The Synthesis And Application Of Molecular Imprinted Polymers Based On In-situ Polymerization SiO₂

In the past few years, molecular imprinting technique has been considered as a promising method to prepare materials with molecular recognition ability, named molecular imprinting polymers (MIPs). MIPs have notable features such as improved stability, effective cost and rapid fabrication. Typically, MIPs are prepared via polymerization in the presence of template molecules followed by removal of the template. After templates are removed, the remaining cavities with complementary size, shape, and orientation of functionalities are left behind.The MIPs has broad prospect of applications, it’s always used as adsorbent in the process of sample pretreatment, due to its specific recognition and enrichment for the templates. Its successful applications in the analytical methods increased the detection sensitivity and decrease detection limit of analytes. Various synthesis strategies have been developed, including bulk polymerization, precipitation polymerization, and suspension polymerization. Although the MIPs prepared using the abovementioned methods exhibit good binding affinity and specificity toward target molecules, they have some shortcomings, such as incomplete template removal, low utilization ratio of binding sites, and slow mass transfer, because of their highly cross-linked nature. To design better synthesis methods of MIPs is important. In situ polymerization is a simple and convenient polymerization reaction. The thickness of the polymer layer synthesized by polymerization in situ was controllable by changing the reaction condition. The silica layer was synthesized by in situ polymerization to modify the surface of the matrix. The new MIPs synthesized may have better properties.This paper mainly performed the innovative research from the following aspects:A new method was designed for the synthesis of MIPs, and two kinds of MIPs were successful synthesized:hollow MIPs (HMIPs) and multi-walled carbon nanotube MIPs (MCNTs/MIPs). The HMIPs:particle size was uniform, and it has a strong specific adsorption for the template. When it was used as adsorbent in the SPE process, it can enrich the Sudan I, and a good analysis results were obtained. The MCNTs/MIPs:The silica layer fixed the structure defect which was caused by strong acid in the carboxylation of MCNTs. The silica layer successfully prevented the leakage of templates compared to the MCNTs/MIPs. The two kinds of MIPs both have good physical and chemical stability. After several extraction processes, the imprinting layer was well-preserved.This paper consists of three chapters:Chapter1:Introduction. This paper generally describes the recognition theory, synthesis methods, and its applications in the analysis of commercially available samples. The development of the combination of molecular imprinting and solid phase extraction in recent years was also expounded.Chapter2:Synthesis, characterization and evaluation of hollow molecularly imprinted polymers for Sudan Ⅰ. Firstly, the polystyrene (PS) nanoparticles with uniform size were synthesized by emulsion polymerization. Then sulfonation reaction was used to introduce sulfo groups on the surface of PS nanoparticles. The sulfo groups could capture the APTES by electrostatic interaction. In situ polymerization reaction was initiated on the surface of PS, after the hydrolysis reaction of TEOS. Then, the PS/SiO2core/cell nanoparticles were obtained. The PS core was removed by THF, and hollow SiO2was obtained finally. Sudan Ⅰ was chosen as template, and imprinting layer was covered on the surface of hollow SiO2, we named the imprinting polymer HMIPs. The HMIPs can be used as adsorbent in the SPE process and it can enrich the Sudan Ⅰ in chilli powder sample.Chapter3:Synthesis, characterization and evaluation of a novel composite imprinted material of Ofloxacin based on multi-walled carbon nanotubes. Through the treatment of the surface of the MCNTs, the chloride modified MCNTs were obtained. The APTES was grafted of the surface of MCNTs by ammonolysis, in situ points for in situ polymerization were imported. Then, TEOS polymerized on the surface of MCNTs. After vinyl functional, imprinting layer was obtained on the surface of MCNTs (MCNTs/SiO2/MIPs). The MCNTs/SiO2/MIPs have excellent specific recognition and enrichment for Ofloxacin and its analogues, after reused several times, the adsorption capacity were retained.