Fabrication Of Silica Monolithic Columns With Ordered Structure Using Colloidal Crystal And F127 As Templates

Silica monolithic columns have found their advantages as chromatography media i n the fields of hi gh-performance l iquid c hromatography ( HPLC) and capillary electrochromatography ( CEC), etc. H owever, t ill now , t he pores o f prepared m onolithic c olumns a re unor dered, w ith weak uniformity a nd connectivity, which are bad for the improvement of column efficiency. So the thesis focuses on the fabrication of well-defined hierarchical silica monolithic columns. Furthermore, we preliminarily inspected chromatographic performance of the acquired silica monolithic columns.The details in the work are summarized as follows:Firstly, monodisperse Polystyrene (PS) spheres with uniform diameter were synthesized by s oap-free emulsion polymerization method. PS colloidal crystals were pre pared in t he chromatography c olumn us ing modified evaporation-induced self-assembly method or filtering method assisted by HPLC. The structure of colloidal crystals made by the former method is relatively better.Secondly, silica monolithic columns with macro-mesopores were synthesized via a f acile dual-templating technique involving colloidal crystals and triblock copolymer templates. The acquired silica monolithic columns were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR), etc. SEM images showed that the silica monolithic c olumns faithfully inherit the structure of c olloidal crystal te mplates. In addition, the r esults of BET and TEM cha racterizations exhibited that t he p resence of F127 c an pr oduce m esopores a bout 1 0nm a nd improve B ET spe cific s urface a rea. To pr ove the c ommonality of t he a bove replication method for f abricating s ilica m onolithic c olumns, f our kinds of colloidal c rystals assembled by various s izes of P S sp heres w ere used as sacrificial macropore templates, and the penetrability of the acquired monolithic columns became more superior as increasing the size of PS spheres.Finally, TiO2-coated silica m onolithic co lumns w ere pre pared by s ol-gel technology and characterized by SEM, TEM, FTIR and X-ray powder diffraction (XRD), it is found that the structure of the raw silica monolithic columns were destroyed little in the process of fabrication. Additionally, the small pores on the skeleton still existed after being coated with titania. XRD analysis exhibited that the t itania on the raw s ilica m onolithic columns is anatase type a fter be ing calcinated at 500 oC for 4 h. Because of the phosphor-selectivity of titania, the acquired TiO₂-coated silica monolithic columns has potential application in the HPLC analysis of organophosphate compounds.