Synthesis Of Polyphenyl Grafted Polysiloxanes Containing Methoxy And Fluoro As Stationary Phases And Their Chromatographic Performance Investigation

With the development of the society, chromatography is faced with both grave challenges and rare opportunities, particularly in the area of gas chromatography. On the one hand, gradual perfection of chromatographic apparatus and analytical methods has provided a firm foundation for the further development of the gas chromatography. On the other hand, along with the appearance of new environment pollutants and all sorts of compounds with similar molecular weight, boiling point, and structure, higher requirements of the gas chromatographic separation ability were put forward.The core of gas chromatographic separation is the stationary phase. Polysiloxanes are widely investigated as gas chromatography stationary phases over the years. However, these stationary phases can not achieve baseline separation for aromatic hydrocarbons in environmental pollutants. So in order to get a series of gas chromatographic stationary phases suitable for the analysis of aromatic pollutants and industrial products, it is necessary to develop some new stationary phases which will theoretically have more specific inter-molecular forces with solutes.The main contents are as follows:(1) Synthesis of polyphenyl grafted polysiloxanes containing methoxy and fluoro. The synthetic routes are as follows:Firstly,3,4-bis(3,4,5-trimethoxyphenyl)-2,5-diphenyl cyclopentadienone,3,4-bis(3,4-difluorinephenyl)-2,5-diphenyl cyclopentadienone were synthesized through a three-step reaction from corresponding benzaldehyde. Secondly, by the polymerization of D4 and D4Vi, methyl vinyl polysiloxane was prepared in the presence of tetramethyl ammonium hydroxide silicon alkoxide. Finally,3,4-bis(3,4,5-trimethoxyphenyl)-2,5-diphenyl phenyl polysiloxane and 3,4-bis(3,4-difluorophenyl)-2,5-diphenyl phenyl polysiloxane were synthesized through Diels-Alder reaction between methyl vinyl polysiloxane and as-synthesized cyclopentadienones, respectively.(2) Chromatographic performance investigation of polyphenyl grafted polysiloxanes containing methoxy and fluoro. The fused silica capillary columns were statically coated with these newly synthesized polymers. Then the prepared capillary columns were investigated in terms of thermal stability, column efficiency, polarity and selectivity, etc. The results of the thermogravimetric analysis reveal the excellent thermal stability of both polymers, and especially, no noticeable decreases could be observed when the 3,4-bis(3,4,5-trimethoxyphenyl)-2,5-diphenyl phenyl polysiloxane was conditioned up to 380℃. The column efficiency of both stationary phases is high, and 3,4-bis(3,4-difluorophenyl)-2,5-diphenyl phenyl polysiloxane has higher efficiencies with almost 3876 plates per m. In addition, both of the as-prepared stationary phases were characterized as moderately polarity by the determined McReynolds constants. The excellent selectivity and inertness in the inner surface of fused-silica capillary columns was proved by the analysis of Grob reagent. What’s more, these novel stationary phases showed good separation performance for analytes, including disubstituted benzene isomers, monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons and aromatic hydrocarbon mixtures. It is because that the side chain of the new stationary phases we made was tetraphenyl group, which contained five benzene rings could produce dozens of conjugated π bond electron. Thus, the stationary phases would have high polarizability and good selectivity. At the same time, because the methoxy and fluorin were introduced to polysiloxane, the polarity of them would be further enhanced. The dipole-induced dipole and dispersion would produce between stationary phase and solute molecular, which played an important role in separation. So, the present work suggests that these novel stationary phases are suitable for the separation of polar and weak-polar analytes and have great potential for further development and application.