution after screening. The specificsurface area from124.3m²·g^-1to597.3m²·g^-1, pore size in the range of2.45nm to13.97nm, pore volume from0.3354cm³·g^-1to0.8314cm³·g^-1can be tuned by adjusting preparation and post-synthesis conditions.Restricted access materials with diol groups on the external surface andoctadecyl groups on the internal surface were prepared using four kinds of sphericalsilica with different average pore size and specific surface area as matrix. The limitedpore sizes of these materials exclude protein and other biological macromoleculeswhile retain small molecule hydrophobic compounds. The surface hydrophilic diolgroups reduce or even eliminate irreversible adsorption of biological macromoleculeson the external surface of the matrix. In addition, restricted access materials withdifferent average pore size showed various performances on adsorption of three kindsof biological polypeptides with different molecule weight, including TP-5, protamineinsulin and BSA, implying their potential applications in separation and analysis ofbiological samples.