Molecularly Imprinted Polymer Beads-Synthesis, Evaluation and Applications
Abstract: Molecularly imprinted polymers (MIPs) are artificial receptors designed for the selective recognition of template molecules. These polymers have been applied in analytical separations, as chemical sensors and in drug delivery system due to their low cost and high stability. In recent years MIP beads, especially those with good selectivity in aqueous solution, have become attractive as they can be potentially used as selective adsorbents for the solid phase extraction (SPE) and chromatographic separation of various target molecules.The aim of this thesis was to investigate and improve the synthetic methods for the preparation of MIP beads, especially those that can be used in aqueous solution. In the first section, Pickering emulsion is utilized to synthesize water-compatible MIP beads. Scanning electron microscopy (SEM) was used to characterize the morphology and surface structure of the particles. As water-soluble monomers were employed during the imprinting process, the MIP beads had a hydrophilic surface and showed high compatibility with aqueousconditions. Additionally, the MIP beads exhibit high selectivity and specificity to template in aqueous solution. Both organic compounds and macromolecules were used as templates separately and MIP beads with specific bindingsites were successfully obtained. The method developed in this thesis has a general applicability and offers a potential approach to synthesize polymer beads for bioseparation and wastewater treatments.Another focus of this thesis was the preparation of multifunctional materials based on MIP beads for the purpose of different applications. Reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization wasused to prepare monodisperse beads with RAFT reagents located on their surfaces, which allowed for the straightforward grafting of polymer brushes, or can be converted into new functional groups for further modification. The specific molecular recognition of the beads was not sacrificed during the aminolysis process, and different functionalities were introduced to the MIP beads under mild conditions. The thiol groups introduced onto the MIP surface allowed the MIP beads to be immobilized on a gold-coated substrate, such that these MIP based sensing surfaces were used for the detection of nicotine by surface enhanced Raman scattering (SERS).The Pickering emulsion systems provide an efficient method with which to prepare water-compatible MIP beads that have high selectivity under aqueous conditions. Further functional materials and new applications can beexpected upon the combination of Pickering emulsion systems with more controllable synthetic chemistry. The RAFT polymerization method, in particular, has a general applicability and introduces new possibilities for the development of other functional materials and devices.
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