Capturing molecules with templated materials: analysis and rational design of molecularly imprinted polymers
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Advantages such as chemical, mechanical and thermal stability together with high selectivity for the templated analyte render molecularly imprinted polymers MIPs interesting alternatives to routinely applied separation materials or antibodies. Nevertheless, many factors such as the choice of functional monomer, cross-linker, and porogenic solvent, as well as the ratio between template, functional monomer, and cross-linker will affect the resulting imprinting efficiency and polymer particle size and morphology. The research described in this thesis contributes to the development of new synthetic strategies for the generation of imprinted micro- and nanospheres for 17beta-estradiol (E2) focusing on accurate control and optimization of the governing parameters for precipitation polymerization, including the polymerization temperature and the cross-linker, yielding a one-step synthetic approach with superior control on the bead diameter, shape, monodispersity and imprinting efficiency. Thus synthesized imprinting materials for E2 were successfully applied in HPLC separation, solid phase extraction and radioligand binding assays. As the optimization of imprinted materials is based on fundamental understanding of the binding site properties, the investigations is aimed at establishing a more rational basis for further tailoring imprinted materials to the desired analytical application. The relationships between the particle porosity and rebinding properties were detailed, providing useful guidelines for controlling the particle properties for the desired application including, SPE pre-concentration, HPLC separations, and biomimetic binding assays. Furthermore, analytical techniques (1H-NMR and IR, etc.) and molecular modeling were combined in this thesis to facilitate advanced understanding of the fundamental principles governing selective recognition of molecularly imprinted polymers at a molecular level. The molecular interactions involved in the templating process of molecularly imprinted polymers based on the self-assembly approach were simulated in molecular dynamic simulation model by building a modeling system include all the imprinting components with correct ratio, which has never been reported before. Molecular level interactions such as hydrogen bonding, π-π stacking interactions as well as the free energy governing complex formation of E2 with the functional monomers 4-vinylpyridine (4VP) and methacrylic acid (MAA), and the cross-linker divinylbenzene (DVB) were discussed.